import type { World, EntityId } from 'db://assets/mx/module/ecs';
import type { ISystem } from 'db://assets/mx/module/ecs';
import type { EffectSpec } from '../config/BattleConfigTypes';
import { ProjectileComp, TransformComp, TeamComp, HealthComp, MovementComp, isBajiaoBlowRetreating, isYanSoulClaimed } from '../ecs/Components';
import { BattleTeamId } from '../ecs/BattleTeamId';
import type { GridMap } from '../battlefield/GridMap';
import type { SpatialGrid } from '../battlefield/SpatialGrid';
import type { EffectExecutor } from './EffectExecutor';
import type { BattleServices } from './BattleServices';
import { createAbilityContext } from './AbilityContext';
import { BattleEventFactory } from '../events/BattleEvents';
import type { BattleEventBus } from '../events/BattleEventBus';
import { createMembershipSet, membershipAdd, type MembershipSet } from 'db://assets/mx/tools/MembershipSet';

/** 投射物生成选项 */
export interface ProjectileOptions {
    /** 飞行模式 */
    mode?: 'homing' | 'linear';
    /** 直线方向（格，无需归一化） */
    direction?: { dr: number; dc: number };
    /** 直线飞行总距离（像素；内部换算为格推进） */
    travel?: number;
    /** 穿透目标数（null=无限穿透） */
    pierce?: number | null;
    /** 表现层资源名 */
    prefab?: string;
    /** 伤害缩放透传给 hitEffects */
    damageScale?: number;
}

/** 投射物系统 */
export class ProjectileSystem implements ISystem {
    readonly priority = 40;
    enabled = true;

    constructor(
        private readonly _world: World,
        private readonly _grid: GridMap,
        private readonly _spatial: SpatialGrid,
        private readonly _effects: EffectExecutor,
        private readonly _services: BattleServices,
        private readonly _events: BattleEventBus,
    ) {}

    /** 本拍待销毁弹道 */
    private readonly _toRemove: EntityId[] = [];
    /** 直线弹道本拍命中缓冲 */
    private readonly _hits: EntityId[] = [];
    /** 空间索引格子 scratch */
    private readonly _cell = { row: 0, col: 0 };

    /**
     * @param caster 发射者实体 ID
     * @param target 目标实体 ID（linear 模式仅用于初始方向参考，可传 INVALID）
     * @param hitEffects 命中效果列表
     * @param speed 飞行速度（格/秒）
     * @param damageScale 伤害缩放，默认 1
     * @param damageType 伤害类型
     * @param options 额外选项（mode/direction/travel/pierce/prefab）
     * @returns 投射物实体 ID
     */
    spawn(
        caster: EntityId,
        target: EntityId,
        hitEffects: EffectSpec[],
        speed: number,
        damageScale = 1,
        damageType?: string,
        options?: ProjectileOptions,
    ): EntityId {
        const world = this._world;
        const id = world.spawn();
        const proj = new ProjectileComp(caster, speed, target, hitEffects, damageScale, damageType);
        proj.damageScale = damageScale;
        if (options) {
            proj.mode = options.mode ?? 'homing';
            proj.prefab = options.prefab;
            if (options.mode === 'linear') {
                if (options.direction) {
                    const len = Math.sqrt(options.direction.dr ** 2 + options.direction.dc ** 2) || 1;
                    proj.direction = { dr: options.direction.dr / len, dc: options.direction.dc / len };
                }
                proj.travelRemaining = (options.travel ?? (10 * this._grid.cellSize)) / Math.max(1, this._grid.cellSize);
                proj.pierceRemaining = options.pierce ?? 1;
                proj.hitSet = createMembershipSet<EntityId>();
            }
        }
        world.addComponent(id, proj);
        const casterTf = world.getComponent(caster, TransformComp);
        if (casterTf) {
            world.addComponent(id, new TransformComp(casterTf.row, casterTf.col));
            this._spatial.updateEntity(id, { row: casterTf.row, col: casterTf.col });
        }
        this._events.emit(BattleEventFactory.projectileSpawned(id, caster, proj.prefab));
        return id;
    }

