# Copyright 2009 the Melange authors.

#

# Licensed under the Apache License, Version 2.0 (the "License");

# you may not use this file except in compliance with the License.

# You may obtain a copy of the License at

#

#   http://www.apache.org/licenses/LICENSE-2.0

#

# Unless required by applicable law or agreed to in writing, software

# distributed under the License is distributed on an "AS IS" BASIS,

# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

# See the License for the specific language governing permissions and

# limitations under the License.

"""Various utilities.

Current contents:

 - Text colorization using ANSI color codes

 - A class to construct and manage paths under a root path.

 - A helper to manage running subprocesses, wrapping the subprocess module.

"""

__authors__ = [

    # alphabetical order by last name, please

    '"David Anderson" <dave@natulte.net>',

    ]

import os.path

import re

try:

  import cStringIO as StringIO

except ImportError:

  import StringIO

import subprocess

import threading

import error

import log

class Error(error.Error):

  pass

class SubprocessFailed(Error):

  """A subprocess returned a non-zero error code."""

  pass

# The magic escape sequence understood by modern terminal emulators to

# configure fore/background colors and other basic text display

# settings.

_ANSI_ESCAPE = '\x1b[%dm'

_ANSI_ESCAPE_RE = re.compile(r'\x1b\[\d+m')

# Some internal non-color settings that we use.

_RESET = 0  # Reset to terminal defaults.

_BOLD = 1   # Brighter colors.

# ANSI color codes.

RED = 31

GREEN = 32

WHITE = 37

def _ansi_escape(code):

  return _ANSI_ESCAPE % code

def colorize(text, color, bold=False):

  """Colorize some text using ANSI color codes.

  Note that while ANSI color codes look good in a terminal they look

  like noise in log files unless viewed in an ANSI color capable

  viewer (such as 'less -R').

  Args:

    text: The text to colorize.

    color: One of the color symbols from this module.

    bold: If True, make the color brighter.

  Returns:

    The input text string, appropriately sprinkled with color

    codes. Colors are reset to terminal defaults after the input

    text.

  """

  bold = _ansi_escape(_BOLD) if bold else ''

  return '%s%s%s%s' % (bold, _ansi_escape(color),

                       text, _ansi_escape(_RESET))

def decolorize(text):

  """Remove ANSI color codes from text."""

  return _ANSI_ESCAPE_RE.sub('', text)

class Paths(object):

  """A helper to construct and check paths under a given root."""

  def __init__(self, root):

    """Initializer.

    Args:

      root: The root of all paths this instance will consider.

    """

    self._root = os.path.abspath(

      os.path.expandvars(os.path.expanduser(root)))

  def path(self, path=''):

    """Construct and return a path under the path root.

    Args:

      path: The desired path string relative to the root.

    Returns:

      The absolute path corresponding to the relative input path.

    """

    assert not os.path.isabs(path)

    return os.path.abspath(os.path.join(self._root, path))

  def exists(self, path=''):

    """Check for the existence of a path under the path root.

    Does not discriminate on the path type (ie. it could be a

    directory, a file, a symbolic link...), just checks for the

    existence of the path.

    Args:

      path: The path string relative to the root.

    Returns:

      True if the path exists, False otherwise.

    """

    return os.path.exists(self.path(path))

class _PipeAdapter(threading.Thread):

  """A thread that connects one file-like object to another"""

  def __init__(self, pipe, logfile):

    threading.Thread.__init__(self)

    self.pipe, self.logfile = pipe, logfile

    self.setDaemon(True)

    self.start()

  def run(self):

    try:

      while True:

        data = self.pipe.read(512)  # Small to retain interactivity

        if not data:

          return

        self.logfile.write(data)

    except (EOFError, OSError):

      pass

def run(argv, cwd=None, capture=False, split_capture=True, stdin=None):

  """Run the given command and optionally return its output.

  Note that if you set capture=True, the command's output is

  buffered in memory. Output capture should only be used with

  commands that output small amounts of data. O(kB) is fine, O(MB)

  is starting to push it a little.

  Args:

    argv: A list containing the name of the program to run, followed

      by its argument vector.

    cwd: Run the program from this directory.

    capture: If True, capture the program's stdout stream. If False,

      stdout will output to sys.stdout.

    split_capture: If True, return the captured output as a list of

      lines. Else, return as a single unaltered string.

    stdin: The string to feed to the program's stdin stream.

  Returns:

    If capture is True, a string containing the combined

    stdout/stderr output of the program. If capture is False,

    nothing is returned.

  Raises:

    SubprocessFailed: The subprocess exited with a non-zero exit code.

  """

  log.debug(colorize('# ' + ' '.join(argv), WHITE, bold=True))

  process = subprocess.Popen(argv,

                             shell=False,

                             cwd=cwd,

                             stdin=(subprocess.PIPE if stdin else None),

                             stdout=subprocess.PIPE,

                             stderr=subprocess.PIPE)

  # Spin up threads to capture stdout and stderr. Depending on the

  # value of the capture parameter, stdout is pushed either into the

  # log or into a string for processing. stderr always goes

  # into the log.

  #

  # Threads are necessary because all of writing to stdin, reading

  # from stdout and reading from stderr must all happen

  # simultaneously. Otherwise, there is a risk that one of the pipes

  # will fill up, causing the subprocess and us to deadlock. So,

  # threads are used to keep the pipes safely flowing.

  stdout = StringIO.StringIO() if capture else log.FileLikeLogger()

  out_adapter = _PipeAdapter(process.stdout, stdout)

  err_adapter = _PipeAdapter(process.stderr, log.FileLikeLogger())

  if stdin:

    process.stdin.write(stdin)

  out_adapter.join()

  err_adapter.join()

  process.wait()

  if process.returncode != 0:

    if capture:

      raise SubprocessFailed('Process %s failed with output: %s' %

                             (argv[0], stdout.getvalue()))

    else:

      raise SubprocessFailed('Process %s failed' % argv[0])

  if capture:

    out = stdout.getvalue()

    stdout.close()

    if split_capture:

      out = out.strip().split('\n')

    return out