function concatenate()

in workbox-v4.3.1/workbox-streams.dev.js [55:136]
28 lines of code
1 McCabe index (conditional complexity)

  function concatenate(sourcePromises) {
    {
      assert_mjs.assert.isArray(sourcePromises, {
        moduleName: 'workbox-streams',
        funcName: 'concatenate',
        paramName: 'sourcePromises'
      });
    }

    const readerPromises = sourcePromises.map(sourcePromise => {
      return Promise.resolve(sourcePromise).then(source => {
        return _getReaderFromSource(source);
      });
    });
    let fullyStreamedResolve;
    let fullyStreamedReject;
    const done = new Promise((resolve, reject) => {
      fullyStreamedResolve = resolve;
      fullyStreamedReject = reject;
    });
    let i = 0;
    const logMessages = [];
    const stream = new ReadableStream({
      pull(controller) {
        return readerPromises[i].then(reader => reader.read()).then(result => {
          if (result.done) {
            {
              logMessages.push(['Reached the end of source:', sourcePromises[i]]);
            }

            i++;

            if (i >= readerPromises.length) {
              // Log all the messages in the group at once in a single group.
              {
                logger_mjs.logger.groupCollapsed(`Concatenating ${readerPromises.length} sources.`);

                for (const message of logMessages) {
                  if (Array.isArray(message)) {
                    logger_mjs.logger.log(...message);
                  } else {
                    logger_mjs.logger.log(message);
                  }
                }

                logger_mjs.logger.log('Finished reading all sources.');
                logger_mjs.logger.groupEnd();
              }

              controller.close();
              fullyStreamedResolve();
              return;
            }

            return this.pull(controller);
          } else {
            controller.enqueue(result.value);
          }
        }).catch(error => {
          {
            logger_mjs.logger.error('An error occurred:', error);
          }

          fullyStreamedReject(error);
          throw error;
        });
      },

      cancel() {
        {
          logger_mjs.logger.warn('The ReadableStream was cancelled.');
        }

        fullyStreamedResolve();
      }

    });
    return {
      done,
      stream
    };
  }