#! /usr/bin/env nix-shell
#! nix-shell -i python -p python3 nix nix-prefetch-git

"""This script automatically updates chromium, google-chrome, chromedriver, and ungoogled-chromium
via upstream-info.json."""

import csv
import json
import re
import subprocess
import sys

from codecs import iterdecode
from collections import OrderedDict
from datetime import datetime
from os.path import abspath, dirname
from urllib.request import urlopen

HISTORY_URL = 'https://omahaproxy.appspot.com/history?os=linux'
DEB_URL = 'https://dl.google.com/linux/chrome/deb/pool/main/g'
BUCKET_URL = 'https://commondatastorage.googleapis.com/chromium-browser-official'

JSON_PATH = dirname(abspath(__file__)) + '/upstream-info.json'


def load_json(path):
    """Loads the given JSON file."""
    with open(path, 'r') as f:
        return json.load(f)


def nix_prefetch_url(url, algo='sha256'):
    """Prefetches the content of the given URL."""
    print(f'nix-prefetch-url {url}')
    out = subprocess.check_output(['nix-prefetch-url', '--type', algo, url])
    return out.decode('utf-8').rstrip()


def nix_prefetch_git(url, rev):
    """Prefetches the requested Git revision of the given repository URL."""
    print(f'nix-prefetch-git {url} {rev}')
    out = subprocess.check_output(['nix-prefetch-git', '--quiet', '--url', url, '--rev', rev])
    return json.loads(out)


def get_file_revision(revision, file_path):
    """Fetches the requested Git revision of the given Chromium file."""
    url = f'https://raw.githubusercontent.com/chromium/chromium/{revision}/{file_path}'
    with urlopen(url) as http_response:
        return http_response.read()


def get_matching_chromedriver(version):
    """Gets the matching chromedriver version for the given Chromium version."""
    # See https://chromedriver.chromium.org/downloads/version-selection
    build = re.sub('.[0-9]+$', '', version)
    chromedriver_version_url = f'https://chromedriver.storage.googleapis.com/LATEST_RELEASE_{build}'
    with urlopen(chromedriver_version_url) as http_response:
        chromedriver_version = http_response.read().decode()
        def get_chromedriver_url(system):
            return ('https://chromedriver.storage.googleapis.com/' +
                    f'{chromedriver_version}/chromedriver_{system}.zip')
        return {
            'version': chromedriver_version,
            'sha256_linux': nix_prefetch_url(get_chromedriver_url('linux64')),
            'sha256_darwin': nix_prefetch_url(get_chromedriver_url('mac64'))
        }


def get_channel_dependencies(channel):
    """Gets all dependencies for the given Chromium version."""
    deps = get_file_revision(channel['version'], 'DEPS')
    gn_pattern = b"'gn_version': 'git_revision:([0-9a-f]{40})'"
    gn_commit = re.search(gn_pattern, deps).group(1).decode()
    gn = nix_prefetch_git('https://gn.googlesource.com/gn', gn_commit)
    return {
        'gn': {
            'version': datetime.fromisoformat(gn['date']).date().isoformat(),
            'url': gn['url'],
            'rev': gn['rev'],
            'sha256': gn['sha256']
        }
    }

channels = {}
last_channels = load_json(JSON_PATH)


print(f'GET {HISTORY_URL}', file=sys.stderr)
with urlopen(HISTORY_URL) as resp:
    builds = csv.DictReader(iterdecode(resp, 'utf-8'))
    for build in builds:
        channel_name = build['channel']

        # If we've already found a newer build for this channel, we're
        # no longer interested in it.
        if channel_name in channels:
            continue

        # If we're back at the last build we used, we don't need to
        # keep going -- there's no new version available, and we can
        # just reuse the info from last time.
        if build['version'] == last_channels[channel_name]['version']:
            channels[channel_name] = last_channels[channel_name]
            continue

        channel = {'version': build['version']}
        suffix = 'unstable' if channel_name == 'dev' else channel_name

        try:
            channel['sha256'] = nix_prefetch_url(f'{BUCKET_URL}/chromium-{build["version"]}.tar.xz')
            channel['sha256bin64'] = nix_prefetch_url(
                f'{DEB_URL}/google-chrome-{suffix}/' +
                f'google-chrome-{suffix}_{build["version"]}-1_amd64.deb')
        except subprocess.CalledProcessError:
            # This build isn't actually available yet.  Continue to
            # the next one.
            continue

        channel['deps'] = get_channel_dependencies(channel)
        if channel_name == 'stable':
            channel['chromedriver'] = get_matching_chromedriver(channel['version'])

        channels[channel_name] = channel


with open(JSON_PATH, 'w') as out:
    def get_channel_key(item):
        """Orders Chromium channels by their name."""
        channel_name = item[0]
        if channel_name == 'stable':
            return 0
        if channel_name == 'beta':
            return 1
        if channel_name == 'dev':
            return 2
        if channel_name == 'ungoogled-chromium':
            return 3
        print(f'Error: Unexpected channel: {channel_name}', file=sys.stderr)
        sys.exit(1)
    # Keep ungoogled-chromium unchanged:
    channels['ungoogled-chromium'] = last_channels['ungoogled-chromium']
    sorted_channels = OrderedDict(sorted(channels.items(), key=get_channel_key))
    json.dump(sorted_channels, out, indent=2)
    out.write('\n')