veloren_common/

combat.rs

use crate::{
    assets::{AssetExt, Ron},
    comp::{
        Alignment, Body, Buffs, CharacterState, Combo, Energy, Group, Health, HealthChange,
        InputKind, Inventory, Mass, Ori, Player, Poise, PoiseChange, SkillSet, Stats,
        ability::Capability,
        aura::{AuraKindVariant, EnteredAuras},
        buff::{Buff, BuffChange, BuffData, BuffDescriptor, BuffKind, BuffSource, DestInfo},
        inventory::{
            item::{
                ItemDesc, ItemKind, MaterialStatManifest,
                armor::Protection,
                tool::{self, ToolKind},
            },
            slot::EquipSlot,
        },
        skillset::SkillGroupKind,
    },
    effect::BuffEffect,
    event::{
        BuffEvent, ComboChangeEvent, EmitExt, EnergyChangeEvent, EntityAttackedHookEvent,
        HealthChangeEvent, KnockbackEvent, ParryHookEvent, PoiseChangeEvent, TransformEvent,
    },
    generation::{EntityConfig, EntityInfo},
    outcome::Outcome,
    resources::{Secs, Time},
    states::utils::{AbilityInfo, StageSection},
    uid::{IdMaps, Uid},
    util::Dir,
};
use rand::RngExt;
use serde::{Deserialize, Serialize};
use specs::{Entity as EcsEntity, ReadStorage};
use std::ops::{Mul, MulAssign};
use tracing::error;
use vek::*;

pub enum AttackTarget {
    AllInRange(f32),
    Pos(Vec3<f32>),
    Entity(EcsEntity),
}

#[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum GroupTarget {
    InGroup,
    OutOfGroup,
    All,
}

#[derive(Copy, Clone, Debug, Eq, PartialEq, Serialize, Deserialize)]
pub enum StatEffectTarget {
    Attacker,
    Target,
}

#[derive(Copy, Clone, PartialEq, Eq, Debug, Serialize, Deserialize, Hash)]
pub enum AttackSource {
    Melee,
    Projectile,
    Beam,
    GroundShockwave,
    AirShockwave,
    UndodgeableShockwave,
    Explosion,
    Arc,
    Pool,
}

pub const FULL_FLANK_ANGLE: f32 = std::f32::consts::PI / 4.0;
pub const PARTIAL_FLANK_ANGLE: f32 = std::f32::consts::PI * 3.0 / 4.0;
pub const BEAM_DURATION_PRECISION: f32 = 2.5;
pub const MAX_BACK_FLANK_PRECISION: f32 = 0.75;
pub const MAX_SIDE_FLANK_PRECISION: f32 = 0.25;
pub const MAX_HEADSHOT_PRECISION: f32 = 1.0;
pub const MAX_TOP_HEADSHOT_PRECISION: f32 = 0.5;
pub const MAX_BEAM_DUR_PRECISION: f32 = 0.25;
pub const MAX_MELEE_POISE_PRECISION: f32 = 0.5;
pub const MAX_BLOCK_POISE_COST: f32 = 25.0;
pub const FALLBACK_BLOCK_STRENGTH: f32 = 3.3;
pub const BEHIND_TARGET_ANGLE: f32 = 45.0;
pub const BASE_PARRIED_POISE_PUNISHMENT: f32 = 100.0 / 3.5;

#[derive(Copy, Clone)]
pub struct AttackerInfo<'a> {
    pub entity: EcsEntity,
    pub uid: Uid,
    pub group: Option<&'a Group>,
    pub energy: Option<&'a Energy>,
    pub combo: Option<&'a Combo>,
    pub inventory: Option<&'a Inventory>,
    pub stats: Option<&'a Stats>,
    pub mass: Option<&'a Mass>,
    pub pos: Option<Vec3<f32>>,
}

#[derive(Copy, Clone)]
pub struct TargetInfo<'a> {
    pub entity: EcsEntity,
    pub uid: Uid,
    pub inventory: Option<&'a Inventory>,
    pub stats: Option<&'a Stats>,
    pub health: Option<&'a Health>,
    pub pos: Vec3<f32>,
    pub ori: Option<&'a Ori>,
    pub char_state: Option<&'a CharacterState>,
    pub energy: Option<&'a Energy>,
    pub buffs: Option<&'a Buffs>,
    pub mass: Option<&'a Mass>,
    pub player: Option<&'a Player>,
}

#[derive(Clone, Copy)]
pub struct AttackOptions {
    pub target_dodging: bool,
    /// Result of [`permit_pvp`]
    pub permit_pvp: bool,
    pub target_group: GroupTarget,
    /// When set to `true`, entities in the same group or pets & pet owners may
    /// hit eachother albeit the target_group being OutOfGroup
    pub allow_friendly_fire: bool,
    pub precision_mult: Option<f32>,
}

#[derive(Clone, Debug, Serialize, Deserialize)] // TODO: Yeet clone derive
pub struct Attack {
    damages: Vec<AttackDamage>,
    effects: Vec<AttackEffect>,
    precision_multiplier: f32,
    pub(crate) blockable: bool,
    ability_info: Option<AbilityInfo>,
}

impl Attack {
    pub fn new(ability_info: Option<AbilityInfo>) -> Self {
        Self {
            damages: Vec::new(),
            effects: Vec::new(),
            precision_multiplier: 1.0,
            blockable: true,
            ability_info,
        }
    }

    #[must_use]
    pub fn with_damage(mut self, damage: AttackDamage) -> Self {
        self.damages.push(damage);
        self
    }

    #[must_use]
    pub fn with_effect(mut self, effect: AttackEffect) -> Self {
        self.effects.push(effect);
        self
    }

    #[must_use]
    pub fn with_precision(mut self, precision_multiplier: f32) -> Self {
        self.precision_multiplier = precision_multiplier;
        self
    }

    #[must_use]
    pub fn with_blockable(mut self, blockable: bool) -> Self {
        self.blockable = blockable;
        self
    }

    #[must_use]
    pub fn with_combo_requirement(self, combo: i32, requirement: CombatRequirement) -> Self {
        self.with_effect(
            AttackEffect::new(None, CombatEffect::Combo(combo)).with_requirement(requirement),
        )
    }

    #[must_use]
    pub fn with_combo(self, combo: i32) -> Self {
        self.with_combo_requirement(combo, CombatRequirement::AnyDamage)
    }

    #[must_use]
    pub fn with_combo_increment(self) -> Self { self.with_combo(1) }

    pub fn effects(&self) -> impl Iterator<Item = &AttackEffect> { self.effects.iter() }

    pub fn compute_block_damage_decrement(
        blockable: bool,
        attacker: Option<&AttackerInfo>,
        target: &TargetInfo,
        source: AttackSource,
        dir: Dir,
        damage: f32,
        msm: &MaterialStatManifest,
        time: Time,
        emitters: &mut (impl EmitExt<ParryHookEvent> + EmitExt<PoiseChangeEvent>),
        mut emit_outcome: impl FnMut(Outcome),
    ) -> f32 {
        if blockable && damage > 0.0 {
            if let (Some(char_state), Some(ori), Some(inventory)) =
                (target.char_state, target.ori, target.inventory)
            {
                let is_parry = char_state.is_parry(source);
                let is_block = char_state.is_block(source);
                let mut block_strength = block_strength(inventory, char_state);

                if ori.look_vec().angle_between(-dir.with_z(0.0)) < char_state.block_angle()
                    && (is_parry || is_block)
                    && block_strength > 0.0
                {
                    if is_parry {
                        block_strength = damage;

                        emitters.emit(ParryHookEvent {
                            defender: target.entity,
                            attacker: attacker.map(|a| a.entity),
                            source,
                            poise_multiplier: 2.0 - (damage / block_strength).min(1.0),
                        });
                    }

                    let poise_cost = (damage / block_strength).min(1.0) * MAX_BLOCK_POISE_COST;

                    let poise_change = Poise::apply_poise_reduction(
                        poise_cost,
                        target.inventory,
                        msm,
                        target.char_state,
                        target.stats,
                    );

                    emit_outcome(Outcome::Block {
                        parry: is_parry,
                        pos: target.pos,
                        uid: target.uid,
                    });
                    emitters.emit(PoiseChangeEvent {
                        entity: target.entity,
                        change: PoiseChange {
                            amount: -poise_change,
                            impulse: *dir,
                            by: attacker.map(|x| (*x).into()),
                            cause: Some(DamageSource::from(source)),
                            time,
                        },
                    });

                    block_strength
                } else {
                    0.0
                }
            } else {
                0.0
            }
        } else {
            0.0
        }
    }

    pub fn compute_damage_reduction(
        attacker: Option<&AttackerInfo>,
        target: &TargetInfo,
        damage: Damage,
        msm: &MaterialStatManifest,
    ) -> f32 {
        if damage.value > 0.0 {
            let attacker_penetration = attacker
                .and_then(|a| a.stats)
                .map_or(0.0, |s| s.mitigations_penetration)
                .clamp(0.0, 1.0);
            let raw_damage_reduction =
                Damage::compute_damage_reduction(Some(damage), target.inventory, target.stats, msm);

            if raw_damage_reduction >= 1.0 {
                raw_damage_reduction
            } else {
                (1.0 - attacker_penetration) * raw_damage_reduction
            }
        } else {
            0.0
        }
    }

    pub fn apply_attack(
        &self,
        attacker: Option<AttackerInfo>,
        target: &TargetInfo,
        dir: Dir,
        options: AttackOptions,
        // Currently strength_modifier just modifies damage,
        // maybe look into modifying strength of other effects?
        strength_modifier: f32,
        attack_source: AttackSource,
        time: Time,
        emitters: &mut (
                 impl EmitExt<HealthChangeEvent>
                 + EmitExt<EnergyChangeEvent>
                 + EmitExt<ParryHookEvent>
                 + EmitExt<KnockbackEvent>
                 + EmitExt<BuffEvent>
                 + EmitExt<PoiseChangeEvent>
                 + EmitExt<ComboChangeEvent>
                 + EmitExt<EntityAttackedHookEvent>
                 + EmitExt<TransformEvent>
             ),
        mut emit_outcome: impl FnMut(Outcome),
        rng: &mut rand::rngs::ThreadRng,
        damage_instance_offset: u64,
    ) -> bool {
        // TODO: Maybe move this higher and pass it as argument into this function?
        let msm = &MaterialStatManifest::load().read();

        let AttackOptions {
            target_dodging,
            permit_pvp,
            allow_friendly_fire,
            target_group,
            precision_mult,
        } = options;

