#!/usr/bin/env python

import contextlib
import git
import github
import json
import lockfile
import os
import re
import sys

def system(x):
    r = os.system(x)
    if r != 0: raise RuntimeError("%r: Exited with status %d" % (x, r))

workdir = '/home/jepler/src/python-github-webhooks/workdir'
lockfilename = '/home/jepler/src/python-github-webhooks/workdir/.lock'

with open('/home/jepler/.github-credentials', 'r') as f:
    github_credentials = f.read().strip().split(':', 1)      

with open(sys.argv[1], 'r') as jsf:
    payload = json.loads(jsf.read())

### Do something with the payload

g = github.Github(*github_credentials)

pu = payload['pull_request']['base']['user']['login']
if pu != github_credentials[0]:
    raise RuntimeError("surprising user %r in pull request base" % (pu,))
pu = payload['pull_request']['base']['repo']['full_name']
if pu != 'jepler/linuxcnc':
    raise RuntimeError("surprising repo %r in pull request base" % (pu,))

u = g.get_user()
r = u.get_repo('linuxcnc')
head_ref = payload['pull_request']['head']['ref']
c = r.get_commit(head_ref)

@contextlib.contextmanager
def status_update(commit, args):
    args['state'] = 'pending'
    print >>sys.stderr, "create_status", commit, args
    commit.create_status(**args)
    args['state'] = 'error'
    try:
        yield 
    finally:
        print >>sys.stderr, "create_status", commit, args
        commit.create_status(**args)

status_args = dict(
    target_url = 'http://linuxcnc.org/docs/2.7/html/code/contributing-to-linuxcnc.html#_signed_off_by_policy',
    description = 'Do commits conform to policy',
    context = 'linuxcnc.org/signed-off-by'
)

# October 5, 2014
cutoff_date = 1412485200
def is_old(c): return c.authored_date < cutoff_date
def is_merge(c): return len(c.parents) > 1
def is_sob(c): return re.search('^Signed-off-by:', c.message, re.M)

failed = []
with lockfile.FileLock(lockfilename), status_update(c, status_args):
    os.chdir(workdir)
    system("git fetch -f %s %s:base" % (
        payload['pull_request']['base']['repo']['clone_url'],
        payload['pull_request']['base']['ref']))
    system("git fetch -f %s %s:head" % (
        payload['pull_request']['head']['repo']['clone_url'],
        payload['pull_request']['head']['ref']))
    git_repo = git.repo.Repo('.')
    for c in git_repo.iter_commits('base..head'):
        if is_old(c): continue
        if is_merge(c): continue
        if is_sob(c): continue
        failed.append(c.hexsha)
    if failed:
        status_args['description'] = "Commits do not conform to signed-off-by policy: %s" % (
            " ".join(failed))
        status_args['state'] = 'failure'
    else:
        status_args['description'] = "All commits conform to signed-off-by policy"
        status_args['state'] = 'success'