#!/usr/bin/python -tt

# (c) 2012, Luis Alberto Perez Lazaro <luisperlazaro@gmail.com>
#
# This module is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This software is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this software.  If not, see <http://www.gnu.org/licenses/>.
#

DOCUMENTATION = '''
---
module: patch
author: Luis Alberto Perez Lazaro
version_added: 0.9
short_description: apply patch files 
description:
    - Apply patch files using the GNU patch tool. Before using this module make sure the patch tool is installed.
options:
    patchfile:
        required: true
        description:
            - A patch file as accepted by the gnu patch tool
    strip:
        required: true
        aliases: [ p ]
        description:
            - Number that indicates the smallest prefix containing leading slashes that 
          will be stripped from each file name found in the patch file. For more information
          see the strip parameter of the gnu patch tool.
    basedir:
        required: true
        description:
            - base directory in which the patch file will be applied
examples:
    - code: "patch: patchfile=/tmp/critical.patch strip=1 basedir=/usr/share/pyshared/paramiko"
      description: Example git checkout from Ansible Playbooks
'''

def _run(args):
    cmd = subprocess.Popen(args, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = cmd.communicate()
    rc = cmd.returncode
    return (rc, out, err)

def _is_already_applied(patch_file, strip):
    reverse_cmd = "patch -s -R -N -p%s --dry-run < %s" % (strip, patch_file)
    (rc, _, _) = _run(reverse_cmd)
    return rc == 0

def _apply_patch(module, patch_file, strip):
    patch_cmd = "patch -s -N -t -r - -p%s < %s" % (strip, patch_file)
    (rc, out, err) = _run(patch_cmd)
    if rc != 0:
        msg = out if not err else err
        module.fail_json(msg=msg)

def _get_params(module):
    patchfile = os.path.expanduser(module.params['patchfile'])
    strip = module.params['strip']
    basedir = module.params['basedir']

    if basedir:
        os.chdir(os.path.expanduser(basedir))

    if not os.path.exists(patchfile):
        module.fail_json(msg="patchfile %s doesn't exist" % (patchfile))
    if not os.access(patchfile, os.R_OK):
        module.fail_json(msg="patchfile %s not readable" % (patchfile))

    if not os.path.exists(basedir):
        module.fail_json(msg="basedir %s doesn't exist" % (patchfile))

    try:
        strip = int(strip)
    except Exception:
        module.fail_json(msg="p must be a number")

    return patchfile, strip, basedir

# ===========================================

def main():
    module = AnsibleModule(
        argument_spec = dict(
            patchfile=dict(required=True),
            basedir=dict(),
            strip=dict(default=0, aliases=['p'])	
        ),
    )
    patchfile, strip, basedir = _get_params(module)

    changed = False

    if not _is_already_applied(patchfile, strip):
        _apply_patch(module, patchfile, strip)
        changed = True

    module.exit_json(changed=changed)

# include magic from lib/ansible/module_common.py
#<<INCLUDE_ANSIBLE_MODULE_COMMON>>
main()