tsgames/src/common/rpg/systems/combat.ts

import { Attacked, Crit, Damage, Defense } from "../components/combat";
import { Effect, EffectTemplate } from "../components/effect";
import { getWorldRandom, Random } from "../components/random";
import { Health } from "../components/stat";
import { System, World } from "../core/world";

let hitEffectCounter = 0;

export interface HitEvent {
    attackerId: string;
    sourceId: string | null;
    amount: number;
    damageType?: string;
}

export class CombatSystem extends System {
    override update(world: World) {
        let random: Random | undefined;
        const rng = () => (random ??= getWorldRandom(world));

        for (const [target] of world.query(Attacked)) {
            const healths = target.getAll(Health).sort((a, b) => b.priority - a.priority);
            if (healths.length === 0) {
                console.warn(`[CombatSystem] Target ${target.id} has no Health component`);
                for (const attack of target.getAll(Attacked)) target.remove(attack);
                continue;
            }

            const hitEvents: HitEvent[] = [];

            for (const attack of target.getAll(Attacked)) {
                const { attackerId, sourceId } = attack.state;
                target.remove(attack);

                const attacker = world.getEntity(attackerId);
                if (!attacker) {
                    console.warn(`[CombatSystem] Attacker ${attackerId} not found`);
                    continue;
                }

                const source = sourceId ? world.getEntity(sourceId) : attacker;
                if (!source) {
                    console.warn(`[CombatSystem] Source ${sourceId} not found`);
                    continue;
                }

                const damages = source.getAll(Damage);
                if (damages.length === 0) {
                    console.warn(`[CombatSystem] No Damage on source ${source.id}`);
                    continue;
                }

                // Crit rolls once per attack; guard so a value < 1 can't reduce damage.
                let critMult = 1;
                const crit = source.get(Crit);
                if (crit) {
                    const roll = rng().use(r => r.nextFloat());
                    if (roll < crit.state.chance) critMult = Math.max(1, crit.value);
                }

                // Each Damage component contributes its own typed hit (multi-type weapons).
                for (const damage of damages) {
                    const { damageType, minDamage = 0, variance = 0 } = damage.state;
                    let damageAmount = damage.value;

                    // symmetric variance: [-variance, +variance]
                    if (variance > 0) {
                        damageAmount += rng().use(r => r.nextInt(-variance, variance + 1));
                    }

                    damageAmount *= critMult;

                    // sum all matching-type + general defenses, so stacked armor accumulates
                    let defense = 0;
                    for (const d of target.getAll(Defense)) {
                        if (d.state.damageType === damageType || d.state.damageType == null) {
                            defense += d.value;
                        }
                    }
                    damageAmount -= defense;

                    damageAmount = Math.max(0, minDamage, damageAmount);

                    hitEvents.push({ attackerId, sourceId, amount: damageAmount, damageType });
                }

                // on-hit effects from source → target, once per attack
                for (const component of source.getAll(EffectTemplate)) {
                    const s = component.state;
                    target.add(
                        new Effect({
                            target: s.target,
                            targetKey: s.targetKey,
                            delta: s.delta,
                            targetField: s.targetField,
                            duration: s.duration ?? undefined,
                            permanent: s.permanent,
                            gradual: s.gradual,
                            condition: s.condition ?? undefined,
                            stacking: s.stacking,
                            tag: s.tag ?? undefined,
                        }),
                        `__hit_${source.id}_${component.key}_${hitEffectCounter++}`,
                    );
                }
            }

            if (hitEvents.length === 0) continue;

            let totalBefore = 0;
            for (const pool of healths) totalBefore += pool.value;

            for (const hit of hitEvents) {
                let remaining = hit.amount;
                let applied = 0;

                if (hit.damageType) {
                    for (const pool of healths) {
                        if (remaining <= 0) break;
                        if (pool.value <= 0) continue;
                        if (!pool.damageTypes.includes(hit.damageType)) continue;
                        const take = Math.min(pool.value, remaining);
                        pool.update(-take);
                        remaining -= take;
                        applied += take;
                    }
                }

                if (remaining > 0) {
                    for (const pool of healths) {
                        if (remaining <= 0) break;
                        if (pool.value <= 0) continue;
                        if (pool.damageTypes.length > 0) continue;
                        const take = Math.min(pool.value, remaining);
                        pool.update(-take);
                        remaining -= take;
                        applied += take;
                    }
                }

                hit.amount = applied; // report damage actually dealt, not pre-mitigation
            }

            const lastHit = hitEvents[hitEvents.length - 1] ?? null;

            for (const info of hitEvents) {
                target.emit('Combat.hit', info);
            }

            let totalAfter = 0;
            for (const pool of healths) totalAfter += pool.value;

            if (totalBefore > 0 && totalAfter <= 0 && lastHit) {
                target.emit('Combat.killed', lastHit);
            }
        }
    }
}