import { assetManager, JsonAsset } from 'cc';
import { PREVIEW } from 'cc/env';

/** assets/level-data/level-prefab-uuids.json（烘焙脚本生成，编辑器预览按 uuid 加载 prefab） */
const EDITOR_UUID_INDEX = 'f7e8d9c0-b1a2-4c3d-9e8f-1a2b3c4d5e6f';

let uuidByLevelId: Record<number, string> | null = null;
let loadPromise: Promise<void> | null = null;

function ingest(data: Record<string, string>) {
    const out: Record<number, string> = {};
    for (const [k, v] of Object.entries(data ?? {})) {
        const id = parseInt(k, 10);
        const uuid = typeof v === 'string' ? v.trim() : '';
        if (!Number.isNaN(id) && uuid) out[id] = uuid;
    }
    uuidByLevelId = out;
}

function loadFromEditorAsset(): Promise<void> {
    return new Promise((resolve, reject) => {
        assetManager.loadAny({ uuid: EDITOR_UUID_INDEX }, (err: Error | null, asset: JsonAsset) => {
            if (err || !asset?.json) {
                reject(err ?? new Error('level-prefab-uuids.json 未找到'));
                return;
            }
            ingest(asset.json as Record<string, string>);
            resolve();
        });
    });
}

/** 编辑器预览：levelId → prefab uuid */
export function loadLevelPrefabUuidIndex(): Promise<void> {
    if (uuidByLevelId) return Promise.resolve();
    if (loadPromise) return loadPromise;
    loadPromise = loadFromEditorAsset().catch((e) => {
        console.warn('[LevelPrefabUuidIndex] 加载失败，将仅用 bundle 路径', e);
        uuidByLevelId = {};
    }).then(() => undefined);
    return loadPromise;
}

export function getLevelPrefabUuid(levelId: number): string | undefined {
    return uuidByLevelId?.[levelId];
}

/** level-prefabs/Level91601 → 91601 */
export function parseLevelIdFromPrefabPath(path: string): number | undefined {
    const m = /Level(\d+)\s*$/.exec(path.trim());
    if (!m) return undefined;
    const id = parseInt(m[1], 10);
    return Number.isNaN(id) ? undefined : id;
}

export function shouldTryEditorUuidLoad(): boolean {
    return PREVIEW;
}