#!/usr/bin/env python
# Copyright 2014 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import argparse
import os.path
import requests
import sys

_MOJO_DEBUGGER_PORT = 7777


def _send_request(request):
  """Sends a request to mojo:debugger."""
  url = 'http://localhost:%s/%s' % (_MOJO_DEBUGGER_PORT, request)
  return requests.get(url)


def _tracing_start(_):
  """Starts tracing."""
  _send_request('start_tracing')
  print "Started tracing."


def _tracing_stop(args):
  """Stops tracing and writes trace to file."""
  if args.file_name:
    file_name = args.file_name
  else:
    for i in xrange(1000):
      candidate_file_name = 'mojo_trace_%03d.json' % i
      if not os.path.exists(candidate_file_name):
        file_name = candidate_file_name
        break
    else:
      print 'Failed to pick a name for the trace output file.'
      return 1

  trace = _send_request('stop_tracing').content
  with open(file_name, "wb") as trace_file:
    trace_file.write('{"traceEvents":[')
    trace_file.write(trace)
    trace_file.write(']}')
  print "Trace saved in %s" % file_name


def _add_tracing_command(subparsers):
  """Sets up the command line parser to manage tracing."""
  tracing_parser = subparsers.add_parser('tracing',
      help='trace event profiler')
  tracing_subparser = tracing_parser.add_subparsers(
      help='the command to run')

  start_tracing_parser = tracing_subparser.add_parser('start',
      help='start tracing')
  start_tracing_parser.set_defaults(func=_tracing_start)

  stop_tracing_parser = tracing_subparser.add_parser('stop',
      help='stop tracing and retrieve the result')
  stop_tracing_parser.add_argument('file_name', type=str, nargs='?',
      help='name of the output file (optional)')
  stop_tracing_parser.set_defaults(func=_tracing_stop)


def main():
  parser = argparse.ArgumentParser(description='Command-line interface for '
                                                'mojo:debugger')
  subparsers = parser.add_subparsers(help='the tool to run')
  _add_tracing_command(subparsers)

  args = parser.parse_args()
  args.func(args)
  return 0

if __name__ == '__main__':
  sys.exit(main())