const EventEmitter = require('events');
const spawn = require('cross-spawn');

const tasks = {};
const taskEvents = new EventEmitter();

module.exports = {
  tasks,
  taskEvents,
  createTask,
  runTask,
  composeSeries,
  composeParallel,
  runInChildProcess,
};

const { setupTaskDisplay } = require('./display');

async function runTask(taskName, { skipStats } = {}) {
  if (!(taskName in tasks)) {
    throw new Error(`MetaMask build: Unrecognized task name "${taskName}"`);
  }
  if (!skipStats) {
    setupTaskDisplay(taskEvents);
    console.log(`Running task "${taskName}"...`);
  }
  try {
    await tasks[taskName]();
  } catch (err) {
    console.error(
      `MetaMask build: Encountered an error while running task "${taskName}".`,
    );
    console.error(err);
    process.exit(1);
  }
  taskEvents.emit('complete');
}

function createTask(taskName, taskFn) {
  if (taskName in tasks) {
    throw new Error(
      `MetaMask build: task "${taskName}" already exists. Refusing to redefine`,
    );
  }
  const task = instrumentForTaskStats(taskName, taskFn);
  task.taskName = taskName;
  tasks[taskName] = task;
  return task;
}

function runInChildProcess(
  task,
  { applyLavaMoat, buildType, isLavaMoat, policyOnly, shouldLintFenceFiles },
) {
  const taskName = typeof task === 'string' ? task : task.taskName;
  if (!taskName) {
    throw new Error(
      `MetaMask build: runInChildProcess unable to identify task name`,
    );
  }

  return instrumentForTaskStats(taskName, async () => {
    const childProcess = spawn(
      'yarn',
      [
        // Use the same build type for subprocesses, and only run them in
        // LavaMoat if the parent process also ran in LavaMoat.
        isLavaMoat ? 'build' : 'build:dev',
        taskName,
        `--apply-lavamoat=${applyLavaMoat ? 'true' : 'false'}`,
        `--build-type=${buildType}`,
        `--lint-fence-files=${shouldLintFenceFiles ? 'true' : 'false'}`,
        `--policyOnly=${policyOnly ? 'true' : 'false'}`,
        '--skip-stats=true',
      ],
      {
        env: process.env,
      },
    );

    // forward logs to main process
    // skip the first stdout event (announcing the process command)
    childProcess.stdout.once('data', () => {
      childProcess.stdout.on('data', (data) =>
        process.stdout.write(`${taskName}: ${data}`),
      );
    });

    childProcess.stderr.on('data', (data) =>
      process.stderr.write(`${taskName}: ${data}`),
    );

    // await end of process
    await new Promise((resolve, reject) => {
      childProcess.once('exit', (errCode) => {
        if (errCode !== 0) {
          reject(
            new Error(
              `MetaMask build: runInChildProcess for task "${taskName}" encountered an error "${errCode}".`,
            ),
          );
          return;
        }
        resolve();
      });
    });
  });
}

function instrumentForTaskStats(taskName, asyncFn) {
  return async () => {
    const start = Date.now();
    taskEvents.emit('start', [taskName, start]);
    await asyncFn();
    const end = Date.now();
    taskEvents.emit('end', [taskName, start, end]);
  };
}

function composeSeries(...subtasks) {
  return async () => {
    const realTasks = subtasks;
    for (const subtask of realTasks) {
      await subtask();
    }
  };
}

function composeParallel(...subtasks) {
  return async () => {
    const realTasks = subtasks;
    await Promise.all(realTasks.map((subtask) => subtask()));
  };
}