#!/usr/bin/env python3

import argparse
import os
import re
import shutil
import subprocess
import sys
import sysconfig
from os.path import basename, relpath
from pathlib import Path
from tempfile import TemporaryDirectory

SCRIPT_NAME = Path(__file__).name
CHECKOUT = Path(__file__).resolve().parent.parent
CROSS_BUILD_DIR = CHECKOUT / "cross-build"


def delete_if_exists(path):
    if path.exists():
        print(f"Deleting {path} ...")
        shutil.rmtree(path)


def subdir(name, *, clean=None):
    path = CROSS_BUILD_DIR / name
    if clean:
        delete_if_exists(path)
    if not path.exists():
        if clean is None:
            sys.exit(
                f"{path} does not exist. Create it by running the appropriate "
                f"`configure` subcommand of {SCRIPT_NAME}.")
        else:
            path.mkdir(parents=True)
    return path


def run(command, *, host=None, **kwargs):
    env = os.environ.copy()
    if host:
        env_script = CHECKOUT / "Android/android-env.sh"
        env_output = subprocess.run(
            f"set -eu; "
            f"HOST={host}; "
            f"PREFIX={subdir(host)}/prefix; "
            f". {env_script}; "
            f"export",
            check=True, shell=True, text=True, stdout=subprocess.PIPE
        ).stdout

        for line in env_output.splitlines():
            # We don't require every line to match, as there may be some other
            # output from installing the NDK.
            if match := re.search(
                "^(declare -x |export )?(\\w+)=['\"]?(.*?)['\"]?$", line
            ):
                key, value = match[2], match[3]
                if env.get(key) != value:
                    print(line)
                    env[key] = value

        if env == os.environ:
            raise ValueError(f"Found no variables in {env_script.name} output:\n"
                             + env_output)

    print(">", " ".join(map(str, command)))
    try:
        subprocess.run(command, check=True, env=env, **kwargs)
    except subprocess.CalledProcessError as e:
        sys.exit(e)


def build_python_path():
    """The path to the build Python binary."""
    build_dir = subdir("build")
    binary = build_dir / "python"
    if not binary.is_file():
        binary = binary.with_suffix(".exe")
        if not binary.is_file():
            raise FileNotFoundError("Unable to find `python(.exe)` in "
                                    f"{build_dir}")

    return binary


def configure_build_python(context):
    os.chdir(subdir("build", clean=context.clean))

    command = [relpath(CHECKOUT / "configure")]
    if context.args:
        command.extend(context.args)
    run(command)


def make_build_python(context):
    os.chdir(subdir("build"))
    run(["make", "-j", str(os.cpu_count())])


def unpack_deps(host):
    deps_url = "https://github.com/beeware/cpython-android-source-deps/releases/download"
    for name_ver in ["bzip2-1.0.8-1", "libffi-3.4.4-2", "openssl-3.0.13-1",
                     "sqlite-3.45.1-0", "xz-5.4.6-0"]:
        filename = f"{name_ver}-{host}.tar.gz"
        download(f"{deps_url}/{name_ver}/{filename}")
        run(["tar", "-xf", filename])
        os.remove(filename)


def download(url, target_dir="."):
    out_path = f"{target_dir}/{basename(url)}"
    run(["curl", "-Lf", "-o", out_path, url])
    return out_path


def configure_host_python(context):
    host_dir = subdir(context.host, clean=context.clean)

    prefix_dir = host_dir / "prefix"
    if not prefix_dir.exists():
        prefix_dir.mkdir()
        os.chdir(prefix_dir)
        unpack_deps(context.host)

    build_dir = host_dir / "build"
    build_dir.mkdir(exist_ok=True)
    os.chdir(build_dir)

    command = [
        # Basic cross-compiling configuration
        relpath(CHECKOUT / "configure"),
        f"--host={context.host}",
        f"--build={sysconfig.get_config_var('BUILD_GNU_TYPE')}",
        f"--with-build-python={build_python_path()}",
        "--without-ensurepip",

        # Android always uses a shared libpython.
        "--enable-shared",
        "--without-static-libpython",

        # Dependent libraries. The others are found using pkg-config: see
        # android-env.sh.
        f"--with-openssl={prefix_dir}",
    ]

    if context.args:
        command.extend(context.args)
    run(command, host=context.host)


def make_host_python(context):
    host_dir = subdir(context.host)
    os.chdir(host_dir / "build")
    run(["make", "-j", str(os.cpu_count())], host=context.host)
    run(["make", "install", f"prefix={host_dir}/prefix"], host=context.host)


def build_all(context):
    steps = [configure_build_python, make_build_python, configure_host_python,
             make_host_python]
    for step in steps:
        step(context)


def clean_all(context):
    delete_if_exists(CROSS_BUILD_DIR)


# To avoid distributing compiled artifacts without corresponding source code,
# the Gradle wrapper is not included in the CPython repository. Instead, we
# extract it from the Gradle release.
def setup_testbed(context):
    ver_long = "8.7.0"
    ver_short = ver_long.removesuffix(".0")
    testbed_dir = CHECKOUT / "Android/testbed"

    for filename in ["gradlew", "gradlew.bat"]:
        out_path = download(
            f"https://raw.githubusercontent.com/gradle/gradle/v{ver_long}/{filename}",
            testbed_dir)
        os.chmod(out_path, 0o755)

    with TemporaryDirectory(prefix=SCRIPT_NAME) as temp_dir:
        os.chdir(temp_dir)
        bin_zip = download(
            f"https://services.gradle.org/distributions/gradle-{ver_short}-bin.zip")
        outer_jar = f"gradle-{ver_short}/lib/plugins/gradle-wrapper-{ver_short}.jar"
        run(["unzip", bin_zip, outer_jar])
        run(["unzip", "-o", "-d", f"{testbed_dir}/gradle/wrapper", outer_jar,
             "gradle-wrapper.jar"])


def main():
    parser = argparse.ArgumentParser()
    subcommands = parser.add_subparsers(dest="subcommand")
    build = subcommands.add_parser("build", help="Build everything")
    configure_build = subcommands.add_parser("configure-build",
                                             help="Run `configure` for the "
                                             "build Python")
    make_build = subcommands.add_parser("make-build",
                                        help="Run `make` for the build Python")
    configure_host = subcommands.add_parser("configure-host",
                                            help="Run `configure` for Android")
    make_host = subcommands.add_parser("make-host",
                                       help="Run `make` for Android")
    subcommands.add_parser(
        "clean", help="Delete the cross-build directory")
    subcommands.add_parser(
        "setup-testbed", help="Download the testbed Gradle wrapper")

    for subcommand in build, configure_build, configure_host:
        subcommand.add_argument(
            "--clean", action="store_true", default=False, dest="clean",
            help="Delete any relevant directories before building")
    for subcommand in build, configure_host, make_host:
        subcommand.add_argument(
            "host", metavar="HOST",
            choices=["aarch64-linux-android", "x86_64-linux-android"],
            help="Host triplet: choices=[%(choices)s]")
    for subcommand in build, configure_build, configure_host:
        subcommand.add_argument("args", nargs="*",
                                help="Extra arguments to pass to `configure`")

    context = parser.parse_args()
    dispatch = {"configure-build": configure_build_python,
                "make-build": make_build_python,
                "configure-host": configure_host_python,
                "make-host": make_host_python,
                "build": build_all,
                "clean": clean_all,
                "setup-testbed": setup_testbed}
    dispatch[context.subcommand](context)


if __name__ == "__main__":
    main()