import { ecsWorldManager } from '../world/ECSWorldManager';
import type { ecs } from '../ECS';
import type { ECSEntity } from '../entity/ECSEntity';
import type { EntityCtor } from '../registry/ECSTypes';
import { IncrementalSerializer, type IncrementalDelta, type Snapshot } from './Incremental';
import {
    serialize,
    getCompCtorByName,
    getEntityCtorByName,
    serializeComponent,
    serializeEntity,
    type SerializedComponent,
    type SerializedEntity,
    type SerializedScene,
} from './SerializationBase';

export {
    serialize,
    getCompCtorByName,
    getEntityCtorByName,
    serializeComponent,
    serializeEntity,
    type SerializedComponent,
    type SerializedEntity,
    type SerializedScene,
} from './SerializationBase';

/** 当前场景序列化格式版本 */
const SCENE_VERSION = 1;

/**
 * 序列化器：场景 / 实体 / 组件 与 JSON 互转。
 * 仅序列化通过 @ecs.serialize 标记的字段；保留实体层级（parentEid）。
 */
export class Serializer {
    /** 序列化单个组件 */
    static serializeComponent(comp: ecs.IComp): SerializedComponent | null {
        return serializeComponent(comp);
    }

    /** 序列化单个实体 */
    static serializeEntity(entity: ECSEntity): SerializedEntity {
        return serializeEntity(entity);
    }

    /** 序列化整个世界 */
    static serializeWorld(pretty = false): string {
        const entities: SerializedEntity[] = [];
        ecsWorldManager.current.entities.forEach((e) => {
            if (e.isValid) entities.push(serializeEntity(e));
        });
        const scene: SerializedScene = { version: SCENE_VERSION, entities };
        return pretty ? JSON.stringify(scene, null, 2) : JSON.stringify(scene);
    }

    /**
     * 反序列化到世界。
     * 两阶段：先建实体+组件，再按 parentEid 重建层级。
     * @param createEntity 由 ecs 注入的实体创建函数（按名）。
     */
    static deserializeWorld(
        json: string,
        createEntity: (ctor: EntityCtor<ECSEntity>) => ECSEntity
    ): void {
        const scene = JSON.parse(json) as SerializedScene;
        const eidMap = new Map<number, ECSEntity>();

        for (const se of scene.entities) {
            const ctor = getEntityCtorByName(se.name);
            if (!ctor) {
                console.warn(`[ECS] 反序列化跳过未注册实体: ${se.name}`);
                continue;
            }
            const entity = createEntity(ctor);
            eidMap.set(se.eid, entity);

            for (const sc of se.components) {
                const cctor = getCompCtorByName(sc.type);
                if (!cctor) {
                    console.warn(`[ECS] 反序列化跳过未注册组件: ${sc.type}`);
                    continue;
                }
                const comp = entity.add(cctor) as ecs.IComp;
                const anyComp = comp as unknown as Record<string, unknown>;
                for (const key in sc.data) anyComp[key] = sc.data[key];
            }
        }

        for (const se of scene.entities) {
            if (se.parentEid !== null) {
                const child = eidMap.get(se.eid);
                const parent = eidMap.get(se.parentEid);
                if (child && parent) parent.addChild(child);
            }
        }
    }
}

/** 序列化 API 集合（`ecs.serialize` 即此对象） */
export const ecsSerialize = {
    /** @ecs.serialize() 字段装饰器：标记组件需要持久化的字段 */
    serialize,
    /**
     * 全量序列化当前世界为 JSON
     * @param pretty 是否格式化输出（缩进）
     */
    serializeWorld(pretty = false): string {
        return Serializer.serializeWorld(pretty);
    },
    /**
     * 从 JSON 反序列化到当前世界
     * @param json 由 serializeWorld 生成的场景 JSON
     */
    deserializeWorld(json: string): void {
        Serializer.deserializeWorld(json, (c) => ecsWorldManager.current.getEntity(c as EntityCtor<ECSEntity>));
    },
    /** 对当前世界拍快照（增量序列化基线） */
    snapshot(): Snapshot {
        return IncrementalSerializer.createSnapshot();
    },
    /**
     * 计算当前世界相对 base 快照的增量
     * @param base 基线快照
     */
    computeDelta(base: Snapshot): { delta: IncrementalDelta; snapshot: Snapshot } {
        return IncrementalSerializer.computeDelta(base);
    },
    /**
     * 将增量应用到当前世界
     * @param delta 增量对象或 JSON 字符串
     */
    applyDelta(delta: IncrementalDelta | string): void {
        IncrementalSerializer.applyDelta(delta, (name) => {
            const ctor = getEntityCtorByName(name);
            return ctor ? ecsWorldManager.current.getEntity(ctor as EntityCtor<ECSEntity>) : undefined;
        });
    },
};