"""Shared fixture loading for the envelope tests.

Fixture files are data (YAML). These helpers only load and merge them; all policy
logic lives in the library under test.
"""

from __future__ import annotations

import copy
from pathlib import Path
from typing import Any

import pytest
import yaml

ROOT = Path(__file__).resolve().parent.parent
ENVELOPES = ROOT / "envelopes"
FIXTURES = Path(__file__).resolve().parent / "fixtures"

DELETE = "~delete"


def load_yaml(path: Path) -> Any:
    with path.open(encoding="utf-8") as handle:
        return yaml.safe_load(handle)


def deep_merge(base: Any, patch: Any) -> Any:
    """Return base with patch merged in; dicts merge recursively, '~delete' removes a key."""
    if not isinstance(base, dict) or not isinstance(patch, dict):
        return copy.deepcopy(patch)
    merged = copy.deepcopy(base)
    for key, value in patch.items():
        if value == DELETE:
            merged.pop(key, None)
        elif key in merged:
            merged[key] = deep_merge(merged[key], value)
        else:
            merged[key] = copy.deepcopy(value)
    return merged


def decision_cases() -> list[pytest.param]:
    """All decision cases from fixtures/decisions/*.yaml, with file context merged per case."""
    params = []
    for path in sorted((FIXTURES / "decisions").glob("*.yaml")):
        document = load_yaml(path)
        file_context = document.get("context", {})
        default_request = document.get("defaults", {}).get("request", {})
        for case in document["cases"]:
            params.append(
                pytest.param(
                    deep_merge(default_request, case["request"]),
                    {**file_context, **case.get("context", {})},
                    case["expect"],
                    id=f"{path.stem}: {case['name']}",
                )
            )
    return params