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

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

Examples:
  $ backport-summary https://gerrit.wikimedia.org/r/603482
  Backport: [[gerrit:603482|Wrap WAN-cached PropertyInfoLookup with an APCu cache (T254536)]]

  $ backport-summary https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/561355
  Config: [[gerrit:561355|Modify $wgArticleCount to 'any' for ta.wiktionary (T241684)]]
  'Config: [[gerrit:561355|Modify $wgArticleCount to '"'"'any'"'"' for ta.wiktionary (T241684)]]'

If the summary contains shell special characters, it will be printed again,
suitably quoted this time (as in the second example).
Various formats of Gerrit URLs are accepted.
"""

import docopt
import json
import re
import requests
import shlex

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 = '{kind}: [[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)
    kind = 'Config' if change['project'] == 'operations/mediawiki-config' else 'Backport'
    revision_id = change['current_revision']
    commit = change['revisions'][revision_id]['commit']
    bugs = re.findall(PHAB_HEADER_RE, commit['message'])

    return SUMMARY_MSG.format(
        kind=kind,
        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__)
    summary = build_summary(arguments['<gerrit-url>'])
    print(summary)
    quoted = shlex.quote(summary)
    if quoted != summary and quoted != "'{}'".format(summary):
        # correctly quoting this is not trivial, do it for the user
        print(quoted)