/**
 * 資源加載類(lèi)
 * 1. 加載完成后自動(dòng)記錄引用關(guān)系，根據(jù)DependKeys記錄反向依賴(lài)
 * 2. 支持資源使用，如某打開(kāi)的UI使用了A資源，其他地方釋放資源B，資源B引用了資源A，如果沒(méi)有其他引用資源A的資源，會(huì)觸發(fā)資源A的釋放，
 * 3. 能夠安全釋放依賴(lài)資源（一個(gè)資源同時(shí)被多個(gè)資源引用，只有當(dāng)其他資源都釋放時(shí)，該資源才會(huì)被釋放）
 * 
 * 2018-7-17 by 寶爺
 */

// 資源加載的處理回調(diào)
export type ProcessCallback = (completedCount: number, totalCount: number, item: any) => void;
// 資源加載的完成回調(diào)
export type CompletedCallback = (error: Error, resource: any) => void;

// 引用和使用的結(jié)構(gòu)體
interface CacheInfo {
    refs: Set<string>,
    uses: Set<string>
}

// LoadRes方法的參數(shù)結(jié)構(gòu)
interface LoadResArgs {
    url: string,
    type?: typeof cc.Asset,
    onCompleted?: CompletedCallback,
    onProgess?: ProcessCallback,
    use?: string,
}

// ReleaseRes方法的參數(shù)結(jié)構(gòu)
interface ReleaseResArgs {
    url: string,
    type?: typeof cc.Asset,
    use?: string,
}

// 兼容性處理
let isChildClassOf = cc.js["isChildClassOf"]
if (!isChildClassOf) {
    isChildClassOf = cc["isChildClassOf"];
}

export default class ResLoader {

    private _resMap: Map<string, CacheInfo> = new Map<string, CacheInfo>();
    private static _resLoader: ResLoader = null;
    public static getInstance(): ResLoader {
        if (!this._resLoader) {
            this._resLoader = new ResLoader();
        }
        return this._resLoader;
    }

    public static destroy(): void {
        if (this._resLoader) {
            this._resLoader = null;
        }
    }

    private constructor() {

    }

    /**
     * 從cc.loader中獲取一個(gè)資源的item
     * @param url 查詢(xún)的url
     * @param type 查詢(xún)的資源類(lèi)型
     */
    private _getResItem(url: string, type: typeof cc.Asset): any {
        let ccloader: any = cc.loader;
        let item = ccloader._cache[url];
        if (!item) {
            let uuid = ccloader._getResUuid(url, type, false);
            if (uuid) {
                let ref = ccloader._getReferenceKey(uuid);
                item = ccloader._cache[ref];
            }
        }
        return item;
    }

    /**
     * loadRes方法的參數(shù)預(yù)處理
     */
    private _makeLoadResArgs(): LoadResArgs {
        if (arguments.length < 1 || typeof arguments[0] != "string") {
            console.error(`_makeLoadResArgs error ${arguments}`);
            return null;
        }
        let ret: LoadResArgs = { url: arguments[0] };
        for (let i = 1; i < arguments.length; ++i) {
            if (i == 1 && isChildClassOf(arguments[i], cc.RawAsset)) {
                // 判斷是不是第一個(gè)參數(shù)type
                ret.type = arguments[i];
            } else if (i == arguments.length - 1 && typeof arguments[i] == "string") {
                // 判斷是不是最后一個(gè)參數(shù)use
                ret.use = arguments[i];
            } else if (typeof arguments[i] == "function") {
                // 其他情況為函數(shù)
                if (arguments.length > i + 1 && typeof arguments[i + 1] == "function") {
                    ret.onProgess = arguments[i];
                } else {
                    ret.onCompleted = arguments[i];
                }
            }
        }
        return ret;
    }

    /**
     * releaseRes方法的參數(shù)預(yù)處理
     */
    private _makeReleaseResArgs(): ReleaseResArgs {
        if (arguments.length < 1 || typeof arguments[0] != "string") {
            console.error(`_makeReleaseResArgs error ${arguments}`);
            return null;
        }
        let ret: ReleaseResArgs = { url: arguments[0] };
        for (let i = 1; i < arguments.length; ++i) {
            if (typeof arguments[i] == "string") {
                ret.use = arguments[i];
            } else {
                ret.type = arguments[i];
            }
        }
        return ret;
    }

