/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 * @format
 * @oncall react_native
 */

import type {BundleOptions} from 'metro/private/shared/types';

import EventEmitter from 'events';
import os from 'os';

// eslint-disable-next-line import/no-commonjs
const VERSION = require('../package.json').version;

export type ActionLogEntryData = {
  action_name: string,
  log_entry_label?: string,
  ...
};

export type ActionStartLogEntry = {
  action_name?: string,
  action_phase?: string,
  log_entry_label: string,
  log_session?: string,
  start_timestamp?: [number, number],
  ...
};

export type LogEntry = {
  action_name?: string,
  action_phase?: string,
  action_result?: string,
  duration_ms?: number,
  entry_point?: string,
  file_name?: string,
  log_entry_label: string,
  log_session?: string,
  start_timestamp?: [number, number],
  outdated_modules?: number,
  bundle_size?: number,
  bundle_options?: BundleOptions,
  bundle_hash?: string,
  build_id?: string,
  error_message?: string,
  error_stack?: string,
  ...
};

const log_session = `${os.hostname()}-${Date.now()}`;
const eventEmitter = new EventEmitter();

function on(event: string, handler: (logEntry: LogEntry) => void): void {
  eventEmitter.on(event, handler);
}

function createEntry(data: LogEntry | string): LogEntry {
  const logEntry: LogEntry =
    typeof data === 'string' ? {log_entry_label: data} : data;

  return {
    ...logEntry,
    log_session,
    metro_bundler_version: VERSION,
  };
}

function createActionStartEntry(data: ActionLogEntryData | string): LogEntry {
  const logEntry = typeof data === 'string' ? {action_name: data} : data;
  const {action_name} = logEntry;

  return createEntry({
    log_entry_label: action_name,
    ...logEntry,
    action_name,
    action_phase: 'start',
    start_timestamp: process.hrtime(),
  });
}

function createActionEndEntry(
  logEntry: ActionStartLogEntry,
  error?: ?Error,
): LogEntry {
  const {action_name, action_phase, start_timestamp} = logEntry;

  if (action_phase !== 'start' || !Array.isArray(start_timestamp)) {
    throw new Error('Action has not started or has already ended');
  }

  const timeDelta = process.hrtime(start_timestamp);
  const duration_ms = Math.round((timeDelta[0] * 1e9 + timeDelta[1]) / 1e6);

  return createEntry({
    log_entry_label: action_name as ?string,
    ...logEntry,
    action_name,
    action_phase: 'end',
    duration_ms,
    ...(error != null
      ? {error_message: error.message, error_stack: error.stack}
      : null),
  });
}

function log(logEntry: LogEntry): LogEntry {
  eventEmitter.emit('log', logEntry);
  return logEntry;
}

export {on, createEntry, createActionStartEntry, createActionEndEntry, log};