#!/usr/bin/env python3
"""
Given a Gerrit URL, build its scap summary in the SWAT deployment format.

Usage:
  swat-summary <gerrit-url>
  swat-summary -h | --help

Examples:
  $ swat-summary https://gerrit.wikimedia.org/r/445240
  SWAT: [[gerrit:445240|Update to use editRevId (T58849)]]
"""

import docopt
import json
import re
import requests

GERRIT_CHANGE_API = 'https://gerrit.wikimedia.org/r/changes/{gerrit_number}?o=CURRENT_REVISION&o=CURRENT_COMMIT'
GERRIT_RE = 'https://gerrit.wikimedia.org/r/(?:(?:#/)?c/[-+_/a-zA-Z0-9]+/)?(?P<gerrit_number>[0-9]+)/?'
PHAB_HEADER_RE = '(?m)^Bug: (?P<phab_task>T[0-9]+)$'
SUMMARY_MSG = 'SWAT: [[gerrit:{gerrit_number}|{commit_message} ({phabricator_task})]]'


def build_summary(gerrit_url):
    matches = re.match(GERRIT_RE, gerrit_url)
    if matches:
        gerrit_number = matches.group('gerrit_number')
    else:
        raise RuntimeError("Couldn't extract gerrit change number from string " + gerrit_url)

    change = get_gerrit(GERRIT_CHANGE_API, gerrit_number=gerrit_number)
    revision_id = change['current_revision']
    commit = change['revisions'][revision_id]['commit']
    bugs = re.findall(PHAB_HEADER_RE, commit['message'])

    return SUMMARY_MSG.format(
        gerrit_number=gerrit_number,
        commit_message=commit['subject'],
        phabricator_task=', '.join(bugs))


def get_gerrit(api_format, **params):
    url = api_format.format(**params)
    r = requests.get(url)
    if r.status_code != 200:
        raise RuntimeError("Bad HTTP response from " + url)
    return json.loads(
        r.text.lstrip(")]}'"))


if __name__ == '__main__':
    arguments = docopt.docopt(__doc__)
    print(build_summary(arguments['<gerrit-url>']))