#!/usr/bin/env python3
"""Apply a strategic-merge patch to selected documents before kubectl apply."""

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


def field(document: str, name: str) -> str:
    match = re.search(rf"(?m)^{re.escape(name)}:\s*(\S+)\s*$", document)
    return match.group(1) if match else ""


def metadata_name(document: str) -> str:
    match = re.search(
        r"(?ms)^metadata:\s*\n(?P<body>(?:[ \t]+.*(?:\n|$))*)",
        document,
    )
    if not match:
        return ""
    name = re.search(r"(?m)^[ \t]+name:\s*(\S+)\s*$", match.group("body"))
    return name.group(1).strip("\"'") if name else ""


def main() -> None:
    parser = argparse.ArgumentParser()
    parser.add_argument("manifest", type=Path)
    parser.add_argument("--kind", action="append", required=True)
    parser.add_argument("--name")
    parser.add_argument("--patch", required=True)
    parser.add_argument("--require-match", action="store_true")
    args = parser.parse_args()

    documents = [
        document.strip()
        for document in re.split(r"(?m)^---\s*$", args.manifest.read_text())
        if document.strip()
    ]
    patched = 0
    environment = dict(os.environ)
    environment["KUBECONFIG"] = os.devnull

    for index, document in enumerate(documents):
        if field(document, "kind") not in set(args.kind):
            continue
        if args.name and metadata_name(document) != args.name:
            continue
        with tempfile.NamedTemporaryFile(mode="w", suffix=".yaml") as source:
            source.write(document + "\n")
            source.flush()
            result = subprocess.run(
                [
                    "kubectl",
                    "patch",
                    "--local",
                    "-f",
                    source.name,
                    "--type=strategic",
                    "--patch",
                    args.patch,
                    "-o",
                    "yaml",
                ],
                check=True,
                env=environment,
                stdout=subprocess.PIPE,
                text=True,
            )
        documents[index] = result.stdout.strip()
        patched += 1

    if args.require_match and patched == 0:
        target = "/".join(args.kind)
        if args.name:
            target += f"/{args.name}"
        raise SystemExit(f"manifest does not contain required patch target {target}")

    args.manifest.write_text("\n---\n".join(documents) + "\n")


if __name__ == "__main__":
    main()