        // target == OutOfGroup is basic heuristic that this
        // "attack" has negative effects.
        //
        // so if target dodges this "attack" or we don't want to harm target,
        // it should avoid such "damage" or effect
        let avoid_damage = |attack_damage: &AttackDamage| {
            target_dodging
                || (!permit_pvp && matches!(attack_damage.target, Some(GroupTarget::OutOfGroup)))
        };
        let avoid_effect = |attack_effect: &AttackEffect| {
            target_dodging
                || (!permit_pvp && matches!(attack_effect.target, Some(GroupTarget::OutOfGroup)))
        };

        let from_precision_mult = attacker
            .and_then(|a| a.stats)
            .and_then(|s| {
                s.conditional_precision_modifiers
                    .iter()
                    .filter_map(|(req, mult, ovrd)| {
                        req.is_none_or(|r| {
                            r.requirement_met(
                                (
                                    target.health,
                                    target.buffs,
                                    target.char_state,
                                    target.ori,
                                    Some(target.uid),
                                ),
                                (
                                    attacker.map(|a| a.entity),
                                    attacker.and_then(|a| a.energy),
                                    attacker.and_then(|a| a.combo),
                                ),
                                attacker.map(|a| a.uid),
                                0.0,
                                emitters,
                                dir,
                                Some(attack_source),
                                self.ability_info,
                            )
                        })
                        .then_some((*mult, *ovrd))
                    })
                    .chain(precision_mult.iter().map(|val| (*val, false)))
                    .reduce(|(val_a, ovrd_a), (val_b, ovrd_b)| {
                        if ovrd_a || ovrd_b {
                            (val_a.min(val_b), true)
                        } else {
                            (val_a.max(val_b), false)
                        }
                    })
            })
            .map(|(val, _)| val);

        let from_precision_vulnerability_mult = target
            .stats
            .and_then(|s| s.precision_vulnerability_multiplier_override);

        let precision_mult = match (from_precision_mult, from_precision_vulnerability_mult) {
            (Some(a), Some(b)) => Some(a.max(b)),
            (Some(a), None) | (None, Some(a)) => Some(a),
            (None, None) => None,
        };

        let precision_power = 1.0
            + ((self.precision_multiplier - 1.0)
                * attacker
                    .and_then(|a| a.stats)
                    .map_or(1.0, |s| s.precision_power_mult));

        let attacked_modifiers = AttackedModification::attacked_modifiers(
            target,
            attacker,
            emitters,
            dir,
            Some(attack_source),
            self.ability_info,
        );

        let mut is_applied = false;
        let mut accumulated_damage = 0.0;
        let damage_modifier = attacker
            .and_then(|a| a.stats)
            .map_or(1.0, |s| s.attack_damage_modifier);
        for damage in self
            .damages
            .iter()
            .filter(|d| {
                allow_friendly_fire
                    || d.target
                        .is_none_or(|t| t == GroupTarget::All || t == target_group)
            })
            .filter(|d| !avoid_damage(d))
        {
            let damage_instance = damage.instance + damage_instance_offset;
            is_applied = true;

            let damage_reduction =
                Attack::compute_damage_reduction(attacker.as_ref(), target, damage.damage, msm);

            let damage_with_modifier = damage.damage.value * strength_modifier * damage_modifier;
            let damage_with_precision = damage_with_modifier
                * (1.0 + precision_mult.unwrap_or(0.0) * (precision_power - 1.0));

            let block_damage_decrement = Attack::compute_block_damage_decrement(
                self.blockable,
                attacker.as_ref(),
                target,
                attack_source,
                dir,
                damage_with_precision,
                msm,
                time,
                emitters,
                &mut emit_outcome,
            );

            let change = damage.damage.calculate_health_change(
                damage_reduction,
                block_damage_decrement,
                attacker.map(|x| x.into()),
                precision_mult,
                precision_power,
                strength_modifier * damage_modifier,
                time,
                damage_instance,
                DamageSource::from(attack_source),
            );
            let applied_damage = -change.amount;
            accumulated_damage += applied_damage;

            if change.amount.abs() > Health::HEALTH_EPSILON {
                emitters.emit(HealthChangeEvent {
                    entity: target.entity,
                    change,
                });
                match damage.damage.kind {
                    DamageKind::Slashing => {
                        // For slashing damage, reduce target energy by some fraction of applied
                        // damage. When target would lose more energy than they have, deal an
                        // equivalent amount of damage
                        if let Some(target_energy) = target.energy {
                            let energy_change = applied_damage * SLASHING_ENERGY_FRACTION;
                            if energy_change > target_energy.current() {
                                let health_damage = energy_change - target_energy.current();
                                accumulated_damage += health_damage;
                                let health_change = HealthChange {
                                    amount: -health_damage,
                                    by: attacker.map(|x| x.into()),
                                    cause: Some(DamageSource::from(attack_source)),
                                    time,
                                    precise: precision_mult.is_some(),
                                    instance: damage_instance,
                                };
                                emitters.emit(HealthChangeEvent {
                                    entity: target.entity,
                                    change: health_change,
                                });
                            }
                            emitters.emit(EnergyChangeEvent {
                                entity: target.entity,
                                change: -energy_change,
                                reset_rate: false,
                            });
                        }
                    },
                    DamageKind::Crushing => {
                        // For crushing damage, reduce target poise by some fraction of the amount
                        // of damage that was reduced by target's protection
                        // Damage reduction should never equal 1 here as otherwise the check above
                        // that health change amount is greater than 0 would fail.
                        let reduced_damage =
                            applied_damage * damage_reduction / (1.0 - damage_reduction);
                        let poise = reduced_damage
                            * CRUSHING_POISE_FRACTION
                            * attacker
                                .and_then(|a| a.stats)
                                .map_or(1.0, |s| s.poise_damage_modifier);
                        let change = -Poise::apply_poise_reduction(
                            poise,
                            target.inventory,
                            msm,
                            target.char_state,
                            target.stats,
                        );
                        let poise_change = PoiseChange {
                            amount: change,
                            impulse: *dir,
                            by: attacker.map(|x| x.into()),
                            cause: Some(DamageSource::from(attack_source)),
                            time,
                        };
                        if change.abs() > Poise::POISE_EPSILON {
                            // If target is in a stunned state, apply extra poise damage as health
                            // damage instead
                            if let Some(CharacterState::Stunned(data)) = target.char_state {
                                let health_change =
                                    change * data.static_data.poise_state.damage_multiplier();
                                let health_change = HealthChange {
                                    amount: health_change,
                                    by: attacker.map(|x| x.into()),
                                    cause: Some(DamageSource::from(attack_source)),
                                    instance: damage_instance,
                                    precise: precision_mult.is_some(),
                                    time,
                                };
                                accumulated_damage -= health_change.amount;
                                emitters.emit(HealthChangeEvent {
                                    entity: target.entity,
                                    change: health_change,
                                });
                            } else {
                                emitters.emit(PoiseChangeEvent {
                                    entity: target.entity,
                                    change: poise_change,
                                });
                            }
                        }
                    },
                    // Piercing damage ignores some penetration, and is handled when damage
                    // reduction is computed Energy is a placeholder damage type
                    DamageKind::Piercing | DamageKind::Energy => {},
                }
                for effect in damage.effects.iter() {
                    match effect {
                        CombatEffect::Knockback(kb) => {
                            let impulse = kb.calculate_impulse(
                                dir,
                                target.char_state,
                                attacker.and_then(|a| a.stats),
                            ) * strength_modifier;
                            if !impulse.is_approx_zero() {
                                emitters.emit(KnockbackEvent {
                                    entity: target.entity,
                                    impulse,
                                });
                            }
                        },
                        CombatEffect::EnergyReward(ec) => {
                            if let Some(attacker) = attacker {
                                emitters.emit(EnergyChangeEvent {
                                    entity: attacker.entity,
                                    change: *ec
                                        * compute_energy_reward_mod(attacker.inventory, msm)
                                        * strength_modifier
                                        * attacker.stats.map_or(1.0, |s| s.energy_reward_modifier)
                                        * attacked_modifiers.energy_reward,
                                    reset_rate: false,
                                });
                            }
                        },
                        CombatEffect::Buff(b) => {
                            if rng.random::<f32>() < b.chance {
                                emitters.emit(BuffEvent {
                                    entity: target.entity,
                                    buff_change: BuffChange::Add(b.to_buff(
                                        time,
                                        (attacker.map(|a| a.uid), attacker.and_then(|a| a.mass)),
                                        (target.stats, target.mass),
                                        applied_damage,
                                        strength_modifier,
                                        self.ability_info,
                                    )),
                                });
                            }
                        },
                        CombatEffect::Lifesteal(l) => {
                            if let Some(attacker_entity) = attacker.map(|a| a.entity) {
                                let change = HealthChange {
                                    amount: applied_damage * l * strength_modifier,
                                    by: attacker.map(|a| a.into()),
                                    cause: None,
                                    time,
                                    precise: false,
                                    instance: rand::random(),
                                };
                                if change.amount.abs() > Health::HEALTH_EPSILON {
                                    emitters.emit(HealthChangeEvent {
                                        entity: attacker_entity,
                                        change,
                                    });
                                }
                            }
                        },
                        CombatEffect::Poise(p) => {
                            let change = -Poise::apply_poise_reduction(
                                *p,
                                target.inventory,
                                msm,
                                target.char_state,
                                target.stats,
                            ) * strength_modifier
                                * attacker
                                    .and_then(|a| a.stats)
                                    .map_or(1.0, |s| s.poise_damage_modifier);
                            if change.abs() > Poise::POISE_EPSILON {
                                let poise_change = PoiseChange {
                                    amount: change,
                                    impulse: *dir,
                                    by: attacker.map(|x| x.into()),
                                    cause: Some(DamageSource::from(attack_source)),
                                    time,
                                };
                                emitters.emit(PoiseChangeEvent {
                                    entity: target.entity,
                                    change: poise_change,
                                });
                            }
                        },
                        CombatEffect::Heal(h) => {
                            let change = HealthChange {
                                amount: *h * strength_modifier,
                                by: attacker.map(|a| a.into()),
                                cause: None,
                                time,
                                precise: false,
                                instance: rand::random(),
                            };
                            if change.amount.abs() > Health::HEALTH_EPSILON {
                                emitters.emit(HealthChangeEvent {
                                    entity: target.entity,
                                    change,
                                });
                            }
                        },
                        CombatEffect::Combo(c) => {
                            if let Some(attacker_entity) = attacker.map(|a| a.entity) {
                                emitters.emit(ComboChangeEvent {
                                    entity: attacker_entity,
                                    change: (*c as f32 * strength_modifier).ceil() as i32,
                                });
                            }
                        },
                        CombatEffect::AdditionalDamage(damage) => {
                            let change = {
                                let mut change = change;
                                change.amount *= damage * strength_modifier;
                                change.instance = rand::random();
                                change
                            };
                            accumulated_damage -= change.amount;
                            emitters.emit(HealthChangeEvent {
                                entity: target.entity,
                                change,
                            });
                        },
                        CombatEffect::RefreshBuff(chance, b) => {
                            if rng.random::<f32>() < *chance {
                                emitters.emit(BuffEvent {
                                    entity: target.entity,
                                    buff_change: BuffChange::Refresh(*b),
                                });
                            }
                        },
                        CombatEffect::SelfBuff(b) => {
                            if let Some(attacker) = attacker
                                && rng.random::<f32>() < b.chance
                            {
                                emitters.emit(BuffEvent {
                                    entity: attacker.entity,
                                    buff_change: BuffChange::Add(b.to_self_buff(
                                        time,
                                        (Some(attacker.uid), attacker.stats, attacker.mass),
                                        applied_damage,
                                        strength_modifier,
                                        self.ability_info,
                                    )),
                                });
                            }
                        },
                        CombatEffect::Energy(e) => {
                            emitters.emit(EnergyChangeEvent {
                                entity: target.entity,
                                change: e * strength_modifier,
                                reset_rate: true,
                            });
                        },
                        CombatEffect::Transform {
                            entity_spec,
                            allow_players,
                        } => {
                            if target.player.is_none() || *allow_players {
                                emitters.emit(TransformEvent {
                                    target_entity: target.uid,
                                    entity_info: {
                                        let Ok(entity_config) = Ron::<EntityConfig>::load(
                                            entity_spec,
                                        )
                                        .inspect_err(|error| {
                                            error!(
                                                ?entity_spec,
                                                ?error,
                                                "Could not load entity configuration for death \
                                                 effect"
                                            )
                                        }) else {
                                            continue;
                                        };

