import { _decorator, Asset, Node, Prefab, instantiate, AssetManager, assetManager, sys } from 'cc';

export class ResManager {
    private static _instance: ResManager = null;

    public static get instance(): ResManager {
        if (!this._instance) {
            this._instance = new ResManager();
        }
        return this._instance;
    }

    async loadPrefabFromBundle(bundleName: string, path: string, progressCallback?: (finished: number, total: number) => void): Promise<Node> {
        try {
            if (!sys.isBrowser) {
                assetManager.cacheManager.cacheEnabled = true;
            }

            const TOTAL = 200;

            let bundle = await new Promise<AssetManager.Bundle>((resolve, reject) => {
                assetManager.loadBundle(
                    bundleName,
                    (finished: number, total: number) => {
                        if (typeof finished === 'number' && typeof total === 'number' && total > 0) {
                            const overallFinished = Math.floor((finished / total) * 100);
                            progressCallback?.(overallFinished, TOTAL);
                        }
                    },
                    (err, bundle) => err ? reject(err) : resolve(bundle)
                );
            });

            // 整包预加载，覆盖所有资源类型
            await new Promise<void>((resolve, reject) => {
                bundle.loadDir(
                    '',
                    (finished: number, total: number) => {
                        if (typeof finished === 'number' && typeof total === 'number' && total > 0) {
                            const overallFinished = 100 + Math.floor((finished / total) * 100);
                            progressCallback?.(overallFinished, TOTAL);
                        }
                    },
                    (err) => err ? reject(err) : resolve()
                );
            });

            // 从缓存获取目标 Prefab，未命中再补一次 load
            let prefab = bundle.get(path, Prefab);
            if (!prefab) {
                prefab = await new Promise<Prefab>((resolve, reject) => {
                    bundle.load(path, Prefab, (e, p) => e ? reject(e) : resolve(p));
                });
            }

            return instantiate(prefab);

        } catch (error) {
            console.error(`加载失败: ${bundleName}/${path}`, error);
            throw error;
        }
    }


}