'use strict';

import * as CDP from 'chrome-remote-interface';
import Protocol from 'devtools-protocol';

import { CompletionTrigger } from './CompletionTrigger';

/**
 * Waits for a variable to be true.
 *
 * @export
 * @class Variable
 * @extends {CompletionTrigger}
 */
export class Variable extends CompletionTrigger {

  /**
   * Creates an instance of the Variable CompletionTrigger.
   * @param {string} [variableName] the variable to listen on.
   *  Defaults to htmlPdfDone.
   * @param {number} [timeout] ms to wait until timing out.
   * @memberof Variable
   */
  constructor(protected variableName?: string, timeout?: number) {
    super(timeout);
  }

  public async wait(client: CDP.Client): Promise<Protocol.Runtime.EvaluateResponse> {
    const {Runtime} = client;
    const varName = this.variableName || 'htmlPdfDone';
    return Runtime.evaluate({
      awaitPromise: true,
      expression: `
        new Promise((resolve, reject) => {
          // check if already set
          if (window['${varName}'] === true) {
            resolve();
            return;
          }
          Object.defineProperty(window, '${varName}', {
            set: (val) => { if (val === true) resolve(); }
          });
          setTimeout(() => reject('${this.timeoutMessage}'), ${this.timeout});
        })`,
    });
  }

}