# Copyright 2013 The Chromium Authors
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

"""Generic utilities for all python scripts."""

import atexit
try:
  from http.client import HTTPConnection
except ImportError:
  from httplib import HTTPConnection

import os
import signal
import stat
import subprocess
import sys
import tempfile
try:
  from urllib.parse import urlparse
except ImportError:
  from urlparse import urlparse


def GetPlatformName():
  """Return a string to be used in paths for the platform."""
  if IsWindows():
    return 'win'
  if IsMac():
    return 'mac'
  if IsLinux():
    return 'linux'
  raise NotImplementedError('Unknown platform "%s".' % sys.platform)


def IsWindows():
  return sys.platform == 'cygwin' or sys.platform.startswith('win')


def IsLinux():
  return sys.platform.startswith('linux')


def IsMac():
  return sys.platform.startswith('darwin')


def _DeleteDir(path):
  """Deletes a directory recursively, which must exist."""
  # Don't use shutil.rmtree because it can't delete read-only files on Win.
  for root, dirs, files in os.walk(path, topdown=False):
    for name in files:
      filename = os.path.join(root, name)
      os.chmod(filename, stat.S_IWRITE)
      os.remove(filename)
    for name in dirs:
      os.rmdir(os.path.join(root, name))
  os.rmdir(path)


def Delete(path):
  """Deletes the given file or directory (recursively), which must exist."""
  if os.path.isdir(path):
    _DeleteDir(path)
  else:
    os.remove(path)


def MaybeDelete(path):
  """Deletes the given file or directory (recurisvely), if it exists."""
  if os.path.exists(path):
    Delete(path)


def MakeTempDir(parent_dir=None):
  """Creates a temporary directory and returns an absolute path to it.

  The temporary directory is automatically deleted when the python interpreter
  exits normally.

  Args:
    parent_dir: the directory to create the temp dir in. If None, the system
                temp dir is used.

  Returns:
    The absolute path to the temporary directory.
  """
  path = tempfile.mkdtemp(dir=parent_dir)
  atexit.register(MaybeDelete, path)
  return path


def Unzip(zip_path, output_dir):
  """Unzips the given zip file using a system installed unzip tool.

  Args:
    zip_path: zip file to unzip.
    output_dir: directory to unzip the contents of the zip file. The directory
                must exist.

  Raises:
    RuntimeError if the unzip operation fails.
  """
  if IsWindows():
    unzip_cmd = ['C:\\Program Files\\7-Zip\\7z.exe', 'x', '-y']
  else:
    unzip_cmd = ['unzip', '-o']
  unzip_cmd += [zip_path]
  if RunCommand(unzip_cmd, output_dir) != 0:
    raise RuntimeError('Unable to unzip %s to %s' % (zip_path, output_dir))


def Kill(pid):
  """Terminate the given pid."""
  if IsWindows():
    subprocess.call(['taskkill.exe', '/T', '/F', '/PID', str(pid)])
  else:
    os.kill(pid, signal.SIGTERM)


def RunCommand(cmd, cwd=None):
  """Runs the given command and returns the exit code.

  Args:
    cmd: list of command arguments.
    cwd: working directory to execute the command, or None if the current
         working directory should be used.

  Returns:
    The exit code of the command.
  """
  process = subprocess.Popen(cmd, cwd=cwd)
  process.wait()
  return process.returncode


def DoesUrlExist(url):
  """Determines whether a resource exists at the given URL.

  Args:
    url: URL to be verified.

  Returns:
    True if url exists, otherwise False.
  """
  parsed = urlparse(url)
  try:
    conn = HTTPConnection(parsed.netloc)
    conn.request('HEAD', parsed.path)
    response = conn.getresponse()
  except (socket.gaierror, socket.error):
    return False
  finally:
    conn.close()
  # Follow both permanent (301) and temporary (302) redirects.
  if response.status == 302 or response.status == 301:
    return DoesUrlExist(response.getheader('location'))
  return response.status == 200