    /**
     * 生成一個(gè)資源使用Key
     * @param where 在哪里使用，如Scene、UI、Pool
     * @param who 使用者，如Login、UIHelp...
     * @param why 使用原因，自定義...
     */
    public static makeUseKey(where: string, who: string = "none", why: string = ""): string {
        return `use_${where}_by_${who}_for_${why}`;
    }

    /**
     * 獲取資源緩存信息
     * @param key 要獲取的資源url
     */
    public getCacheInfo(key: string): CacheInfo {
        if (!this._resMap.has(key)) {
            this._resMap.set(key, {
                refs: new Set<string>(),
                uses: new Set<string>()
            });
        }
        return this._resMap.get(key);
    }

    /**
     * 開(kāi)始加載資源
     * @param url           資源url
     * @param type          資源類(lèi)型，默認(rèn)為null
     * @param onProgess     加載進(jìn)度回調(diào)
     * @param onCompleted   加載完成回調(diào)
     * @param use           資源使用key，根據(jù)makeUseKey方法生成
     */
    public loadRes(url: string, use?: string);
    public loadRes(url: string, onCompleted: CompletedCallback, use?: string);
    public loadRes(url: string, onProgess: ProcessCallback, onCompleted: CompletedCallback, use?: string);
    public loadRes(url: string, type: typeof cc.Asset, use?: string);
    public loadRes(url: string, type: typeof cc.Asset, onCompleted: CompletedCallback, use?: string);
    public loadRes(url: string, type: typeof cc.Asset, onProgess: ProcessCallback, onCompleted: CompletedCallback, use?: string);
    public loadRes() {
        let resArgs: LoadResArgs = this._makeLoadResArgs.apply(this, arguments);
        console.time("loadRes|"+resArgs.url);
        let finishCallback = (error: Error, resource: any) => {
            // 反向關(guān)聯(lián)引用（為所有引用到的資源打上本資源引用到的標(biāo)記）
            let addDependKey = (item, refKey) => {
                if (item && item.dependKeys && Array.isArray(item.dependKeys)) {
                    for (let depKey of item.dependKeys) {
                        // 記錄該資源被我引用
                        this.getCacheInfo(depKey).refs.add(refKey);
                        // cc.log(`${depKey} ref by ${refKey}`);
                        let ccloader: any = cc.loader;
                        let depItem = ccloader._cache[depKey]
                        addDependKey(depItem, refKey)
                    }
                }
            }

            let item = this._getResItem(resArgs.url, resArgs.type);
            if (item && item.url) {
                addDependKey(item, item.url);
            } else {
                cc.warn(`addDependKey item error1! for ${resArgs.url}`);
            }

            // 給自己加一個(gè)自身的引用
            if (item) {
                let info = this.getCacheInfo(item.url);
                info.refs.add(item.url);
                // 更新資源使用
                if (resArgs.use) {
                    info.uses.add(resArgs.use);
                }
            }

            // 執(zhí)行完成回調(diào)
            if (resArgs.onCompleted) {
                resArgs.onCompleted(error, resource);
            }
            console.timeEnd("loadRes|"+resArgs.url);
        };

        // 預(yù)判是否資源已加載
        let res = cc.loader.getRes(resArgs.url, resArgs.type);
        if (res) {
            finishCallback(null, res);
        } else {
            cc.loader.loadRes(resArgs.url, resArgs.type, resArgs.onProgess, finishCallback);
        }
    }

