#!/usr/bin/env python
#
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#  to you 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
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'''The sources module of Mouse.

This module has one public function, get_items(), which returns a generator
for use in Mouse.  It can automatically determine the source type if one is
not specified.  Sources are checked in the order specified by _source_list.

If you want to add another source, simply implement a generator and validator
function pair, and add them to _source_list.'''


import os
import tarfile
import zipfile

import cStringIO as StringIO


class _UnknownArchiveError(Exception):
  '''An exception to communicate we've discovered a type of archive we can't
  handle.'''

  def __init__(self, target):
    self.target = target

  def __str__(self):
    return "Unable to read archive '%s'" % self.target


class Item(object):
  '''An item which needs to be matched.'''

  def __init__(self, name, file):
    '''NAME is a label for the object.  FILE is a file-like object from which
       the file contents will be grabbed.  It does not need to be seekable,
       and its file pointer may not be preserved.'''
    self.name = name
    self.file = file
    self._content = None

  def get_content(self):
    '''Return the contents of this item.'''
    if not self._content:
      self._content = self.file.read()
    return StringIO.StringIO(self._content)


def _get_dir_gen(target):
  '''Return a generator for Items in the filesystem directory given by TARGET'''
  def dir_gen_func():
    for (dirpath, dirnames, filenames) in os.walk(target):
      # ignore .svn directories, if in a working copy
      if '.svn' in dirnames:
        dirnames.remove('.svn')

      for filename in filenames:
        name = os.path.join(dirpath, filename)
        yield Item(name, open(name))

  return dir_gen_func


def _get_tar_gen(target):
  '''Return a generator for Items in the tarfile (potentially bzip'd or gzip'd)
     given by TARGET'''
  tar = tarfile.open(target, 'r')

  def tar_gen_func():
    for info in tar.getmembers():
      if info.isdir():
        continue
      yield Item(info.name, tar.extractfile(info))

  return tar_gen_func


def _get_zip_gen(target):
  '''Return a generator for Items in the zipfile given by TARGET'''
  zip = zipfile.ZipFile(target, 'r')

  def zip_gen_func():
    for info in zip.infolist():
      if info.filename[-1] == '/':
        continue
      yield Item(info.filename, zip.open(info))

  return zip_gen_func


_source_list = [
    ("dir", os.path.isdir,      _get_dir_gen),
    ("tar", tarfile.is_tarfile, _get_tar_gen),
    ("zip", zipfile.is_zipfile, _get_zip_gen),
  ]


def get_items(target):
  '''Using TARGET as the source, return a generator or iterable suitable for
  use as input to generate_report().'''

  for name, check_func, get_gen_func in _source_list:
    if not check_func(target):
      continue
    return get_gen_func(target)

  # if we get to this point, we've no idea what the user gave us, so throw
  # an appropriate exception
  raise _UnknownArchiveError(target)