/** @format */

import {ComPoolIndex} from './Const'
import {ECSTypedComConstructor} from './ECSComponent'

/**
 * 组件池
 */
export class ECSComponentPool<T> {
    private _componentConstructor: ECSTypedComConstructor<T>

    public constructor(comCons: ECSTypedComConstructor<T>) {
        this._componentConstructor = comCons
    }

    private _components: T[] = [] // components
    private _reservedIdxs: ComPoolIndex[] = [] // 缓存的component idx

    public get(idx: ComPoolIndex): T {
        return this._components[idx]
    }

    public alloc(): ComPoolIndex {
        if (this._reservedIdxs.length > 0) {
            let ret = this._reservedIdxs.pop()
            this._componentConstructor.apply(this._components[ret]) // 重置对象
            return ret
        }
        let newInstance = new this._componentConstructor()
        this._components.push(newInstance)
        return this._components.length - 1
    }

    public free(idx: ComPoolIndex) {
        this._reservedIdxs.push(idx)
    }
}