#!/usr/bin/env python
""" Git post-receive hook to publish commit data to an AMQP topic.

    apt-get install python-git python-amqplib
    or:
    easy_install amqplib gitpython
"""
import os, sys, json
from datetime import datetime
from git import *
from amqplib import client_0_8 as amqp

AMQP_HOST = 'localhost'
AMQP_PORT = 5672
AMQP_USER = 'git'
AMQP_PASSWORD = 'git'
AMQP_VHOST = '/development'
AMQP_EXCHANGE = 'git'

def get_commits(repo, ref, from_commit, to_commit):
    if from_commit == '0' * 40:
        # Branch create
        return get_new_revisions(repo, ref, to_commit)
    if to_commit == '0' * 40:
        # Branch delete
        return []
    return get_new_revisions(repo, ref, '%s..%s' % (from_commit, to_commit))

def format_actor(actor):
    return {'name': actor.name, 'email': actor.email}

def format_commit(commit):
    return {'author': format_actor(commit.author),
            'committer': format_actor(commit.committer),
            'message': commit.message,
            'sha': commit.hexsha,
            'date': commit.committed_date}

def format_branch(commits):
    return [format_commit(commit) for commit in commits]

def get_new_revisions(repo, ref, revspec):
    """ This magic fetches previously-unseen revisions, and is based on the
        show-new-revisions function in git's post-receive-email hook."""
    other_branches = repo.git.for_each_ref('refs/heads', format='%(refname)').split("\n")
    other_branches.remove(ref)
    revs = repo.git.rev_parse("--not", other_branches).split("\n")
    return repo.iter_commits(revs + [revspec])

def send_message(host, port, user, password, vhost, exchange_name, key, message):
    conn = amqp.Connection(host=host, port=port, userid=user, password=password, virtual_host=vhost)
    channel = conn.channel()
    channel.access_request('/data', active=True, read=True)
    channel.exchange_declare(exchange_name, type='topic', durable=True, auto_delete=False)
    message = amqp.Message(timestamp=datetime.utcnow(), body=json.dumps(message),
                        content_type='application/json', routing_key=key)
    channel.basic_publish(message, exchange_name)

if __name__ == '__main__':
    repo = Repo(os.environ['GIT_DIR'])
    out = {}
    for line in sys.stdin.xreadlines():
        old, new, ref = line.strip().split(' ')
        commits = list(get_commits(repo, ref, old, new))
        if len(commits) > 0:
            out[ref] = format_branch(commits)
    if len(out) > 0:
        key = os.path.basename(repo.working_dir)
        send_message(AMQP_HOST, AMQP_PORT, AMQP_USER, AMQP_PASSWORD, AMQP_VHOST, AMQP_EXCHANGE, key, out)