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

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):
    with open(path, 'r') as f:
        return json.load(f)

def nix_prefetch_url(url, algo='sha256'):
    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):
    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):
    url = f'https://raw.githubusercontent.com/chromium/chromium/{revision}/{file_path}'
    with urlopen(url) as http_response:
        return http_response.read()

def get_channel_dependencies(channel):
    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}/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)

        channels[channel_name] = channel

with open(JSON_PATH, 'w') as out:
    def get_channel_key(item):
        channel_name = item[0]
        if channel_name == 'stable':
            return 0
        elif channel_name == 'beta':
            return 1
        elif channel_name == 'dev':
            return 2
        else:
            print(f'Error: Unexpected channel: {channel_name}', file=sys.stderr)
            sys.exit(1)
    sorted_channels = OrderedDict(sorted(channels.items(), key=get_channel_key))
    json.dump(sorted_channels, out, indent=2)
    out.write('\n')