                                        EntityInfo::at(target.pos).with_entity_config(
                                            entity_config.read().clone().into_inner(),
                                            Some(entity_spec),
                                            rng,
                                            None,
                                        )
                                    },
                                    allow_players: *allow_players,
                                    delete_on_failure: false,
                                });
                            }
                        },
                        CombatEffect::DebuffsVulnerable {
                            mult,
                            scaling,
                            filter_attacker,
                            filter_weapon,
                        } => {
                            if let Some(buffs) = target.buffs {
                                let num_debuffs = buffs.iter_active().flatten().filter(|b| {
                                    let debuff_filter = matches!(b.kind.differentiate(), BuffDescriptor::SimpleNegative);
                                    let attacker_filter = !filter_attacker || matches!(b.source, BuffSource::Character { by, .. } if Some(by) == attacker.map(|a| a.uid));
                                    let weapon_filter = filter_weapon.is_none_or(|w| matches!(b.source, BuffSource::Character { tool_kind, .. } if Some(w) == tool_kind));
                                    debuff_filter && attacker_filter && weapon_filter
                                }).count();
                                if num_debuffs > 0 {
                                    let change = {
                                        let mut change = change;
                                        change.amount *= scaling.factor(num_debuffs as f32, 1.0)
                                            * mult
                                            * strength_modifier;
                                        change.instance = rand::random();
                                        change
                                    };
                                    accumulated_damage -= change.amount;
                                    emitters.emit(HealthChangeEvent {
                                        entity: target.entity,
                                        change,
                                    });
                                }
                            }
                        },
                    }
                }
            }
        }
        for effect in self
            .effects
            .iter()
            .chain(
                attacker
                    .and_then(|a| a.stats)
                    .map(|s| s.effects_on_attack.iter())
                    .into_iter()
                    .flatten(),
            )
            .filter(|e| {
                allow_friendly_fire
                    || e.target
                        .is_none_or(|t| t == GroupTarget::All || t == target_group)
            })
            .filter(|e| !avoid_effect(e))
        {
            let requirements_met = effect.requirements.iter().all(|req| {
                req.requirement_met(
                    (
                        target.health,
                        target.buffs,
                        target.char_state,
                        target.ori,
                        Some(target.uid),
                    ),
                    (
                        attacker.map(|a| a.entity),
                        attacker.and_then(|a| a.energy),
                        attacker.and_then(|a| a.combo),
                    ),
                    attacker.map(|a| a.uid),
                    accumulated_damage,
                    emitters,
                    dir,
                    Some(attack_source),
                    self.ability_info,
                )
            });
            if requirements_met {
                let mut strength_modifier = strength_modifier;
                for modification in effect.modifications.iter() {
                    modification.apply_mod(
                        attacker.and_then(|a| a.pos),
                        Some(target.pos),
                        &mut strength_modifier,
                    );
                }
                let strength_modifier = strength_modifier;
                is_applied = true;
                match &effect.effect {
                    CombatEffect::Knockback(kb) => {
                        let impulse = kb.calculate_impulse(
                            dir,
                            target.char_state,
                            attacker.and_then(|a| a.stats),
                        ) * strength_modifier;
                        if !impulse.is_approx_zero() {
                            emitters.emit(KnockbackEvent {
                                entity: target.entity,
                                impulse,
                            });
                        }
                    },
                    CombatEffect::EnergyReward(ec) => {
                        if let Some(attacker) = attacker {
                            emitters.emit(EnergyChangeEvent {
                                entity: attacker.entity,
                                change: ec
                                    * compute_energy_reward_mod(attacker.inventory, msm)
                                    * strength_modifier
                                    * attacker.stats.map_or(1.0, |s| s.energy_reward_modifier)
                                    * attacked_modifiers.energy_reward,
                                reset_rate: false,
                            });
                        }
                    },
                    CombatEffect::Buff(b) => {
                        if rng.random::<f32>() < b.chance {
                            emitters.emit(BuffEvent {
                                entity: target.entity,
                                buff_change: BuffChange::Add(b.to_buff(
                                    time,
                                    (attacker.map(|a| a.uid), attacker.and_then(|a| a.mass)),
                                    (target.stats, target.mass),
                                    accumulated_damage,
                                    strength_modifier,
                                    self.ability_info,
                                )),
                            });
                        }
                    },
                    CombatEffect::Lifesteal(l) => {
                        if let Some(attacker_entity) = attacker.map(|a| a.entity) {
                            let change = HealthChange {
                                amount: accumulated_damage * l * strength_modifier,
                                by: attacker.map(|a| a.into()),
                                cause: None,
                                time,
                                precise: false,
                                instance: rand::random(),
                            };
                            if change.amount.abs() > Health::HEALTH_EPSILON {
                                emitters.emit(HealthChangeEvent {
                                    entity: attacker_entity,
                                    change,
                                });
                            }
                        }
                    },
                    CombatEffect::Poise(p) => {
                        let change = -Poise::apply_poise_reduction(
                            *p,
                            target.inventory,
                            msm,
                            target.char_state,
                            target.stats,
                        ) * strength_modifier
                            * attacker
                                .and_then(|a| a.stats)
                                .map_or(1.0, |s| s.poise_damage_modifier);
                        if change.abs() > Poise::POISE_EPSILON {
                            let poise_change = PoiseChange {
                                amount: change,
                                impulse: *dir,
                                by: attacker.map(|x| x.into()),
                                cause: Some(attack_source.into()),
                                time,
                            };
                            emitters.emit(PoiseChangeEvent {
                                entity: target.entity,
                                change: poise_change,
                            });
                        }
                    },
                    CombatEffect::Heal(h) => {
                        let change = HealthChange {
                            amount: h * strength_modifier,
                            by: attacker.map(|a| a.into()),
                            cause: None,
                            time,
                            precise: false,
                            instance: rand::random(),
                        };
                        if change.amount.abs() > Health::HEALTH_EPSILON {
                            emitters.emit(HealthChangeEvent {
                                entity: target.entity,
                                change,
                            });
                        }
                    },
                    CombatEffect::Combo(c) => {
                        if let Some(attacker_entity) = attacker.map(|a| a.entity) {
                            emitters.emit(ComboChangeEvent {
                                entity: attacker_entity,
                                change: (*c as f32 * strength_modifier).ceil() as i32,
                            });
                        }
                    },
                    CombatEffect::AdditionalDamage(damage) => {
                        let change = HealthChange {
                            amount: -accumulated_damage * damage * strength_modifier,
                            by: attacker.map(|a| a.into()),
                            cause: Some(DamageSource::from(attack_source)),
                            time,
                            precise: precision_mult.is_some(),
                            instance: rand::random(),
                        };
                        accumulated_damage -= change.amount;
                        emitters.emit(HealthChangeEvent {
                            entity: target.entity,
                            change,
                        });
                    },
                    CombatEffect::RefreshBuff(chance, b) => {
                        if rng.random::<f32>() < *chance {
                            emitters.emit(BuffEvent {
                                entity: target.entity,
                                buff_change: BuffChange::Refresh(*b),
                            });
                        }
                    },
                    CombatEffect::SelfBuff(b) => {
                        if let Some(attacker) = attacker
                            && rng.random::<f32>() < b.chance
                        {
                            emitters.emit(BuffEvent {
                                entity: attacker.entity,
                                buff_change: BuffChange::Add(b.to_self_buff(
                                    time,
                                    (Some(attacker.uid), attacker.stats, attacker.mass),
                                    accumulated_damage,
                                    strength_modifier,
                                    self.ability_info,
                                )),
                            });
                        }
                    },
                    CombatEffect::Energy(e) => {
                        emitters.emit(EnergyChangeEvent {
                            entity: target.entity,
                            change: e * strength_modifier,
                            reset_rate: true,
                        });
                    },
                    CombatEffect::Transform {
                        entity_spec,
                        allow_players,
                    } => {
                        if target.player.is_none() || *allow_players {
                            emitters.emit(TransformEvent {
                                target_entity: target.uid,
                                entity_info: {
                                    let Ok(entity_config) = Ron::<EntityConfig>::load(entity_spec)
                                        .inspect_err(|error| {
                                            error!(
                                                ?entity_spec,
                                                ?error,
                                                "Could not load entity configuration for death \
                                                 effect"
                                            )
                                        })
                                    else {
                                        continue;
                                    };

