#!/usr/bin/env python

import jwt, time, urllib.request, json, datetime, argparse, sys, textwrap
from github import Github
from colorama import Fore, Style
from time import sleep

parser = argparse.ArgumentParser(description='Create PR to update nixpkgs fork')
parser.add_argument('--private-key')
parser.add_argument('--app-id')
parser.add_argument('--installation-id')
parser.add_argument('--repo')
parser.add_argument('--cache-dir')
args = vars(parser.parse_args())

channel_req = urllib.request.Request(url='https://nixos.org/channels/nixos-18.09/git-revision')
latest_commit = urllib.request.urlopen(channel_req).read().decode('utf-8')
try:
    previous_commit = open(args['cache_dir'] + '/git-revision', 'r').read()
except FileNotFoundError:
    open(args['cache_dir'] + '/git-revision', 'w').write(latest_commit)
    print("Premier lancement, le hash du dernier commit à été sauvegardé")
    sys.exit(0)

print("Dernier commit : " + latest_commit)
print("Commit précédent : " + previous_commit)

if latest_commit != previous_commit:
    bearer_token = jwt.encode({
                                'iat': int(time.time()),
                                'exp': int(time.time()) + (10 * 60),
                                'iss': args['app_id']
                              },
                              open(args['private_key'],"r").read(),
                              algorithm='RS256')

    req = urllib.request.Request(url='https://api.github.com/app/installations/' +
                                    args['installation_id'] +
                                    '/access_tokens',
                                 method='POST')

    req.add_header('Authorization', 'Bearer ' + bearer_token.decode('utf-8'))
    req.add_header('Accept', 'application/vnd.github.machine-man-preview+json')

    token = json.loads(urllib.request.urlopen(req).read().decode('utf-8'))['token']

    g = Github(token)
    repo = g.get_repo(args['repo'])

    branch = "upgrade-" + datetime.datetime.now().strftime('%Y-%m-%d') + '-' + latest_commit[:11];

    repo.create_git_ref('refs/heads/' + branch, latest_commit)

    pr_message = textwrap.dedent("""\
                    ### Pull request automatique
                    ### Avancement mise à jour
                    - [ ] Fusionner la branche
                 """)

    pr = repo.create_pull(title=branch, body=pr_message, base='nixos-18.09', head=branch)

    print("Pull request numéro " + str(pr.number) + " créée")
    print("URL : " + pr.html_url)

    while pr.mergeable == None:
        pr = repo.get_pull(pr.number)
        sleep(1)

    pr.edit(body = pr.body + "\n- [ ] Exécuter `nixos-rebuild -I nixpkgs=https://github.com/nyanloutre/nixpkgs/archive/" + pr.merge_commit_sha + ".tar.gz switch`")
    print("État : " + ((Fore.GREEN + "Fusionnable") if pr.mergeable else (Fore.RED + "Conflit")) + Style.RESET_ALL)

    open(args['cache_dir'] + '/git-revision', 'w').write(latest_commit)
else:
    print(Fore.GREEN + "Aucun changement détecté" + Style.RESET_ALL)