    /**
     * 釋放資源
     * @param url   要釋放的url
     * @param type  資源類(lèi)型
     * @param use   要解除的資源使用key，根據(jù)makeUseKey方法生成
     */
    public releaseRes(url: string, use?: string);
    public releaseRes(url: string, type: typeof cc.Asset, use?: string)
    public releaseRes() {
        /**暫時(shí)不釋放資源 */
        // return;

        let resArgs: ReleaseResArgs = this._makeReleaseResArgs.apply(this, arguments);
        let item = this._getResItem(resArgs.url, resArgs.type);
        if (!item) {
            console.warn(`releaseRes item is null ${resArgs.url} ${resArgs.type}`);
            return;
        }
        cc.log("resloader release item");
        // cc.log(arguments);
        let cacheInfo = this.getCacheInfo(item.url);
        if (resArgs.use) {
            cacheInfo.uses.delete(resArgs.use)
        }
        this._release(item, item.url);
    }

    // 釋放一個(gè)資源
    private _release(item, itemUrl) {
        if (!item) {
            return;
        }
        let cacheInfo = this.getCacheInfo(item.url);
        // 解除自身對(duì)自己的引用
        cacheInfo.refs.delete(itemUrl);

        if (cacheInfo.uses.size == 0 && cacheInfo.refs.size == 0) {
            // 解除引用
            let delDependKey = (item, refKey) => {
                if (item && item.dependKeys && Array.isArray(item.dependKeys)) {
                    for (let depKey of item.dependKeys) {
                        let ccloader: any = cc.loader;
                        let depItem = ccloader._cache[depKey]
                        this._release(depItem, refKey);
                    }
                }
            }
            delDependKey(item, itemUrl);
            //如果沒(méi)有uuid,就直接釋放url
            if (item.uuid) {
                cc.loader.release(item.uuid);
                cc.log("resloader release item by uuid :" + item.url);
            } else {
                cc.loader.release(item.url);
                cc.log("resloader release item by url:" + item.url);
            }
        }
    }

    /**
     * 判斷一個(gè)資源能否被釋放
     * @param url 資源url
     * @param type  資源類(lèi)型
     * @param use   要解除的資源使用key，根據(jù)makeUseKey方法生成
     */
    public checkReleaseUse(url: string, use?: string): boolean;
    public checkReleaseUse(url: string, type: typeof cc.Asset, use?: string): boolean
    public checkReleaseUse() {
        let resArgs: ReleaseResArgs = this._makeReleaseResArgs.apply(this, arguments);
        let item = this._getResItem(resArgs.url, resArgs.type);
        if (!item) {
            console.log(`cant release,item is null ${resArgs.url} ${resArgs.type}`);
            return true;
        }

        let cacheInfo = this.getCacheInfo(item.url);
        let checkUse = false;
        let checkRef = false;

        if (resArgs.use && cacheInfo.uses.size > 0) {
            if (cacheInfo.uses.size == 1 && cacheInfo.uses.has(resArgs.use)) {
                checkUse = true;
            } else {
                checkUse = false;
            }
        } else {
            checkUse = true;
        }

        if ((cacheInfo.refs.size == 1 && cacheInfo.refs.has(item.url)) || cacheInfo.refs.size == 0) {
            checkRef = true;
        } else {
            checkRef = false;
        }

        return checkUse && checkRef;
    }
}

@ccclass
export default class NetExample extends cc.Component {
    @property(cc.Node)
    attachNode: cc.Node = null;
    @property(cc.Label)
    dumpLabel: cc.Label = null;

    onLoadRes() {
        cc.loader.loadRes("Prefab/HelloWorld", cc.Prefab, (error: Error, prefab: cc.Prefab) => {
            if (!error) {
                cc.instantiate(prefab).parent = this.attachNode;
            }
        });
    }

    onUnloadRes() {
        this.attachNode.removeAllChildren(true);
        cc.loader.releaseRes("Prefab/HelloWorld");
    }

    onMyLoadRes() {
        ResLoader.getInstance().loadRes("Prefab/HelloWorld", cc.Prefab, (error: Error, prefab: cc.Prefab) => {
            if (!error) {
                cc.instantiate(prefab).parent = this.attachNode;
            }
        });
    }

    onMyUnloadRes() {
        this.attachNode.removeAllChildren(true);
        ResLoader.getInstance().releaseRes("Prefab/HelloWorld");
    }

    onDump() {
        let Loader:any = cc.loader;
        this.dumpLabel.string = `當(dāng)前資源總數(shù):${Object.keys(Loader._cache).length}`;
    }
}