                                    EntityInfo::at(target.pos).with_entity_config(
                                        entity_config.read().clone().into_inner(),
                                        Some(entity_spec),
                                        rng,
                                        None,
                                    )
                                },
                                allow_players: *allow_players,
                                delete_on_failure: false,
                            });
                        }
                    },
                    CombatEffect::DebuffsVulnerable {
                        mult,
                        scaling,
                        filter_attacker,
                        filter_weapon,
                    } => {
                        if let Some(buffs) = target.buffs {
                            let num_debuffs = buffs.iter_active().flatten().filter(|b| {
                                let debuff_filter = matches!(b.kind.differentiate(), BuffDescriptor::SimpleNegative);
                                let attacker_filter = !filter_attacker || matches!(b.source, BuffSource::Character { by, .. } if Some(by) == attacker.map(|a| a.uid));
                                let weapon_filter = filter_weapon.is_none_or(|w| matches!(b.source, BuffSource::Character { tool_kind, .. } if Some(w) == tool_kind));
                                debuff_filter && attacker_filter && weapon_filter
                            }).count();
                            if num_debuffs > 0 {
                                let change = HealthChange {
                                    amount: -accumulated_damage
                                        * scaling.factor(num_debuffs as f32, 1.0)
                                        * mult
                                        * strength_modifier,
                                    by: attacker.map(|a| a.into()),
                                    cause: Some(DamageSource::from(attack_source)),
                                    time,
                                    precise: precision_mult.is_some(),
                                    instance: rand::random(),
                                };
                                accumulated_damage -= change.amount;
                                emitters.emit(HealthChangeEvent {
                                    entity: target.entity,
                                    change,
                                });
                            }
                        }
                    },
                }
            }
        }
        // Emits event to handle things that should happen for any successful attack,
        // regardless of if the attack had any damages or effects in it
        if is_applied {
            emitters.emit(EntityAttackedHookEvent {
                entity: target.entity,
                attacker: attacker.map(|a| a.entity),
                attack_dir: dir,
                damage_dealt: accumulated_damage,
                attack_source,
            });
        }
        is_applied
    }
}

pub fn allow_friendly_fire(
    entered_auras: &ReadStorage<EnteredAuras>,
    attacker: EcsEntity,
    target: EcsEntity,
) -> bool {
    entered_auras
        .get(attacker)
        .zip(entered_auras.get(target))
        .and_then(|(attacker, target)| {
            Some((
                attacker.auras.get(&AuraKindVariant::FriendlyFire)?,
                target.auras.get(&AuraKindVariant::FriendlyFire)?,
            ))
        })
        // Only allow friendly fire if both entities are affectd by the same FriendlyFire aura
        .is_some_and(|(attacker, target)| attacker.intersection(target).next().is_some())
}

/// Function that checks for unintentional PvP between players.
///
/// Returns `false` if attack will create unintentional conflict,
/// e.g. if player with PvE mode will harm pets of other players
/// or other players will do the same to such player.
///
/// If both players have PvP mode enabled, interact with NPC and
/// in any other case, this function will return `true`
// TODO: add parameter for doing self-harm?
pub fn permit_pvp(
    alignments: &ReadStorage<Alignment>,
    players: &ReadStorage<Player>,
    entered_auras: &ReadStorage<EnteredAuras>,
    id_maps: &IdMaps,
    attacker: Option<EcsEntity>,
    target: EcsEntity,
) -> bool {
    // Return owner entity if pet,
    // or just return entity back otherwise
    let owner_if_pet = |entity| {
        let alignment = alignments.get(entity).copied();
        if let Some(Alignment::Owned(uid)) = alignment {
            // return original entity
            // if can't get owner
            id_maps.uid_entity(uid).unwrap_or(entity)
        } else {
            entity
        }
    };

    // Just return ok if attacker is unknown, it's probably
    // environment or command.
    let attacker = match attacker {
        Some(attacker) => attacker,
        None => return true,
    };

    // "Dereference" to owner if this is a pet.
    let attacker_owner = owner_if_pet(attacker);
    let target_owner = owner_if_pet(target);

    // If both players are in the same ForcePvP aura, allow them to harm eachother
    if let (Some(attacker_auras), Some(target_auras)) = (
        entered_auras.get(attacker_owner),
        entered_auras.get(target_owner),
    ) && attacker_auras
        .auras
        .get(&AuraKindVariant::ForcePvP)
        .zip(target_auras.auras.get(&AuraKindVariant::ForcePvP))
        // Only allow forced pvp if both entities are affectd by the same FriendlyFire aura
        .is_some_and(|(attacker, target)| attacker.intersection(target).next().is_some())
    {
        return true;
    }

    // Prevent PvP between pets, unless friendly fire is enabled
    //
    // This code is NOT intended to prevent pet <-> owner combat,
    // pets and their owners being in the same group should take care of that
    if attacker_owner == target_owner {
        return allow_friendly_fire(entered_auras, attacker, target);
    }

    // Get player components
    let attacker_info = players.get(attacker_owner);
    let target_info = players.get(target_owner);

    // Return `true` if not players.
    attacker_info
        .zip(target_info)
        .is_none_or(|(a, t)| a.may_harm(t))
}

#[derive(Clone, Debug, Serialize, Deserialize)]
pub struct AttackDamage {
    damage: Damage,
    target: Option<GroupTarget>,
    effects: Vec<CombatEffect>,
    /// A random ID, used to group up attacks
    instance: u64,
}

impl AttackDamage {
    pub fn new(damage: Damage, target: Option<GroupTarget>, instance: u64) -> Self {
        Self {
            damage,
            target,
            effects: Vec::new(),
            instance,
        }
    }

    #[must_use]
    pub fn with_effect(mut self, effect: CombatEffect) -> Self {
        self.effects.push(effect);
        self
    }
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct AttackEffect {
    target: Option<GroupTarget>,
    effect: CombatEffect,
    requirements: Vec<CombatRequirement>,
    modifications: Vec<CombatModification>,
}

impl AttackEffect {
    pub fn new(target: Option<GroupTarget>, effect: CombatEffect) -> Self {
        Self {
            target,
            effect,
            requirements: Vec::new(),
            modifications: Vec::new(),
        }
    }

    #[must_use]
    pub fn with_requirement(mut self, requirement: CombatRequirement) -> Self {
        self.requirements.push(requirement);
        self
    }

    #[must_use]
    pub fn with_modification(mut self, modification: CombatModification) -> Self {
        self.modifications.push(modification);
        self
    }

    pub fn effect(&self) -> &CombatEffect { &self.effect }
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct StatEffect {
    pub target: StatEffectTarget,
    pub effect: CombatEffect,
    requirements: Vec<CombatRequirement>,
    modifications: Vec<CombatModification>,
}

impl StatEffect {
    pub fn new(target: StatEffectTarget, effect: CombatEffect) -> Self {
        Self {
            target,
            effect,
            requirements: Vec::new(),
            modifications: Vec::new(),
        }
    }

    #[must_use]
    pub fn with_requirement(mut self, requirement: CombatRequirement) -> Self {
        self.requirements.push(requirement);
        self
    }

