# SPDX-License-Identifier: GPL-2.0-or-later
# SPDX-FileCopyrightText: 2022 Bartosz Golaszewski <brgl@bgdev.pl>

from collections.abc import Callable
from logging import getLogger
from os import getenv, path, unlink
from shutil import copy, copytree, rmtree
from typing import TypeVar, cast

from setuptools import Extension, setup
from setuptools.command.build_ext import build_ext as orig_build_ext
from setuptools.command.sdist import sdist as orig_sdist
from setuptools.errors import BaseError

T = TypeVar("T", "sdist", "build_ext")

log = getLogger(__name__)

LINK_SYSTEM_LIBGPIOD = getenv("LINK_SYSTEM_LIBGPIOD") == "1"
LIBGPIOD_MINIMUM_VERSION = "2.1"
LIBGPIOD_VERSION = getenv("LIBGPIOD_VERSION")
SRC_BASE_URL = "https://mirrors.edge.kernel.org/pub/software/libs/libgpiod/"
TAR_FILENAME = "libgpiod-{version}.tar.gz"
ASC_FILENAME = "sha256sums.asc"
SHA256_CHUNK_SIZE = 2048
LICENSE_FILE = "LICENSE"


def sha256(filename: str) -> str:
    """
    Return a sha256sum for a specific filename, loading the file in chunks
    to avoid potentially excessive memory use.
    """
    from hashlib import sha256

    sha256sum = sha256()
    with open(filename, "rb") as f:
        for chunk in iter(lambda: f.read(SHA256_CHUNK_SIZE), b""):
            sha256sum.update(chunk)

    return sha256sum.hexdigest()


def find_sha256sum(asc_file: str, tar_filename: str) -> str:
    """
    Search through a local copy of sha256sums.asc for a specific filename
    and return the associated sha256 sum.
    """
    with open(asc_file) as f:
        for line in f:
            _line = line.strip().split("  ")
            if len(_line) == 2 and _line[1] == tar_filename:
                return _line[0]

    raise BaseError(f"no signature found for {tar_filename}")


def fetch_tarball(func: Callable[[T], None]) -> Callable[[T], None]:
    """
    Verify the requested LIBGPIOD_VERSION tarball exists in sha256sums.asc,
    fetch it from https://mirrors.edge.kernel.org/pub/software/libs/libgpiod/
    and verify its sha256sum.

    If the check passes, extract the tarball and copy the lib and include
    dirs into our source tree.
    """

    # If no LIBGPIOD_VERSION is specified in env, just run the command
    if LIBGPIOD_VERSION is None:
        return func

    # If LIBGPIOD_VERSION is specified, apply the tarball wrapper
    def wrapper(cmd: T) -> None:
        # Just-in-time import of tarfile and urllib.request so these are
        # not required for Yocto to build a vendored or linked package
        import sys
        import tarfile
        from tempfile import TemporaryDirectory
        from urllib.request import urlretrieve

        from packaging.version import Version

        # The "build" frontend will run setup.py twice within the same
        # temporary output directory. First for "sdist" and then for "wheel"
        # This would cause the build to fail with dirty "lib" and "include"
        # directories.
        # If the version in "libgpiod-version.txt" already matches our
        # requested tarball, then skip the fetch altogether.
        try:
            if open("libgpiod-version.txt").read() == LIBGPIOD_VERSION:
                log.info("skipping tarball fetch")
                func(cmd)
                return
        except OSError:
            pass

        # Early exit for build tree with dirty lib/include dirs
        for check_dir in "lib", "include":
            if path.isdir(f"./{check_dir}"):
                raise BaseError(f"refusing to overwrite ./{check_dir}")

        with TemporaryDirectory(prefix="libgpiod-") as temp_dir:
            tarball_filename = TAR_FILENAME.format(version=LIBGPIOD_VERSION)
            tarball_url = f"{SRC_BASE_URL}{tarball_filename}"
            asc_url = f"{SRC_BASE_URL}{ASC_FILENAME}"

            log.info(f"fetching: {asc_url}")

            asc_filename, _ = urlretrieve(asc_url, path.join(temp_dir, ASC_FILENAME))

            tarball_sha256 = find_sha256sum(asc_filename, tarball_filename)

            if Version(LIBGPIOD_VERSION) < Version(LIBGPIOD_MINIMUM_VERSION):
                raise BaseError(f"requires libgpiod>={LIBGPIOD_MINIMUM_VERSION}")

            log.info(f"fetching: {tarball_url}")

            downloaded_tarball, _ = urlretrieve(
                tarball_url, path.join(temp_dir, tarball_filename)
            )

            log.info(f"verifying: {tarball_filename}")
            if sha256(downloaded_tarball) != tarball_sha256:
                raise BaseError(f"signature mismatch for {tarball_filename}")

            # Unpack the downloaded tarball
            log.info(f"unpacking: {tarball_filename}")
            with tarfile.open(downloaded_tarball) as f:
                if sys.version_info < (3, 12):
                    f.extractall(temp_dir)
                else:
                    f.extractall(temp_dir, filter=tarfile.fully_trusted_filter)

            # Copy the include and lib directories we need to build libgpiod
            base_dir = path.join(temp_dir, f"libgpiod-{LIBGPIOD_VERSION}")
            copytree(path.join(base_dir, "include"), "./include")
            copytree(path.join(base_dir, "lib"), "./lib")

