#!/usr/bin/env python3

import argparse
import os
import re
import subprocess
import sys
from pathlib import Path


ROOT_DIR = Path(__file__).resolve().parent.parent
CARGO_TOML = ROOT_DIR / "Cargo.toml"


def parse_args(argv: list[str]) -> argparse.Namespace:
    parser = argparse.ArgumentParser(description="Create a tagged Codex release.")
    parser.add_argument(
        "version",
        help="Version string used for Cargo.toml and the Git tag (e.g. 0.1.0-alpha.4).",
    )
    return parser.parse_args(argv[1:])


def main(argv: list[str]) -> int:
    os.chdir(ROOT_DIR)
    args = parse_args(argv)
    try:
        ensure_clean_worktree()
        branch = current_branch()
        ensure_on_main(branch)
        ensure_on_origin_main()
        create_release(args.version, branch)
    except ReleaseError as error:
        print(f"ERROR: {error}", file=sys.stderr)
        return 1
    return 0


def ensure_clean_worktree() -> None:
    commands = [
        ["diff", "--quiet"],
        ["diff", "--cached", "--quiet"],
    ]
    for command in commands:
        result = run_git(command, check=False)
        if result.returncode != 0:
            raise ReleaseError("You have uncommitted changes.")

    untracked = run_git(["ls-files", "--others", "--exclude-standard"], capture_output=True)
    if untracked.stdout.strip():
        raise ReleaseError("You have untracked files.")


def ensure_on_main(branch: str) -> None:
    if branch != "main":
        raise ReleaseError(
            f"Releases must be created from the 'main' branch (current: '{branch}')."
        )


def ensure_on_origin_main() -> None:
    try:
        run_git(["fetch", "--quiet", "origin", "main"])
    except ReleaseError as error:
        raise ReleaseError(
            "Failed to fetch 'origin/main'. Ensure the 'origin' remote is configured and reachable."
        ) from error

    result = run_git(["merge-base", "--is-ancestor", "HEAD", "origin/main"], check=False)
    if result.returncode != 0:
        raise ReleaseError(
            "Your local 'main' HEAD commit is not present on 'origin/main'. "
            "Please push first (git push origin main) or check out a commit on 'origin/main'."
        )


def current_branch() -> str:
    result = run_git(["symbolic-ref", "--short", "-q", "HEAD"], capture_output=True, check=False)
    branch = result.stdout.strip()
    if result.returncode != 0 or not branch:
        raise ReleaseError("Could not determine the current branch (detached HEAD?).")
    return branch


def update_version(version: str) -> None:
    content = CARGO_TOML.read_text(encoding="utf-8")
    new_content, matches = re.subn(
        r'^version = "[^"]+"', f'version = "{version}"', content, count=1, flags=re.MULTILINE
    )
    if matches != 1:
        raise ReleaseError("Unable to update version in Cargo.toml.")
    CARGO_TOML.write_text(new_content, encoding="utf-8")


def create_release(version: str, branch: str) -> None:
    tag = f"rust-v{version}"
    run_git(["checkout", "-b", tag])
    try:
        update_version(version)
        run_git(["add", "Cargo.toml"])
        run_git(["commit", "-m", f"Release {version}"])
        run_git(["tag", "-a", tag, "-m", f"Release {version}"])
        run_git(["push", "origin", f"refs/tags/{tag}"])
    finally:
        run_git(["checkout", branch])


class ReleaseError(RuntimeError):
    pass


def run_git(
    args: list[str], *, capture_output: bool = False, check: bool = True
) -> subprocess.CompletedProcess:
    result = subprocess.run(
        ["git", *args],
        cwd=ROOT_DIR,
        text=True,
        capture_output=capture_output,
    )
    if check and result.returncode != 0:
        stderr = result.stderr.strip() if result.stderr else ""
        stdout = result.stdout.strip() if result.stdout else ""
        message = stderr if stderr else stdout
        raise ReleaseError(message or f"git {' '.join(args)} failed")
    return result


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