    #[must_use]
    pub fn with_modification(mut self, modification: CombatModification) -> Self {
        self.modifications.push(modification);
        self
    }

    pub fn requirements(&self) -> impl Iterator<Item = &CombatRequirement> {
        self.requirements.iter()
    }

    pub fn modifications(&self) -> impl Iterator<Item = &CombatModification> {
        self.modifications.iter()
    }
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub enum CombatEffect {
    Heal(f32),
    Buff(CombatBuff),
    Knockback(Knockback),
    EnergyReward(f32),
    Lifesteal(f32),
    Poise(f32),
    Combo(i32),
    /// Intended to be used when gating additional damage behind some
    /// requirement
    AdditionalDamage(f32),
    /// Resets duration of all buffs of this buffkind, with some probability
    RefreshBuff(f32, BuffKind),
    /// Applies buff to yourself after attack is applied
    SelfBuff(CombatBuff),
    /// Changes energy of target
    Energy(f32),
    /// String is the entity_spec
    Transform {
        entity_spec: String,
        /// Whether this effect applies to players or not
        #[serde(default)]
        allow_players: bool,
    },
    /// If the target hit by an attack has debuffs, they will take increased
    /// damage scaling with the number of active debuffs they have
    DebuffsVulnerable {
        mult: f32,
        scaling: ScalingKind,
        /// Should debuffs only be counted if they were inflicted by the
        /// attacker
        filter_attacker: bool,
        /// Should debuffs only be counted if they were inflicted by a specific
        /// weapon
        filter_weapon: Option<ToolKind>,
    },
}

impl CombatEffect {
    pub fn apply_multiplier(self, mult: f32) -> Self {
        match self {
            CombatEffect::Heal(h) => CombatEffect::Heal(h * mult),
            CombatEffect::Buff(CombatBuff {
                kind,
                dur_secs,
                strength,
                chance,
            }) => CombatEffect::Buff(CombatBuff {
                kind,
                dur_secs,
                strength: strength * mult,
                chance,
            }),
            CombatEffect::Knockback(Knockback {
                direction,
                strength,
            }) => CombatEffect::Knockback(Knockback {
                direction,
                strength: strength * mult,
            }),
            CombatEffect::EnergyReward(e) => CombatEffect::EnergyReward(e * mult),
            CombatEffect::Lifesteal(l) => CombatEffect::Lifesteal(l * mult),
            CombatEffect::Poise(p) => CombatEffect::Poise(p * mult),
            CombatEffect::Combo(c) => CombatEffect::Combo((c as f32 * mult).ceil() as i32),
            CombatEffect::AdditionalDamage(v) => CombatEffect::AdditionalDamage(v * mult),
            CombatEffect::RefreshBuff(c, b) => CombatEffect::RefreshBuff(c, b),
            CombatEffect::SelfBuff(CombatBuff {
                kind,
                dur_secs,
                strength,
                chance,
            }) => CombatEffect::SelfBuff(CombatBuff {
                kind,
                dur_secs,
                strength: strength * mult,
                chance,
            }),
            CombatEffect::Energy(e) => CombatEffect::Energy(e * mult),
            effect @ CombatEffect::Transform { .. } => effect,
            CombatEffect::DebuffsVulnerable {
                mult: a,
                scaling,
                filter_attacker,
                filter_weapon,
            } => CombatEffect::DebuffsVulnerable {
                mult: a * mult,
                scaling,
                filter_attacker,
                filter_weapon,
            },
        }
    }

    pub fn adjusted_by_stats(self, stats: tool::Stats) -> Self {
        match self {
            CombatEffect::Heal(h) => CombatEffect::Heal(h * stats.effect_power),
            CombatEffect::Buff(CombatBuff {
                kind,
                dur_secs,
                strength,
                chance,
            }) => CombatEffect::Buff(CombatBuff {
                kind,
                dur_secs,
                strength: strength * stats.buff_strength,
                chance,
            }),
            CombatEffect::Knockback(Knockback {
                direction,
                strength,
            }) => CombatEffect::Knockback(Knockback {
                direction,
                strength: strength * stats.effect_power,
            }),
            CombatEffect::EnergyReward(e) => CombatEffect::EnergyReward(e),
            CombatEffect::Lifesteal(l) => CombatEffect::Lifesteal(l * stats.effect_power),
            CombatEffect::Poise(p) => CombatEffect::Poise(p * stats.effect_power),
            CombatEffect::Combo(c) => CombatEffect::Combo(c),
            CombatEffect::AdditionalDamage(v) => {
                CombatEffect::AdditionalDamage(v * stats.effect_power)
            },
            CombatEffect::RefreshBuff(c, b) => CombatEffect::RefreshBuff(c, b),
            CombatEffect::SelfBuff(CombatBuff {
                kind,
                dur_secs,
                strength,
                chance,
            }) => CombatEffect::SelfBuff(CombatBuff {
                kind,
                dur_secs,
                strength: strength * stats.buff_strength,
                chance,
            }),
            CombatEffect::Energy(e) => CombatEffect::Energy(e * stats.effect_power),
            effect @ CombatEffect::Transform { .. } => effect,
            CombatEffect::DebuffsVulnerable {
                mult,
                scaling,
                filter_attacker,
                filter_weapon,
            } => CombatEffect::DebuffsVulnerable {
                mult: mult * stats.effect_power,
                scaling,
                filter_attacker,
                filter_weapon,
            },
        }
    }
}

#[derive(Clone, Copy, Debug, Serialize, Deserialize, PartialEq)]
struct AttackedModifiers {
    energy_reward: f32,
    damage_mult: f32,
}

impl Default for AttackedModifiers {
    fn default() -> Self {
        Self {
            energy_reward: 1.0,
            damage_mult: 1.0,
        }
    }
}

#[derive(Clone, Debug, Serialize, Deserialize, PartialEq)]
pub struct AttackedModification {
    modifier: AttackedModifier,
    requirements: Vec<CombatRequirement>,
    modifications: Vec<CombatModification>,
}

impl AttackedModification {
    pub fn new(modifier: AttackedModifier) -> Self {
        Self {
            modifier,
            requirements: Vec::new(),
            modifications: Vec::new(),
        }
    }

    #[must_use]
    pub fn with_requirement(mut self, requirement: CombatRequirement) -> Self {
        self.requirements.push(requirement);
        self
    }

    #[must_use]
    pub fn with_modification(mut self, modification: CombatModification) -> Self {
        self.modifications.push(modification);
        self
    }

    fn attacked_modifiers(
        target: &TargetInfo,
        attacker: Option<AttackerInfo>,
        emitters: &mut (impl EmitExt<EnergyChangeEvent> + EmitExt<ComboChangeEvent>),
        dir: Dir,
        attack_source: Option<AttackSource>,
        ability_info: Option<AbilityInfo>,
    ) -> AttackedModifiers {
        if let Some(stats) = target.stats {
            stats.attacked_modifications.iter().fold(
                AttackedModifiers::default(),
                |mut a_mods, a_mod| {
                    let requirements_met = a_mod.requirements.iter().all(|req| {
                        req.requirement_met(
                            (
                                target.health,
                                target.buffs,
                                target.char_state,
                                target.ori,
                                Some(target.uid),
                            ),
                            (
                                attacker.map(|a| a.entity),
                                attacker.and_then(|a| a.energy),
                                attacker.and_then(|a| a.combo),
                            ),
                            attacker.map(|a| a.uid),
                            0.0, /* When we call this function, no damage has been
                                  * calculated yet, so the AnyDamage requirement is
                                  * effectively broken, not sure if this will be issue in
                                  * future? */
                            emitters,
                            dir,
                            attack_source,
                            ability_info,
                        )
                    });

                    let mut strength_modifier = 1.0;
                    for modification in a_mod.modifications.iter() {
                        modification.apply_mod(
                            attacker.and_then(|a| a.pos),
                            Some(target.pos),
                            &mut strength_modifier,
                        );
                    }
                    let strength_modifier = strength_modifier;

                    if requirements_met {
                        match a_mod.modifier {
                            AttackedModifier::EnergyReward(er) => {
                                a_mods.energy_reward *= 1.0 + (er * strength_modifier);
                            },
                            AttackedModifier::DamageMultiplier(dm) => {
                                a_mods.damage_mult *= 1.0 + (dm * strength_modifier);
                            },
                        }
                    }

                    a_mods
                },
            )
        } else {
            AttackedModifiers::default()
        }
    }
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq)]
pub enum AttackedModifier {
    EnergyReward(f32),
    DamageMultiplier(f32),
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq)]
pub enum CombatRequirement {
    AnyDamage,
    Energy(f32),
    Combo(u32),
    TargetHasBuff(BuffKind),
    TargetPoised,
    BehindTarget,
    TargetBlocking,
    TargetUnwielded,
    AttackSource(AttackSource),
    AttackInput(InputKind),
    Attacker(Uid),
    Target(Uid),
    StageSection(StageSection),
}

