#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p "python3.withPackages (ps: [ ps.beautifulsoup4 ps.lxml ps.packaging ])"
from functools import cached_property
from itertools import groupby
import json
import os
import pathlib
import subprocess
import sys
import urllib.request
from dataclasses import dataclass
from enum import Enum

from bs4 import BeautifulSoup, NavigableString, Tag
from packaging.version import parse as parse_version, Version


HERE = pathlib.Path(__file__).parent
ROOT = HERE.parent.parent.parent.parent
VERSIONS_FILE = HERE / "kernels-org.json"


class KernelNature(Enum):
    MAINLINE = 1
    STABLE = 2
    LONGTERM = 3


@dataclass
class KernelRelease:
    nature: KernelNature
    version: str
    date: str
    link: str
    eol: bool = False

    @cached_property
    def parsed_version(self) -> Version:
        return parse_version(self.version)

    @cached_property
    def branch(self) -> str:
        version = self.parsed_version
        # This is a testing kernel.
        if version.is_prerelease:
            return "testing"
        else:
            return f"{version.major}.{version.minor}"


def parse_release(release: Tag) -> KernelRelease | None:
    columns: list[Tag] = list(release.find_all("td"))
    try:
        nature = KernelNature[columns[0].get_text().rstrip(":").upper()]
    except KeyError:
        # skip linux-next
        return None

    version = columns[1].get_text().rstrip(" [EOL]")
    date = columns[2].get_text()
    link = columns[3].find("a")
    if link is not None and isinstance(link, Tag):
        link = link.attrs.get("href")
    assert link is not None, f"link for kernel {version} is non-existent"
    eol = bool(release.find(class_="eolkernel"))

    return KernelRelease(
        nature=nature,
        version=version,
        date=date,
        link=link,
        eol=eol,
    )


def get_hash(kernel: KernelRelease):
    if kernel.branch == "testing":
        args = ["--unpack"]
    else:
        args = []

    hash = (
        subprocess.check_output(["nix-prefetch-url", kernel.link] + args)
        .decode()
        .strip()
    )
    return f"sha256:{hash}"


def get_oldest_branch(kernels) -> Version:
    return min(parse_version(v) for v in kernels.keys() if v != "testing")


def predates_oldest_branch(oldest: Version, to_compare: str) -> bool:
    if to_compare == "testing":
        return False

    return parse_version(to_compare) < oldest


def commit(message):
    return subprocess.check_call(["git", "commit", "-m", message, VERSIONS_FILE])


def main():
    kernel_org = urllib.request.urlopen("https://kernel.org/")
    soup = BeautifulSoup(kernel_org.read().decode(), "lxml")
    release_table = soup.find(id="releases")
    if not release_table or isinstance(release_table, NavigableString):
        print(release_table, file=sys.stderr)
        print("Failed to find the release table on https://kernel.org", file=sys.stderr)
        sys.exit(1)

    releases = release_table.find_all("tr")
    parsed_releases = [
        parsed for release in releases
        if (parsed := parse_release(release)) is not None
    ]
    all_kernels = json.load(VERSIONS_FILE.open())
    oldest_branch = get_oldest_branch(all_kernels)

    for (branch, kernels) in groupby(parsed_releases, lambda kernel: kernel.branch):
        kernel = max(kernels, key=lambda kernel: kernel.parsed_version)
        nixpkgs_branch = branch.replace(".", "_")

        old_version = all_kernels.get(branch, {}).get("version")
        if old_version == kernel.version:
            print(f"linux_{nixpkgs_branch}: {kernel.version} is latest, skipping...")
            continue

        if predates_oldest_branch(oldest_branch, kernel.branch):
            print(
                f"{kernel.branch} is too old and not supported anymore, skipping...",
                file=sys.stderr
            )
            continue

        if old_version is None:
            if kernel.eol:
                print(
                    f"{kernel.branch} is EOL, not adding...",
                    file=sys.stderr
                )
                continue

            message = f"linux_{nixpkgs_branch}: init at {kernel.version}"
        else:
            message = f"linux_{nixpkgs_branch}: {old_version} -> {kernel.version}"

        print(message, file=sys.stderr)

        all_kernels[branch] = {
            "version": kernel.version,
            "hash": get_hash(kernel),
            "lts": kernel.nature == KernelNature.LONGTERM,
        }

        with VERSIONS_FILE.open("w") as fd:
            json.dump(all_kernels, fd, indent=4)
            fd.write("\n")  # makes editorconfig happy

        if os.environ.get("COMMIT") == "1":
            commit(message)


if __name__ == "__main__":
    main()