#!/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

import re

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):
    ''' makes a new git repo if it does not already exist '''
    try:
        os.makedirs(os.path.dirname(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
    return (rc, out, err)

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 get_branches(module, dest):
    os.chdir(dest)
    branches = []
    cmd = "git branch -a"
    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = cmd.communicate()
    if cmd.returncode != 0:
        module.fail_json(msg="Could not determine branch data - received %s" % out)
    for line in out.split('\n'):
        branches.append(line.strip())
    return branches

def is_remote_branch(module, dest, remote, branch):
    branches = get_branches(module, dest)
    rbranch = 'remotes/%s/%s' % (remote, branch)
    if rbranch in branches:
        return True
    else:
        return False

def is_local_branch(module, dest, branch):
    branches = get_branches(module, dest)
    lbranch = '%s' % branch
    if lbranch in branches:
        return True
    elif '* %s' % branch in branches:
        return True
    else:
        return False

def is_current_branch(module, dest, branch):
    branches = get_branches(module, dest)
    for b in branches:
        if b.startswith('* '):
            cur_branch = b
    if branch == cur_branch or '* %s' % branch == cur_branch:
        return True
    else:
        return True

def pull(module, repo, dest, version):
    ''' updates repo from remote sources '''
    os.chdir(dest)
    branches = get_branches(module, dest)
    cur_branch = ''
    for b in branches:
        if b.startswith('* '):
            cur_branch = b
    if is_local_branch(module, dest, version) and not is_current_branch(module, dest, version):
        (out, err) = switch_version(module, dest, remote, version)

    cmd = "git pull -u origin"
    cmd = subprocess.Popen(cmd, shell=True, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
    out, err = cmd.communicate()
    rc = cmd.returncode
    return (rc, out, err)

def switch_version(module, dest, remote, version):
    ''' once pulled, switch to a particular SHA, tag, or branch '''
    os.chdir(dest)
    cmd = ''
    if version != 'HEAD':
        if not is_local_branch(module, dest, version) and is_remote_branch(module, dest, remote, version):
            cmd = "git checkout --track -b %s %s/%s" % (version, remote, version)
        else:
            cmd = "git checkout --force %s" % 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()
    rc = cmd.returncode
    return (rc, out, err)

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

def main():
    module = AnsibleModule(
        argument_spec = dict(
            dest=dict(required=True),
            repo=dict(required=True),
            version=dict(default='HEAD'),
            remote=dict(default='origin')
        )
    )

    dest    = module.params['dest']
    repo    = module.params['repo']
    version = module.params['version']
    remote  = module.params['remote']

    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):
        (rc, out, err) = clone(repo, dest)
        if rc != 0:
            module.fail_json(msg=err)
    else:
        # else do a pull   
        before = get_version(dest)
        (rc, out, err) = reset(dest)
        if rc != 0:
            module.fail_json(msg=err)
        (rc, out, err) = pull(module, repo, dest, version)

    # handle errors from clone or pull
    if out.find('error') != -1 or err.find('ERROR') != -1:
        module.fail_json(msg=err)

    # switch to version specified regardless of whether
    # we cloned or pulled
    (rc, out, err) = switch_version(module, dest, remote, version)
    if err.find('error') != -1:
        module.fail_json(msg=err)

    # determine if we changed anything
    after = get_version(dest)
    changed = False

    if before != after:
        changed = True

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

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