impl CombatRequirement {
    pub fn requirement_met(
        &self,
        target: (
            Option<&Health>,
            Option<&Buffs>,
            Option<&CharacterState>,
            Option<&Ori>,
            Option<Uid>,
        ),
        // originator refers to the cause of the effect that requirements are being checked for.
        // For combat effects on an attack this will be the attacker, for damaged and death effects
        // this will be the target.
        originator: (Option<EcsEntity>, Option<&Energy>, Option<&Combo>),
        attacker: Option<Uid>,
        damage: f32,
        emitters: &mut (impl EmitExt<EnergyChangeEvent> + EmitExt<ComboChangeEvent>),
        dir: Dir,
        attack_source: Option<AttackSource>,
        ability_info: Option<AbilityInfo>,
    ) -> bool {
        let (target_health, target_buffs, target_char_state, target_ori, target_uid) = target;
        let (originator_entity, originator_energy, originator_combo) = originator;
        match self {
            CombatRequirement::AnyDamage => {
                damage > Health::HEALTH_EPSILON && target_health.is_some()
            },
            CombatRequirement::Energy(r) => {
                if let (Some(entity), Some(energy)) = (originator_entity, originator_energy) {
                    let sufficient_energy = energy.current() >= *r;
                    if sufficient_energy {
                        emitters.emit(EnergyChangeEvent {
                            entity,
                            change: -*r,
                            reset_rate: false,
                        });
                    }

                    sufficient_energy
                } else {
                    false
                }
            },
            CombatRequirement::Combo(r) => {
                if let (Some(entity), Some(combo)) = (originator_entity, originator_combo) {
                    let sufficient_combo = combo.counter() >= *r;
                    if sufficient_combo {
                        emitters.emit(ComboChangeEvent {
                            entity,
                            change: -(*r as i32),
                        });
                    }

                    sufficient_combo
                } else {
                    false
                }
            },
            CombatRequirement::TargetHasBuff(buff) => {
                target_buffs.is_some_and(|buffs| buffs.contains(*buff))
            },
            CombatRequirement::TargetPoised => target_char_state.is_some_and(|cs| cs.is_stunned()),
            CombatRequirement::BehindTarget => {
                if let Some(ori) = target_ori {
                    ori.look_vec().angle_between(dir.with_z(0.0)) < BEHIND_TARGET_ANGLE.to_radians()
                } else {
                    false
                }
            },
            CombatRequirement::TargetBlocking => target_char_state
                .zip(attack_source)
                .is_some_and(|(cs, attack)| cs.is_block(attack) || cs.is_parry(attack)),
            CombatRequirement::TargetUnwielded => {
                target_char_state.is_some_and(|cs| !cs.is_wield())
            },
            CombatRequirement::AttackSource(source) => attack_source == Some(*source),
            CombatRequirement::AttackInput(input) => {
                ability_info.is_some_and(|ai| ai.input == *input)
            },
            CombatRequirement::Attacker(uid) => Some(*uid) == attacker,
            CombatRequirement::Target(uid) => Some(*uid) == target_uid,
            CombatRequirement::StageSection(s) => {
                Some(*s) == target_char_state.and_then(|cs| cs.stage_section())
            },
        }
    }
}

#[derive(Copy, Clone, Debug, Serialize, Deserialize, PartialEq)]
pub enum CombatModification {
    /// Linearly decreases effect strength starting with 1 strength at some
    /// distance, ending at a minimum strength by some end distance
    RangeWeakening {
        start_dist: f32,
        end_dist: f32,
        min_str: f32,
    },
}

impl CombatModification {
    pub fn apply_mod(
        &self,
        attacker_pos: Option<Vec3<f32>>,
        target_pos: Option<Vec3<f32>>,
        strength_mod: &mut f32,
    ) {
        match self {
            Self::RangeWeakening {
                start_dist,
                end_dist,
                min_str,
            } => {
                if let Some((attacker_pos, target_pos)) = attacker_pos.zip(target_pos) {
                    let dist = attacker_pos.distance(target_pos);
                    // a = (y2 - y1) / (x2 - x1)
                    let gradient = (*min_str - 1.0) / (end_dist - start_dist).max(0.1);
                    // c = y2 - a*x1
                    let intercept = 1.0 - gradient * start_dist;
                    // y = clamp(a*x + c)
                    let strength = (gradient * dist + intercept).clamp(*min_str, 1.0);
                    *strength_mod *= strength;
                }
            },
        }
    }
}

/// Effects applied to the rider of this entity while riding.
#[derive(Clone, Debug, PartialEq)]
pub struct RiderEffects(pub Vec<BuffEffect>);

impl specs::Component for RiderEffects {
    type Storage = specs::DenseVecStorage<RiderEffects>;
}

#[derive(Clone, Debug, PartialEq)]
/// Permanent entity death effects (unlike `Stats::effects_on_death` which is
/// only active as long as ie. it has a certain buff)
pub struct DeathEffects(pub Vec<StatEffect>);

impl specs::Component for DeathEffects {
    type Storage = specs::DenseVecStorage<DeathEffects>;
}

#[derive(Clone, Copy, Debug, Hash, Eq, PartialEq, Serialize, Deserialize)]
pub enum DamageContributor {
    Solo(Uid),
    Group { entity_uid: Uid, group: Group },
}

impl DamageContributor {
    pub fn new(uid: Uid, group: Option<Group>) -> Self {
        if let Some(group) = group {
            DamageContributor::Group {
                entity_uid: uid,
                group,
            }
        } else {
            DamageContributor::Solo(uid)
        }
    }

    pub fn uid(&self) -> Uid {
        match self {
            DamageContributor::Solo(uid) => *uid,
            DamageContributor::Group {
                entity_uid,
                group: _,
            } => *entity_uid,
        }
    }
}

impl From<AttackerInfo<'_>> for DamageContributor {
    fn from(attacker_info: AttackerInfo) -> Self {
        DamageContributor::new(attacker_info.uid, attacker_info.group.copied())
    }
}

#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, Serialize, Deserialize)]
pub enum DamageSource {
    Buff(BuffKind),
    Attack(AttackSource),
    Falling,
    Other,
}

impl From<AttackSource> for DamageSource {
    fn from(attack: AttackSource) -> Self { DamageSource::Attack(attack) }
}

/// DamageKind for the purpose of differentiating damage reduction
#[derive(Copy, Clone, Debug, Hash, PartialEq, Eq, Serialize, Deserialize)]
pub enum DamageKind {
    /// Bypasses some protection from armor
    Piercing,
    /// Reduces energy of target, dealing additional damage when target energy
    /// is 0
    Slashing,
    /// Deals additional poise damage the more armored the target is
    Crushing,
    /// Catch all for remaining damage kinds (TODO: differentiate further with
    /// staff/sceptre reworks
    Energy,
}

const PIERCING_PENETRATION_FRACTION: f32 = 0.75;
const SLASHING_ENERGY_FRACTION: f32 = 0.5;
const CRUSHING_POISE_FRACTION: f32 = 1.0;

#[derive(Copy, Clone, Debug, PartialEq, Serialize, Deserialize)]
#[serde(deny_unknown_fields)]
pub struct Damage {
    pub kind: DamageKind,
    pub value: f32,
}

impl Damage {
    /// Returns the total damage reduction provided by all equipped items
    pub fn compute_damage_reduction(
        damage: Option<Self>,
        inventory: Option<&Inventory>,
        stats: Option<&Stats>,
        msm: &MaterialStatManifest,
    ) -> f32 {
        let protection = compute_protection(inventory, msm);

        let penetration = if let Some(damage) = damage {
            if let DamageKind::Piercing = damage.kind {
                (damage.value * PIERCING_PENETRATION_FRACTION)
                    .clamp(0.0, protection.unwrap_or(0.0).max(0.0))
            } else {
                0.0
            }
        } else {
            0.0
        };

        let protection = protection.map(|p| p - penetration);

        const FIFTY_PERCENT_DR_THRESHOLD: f32 = 60.0;

        let inventory_dr = match protection {
            Some(dr) => dr / (FIFTY_PERCENT_DR_THRESHOLD + dr.abs()),
            None => 1.0,
        };

        let stats_dr = if let Some(stats) = stats {
            stats.damage_reduction.modifier()
        } else {
            0.0
        };
        // Return 100% if either DR is at 100% (admin tabard or safezone buff)
        if protection.is_none() || stats_dr >= 1.0 {
            1.0
        } else {
            1.0 - (1.0 - inventory_dr) * (1.0 - stats_dr)
        }
    }

    pub fn calculate_health_change(
        self,
        damage_reduction: f32,
        block_damage_decrement: f32,
        damage_contributor: Option<DamageContributor>,
        precision_mult: Option<f32>,
        precision_power: f32,
        damage_modifier: f32,
        time: Time,
        instance: u64,
        damage_source: DamageSource,
    ) -> HealthChange {
        let mut damage = self.value * damage_modifier;
        let precise_damage = damage * precision_mult.unwrap_or(0.0) * (precision_power - 1.0);
        match damage_source {
            DamageSource::Attack(_) => {
                // Precise hit
                damage += precise_damage;
                // Block
                damage = f32::max(damage - block_damage_decrement, 0.0);
                // Armor
                damage *= 1.0 - damage_reduction;

                HealthChange {
                    amount: -damage,
                    by: damage_contributor,
                    cause: Some(damage_source),
                    time,
                    precise: precision_mult.is_some(),
                    instance,
                }
            },
            DamageSource::Falling => {
                // Armor
                if (damage_reduction - 1.0).abs() < f32::EPSILON {
                    damage = 0.0;
                }
                HealthChange {
                    amount: -damage,
                    by: None,
                    cause: Some(damage_source),
                    time,
                    precise: false,
                    instance,
                }
            },
            DamageSource::Buff(_) | DamageSource::Other => HealthChange {
                amount: -damage,
                by: None,
                cause: Some(damage_source),
                time,
                precise: false,
                instance,
            },
        }
    }

    pub fn interpolate_damage(&mut self, frac: f32, min: f32) {
        let new_damage = min + frac * (self.value - min);
        self.value = new_damage;
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct Knockback {
    pub direction: KnockbackDir,
    pub strength: f32,
}

