import * as plugins from './lik.plugins.js';

interface IExecutionSlot<T> {
  executionDeferred: plugins.smartpromise.Deferred<T>;
  funcToExecute: () => Promise<T>;
  timeout?: number;
  mode: 'exclusive' | 'nonexclusive';
}

/**
 * allows for avoiding race condition
 */
export class AsyncExecutionStack {
  private executionSlots: IExecutionSlot<any>[] = [];
  public async getExclusiveExecutionSlot<T = any>(funcArg: () => Promise<T>, timeoutArg?: number) {
    const executionDeferred = plugins.smartpromise.defer<T>();
    const executionSlot: IExecutionSlot<T> = {
      funcToExecute: funcArg,
      executionDeferred,
      timeout: timeoutArg,
      mode: 'exclusive',
    };
    this.executionSlots.push(executionSlot);
    this.processExecutionSlots();
    return executionDeferred.promise;
  }
  public async getNonExclusiveExecutionSlot<T = any>(
    funcArg: () => Promise<T>,
    timeoutArg?: number
  ) {
    const executionDeferred = plugins.smartpromise.defer<T>();
    const executionSlot: IExecutionSlot<T> = {
      funcToExecute: funcArg,
      executionDeferred,
      timeout: timeoutArg,
      mode: 'nonexclusive',
    };
    this.executionSlots.push(executionSlot);
    this.processExecutionSlots();
    return executionDeferred.promise;
  }

  private currentlyExecutingDeferred: plugins.smartpromise.Deferred<any>;
  private async processExecutionSlots() {
    if (this.currentlyExecutingDeferred) {
      return;
    }
    this.currentlyExecutingDeferred = plugins.smartpromise.defer();
    let nonExclusiveRunningSlots: IExecutionSlot<any>[] = [];
    const checkNonExclusiveRunningSlots = async (cleanArg = false) => {
      if (nonExclusiveRunningSlots.length > 100 || cleanArg) {
        await Promise.all(nonExclusiveRunningSlots.map(nonExclusiveRunningSlotArg => nonExclusiveRunningSlotArg.executionDeferred.promise));
        nonExclusiveRunningSlots = [];
      }
    };
    while (this.executionSlots.length > 0) {
      const nextExecutionSlot = this.executionSlots.shift();
      const runNextExecution = async () => {
        if (nextExecutionSlot.timeout) {
          const result = await Promise.race([
            nextExecutionSlot.funcToExecute(),
            plugins.smartdelay.delayFor(nextExecutionSlot.timeout),
          ]);
          nextExecutionSlot.executionDeferred.resolve(result);
        } else {
          nextExecutionSlot.executionDeferred.resolve(await nextExecutionSlot.funcToExecute());
        }
      };
      if (nextExecutionSlot.mode === 'exclusive') {
        await checkNonExclusiveRunningSlots(true);
        await runNextExecution();
      } else {
        nonExclusiveRunningSlots.push(nextExecutionSlot);
        await checkNonExclusiveRunningSlots(false);
        runNextExecution();
      }
    }
    this.currentlyExecutingDeferred.resolve();
    this.currentlyExecutingDeferred = null;
    
  }
}