#!/usr/bin/python

# (c) 2012, Michael DeHaan <michael.dehaan@gmail.com>
#
# This file is part of Ansible
#
# Ansible 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.
#
# Ansible 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 Ansible.  If not, see <http://www.gnu.org/licenses/>.

# I wanted to keep this simple at first, so for now this checks out
# from the given branch of a repo at a particular SHA or
# tag.  Latest is not supported, you should not be doing
# that. Contribs welcome! -- MPD

try:
    import json
except ImportError:
    import simplejson as json
import os
import re
import sys
import shlex
import subprocess
import syslog

# ===========================================
# Basic support methods

def exit_json(rc=0, **kwargs):
   print json.dumps(kwargs)
   sys.exit(rc)

def fail_json(**kwargs):
   kwargs['failed'] = True
   exit_json(rc=1, **kwargs)

# ===========================================
# convert arguments of form a=b c=d
# to a dictionary
# FIXME: make more idiomatic

if len(sys.argv) == 1:
   fail_json(msg="the command module requires arguments (-a)")

argfile = sys.argv[1]
if not os.path.exists(argfile):
   fail_json(msg="Argument file not found")

args = open(argfile, 'r').read()
items = shlex.split(args)
syslog.openlog('ansible-%s' % os.path.basename(__file__))
syslog.syslog(syslog.LOG_NOTICE, 'Invoked with %s' % args)

if not len(items):
   fail_json(msg="the command module requires arguments (-a)")

params = {}
for x in items:
    (k, v) = x.split("=")
    params[k] = v

dest = params['dest']
repo = params['repo']
branch  = params.get('branch')
version = params.get('version', 'HEAD')

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

def get_version(dest):
   ''' samples the version of the git repo '''
   os.chdir(dest)
   cmd = "git show --abbrev-commit"
   sha = os.popen(cmd).read().split("\n")
   sha = sha[0].split()[1]
   return sha

def clone(repo, dest, branch):
   ''' makes a new git repo if it does not already exist '''
   try:
       os.makedirs(dest)
   except:
       pass
   cmd = "git clone %s %s" % (repo, dest)
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   (out, err) = cmd.communicate()
   rc = cmd.returncode
   
   if branch is None or rc != 0: 
     return (out, err)

   os.chdir(dest)
   cmd = "git checkout -b %s origin/%s" % (branch, branch) 
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   return cmd.communicate()

def reset(dest):
   '''
   Resets the index and working tree to HEAD.
   Discards any changes to tracked files in working
   tree since that commit.
   '''
   os.chdir(dest)
   cmd = "git reset --hard HEAD"
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   (out, err) = cmd.communicate()
   rc = cmd.returncode
   return (rc, out, err)

def switchLocalBranch( branch ):
   cmd = "git checkout %s" % branch
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   return cmd.communicate()

def pull(repo, dest, branch):
   ''' updates repo from remote sources '''
   os.chdir(dest)
   cmd = "git branch -a"
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   (gbranch_out, gbranch_err) = cmd.communicate()

   try:
      m = re.search( '^\* (\S+|\(no branch\))$', gbranch_out, flags=re.M )
      cur_branch = m.group(1)
      m = re.search( '\s+remotes/origin/HEAD -> origin/(\S+)', gbranch_out, flags=re.M )
      default_branch = m.group(1)
   except:
      fail_json(msg="could not determine branch data - received: %s" % gbranch_out)

   if branch is None:
      if cur_branch != default_branch:
         (out, err) = switchLocalBranch( default_branch )

      cmd = "git pull -u origin"

   elif branch == cur_branch:
      cmd = "git pull -u origin"

   else:
      m = re.search( '^\s+%s$' % branch, gbranch_out, flags=re.M ) #see if we've already checked it out
      if m is None:
         cmd = "git checkout -b %s origin/%s" % (branch, branch)

      else:
         (out, err) = switchLocalBranch( branch )
         cmd = "git pull -u origin"

   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   return cmd.communicate()

def switchver(version, dest):
   ''' once pulled, switch to a particular SHA or tag '''
   os.chdir(dest)
   if version != 'HEAD':
      cmd = "git checkout %s --force" % version
   else:
      # is there a better way to do this?
      cmd = "git rebase origin"
   cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
   (out, err) = cmd.communicate()
   return (out, err)
 

gitconfig = os.path.join(dest, '.git', 'config')

out, err, status = (None, None, None)

# if there is no git configuration, do a clone operation
# else pull and switch the version

before = None
if not os.path.exists(gitconfig):
   (out, err) = clone(repo, dest, branch)
else:
   # else do a pull   
   before = get_version(dest)
   (rc, out, err) = reset(dest)
   if rc != 0:
      fail_json(out=out, err=err)
   (out, err) = pull(repo, dest, branch)

# handle errors from clone or pull

if out.find('error') != -1:
   fail_json(out=out, err=err)

# switch to version specified regardless of whether
# we cloned or pulled

(out, err) = switchver(version, dest)
if err.find('error') != -1:
   fail_json(out=out, err=err)

# determine if we changed anything

after = get_version(dest)
changed = False

if before != after:
   changed = True

exit_json(changed=changed, before=before, after=after)