#!/usr/bin/env python3
"""Downloads a prebuilt gn binary to a place where gn.py can find it."""

import io
import os
import sys
import urllib.request
import zipfile


def download_and_unpack(url, output_dir, gn):
    """Download an archive from url and extract gn from it into output_dir."""
    print("downloading %s ..." % url, end="")
    sys.stdout.flush()
    data = urllib.request.urlopen(url).read()
    print(" done")
    zipfile.ZipFile(io.BytesIO(data)).extract(gn, path=output_dir)


def set_executable_bit(path):
    mode = os.stat(path).st_mode
    mode |= (mode & 0o444) >> 2  # Copy R bits to X.
    os.chmod(path, mode)  # No-op on Windows.


def get_platform():
    import platform

    if sys.platform == "darwin":
        return "mac-amd64" if platform.machine() != "arm64" else "mac-arm64"
    if platform.machine() not in ("AMD64", "x86_64"):
        return None
    if sys.platform.startswith("linux"):
        return "linux-amd64"
    if sys.platform == "win32":
        return "windows-amd64"


def main():
    platform = get_platform()
    if not platform:
        print("no prebuilt binary for", sys.platform)
        print("build it yourself with:")
        print("  rm -rf /tmp/gn &&")
        print("  pushd /tmp && git clone https://gn.googlesource.com/gn &&")
        print("  cd gn && build/gen.py && ninja -C out gn && popd &&")
        print("  cp /tmp/gn/out/gn somewhere/on/PATH")
        return 1
    dirname = os.path.join(os.path.dirname(__file__), "bin", platform)
    if not os.path.exists(dirname):
        os.makedirs(dirname)

    url = "https://chrome-infra-packages.appspot.com/dl/gn/gn/%s/+/latest"
    gn = "gn" + (".exe" if sys.platform == "win32" else "")
    if platform == "mac-arm64":  # For https://openradar.appspot.com/FB8914243
        try:
            os.remove(os.path.join(dirname, gn))
        except OSError:
            pass
    download_and_unpack(url % platform, dirname, gn)
    set_executable_bit(os.path.join(dirname, gn))


if __name__ == "__main__":
    sys.exit(main())