    /** @param dt 帧间隔（秒） */
    tick(dt: number): void {
        const world = this._world;
        const toRemove = this._toRemove;
        toRemove.length = 0;
        world.view2(ProjectileComp, TransformComp).forEach((id, proj, tf) => {
            if (proj.mode === 'linear') {
                this._tickLinear(id, proj, tf, dt, toRemove);
            } else {
                this._tickHoming(id, proj, tf, dt, toRemove);
            }
        });

        for (const id of toRemove) {
            this._spatial.removeEntity(id);
            this._world.destroy(id);
        }
    }

    /** 制导追踪 */
    private _tickHoming(id: EntityId, proj: ProjectileComp, tf: TransformComp, dt: number, toRemove: EntityId[]): void {
        const world = this._world;
        const targetTf = world.getComponent(proj.target, TransformComp);
        if (!targetTf) {
            toRemove.push(id);
            return;
        }
        const dx = targetTf.col - tf.col;
        const dy = targetTf.row - tf.row;
        const dist = Math.sqrt(dx * dx + dy * dy);
        const move = proj.speed * dt / Math.max(this._grid.cellSize, 1);
        if (dist <= move || dist < 0.15) {
            // 出生保护 / 阎王拘魂归属：弹道消散，不结算命中
            const targetMove = world.getComponent(proj.target, MovementComp);
            if (targetMove?.spawnProtected || isYanSoulClaimed(targetMove) || isBajiaoBlowRetreating(targetMove)) {
                toRemove.push(id);
                return;
            }
            this._hit(id, proj, [proj.target]);
            toRemove.push(id);
        } else {
            tf.col += (dx / dist) * move;
            tf.row += (dy / dist) * move;
            this._cell.row = Math.round(tf.row);
            this._cell.col = Math.round(tf.col);
            this._spatial.updateEntity(id, this._cell);
        }
    }

    /** 直线穿透 */
    private _tickLinear(id: EntityId, proj: ProjectileComp, tf: TransformComp, dt: number, toRemove: EntityId[]): void {
        const dir = proj.direction;
        if (!dir) {
            toRemove.push(id);
            return;
        }
        const move = proj.speed * dt / Math.max(this._grid.cellSize, 1); // speed 为像素/秒 → 格
        tf.row += dir.dr * move;
        tf.col += dir.dc * move;
        proj.travelRemaining = (proj.travelRemaining ?? 0) - move;
        this._cell.row = Math.round(tf.row);
        this._cell.col = Math.round(tf.col);
        this._spatial.updateEntity(id, this._cell);

        // 命中当前格子上的敌对实体（穿透；不含己方口/营召唤）
        const casterTeam = this._world.getComponent(proj.caster, TeamComp);
        const occupants = this._spatial.queryRadius(this._cell, 0.5);
        const hits = this._hits;
        hits.length = 0;
        for (const occ of occupants) {
            if (occ === proj.caster) continue;
            if (proj.hitSet?.has(occ)) continue;
            const team = this._world.getComponent(occ, TeamComp);
            if (!BattleTeamId.isHostile(casterTeam, team)) continue;
            if (!this._world.getComponent(occ, HealthComp)) continue;
            const occMove = this._world.getComponent(occ, MovementComp);
            if (occMove?.spawnProtected || isYanSoulClaimed(occMove) || isBajiaoBlowRetreating(occMove)) continue;
            hits.push(occ);
            proj.hitSet?.set(occ, true);
        }
        if (hits.length) {
            this._hit(id, proj, hits);
            if (proj.pierceRemaining != null) {
                proj.pierceRemaining -= hits.length;
                if (proj.pierceRemaining <= 0) toRemove.push(id);
            }
        }
        if (proj.travelRemaining != null && proj.travelRemaining <= 0 && !toRemove.includes(id)) {
            toRemove.push(id);
        }
    }

    /** 执行命中效果（damageScale 透传）+ 派发事件 */
    private _hit(projectile: EntityId, proj: ProjectileComp, targets: EntityId[]): void {
        const scaledEffects = proj.damageScale !== 1
            ? proj.hitEffects.map(s => s.params?.scale != null
                ? { ...s, params: { ...s.params, scale: (s.params.scale as number) * proj.damageScale } }
                : s)
            : proj.hitEffects;
        for (const targetId of targets) {
            const ctx = createAbilityContext(this._services, proj.caster, 'projectile_hit', [targetId]);
            for (const spec of scaledEffects) {
                this._effects.execute(ctx, spec);
            }
        }
        this._events.emit(BattleEventFactory.projectileHit(projectile, proj.caster, targets[0], proj.hitEffects));
    }
}