/**
 * 可限制尺寸的键值对缓存
 *
 */
export class LimitKeyValueCache<K = any, V = any> {
    options: { limit: number; popSize: number }

    /**
     *  @param options.limit {number} 限制尺寸
     *  @param options.popSize {number} 当超过尺寸时，删除多少元素，默认为 1
     */
    constructor(options: { limit: number; popSize?: number }) {
        this.options = Object.assign({ limit: 921024, popSize: 1 }, options)
    }
    caches = new Map<K, V>()
    keySet = new Set<K>()
    _size = 0

    set(key: K, value: V) {
        if (this.keySet.size >= this.options.limit) {
            this._pop(this.options.popSize)
        }

        this.keySet.add(key)
        if (this.caches) return this.caches.set(key, value)
    }
    get(key: K) {
        return this.caches.get(key)
    }
    has(key: K) {
        return this.caches.has(key)
    }
    delete(key: K) {
        this.keySet.delete(key)

        return this.caches.delete(key)
    }

    _pop(popSize: number) {
        let count = 0
        for (let item of this.keySet) {
            if (count < popSize) {
                this.keySet.delete(item)
                this.caches.delete(item)
                count++
            } else {
                break
            }
        }
    }

    get size() {
        return this.keySet.size
    }
}