#!/usr/bin/env nix-shell
#!nix-shell -i python3 -p "python3.withPackages (ps: [ ps.beautifulsoup4 ps.lxml ps.packaging ])"
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
from typing import List

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
    branch: str
    date: str
    link: str
    eol: bool = False


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:
        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,
        branch=get_branch(version),
        version=version,
        date=date,
        link=link,
        eol=eol,
    )


def get_branch(version: str):
    # This is a testing kernel.
    if "rc" in version:
        return "testing"
    else:
        major, minor, *_ = version.split(".")
        return f"{major}.{minor}"


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() -> Version:
    with open(VERSIONS_FILE) as f:
        return parse_version(sorted(json.load(f).keys())[0])


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 = filter(None, [parse_release(release) for release in releases])
    all_kernels = json.load(VERSIONS_FILE.open())

    oldest_branch = get_oldest_branch()

    for kernel in parsed_releases:
        branch = get_branch(kernel.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:
            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),
        }

        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()