lock.ts

export default class {
  processKeyList:string[];
  waitingList:{ key: string, resolve:(value:unknown) => any }[];
  maxProcessing:number;

  constructor(props:{maxProcessing: number} = {maxProcessing: 99999} ) {
    this.processKeyList = [];
    this.waitingList = [];
    this.maxProcessing = props.maxProcessing;
  }
  
  public lock = async(key: string) => {
    return new Promise((resolve) =>{
      if (this.processKeyList.includes(key) || this.processKeyList.length >= this.maxProcessing) {
        //  加入列隊，等候可以開始通知
        this.waitingList.push( { key: key, resolve: resolve } );
      } else {
        // 開始現時的工作
        this.processKeyList.push(key);
        resolve(true);
      }
    })
  }

  public unlock = (key: string) => {
    // 完成現在的工作
    let delIndex = this.processKeyList.indexOf(key);
    if (delIndex !== -1) {
      this.processKeyList.splice(delIndex, 1);
    }
    // 尋找下一個工作通知執行
    let startProcessingIndex = this.waitingList.findIndex((item) => {
      return !this.processKeyList.includes(item.key);
    });
    if (startProcessingIndex !== -1 && this.processKeyList.length < this.maxProcessing) {
      let startProcessing = this.waitingList[startProcessingIndex];
      this.waitingList.splice(startProcessingIndex, 1);

      this.processKeyList.push(startProcessing.key);
      startProcessing.resolve(true);
    }
  }
}