import { Component, Node, Prefab, director, instantiate } from 'cc';
import IPoolable from './IPoolable';

export default class ObjectPool {
    private _inactives: Node[] = [];
    private _actives: Node[] = [];
    private _prefab: Prefab;
    private _expandable;
    private _poolHandlerComp: new () => any;

    public get countInactive() {
        return this._inactives.length;
    }

    public get countActive() {
        return this._actives.length;
    }

    public get countAll() {
        return this.countInactive + this.countActive;
    }

    constructor(prefab: Prefab, size: number, expandable = true, poolHandlerComp?: new () => any | string) {
        this._prefab = prefab;
        this._expandable = expandable;
        this._poolHandlerComp = poolHandlerComp;
        for (let i = 0; i < size; ++i) {
            let obj = instantiate(this._prefab); // create node instance
            obj.removeFromParent();
            this._inactives.push(obj);
            ObjectPool._poolLookUp[obj.uuid] = this;
        }
    }

    //#region Static
    private static _poolLookUp: { [key: string]: ObjectPool } = {};
    public static release(obj: Node) {
        ObjectPool._poolLookUp[obj.uuid].release(obj);
    }
    //#endregion

    public get(parent?: Node): Node;
    public get<T extends Component>(parent?: Node, classConstructor?: new () => T): T;
    public get<T extends Component>(parent?: Node, classConstructor?: new () => T): T | Node {
        let obj: Node = null;
        let p = parent || director.getScene();
        if (this._inactives.length > 0) {
            // Pop the last object in pool
            obj = this._inactives.pop();
        } else if (this._expandable) {
            // if not enough node in the pool, we call cc.instantiate to create node
            obj = instantiate(this._prefab);
            ObjectPool._poolLookUp[obj.uuid] = this;
        } else {
            obj = this._actives.shift();
        }

        obj.setParent(p);
        this._actives.push(obj);
        // Invoke pool handler
        const handler = this._poolHandlerComp ? obj.getComponent(this._poolHandlerComp) : null;
        if (handler) {
            (handler as unknown as IPoolable)?.onGet();
        }

        if (classConstructor) {
            return handler == classConstructor ? handler : obj.getComponent(classConstructor);
        }
        return obj;
    }

    public release(obj: Node): void;
    public release<T extends Component>(obj: T): void;
    public release<T extends Component>(obj: T | Node): void {
        let node = obj instanceof Node ? obj : obj.node;
        const index = this._actives.indexOf(node);
        //check obj is belongs to pool
        if (index === -1) return;
        this._actives.splice(index, 1);
        this._inactives.push(node);
        // Invoke pool handler

        const handler = this._poolHandlerComp ? node.getComponent(this._poolHandlerComp) : null;
        if (handler) {
            (handler as unknown as IPoolable)?.onRelease();
        }
        // Remove from parent, but don't cleanup
        node.removeFromParent();
    }

    public clear() {
        this._inactives.forEach((obj) => obj.destroy());
        this._inactives = [];
        this._actives = [];
        Object.keys(ObjectPool._poolLookUp).forEach((key) => {
            if (ObjectPool._poolLookUp[key] === this) {
                delete ObjectPool._poolLookUp[key];
            }
        });
    }
}