            # Since the license file is not in the bindings directory, we cannot
            # use the PEP-639 `license-files` property since the `Distribution`
            # class is constructed during `setup`, parses pyproject.toml, and
            # searches for the license file before we can copy files in to the
            # directory*. If the file is not there, we get an error.
            #
            # To work around this, we manually copy the license file to the
            # current directory and insert the license file into the metadata of
            # the `Distribution` prior to the cmdclass building the distribution.
            #
            # Copying the file as `LICENSE` allows wheels built off of the sdist
            # to automatically include the LICENSE, see:
            # https://setuptools.pypa.io/en/latest/userguide/miscellaneous.html
            #
            # *Note: this is not technically true, but it would require doing
            # something more complex like a custom build backend or to wrap
            # `setup` or the `Distrubtion` object which get invoked/created
            # multiple times and could fetch the tarball sources multiple times.
            # Further, we only really care about the license file when building
            # the released distribution files (sdist and wheels).

            # Read the SPDX license identifier from pyproject.toml
            license_file = None
            with open("pyproject.toml", "rb") as f:
                if sys.version_info >= (3, 11):
                    import tomllib

                    project = cast("dict[str,str]", tomllib.load(f).get("project"))
                    license_file = project.get("license")
                else:  # tomllib isn't standard, fall back to parsing by line
                    for line in f.readlines():
                        _line = line.decode()
                        if _line.startswith("license = "):
                            license_file = _line.split("=")[1].strip(' \r\n"')
                            break

            if license_file:  # Do not allow empty string or None
                _path = path.join(base_dir, "LICENSES", f"{license_file}.txt")
                if path.isfile(_path):
                    # manually set the license list for the distribution after
                    # the license file has been copied into the build directory.
                    #
                    # Note: that this must be in place prior to `egg_info.run`.
                    # For further details, see `egg_info.find_sources` and
                    # `manifest_maker.add_license_files`
                    copy(_path, LICENSE_FILE)
                    cmd.distribution.metadata.license_files = [LICENSE_FILE]  # type: ignore[attr-defined]

        # Save the libgpiod version for sdist
        open("libgpiod-version.txt", "w").write(LIBGPIOD_VERSION)

        # Run the command
        func(cmd)

        # Clean up the build directory
        if path.exists(LICENSE_FILE):
            unlink(LICENSE_FILE)
        rmtree("./lib", ignore_errors=True)
        rmtree("./include", ignore_errors=True)
        unlink("libgpiod-version.txt")

    return wrapper


class build_ext(orig_build_ext):
    """
    Wrap build_ext to amend the module sources and settings to build
    the bindings and gpiod into a combined module when a version is
    specified and LINK_SYSTEM_LIBGPIOD=1 is not present in env.

    run is wrapped with @fetch_tarball in order to fetch the sources
    needed to build binary wheels when LIBGPIOD_VERSION is specified, eg:

    LIBGPIOD_VERSION="2.0.2" python3 -m build .
    """

    @fetch_tarball
    def run(self) -> None:
        # Try to get the gpiod version from the .txt file included in sdist
        libgpiod_version: str | None
        try:
            libgpiod_version = open("libgpiod-version.txt").read()
        except OSError:
            libgpiod_version = LIBGPIOD_VERSION

        if libgpiod_version and not LINK_SYSTEM_LIBGPIOD:
            # When building the extension from an sdist with a vendored
            # amend gpiod._ext sources and settings accordingly.
            gpiod_ext = self.ext_map["gpiod._ext"]
            gpiod_ext.sources += [
                "lib/chip.c",
                "lib/chip-info.c",
                "lib/edge-event.c",
                "lib/info-event.c",
                "lib/internal.c",
                "lib/line-config.c",
                "lib/line-info.c",
                "lib/line-request.c",
                "lib/line-settings.c",
                "lib/misc.c",
                "lib/request-config.c",
            ]
            gpiod_ext.libraries = []
            gpiod_ext.include_dirs = ["include", "lib", "gpiod/ext"]
            gpiod_ext.extra_compile_args.append(
                f'-DGPIOD_API_VERSION_STR="{libgpiod_version}"',
            )

        super().run()


class sdist(orig_sdist):
    """
    Wrap sdist in order to fetch the libgpiod source files for vendoring
    into a source distribution.

    run is wrapped with @fetch_tarball in order to fetch the sources
    needed to build binary wheels when LIBGPIOD_VERSION is specified, eg:

    LIBGPIOD_VERSION="2.0.2" python3 -m build . --sdist
    """

    @fetch_tarball
    def run(self) -> None:
        super().run()


gpiod_ext = Extension(
    "gpiod._ext",
    sources=[
        "gpiod/ext/chip.c",
        "gpiod/ext/common.c",
        "gpiod/ext/line-config.c",
        "gpiod/ext/line-settings.c",
        "gpiod/ext/module.c",
        "gpiod/ext/request.c",
    ],
    define_macros=[("_GNU_SOURCE", "1")],
    libraries=["gpiod"],
    extra_compile_args=["-Wall", "-Wextra"],
)

setup(
    ext_modules=[gpiod_ext],
    cmdclass={"build_ext": build_ext, "sdist": sdist},
)