#!/usr/bin/env python
# Copyright 2022 The Chromium Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import argparse
import json
import os
import re
import urllib.request

# NOTE: There are three potential sources for Bazel binaries:
#
# - The latest stable release (e.g. 5.3.2 currently), available from GitHub,
#   and whose version is obtainable from the following API file:
#
#     https://api.github.com/repos/bazelbuild/bazel/releases/latest
#
# - The latest pre-release binary, which is also available from GitHub, and
#   whose version is obtained by scanning the content of the following API file,
#   then sorting the entries in "natural order":
#
#     https://api.github.com/repos/bazelbuild/bazel/tags
#
# - The release candidates, which are _not_ available from GitHub, but from
#   releases.bazel.build instead, and which do not have an API file, and
#   must be specified with explicit version/candidate name below.
#
# Which version is downloaded depends on the definition of the _BAZEL_VERSION
# configuration variable below, which should be one of the following constants:
_BAZEL_VERSION_LATEST_PRERELEASE = "latest-prerelease"
_BAZEL_VERSION_LATEST_RELEASE = "latest-release"
_BAZEL_VERSION_RELEASE_CANDIDATE = "6.0.0/rc4"  # Must be <version>/<candidate>

# Which Bazel binary to download, see notes above.
_BAZEL_VERSION = _BAZEL_VERSION_LATEST_RELEASE

# Consistency check.
assert _BAZEL_VERSION in (
    _BAZEL_VERSION_LATEST_PRERELEASE,
    _BAZEL_VERSION_LATEST_RELEASE,
    _BAZEL_VERSION_RELEASE_CANDIDATE,
)


def natural_sort_key(item):
    """Convert a version number to a sorting key for natural ordering."""
    # Split the input item into a list of words and numbers (ignore everything else).
    # E.g. "6.0-pre2022:1" -> ("6", "0", "pre", "2022", "1")
    tups = re.findall("[^\W\d_]|\d+", item)
    # Convert all numbers to their integer representation in the output list, but
    # keep words as is. For example (6, 0, "pre", 2022, 1)
    # Python will naturally sort tuple items in ascending order.
    return [int(tup) if tup.isdigit() else tup for tup in tups]


def get_release_candidate_version(bazel_version):
    """Return (version, candidate) information from formatted version string."""
    version, _, candidate = bazel_version.partition("/")
    assert candidate, "Missing release candidate /<suffix> in: " + bazel_version
    return version, candidate


def do_latest():
    """Retrieve tag of the latest pre-release to fetch."""
    if _BAZEL_VERSION == _BAZEL_VERSION_RELEASE_CANDIDATE:
        # A release candidate is only available from releases.bazel.build
        # and there is no API file provided to list them, which forces the use
        # of hard-coded version + candidate
        version, candidate = get_release_candidate_version(_BAZEL_VERSION)
        print(f"{version}{candidate}")
    elif _BAZEL_VERSION == _BAZEL_VERSION_LATEST_PRERELEASE:
        # Pre-release versions are needed for the Fuchsia SDK and platform build.
        # To solve this, download the full list of tags as a JSON array of objects,
        # whose 'name' field gives the tag. Sort by increasing natural order, and
        # keep the last one.
        tags = json.load(
            urllib.request.urlopen("https://api.github.com/repos/bazelbuild/bazel/tags")
        )
        tag_names = sorted([tag["name"] for tag in tags], key=natural_sort_key)
        assert len(tag_names) > 0, "Empty tags list?"
        print(tag_names[-1])
    elif _BAZEL_VERSION == _BAZEL_VERSION_LATEST_RELEASE:
        # This codes get the latest official release tag directly instead.
        print(
            json.load(
                urllib.request.urlopen(
                    "https://api.github.com/repos/bazelbuild/bazel/releases/latest"
                )
            )["tag_name"]
        )
    else:
        assert False, (
            "Invalid or unrecognized value for _BAZEL_VERSION: " + _BAZEL_VERSION
        )


_PLATFORMS = {
    "linux-amd64": "linux-x86_64",
    "linux-arm64": "linux-arm64",
    "mac-amd64": "darwin-x86_64",
    "mac-arm64": "darwin-arm64",
    "windows-amd64": "windows-x86_64",
    "windows-arm64": "windows-arm64",
}

_EXTENSION = {
    "linux": "",
    "mac": "",
    "windows": ".zip",
}


def get_download_url(version, platform):
    if platform not in _PLATFORMS:
        raise ValueError("unsupported platform {}".format(platform))

    extension = _EXTENSION[platform.split("-")[0]]

    if _BAZEL_VERSION == _BAZEL_VERSION_RELEASE_CANDIDATE:
        version, candidate = get_release_candidate_version(_BAZEL_VERSION)
        url = (
            "https://releases.bazel.build/{version}/{candidate}/"
            "bazel-{version}{candidate}-{platform}{extension}".format(
                version=version,
                candidate=candidate,
                platform=_PLATFORMS[platform],
                extension=extension,
            )
        )
    else:
        url = (
            "https://github.com/bazelbuild/bazel/releases/download/{version}/"
            "bazel-{version}-{platform}{extension}".format(
                version=version,
                platform=_PLATFORMS[platform],
                extension=extension,
            )
        )

    manifest = {
        "url": [url],
        "ext": extension,
    }

    print(json.dumps(manifest))


def main():
    ap = argparse.ArgumentParser()
    sub = ap.add_subparsers()

    latest = sub.add_parser("latest")
    latest.set_defaults(func=lambda _opts: do_latest())

    download = sub.add_parser("get_url")
    download.set_defaults(
        func=lambda opts: get_download_url(
            os.environ["_3PP_VERSION"], os.environ["_3PP_PLATFORM"]
        )
    )

    opts = ap.parse_args()
    opts.func(opts)


if __name__ == "__main__":
    main()