// forked from https://github.com/NapNeko/NapCatQQ/blob/6f6b258f22d7563f15d84e7172c4d4cbb547f47e/src/common/utils/MessageUnique.ts#L5
export class LimitedHashTable<K, V> {
  private keyToValue: Map<K, V> = new Map()
  private valueToKey: Map<V, K> = new Map()
  private maxSize: number

  constructor(maxSize: number) {
    this.maxSize = maxSize
  }

  resize(count: number) {
    this.maxSize = count
  }

  set(key: K, value: V): void {
    this.keyToValue.set(key, value)
    this.valueToKey.set(value, key)
    while (this.keyToValue.size !== this.valueToKey.size) {
      this.keyToValue.clear()
      this.valueToKey.clear()
    }
    while (this.keyToValue.size > this.maxSize || this.valueToKey.size > this.maxSize) {
      const oldestKey = this.keyToValue.keys().next().value!
      this.valueToKey.delete(this.keyToValue.get(oldestKey)!)
      this.keyToValue.delete(oldestKey)
    }
  }

  getValue(key: K): V | undefined {
    return this.keyToValue.get(key)
  }

  getKey(value: V): K | undefined {
    return this.valueToKey.get(value)
  }

  deleteByValue(value: V): void {
    const key = this.valueToKey.get(value)
    if (key !== undefined) {
      this.keyToValue.delete(key)
      this.valueToKey.delete(value)
    }
  }

  deleteByKey(key: K): void {
    const value = this.keyToValue.get(key)
    if (value !== undefined) {
      this.keyToValue.delete(key)
      this.valueToKey.delete(value)
    }
  }

  getKeyList(): K[] {
    return Array.from(this.keyToValue.keys())
  }

  //获取最近刚写入的几个值
  getHeads(size: number): { key: K, value: V }[] | undefined {
    const keyList = this.getKeyList()
    if (keyList.length === 0) {
      return undefined
    }
    const result: { key: K; value: V }[] = []
    const listSize = Math.min(size, keyList.length)
    for (let i = 0; i < listSize; i++) {
      const key = keyList[listSize - i]
      result.push({ key, value: this.keyToValue.get(key)! })
    }
    return result
  }
}