CocosCreator general framework design resource management

/**
 * Resource loading class* 1. Automatically record the reference relationship after loading is completed, and record the reverse dependency according to DependKeys* 2. Support resource usage. For example, if a certain opened UI uses resource A, and resource B is released elsewhere, resource B references resource A. If there is no other resource that references resource A, the release of resource A will be triggered.
 * 3. Ability to safely release dependent resources (a resource is referenced by multiple resources at the same time, and the resource will be released only when all other resources are released)
 * 
 * 2018-7-17 by Bao Ye*/

// Resource loading processing callback export type ProcessCallback = (completedCount: number, totalCount: number, item: any) => void;
// Resource loading completion callback export type CompletedCallback = (error: Error, resource: any) => void;

// Reference and use structure interface CacheInfo {
    refs: Set<string>,
    uses: Set<string>
}

// LoadRes method parameter structure interface LoadResArgs {
    url: string,
    type?: typeof cc.Asset,
    onCompleted?: CompletedCallback,
    onProgess?: ProcessCallback,
    use?: string,
}

// ReleaseRes method parameter structure interface ReleaseResArgs {
    url: string,
    type?: typeof cc.Asset,
    use?: string,
}

// Compatibility processing 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() {

    }

    /**
     * Get a resource item from cc.loader
     * @param url query url
     * @param type The resource type to query*/
    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;
    }

    /**
     * Parameter preprocessing of loadRes method */
    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)) {
                // Determine whether it is the first parameter type
                ret.type = arguments[i];
            } else if (i == arguments.length - 1 && typeof arguments[i] == "string") {
                // Determine whether it is the last parameter use
                ret.use = arguments[i];
            } else if (typeof arguments[i] == "function") {
                // Otherwise it's a function if (arguments.length > i + 1 && typeof arguments[i + 1] == "function") {
                    ret.onProgess = arguments[i];
                } else {
                    ret.onCompleted = arguments[i];
                }
            }
        }
        return ret;
    }

    /**
     * Parameter preprocessing of releaseRes method */
    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;
    }

    /**
     * Generate a resource using Key
     * @param where where to use, such as Scene, UI, Pool
     * @param who user, such as Login, UIHelp...
     * @param why Reason for use, custom...
     */
    public static makeUseKey(where: string, who: string = "none", why: string = ""): string {
        return `use_${where}_by_${who}_for_${why}`;
    }

    /**
     * Get resource cache information * @param key The resource url to be obtained
     */
    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);
    }

    /**
     * Start loading resources * @param url resource url
     * @param type resource type, default is null
     * @param onProgess loading progress callback* @param onCompleted loading completion callback* @param use resource usage key, generated according to the makeUseKey method*/
    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) => {
            // Reverse association reference (mark all referenced resources with the mark that this resource references them)
            let addDependKey = (item, refKey) => {
                if (item && item.dependKeys && Array.isArray(item.dependKeys)) {
                    for (let depKey of item.dependKeys) {
                        //Record that the resource is referenced by me 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}`);
            }

            // Add a reference to itself if (item) {
                let info = this.getCacheInfo(item.url);
                info.refs.add(item.url);
                // Update resource usage if (resArgs.use) {
                    info.uses.add(resArgs.use);
                }
            }

            // Execution completion callback if (resArgs.onCompleted) {
                resArgs.onCompleted(error, resource);
            }
            console.timeEnd("loadRes|"+resArgs.url);
        };

        // Predict whether the resource has been loaded 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);
        }
    }

    /**
     * Release resources * @param url The url to be released
     * @param type resource type* @param use resource usage key to be released, generated according to the makeUseKey method*/
    public releaseRes(url: string, use?: string);
    public releaseRes(url: string, type: typeof cc.Asset, use?: string)
    public releaseRes() {
        /**Do not release resources temporarily*/
        // 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);
    }

    // Release a resource private _release(item, itemUrl) {
        if (!item) {
            return;
        }
        let cacheInfo = this.getCacheInfo(item.url);
        // Remove the reference to itself cacheInfo.refs.delete(itemUrl);

        if (cacheInfo.uses.size == 0 && cacheInfo.refs.size == 0) {
            // Dereference 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);
            //If there is no uuid, release the url directly
            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);
            }
        }
    }

    /**
     * Determine whether a resource can be released * @param url resource url
     * @param type resource type* @param use resource usage key to be released, generated according to the makeUseKey method*/
    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 = `Current total number of resources: ${Object.keys(Loader._cache).length}`;
    }
}