#[derive(Copy, Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum KnockbackDir {
    Away,
    Towards,
    Up,
    TowardsUp,
}

impl Knockback {
    pub fn calculate_impulse(
        self,
        dir: Dir,
        tgt_char_state: Option<&CharacterState>,
        attacker_stats: Option<&Stats>,
    ) -> Vec3<f32> {
        let from_char = {
            let resistant = tgt_char_state
                .and_then(|cs| cs.ability_info())
                .map(|a| a.ability_meta)
                .is_some_and(|a| a.capabilities.contains(Capability::KNOCKBACK_RESISTANT));
            if resistant { 0.5 } else { 1.0 }
        };
        // TEMP: 50.0 multiplication kept until source knockback values have been
        // updated
        50.0 * self.strength
            * from_char
            * attacker_stats.map_or(1.0, |s| s.knockback_mult)
            * match self.direction {
                KnockbackDir::Away => *Dir::slerp(dir, Dir::new(Vec3::unit_z()), 0.5),
                KnockbackDir::Towards => *Dir::slerp(-dir, Dir::new(Vec3::unit_z()), 0.5),
                KnockbackDir::Up => Vec3::unit_z(),
                KnockbackDir::TowardsUp => *Dir::slerp(-dir, Dir::new(Vec3::unit_z()), 0.85),
            }
    }

    #[must_use]
    pub fn modify_strength(mut self, power: f32) -> Self {
        self.strength *= power;
        self
    }
}

#[derive(Clone, Copy, Debug, Serialize, Deserialize, PartialEq)]
pub struct CombatBuff {
    pub kind: BuffKind,
    pub dur_secs: Secs,
    pub strength: CombatBuffStrength,
    pub chance: f32,
}

#[derive(Clone, Copy, Debug, Serialize, Deserialize, PartialEq)]
pub enum CombatBuffStrength {
    DamageFraction(f32),
    Value(f32),
}

impl CombatBuffStrength {
    fn to_strength(self, damage: f32, strength_modifier: f32) -> f32 {
        match self {
            // Not affected by strength modifier as damage already is
            CombatBuffStrength::DamageFraction(f) => damage * f,
            CombatBuffStrength::Value(v) => v * strength_modifier,
        }
    }
}

impl MulAssign<f32> for CombatBuffStrength {
    fn mul_assign(&mut self, mul: f32) { *self = *self * mul; }
}

impl Mul<f32> for CombatBuffStrength {
    type Output = Self;

    fn mul(self, mult: f32) -> Self {
        match self {
            Self::DamageFraction(val) => Self::DamageFraction(val * mult),
            Self::Value(val) => Self::Value(val * mult),
        }
    }
}

impl CombatBuff {
    pub fn to_buff(
        self,
        time: Time,
        attacker_info: (Option<Uid>, Option<&Mass>),
        target_info: (Option<&Stats>, Option<&Mass>),
        damage: f32,
        strength_modifier: f32,
        ability_info: Option<AbilityInfo>,
    ) -> Buff {
        let (attacker_uid, attacker_mass) = attacker_info;
        let (target_stats, target_mass) = target_info;
        // TODO: Generate BufCategoryId vec (probably requires damage overhaul?)
        let source = if let Some(uid) = attacker_uid {
            BuffSource::Character {
                by: uid,
                tool_kind: ability_info.and_then(|ai| ai.tool),
            }
        } else {
            BuffSource::Unknown
        };
        let dest_info = DestInfo {
            stats: target_stats,
            mass: target_mass,
        };
        let target_uid = ability_info
            .and_then(|ai| ai.input_attr)
            .and_then(|ia| ia.target_entity);
        Buff::new(
            self.kind,
            BuffData::new(
                self.strength.to_strength(damage, strength_modifier),
                Some(self.dur_secs),
            ),
            Vec::new(),
            source,
            time,
            dest_info,
            attacker_mass,
            target_uid,
        )
    }

    pub fn to_self_buff(
        self,
        time: Time,
        entity_info: (Option<Uid>, Option<&Stats>, Option<&Mass>),
        damage: f32,
        strength_modifier: f32,
        ability_info: Option<AbilityInfo>,
    ) -> Buff {
        let (entity_uid, entity_stats, entity_mass) = entity_info;
        // TODO: Generate BufCategoryId vec (probably requires damage overhaul?)
        let source = if let Some(uid) = entity_uid {
            BuffSource::Character {
                by: uid,
                tool_kind: ability_info.and_then(|ai| ai.tool),
            }
        } else {
            BuffSource::Unknown
        };
        let dest_info = DestInfo {
            stats: entity_stats,
            mass: entity_mass,
        };
        let target_uid = ability_info
            .and_then(|ai| ai.input_attr)
            .and_then(|ia| ia.target_entity);
        Buff::new(
            self.kind,
            BuffData::new(
                self.strength.to_strength(damage, strength_modifier),
                Some(self.dur_secs),
            ),
            Vec::new(),
            source,
            time,
            dest_info,
            entity_mass,
            target_uid,
        )
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
pub enum ScalingKind {
    Linear,
    Sqrt,
}

impl ScalingKind {
    pub fn factor(&self, val: f32, norm: f32) -> f32 {
        match self {
            Self::Linear => val / norm,
            Self::Sqrt => (val / norm).sqrt(),
        }
    }
}

pub fn get_weapon_kinds(inv: &Inventory) -> (Option<ToolKind>, Option<ToolKind>) {
    (
        inv.equipped(EquipSlot::ActiveMainhand).and_then(|i| {
            if let ItemKind::Tool(tool) = &*i.kind() {
                Some(tool.kind)
            } else {
                None
            }
        }),
        inv.equipped(EquipSlot::ActiveOffhand).and_then(|i| {
            if let ItemKind::Tool(tool) = &*i.kind() {
                Some(tool.kind)
            } else {
                None
            }
        }),
    )
}

// TODO: Either remove msm or use it as argument in fn kind
fn weapon_rating<T: ItemDesc>(item: &T, _msm: &MaterialStatManifest) -> f32 {
    const POWER_WEIGHT: f32 = 2.0;
    const SPEED_WEIGHT: f32 = 3.0;
    const RANGE_WEIGHT: f32 = 0.8;
    const EFFECT_WEIGHT: f32 = 1.5;
    const EQUIP_TIME_WEIGHT: f32 = 0.0;
    const ENERGY_EFFICIENCY_WEIGHT: f32 = 1.5;
    const BUFF_STRENGTH_WEIGHT: f32 = 1.5;

    let rating = if let ItemKind::Tool(tool) = &*item.kind() {
        let stats = tool.stats(item.stats_durability_multiplier());

        // TODO: Look into changing the 0.5 to reflect armor later maybe?
        // Since it is only for weapon though, it probably makes sense to leave
        // independent for now

        let power_rating = stats.power;
        let speed_rating = stats.speed - 1.0;
        let range_rating = stats.range - 1.0;
        let effect_rating = stats.effect_power - 1.0;
        let equip_time_rating = 0.5 - stats.equip_time_secs;
        let energy_efficiency_rating = stats.energy_efficiency - 1.0;
        let buff_strength_rating = stats.buff_strength - 1.0;

        power_rating * POWER_WEIGHT
            + speed_rating * SPEED_WEIGHT
            + range_rating * RANGE_WEIGHT
            + effect_rating * EFFECT_WEIGHT
            + equip_time_rating * EQUIP_TIME_WEIGHT
            + energy_efficiency_rating * ENERGY_EFFICIENCY_WEIGHT
            + buff_strength_rating * BUFF_STRENGTH_WEIGHT
    } else {
        0.0
    };
    rating.max(0.0)
}

fn weapon_skills(inventory: &Inventory, skill_set: &SkillSet) -> f32 {
    let (mainhand, offhand) = get_weapon_kinds(inventory);
    let mainhand_skills = if let Some(tool) = mainhand {
        skill_set.earned_sp(SkillGroupKind::Weapon(tool)) as f32
    } else {
        0.0
    };
    let offhand_skills = if let Some(tool) = offhand {
        skill_set.earned_sp(SkillGroupKind::Weapon(tool)) as f32
    } else {
        0.0
    };
    mainhand_skills.max(offhand_skills)
}

fn get_weapon_rating(inventory: &Inventory, msm: &MaterialStatManifest) -> f32 {
    let mainhand_rating = if let Some(item) = inventory.equipped(EquipSlot::ActiveMainhand) {
        weapon_rating(item, msm)
    } else {
        0.0
    };

    let offhand_rating = if let Some(item) = inventory.equipped(EquipSlot::ActiveOffhand) {
        weapon_rating(item, msm)
    } else {
        0.0
    };

    mainhand_rating.max(offhand_rating)
}

pub fn combat_rating(
    inventory: &Inventory,
    health: &Health,
    energy: &Energy,
    poise: &Poise,
    skill_set: &SkillSet,
    body: Body,
    msm: &MaterialStatManifest,
) -> f32 {
    const WEAPON_WEIGHT: f32 = 1.0;
    const HEALTH_WEIGHT: f32 = 1.5;
    const ENERGY_WEIGHT: f32 = 0.5;
    const SKILLS_WEIGHT: f32 = 1.0;
    const POISE_WEIGHT: f32 = 0.5;
    const PRECISION_WEIGHT: f32 = 0.5;
    // Normalized with a standard max health of 100
    let health_rating = health.base_max()
        / 100.0
        / (1.0 - Damage::compute_damage_reduction(None, Some(inventory), None, msm)).max(0.00001);

    // Normalized with a standard max energy of 100 and energy reward multiplier of
    // x1
    let energy_rating = (energy.base_max() + compute_max_energy_mod(Some(inventory), msm)) / 100.0
        * compute_energy_reward_mod(Some(inventory), msm);

