"""Basic tests for the backend application."""

from importlib import metadata
from pathlib import Path
from typing import Any, cast
from unittest.mock import AsyncMock

import pytest
from fastapi.testclient import TestClient
from sqlalchemy.exc import SQLAlchemyError
from sqlalchemy.ext.asyncio import AsyncSession

from backend import main as backend_main
from backend.main import (
    app,
    compatibility_check,
    compatibility_status,
    get_api_session,
    read_root,
    validate_runtime_policy,
)

parse_exact_pin = backend_main.__dict__["_parse_exact_pin"]
required_package_pins = backend_main.__dict__["_required_package_pins"]
required_package_pins_from_dependencies = backend_main.__dict__[
    "_required_package_pins_from_dependencies"
]


def test_app_creation():
    """Test that the FastAPI app is created properly."""
    assert app is not None
    assert app.title == "Plex Playlist Backend"
    assert app.version == "0.1.0"


def test_read_root():
    """Test the root endpoint function."""
    result = read_root()
    assert result == {"message": "Plex Playlist Backend API"}


def test_health_check():
    """Test the health check endpoint function."""

    healthy_session = cast("AsyncSession", AsyncMock(spec=AsyncSession))
    healthy_session.execute = AsyncMock(return_value=1)

    async def override_get_session():
        """Provide a healthy session dependency override for tests."""
        yield healthy_session

    app.dependency_overrides[get_api_session] = override_get_session
    try:
        with TestClient(app) as client:
            response = client.get("/health")

        assert response.status_code == 200
        assert response.json() == {"status": "healthy", "database": "connected"}
    finally:
        app.dependency_overrides.clear()


def test_typeguard_validation():
    """Test that typeguard is working for type validation."""

    # Test a function with type hints to ensure typeguard is active
    def typed_function(x: int, y: str) -> str:
        return f"{x}: {y}"

    # This should work fine
    result = typed_function(42, "test")
    assert result == "42: test"

    # This would fail with typeguard active, but we'll just test the happy path
    # to ensure coverage of our code without breaking the test


def test_health_check_db_unavailable():
    """Health endpoint should return unavailable when DB probe fails."""

    unhealthy_session = cast("AsyncSession", AsyncMock(spec=AsyncSession))
    unhealthy_session.execute = AsyncMock(
        side_effect=SQLAlchemyError("database unavailable")
    )

    async def override_get_session():
        """Provide an unhealthy session dependency override for tests."""
        yield unhealthy_session

    app.dependency_overrides[get_api_session] = override_get_session
    try:
        with TestClient(app) as client:
            response = client.get("/health")

        assert response.status_code == 503
        assert response.json() == {
            "status": "unhealthy",
            "database": "disconnected",
        }
    finally:
        app.dependency_overrides.clear()


def test_compatibility_status_success(monkeypatch: pytest.MonkeyPatch):
    """Compatibility status should be healthy when all checks match policy."""

    monkeypatch.setenv("BACKEND_REQUIRED_PYTHON", "3.14")
    required_pins = cast("dict[str, str]", compatibility_status()["required_packages"])

    def installed_version(package_name: str) -> str:
        return required_pins[package_name]

    monkeypatch.setattr("backend.main._installed_version", installed_version)
    status = cast("dict[str, Any]", compatibility_status())

    assert status["ok"] is True
    assert status["package_errors"] == {}


def test_compatibility_status_missing_package(monkeypatch: pytest.MonkeyPatch):
    """Compatibility status should record metadata lookup failures."""

    def missing_version(_: str) -> str:
        raise metadata.PackageNotFoundError("missing")

    monkeypatch.setattr("backend.main._installed_version", missing_version)
    status = cast("dict[str, Any]", compatibility_status())
    package_checks = cast("dict[str, bool]", status["package_checks"])
    package_errors = cast("dict[str, str]", status["package_errors"])

    assert status["ok"] is False
    assert package_checks["fastapi"] is False
    assert "fastapi" in package_errors


def test_validate_runtime_policy_raises(monkeypatch: pytest.MonkeyPatch):
    """Runtime policy validation should fail when compatibility is not ok."""

