#!/usr/bin/env python3
"""Describe the Gitea request that creates or resynchronizes a release."""
from __future__ import annotations

import argparse
import json
from pathlib import Path
import re
import sys
from typing import Any


_SEMVER = r"(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)\.(?:0|[1-9]\d*)"


class ReleaseRequestError(ValueError):
    """A release request could not be prepared safely."""


def build_release_request(
    version: str, body: str, existing_release: dict[str, Any] | None
) -> dict[str, Any]:
    """Return the observable POST or PATCH request for a Gitea release."""
    if not re.fullmatch(_SEMVER, version):
        raise ReleaseRequestError(f"version is not bare semver: {version!r}")
    if existing_release is None:
        return {
            "method": "POST",
            "path": "/releases",
            "payload": {"tag_name": f"v{version}", "name": f"v{version}", "body": body},
        }

    release_id = existing_release.get("id")
    if not isinstance(release_id, int):
        raise ReleaseRequestError("existing release does not contain an integer id")
    return {
        "method": "PATCH",
        "path": f"/releases/{release_id}",
        "payload": {"body": body},
    }


def _read_json(path: Path) -> dict[str, Any]:
    try:
        value = json.loads(path.read_text(encoding="utf-8"))
    except (OSError, json.JSONDecodeError) as error:
        raise ReleaseRequestError(f"cannot read existing release {path}: {error}") from error
    if not isinstance(value, dict):
        raise ReleaseRequestError("existing release must be a JSON object")
    return value


def main(argv: list[str] | None = None) -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--version", required=True)
    parser.add_argument("--body-file", type=Path, required=True)
    parser.add_argument("--existing-release", type=Path)
    args = parser.parse_args(argv)
    try:
        body = args.body_file.read_text(encoding="utf-8")
        existing = _read_json(args.existing_release) if args.existing_release else None
        print(json.dumps(build_release_request(args.version, body, existing)))
    except (OSError, ReleaseRequestError) as error:
        print(f"::error::{error}", file=sys.stderr)
        return 1
    return 0


if __name__ == "__main__":
    raise SystemExit(main())