    // Normalized with a standard max poise of 100
    let poise_rating = poise.base_max()
        / 100.0
        / (1.0 - Poise::compute_poise_damage_reduction(Some(inventory), msm, None, None))
            .max(0.00001);

    // Normalized with a standard precision multiplier of 1.2
    let precision_rating = compute_precision_mult(Some(inventory), msm) / 1.2;

    // Assumes a standard person has earned 20 skill points in the general skill
    // tree and 10 skill points for the weapon skill tree
    let skills_rating = (skill_set.earned_sp(SkillGroupKind::General) as f32 / 20.0
        + weapon_skills(inventory, skill_set) / 10.0)
        / 2.0;

    let weapon_rating = get_weapon_rating(inventory, msm);

    let combined_rating = (health_rating * HEALTH_WEIGHT
        + energy_rating * ENERGY_WEIGHT
        + poise_rating * POISE_WEIGHT
        + precision_rating * PRECISION_WEIGHT
        + skills_rating * SKILLS_WEIGHT
        + weapon_rating * WEAPON_WEIGHT)
        / (HEALTH_WEIGHT
            + ENERGY_WEIGHT
            + POISE_WEIGHT
            + PRECISION_WEIGHT
            + SKILLS_WEIGHT
            + WEAPON_WEIGHT);

    // Body multiplier meant to account for an enemy being harder than equipment and
    // skills would account for. It should only not be 1.0 for non-humanoids
    combined_rating * body.combat_multiplier()
}

pub fn compute_precision_mult(inventory: Option<&Inventory>, msm: &MaterialStatManifest) -> f32 {
    // Starts with a value of 0.1 when summing the stats from each armor piece, and
    // defaults to a value of 0.1 if no inventory is equipped. Precision multiplier
    // cannot go below 1
    1.0 + inventory
        .map_or(0.1, |inv| {
            inv.equipped_items()
                .filter_map(|item| {
                    if let ItemKind::Armor(armor) = &*item.kind() {
                        armor
                            .stats(msm, item.stats_durability_multiplier())
                            .precision_power
                    } else {
                        None
                    }
                })
                .fold(0.1, |a, b| a + b)
        })
        .max(0.0)
}

/// Computes the energy reward modifier from worn armor
pub fn compute_energy_reward_mod(inventory: Option<&Inventory>, msm: &MaterialStatManifest) -> f32 {
    // Starts with a value of 1.0 when summing the stats from each armor piece, and
    // defaults to a value of 1.0 if no inventory is present
    inventory.map_or(1.0, |inv| {
        inv.equipped_items()
            .filter_map(|item| {
                if let ItemKind::Armor(armor) = &*item.kind() {
                    armor
                        .stats(msm, item.stats_durability_multiplier())
                        .energy_reward
                } else {
                    None
                }
            })
            .fold(1.0, |a, b| a + b)
    })
}

/// Computes the additive modifier that should be applied to max energy from the
/// currently equipped items
pub fn compute_max_energy_mod(inventory: Option<&Inventory>, msm: &MaterialStatManifest) -> f32 {
    // Defaults to a value of 0 if no inventory is present
    inventory.map_or(0.0, |inv| {
        inv.equipped_items()
            .filter_map(|item| {
                if let ItemKind::Armor(armor) = &*item.kind() {
                    armor
                        .stats(msm, item.stats_durability_multiplier())
                        .energy_max
                } else {
                    None
                }
            })
            .sum()
    })
}

/// Returns a value to be included as a multiplicative factor in perception
/// distance checks.
pub fn perception_dist_multiplier_from_stealth(
    inventory: Option<&Inventory>,
    character_state: Option<&CharacterState>,
    msm: &MaterialStatManifest,
) -> f32 {
    const SNEAK_MULTIPLIER: f32 = 0.7;

    let item_stealth_multiplier = stealth_multiplier_from_items(inventory, msm);
    let is_sneaking = character_state.is_some_and(|state| state.is_stealthy());

    let multiplier = item_stealth_multiplier * if is_sneaking { SNEAK_MULTIPLIER } else { 1.0 };

    multiplier.clamp(0.0, 1.0)
}

pub fn compute_stealth(inventory: Option<&Inventory>, msm: &MaterialStatManifest) -> f32 {
    inventory.map_or(0.0, |inv| {
        inv.equipped_items()
            .filter_map(|item| {
                if let ItemKind::Armor(armor) = &*item.kind() {
                    armor.stats(msm, item.stats_durability_multiplier()).stealth
                } else {
                    None
                }
            })
            .sum()
    })
}

pub fn stealth_multiplier_from_items(
    inventory: Option<&Inventory>,
    msm: &MaterialStatManifest,
) -> f32 {
    let stealth_sum = compute_stealth(inventory, msm);

    (1.0 / (1.0 + stealth_sum)).clamp(0.0, 1.0)
}

/// Computes the total protection provided from armor. Is used to determine the
/// damage reduction applied to damage received by an entity None indicates that
/// the armor equipped makes the entity invulnerable
pub fn compute_protection(
    inventory: Option<&Inventory>,
    msm: &MaterialStatManifest,
) -> Option<f32> {
    inventory.map_or(Some(0.0), |inv| {
        inv.equipped_items()
            .filter_map(|item| {
                if let ItemKind::Armor(armor) = &*item.kind() {
                    armor
                        .stats(msm, item.stats_durability_multiplier())
                        .protection
                } else {
                    None
                }
            })
            .map(|protection| match protection {
                Protection::Normal(protection) => Some(protection),
                Protection::Invincible => None,
            })
            .sum::<Option<f32>>()
    })
}

/// Computes the total resilience provided from armor. Is used to determine the
/// reduction applied to poise damage received by an entity. None indicates that
/// the armor equipped makes the entity invulnerable to poise damage.
pub fn compute_poise_resilience(
    inventory: Option<&Inventory>,
    msm: &MaterialStatManifest,
) -> Option<f32> {
    inventory.map_or(Some(0.0), |inv| {
        inv.equipped_items()
            .filter_map(|item| {
                if let ItemKind::Armor(armor) = &*item.kind() {
                    armor
                        .stats(msm, item.stats_durability_multiplier())
                        .poise_resilience
                } else {
                    None
                }
            })
            .map(|protection| match protection {
                Protection::Normal(protection) => Some(protection),
                Protection::Invincible => None,
            })
            .sum::<Option<f32>>()
    })
}

/// Used to compute the precision multiplier achieved by flanking a target
pub fn precision_mult_from_flank(
    attack_dir: Vec3<f32>,
    target_ori: Option<&Ori>,
    precision_flank_multipliers: FlankMults,
    precision_flank_invert: bool,
) -> Option<f32> {
    let angle = target_ori.map(|t_ori| {
        t_ori.look_dir().angle_between(if precision_flank_invert {
            -attack_dir
        } else {
            attack_dir
        })
    });
    match angle {
        Some(angle) if angle < FULL_FLANK_ANGLE => Some(
            MAX_BACK_FLANK_PRECISION
                * if precision_flank_invert {
                    precision_flank_multipliers.front
                } else {
                    precision_flank_multipliers.back
                },
        ),
        Some(angle) if angle < PARTIAL_FLANK_ANGLE => {
            Some(MAX_SIDE_FLANK_PRECISION * precision_flank_multipliers.side)
        },
        Some(_) | None => None,
    }
}

#[derive(Copy, Clone, Debug, PartialEq, Serialize, Deserialize)]
pub struct FlankMults {
    pub back: f32,
    pub front: f32,
    pub side: f32,
}

impl Default for FlankMults {
    fn default() -> Self {
        FlankMults {
            back: 1.0,
            front: 1.0,
            side: 1.0,
        }
    }
}

pub fn block_strength(inventory: &Inventory, char_state: &CharacterState) -> f32 {
    let (ability_block_strength, hand) = match char_state {
        CharacterState::BasicBlock(data) => (
            data.static_data.block_strength,
            data.static_data.ability_info.hand,
        ),
        CharacterState::RiposteMelee(data) => (
            data.static_data.block_strength,
            data.static_data.ability_info.hand,
        ),
        _ => char_state
            .ability_info()
            .map(|ability| (ability.ability_meta.capabilities, ability.hand))
            .map_or((0.0, None), |(capabilities, hand)| {
                (
                    if capabilities.contains(Capability::PARRIES)
                        || capabilities.contains(Capability::PARRIES_MELEE)
                        || capabilities.contains(Capability::BLOCKS)
                    {
                        FALLBACK_BLOCK_STRENGTH
                    } else {
                        0.0
                    },
                    hand,
                )
            }),
    };

    let tool_block_strength = hand
        .and_then(|hand| inventory.equipped(hand.to_equip_slot()))
        .map_or(1.0, |item| match &*item.kind() {
            ItemKind::Tool(tool) => tool.stats(item.stats_durability_multiplier()).power,
            _ => 1.0,
        });

    ability_block_strength * tool_block_strength
}

pub fn get_equip_slot_by_block_priority(inventory: Option<&Inventory>) -> EquipSlot {
    inventory
        .map(get_weapon_kinds)
        .map_or(
            EquipSlot::ActiveMainhand,
            |weapon_kinds| match weapon_kinds {
                (Some(mainhand), Some(offhand)) => {
                    if mainhand.block_priority() >= offhand.block_priority() {
                        EquipSlot::ActiveMainhand
                    } else {
                        EquipSlot::ActiveOffhand
                    }
                },
                (Some(_), None) => EquipSlot::ActiveMainhand,
                (None, Some(_)) => EquipSlot::ActiveOffhand,
                (None, None) => EquipSlot::ActiveMainhand,
            },
        )
}