    def invalid_status() -> dict[str, object]:
        return {"ok": False}

    monkeypatch.setattr("backend.main.compatibility_status", invalid_status)

    with pytest.raises(RuntimeError):
        validate_runtime_policy()


def test_compatibility_check_returns_status() -> None:
    """Compatibility endpoint helper should return policy payload."""
    payload = compatibility_check()
    assert "ok" in payload


def test_parse_exact_pin_handles_valid_and_invalid_requirements() -> None:
    """Exact pin parsing should normalize extras and reject malformed pins."""
    assert parse_exact_pin("psycopg[binary]==3.2.12 ; python_version >= '3.14'") == (
        "psycopg",
        "3.2.12",
    )
    assert parse_exact_pin("uvicorn>=0.51.0") is None
    assert parse_exact_pin("==0.51.0") is None
    assert parse_exact_pin("uvicorn==") is None


def test_required_package_pins_from_dependencies_filters_non_exact_pins() -> None:
    """Only exact dependency pins should be included in runtime policy."""
    dependencies = [
        "fastapi==0.139.0",
        "uvicorn>=0.51.0",
        "psycopg[binary]==3.2.12",
    ]

    assert required_package_pins_from_dependencies(dependencies) == {
        "fastapi": "0.139.0",
        "psycopg": "3.2.12",
    }


def test_required_package_pins_uses_installed_metadata(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    """Installed project metadata should be the primary pin source."""

    def fake_requires(_: str) -> list[str]:
        return ["fastapi==0.139.0", "psycopg[binary]==3.2.12"]

    def unexpected_read_text(_: Path, encoding: str = "utf-8") -> str:
        del encoding
        raise AssertionError("pyproject fallback should not run")

    monkeypatch.setattr(backend_main.metadata, "requires", fake_requires)
    monkeypatch.setattr(Path, "read_text", unexpected_read_text)

    assert required_package_pins() == {
        "fastapi": "0.139.0",
        "psycopg": "3.2.12",
    }


def test_required_package_pins_falls_back_to_pyproject(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    """Pyproject should be used when installed metadata is unavailable or unusable."""

    def missing_requires(_: str) -> list[str]:
        raise metadata.PackageNotFoundError("missing")

    def fake_read_text(_: Path, encoding: str = "utf-8") -> str:
        del encoding
        return "[project]\ndependencies = []\n"

    def fake_toml_loads(_: str) -> dict[str, object]:
        return {
            "project": {
                "dependencies": [
                    "fastapi==0.139.0",
                    123,
                    "psycopg[binary]==3.2.12",
                ]
            }
        }

    monkeypatch.setattr(backend_main.metadata, "requires", missing_requires)
    monkeypatch.setattr(Path, "read_text", fake_read_text)
    monkeypatch.setattr(backend_main.tomllib, "loads", fake_toml_loads)

    assert required_package_pins() == {
        "fastapi": "0.139.0",
        "psycopg": "3.2.12",
    }


def test_required_package_pins_handles_invalid_pyproject_shapes(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    """Invalid pyproject structures should safely produce no required pins."""

    def missing_requires(_: str) -> list[str]:
        raise metadata.PackageNotFoundError("missing")

    def fake_read_text(_: Path, encoding: str = "utf-8") -> str:
        del encoding
        return "[project]\ndependencies = []\n"

    def invalid_project_loads(_: str) -> dict[str, object]:
        return {"project": []}

    def missing_dependencies_loads(_: str) -> dict[str, object]:
        return {"project": {}}

    monkeypatch.setattr(backend_main.metadata, "requires", missing_requires)
    monkeypatch.setattr(Path, "read_text", fake_read_text)

    monkeypatch.setattr(backend_main.tomllib, "loads", invalid_project_loads)
    assert required_package_pins() == {}

    monkeypatch.setattr(backend_main.tomllib, "loads", missing_dependencies_loads)
    assert required_package_pins() == {}


def test_compatibility_status_rejects_malformed_required_python(
    monkeypatch: pytest.MonkeyPatch,
) -> None:
    """Malformed Python policy strings should fail compatibility checks."""

    def empty_required_package_pins() -> dict[str, str]:
        return {}

    monkeypatch.setenv("BACKEND_REQUIRED_PYTHON", "3.14.1")
    monkeypatch.setattr(
        backend_main,
        "_required_package_pins",
        empty_required_package_pins,
    )

    status = cast("dict[str, Any]", compatibility_status())

    assert status["ok"] is False
    assert status["python_policy_valid"] is False