#!/usr/bin/env python3
#
# Copyright 2017 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

# A script to fetch missing LICENSE files when building a vendored repo

# Should be run from top-level of third_party/rust_crates repository.

import argparse
import json
import os
import re
import shutil
import sys
import urllib.request
from multiprocessing import Pool

repo_re = re.compile('\s*repository\s*=\s*"(.*)"\s*$')


def die(reason):
    raise Exception(reason)


def get_repo_path(subdir):
    for line in open(os.path.join(subdir, 'Cargo.toml')):
        m = repo_re.match(line)
        if m:
            return m.group(1)


def find_github_blob_path(path):
    s = path.split('/')
    if s[2] == 'github.com':
        s[2] = 'raw.githubusercontent.com'
        # github redirects "github.com/$USER/$PROJECT.git" to
        # "github.com/$USER/$PROJECT".
        if s[4].endswith('.git'):
            s[4] = s[4][:len('.git')]
    else:
        die('don\'t know raw content path for ' + path)
    if s[-1] == '':
        del s[-1]
    if len(s) >= 6 and s[5] == 'tree':
        del s[5]
    else:
        s.append('HEAD')
    return '/'.join(s)


def fetch_license(subdir):
    repo_path = get_repo_path(subdir)
    if repo_path is None:
        die('can\'t find repo path for ' + subdir)
    base_path = find_github_blob_path(repo_path)
    first = True
    with open(os.path.join(subdir, 'LICENSE'), 'wb') as license_out:
        # 'LICENCE' is a British English spelling variant used in https://github.com/ebarnard/rust-plist
        for filename in ('LICENSE', 'LICENSE-APACHE', 'LICENSE-MIT', 'COPYING',
                         'LICENCE', 'LICENSE.md'):
            url = '/'.join((base_path, filename))
            try:
                with urllib.request.urlopen(url) as resp:
                    if first:
                        first = False
                    else:
                        license_out.write(bytearray('=' * 40 + '\n', 'utf-8'))
                    license_out.write(bytearray(url + ':\n\n', 'utf-8'))
                    license_out.write(resp.read())
            except urllib.error.HTTPError as err:
                if err.code != 404:
                    raise
    if first:
        die('no licenses found under ' + repo_path)


def check_subdir_license(arg):
    # it seems multiprocessing only passes one argument to each function
    (subdir, verify) = arg

    if subdir.startswith('.') or not os.path.isdir(subdir):
        sys.stdout.write("-")
        sys.stdout.flush()
        return

    # delete crates that are empty except for an OWNERS file
    if os.listdir(subdir) == ["OWNERS"]:
        shutil.rmtree(subdir)
        return

    license_files = [
        file for file in os.listdir(subdir) if file.startswith('LICENSE') or
        file.startswith('LICENCE') or file.startswith('license')
    ]
    if license_files:
        sys.stdout.write(".")
        sys.stdout.flush()
        return

    if verify:
        die('MISSING  %s' % subdir)

    fetch_license(subdir)
    sys.stdout.write("*")
    sys.stdout.flush()


def check_licenses(directory, verify=False):
    success = True
    os.chdir(directory)
    print("Checking licenses.")
    subdirs = sorted(os.listdir(os.getcwd()))
    try:
        with Pool(16) as p:
            p.map(check_subdir_license, [(s, verify) for s in subdirs])
    except Exception as err:
        print('ERROR    %s' % err)
        success = False
    print("\nDone checking licenses.")
    return success


def main():
    parser = argparse.ArgumentParser(
        'Verifies licenses for third-party Rust crates')
    parser.add_argument(
        '--directory',
        help='Directory containing the crates',
        default=os.getcwd())
    parser.add_argument(
        '--verify',
        help='Simply check whether licenses are up-to-date',
        action='store_true')
    args = parser.parse_args()
    if not check_licenses(args.directory, verify=args.verify):
        sys.exit(1)


if __name__ == '__main__':
    main()