"""Pytest plugin for using FixtureRegistry fixtures in tests."""

from collections.abc import Callable, Sequence
from typing import Any, cast

import pytest
from sqlalchemy import select
from sqlalchemy.ext.asyncio import AsyncSession
from sqlalchemy.orm import DeclarativeBase, selectinload
from sqlalchemy.orm.interfaces import ExecutableOption, ORMOption

from ..db import get_transaction
from ..fixtures import FixtureRegistry, LoadStrategy


def register_fixtures(
    registry: FixtureRegistry,
    namespace: dict[str, Any],
    *,
    prefix: str = "fixture_",
    session_fixture: str = "db_session",
    strategy: LoadStrategy = LoadStrategy.MERGE,
) -> list[str]:
    """Register pytest fixtures from a FixtureRegistry.

    Automatically creates pytest fixtures for each fixture in the registry.
    Dependencies are resolved via pytest fixture dependencies.

    Args:
        registry: The FixtureRegistry containing fixtures
        namespace: The module's globals() dict to add fixtures to
        prefix: Prefix for generated fixture names (default: "fixture_")
        session_fixture: Name of the db session fixture (default: "db_session")
        strategy: Loading strategy for fixtures (default: MERGE)

    Returns:
        List of created fixture names

    Example:
        ```python
        # conftest.py
        from app.fixtures import fixtures
        from fastapi_toolsets.pytest_plugin import register_fixtures

        register_fixtures(fixtures, globals())

        # Creates fixtures like:
        # - fixture_roles
        # - fixture_users (depends on fixture_roles if users depends on roles)
        # - fixture_posts (depends on fixture_users if posts depends on users)
        ```
    """
    created_fixtures: list[str] = []

    for fixture in registry.get_all():
        fixture_name = f"{prefix}{fixture.name}"

        # Build list of pytest fixture dependencies
        pytest_deps = [session_fixture]
        for dep in fixture.depends_on:
            pytest_deps.append(f"{prefix}{dep}")

        # Create the fixture function
        fixture_func = _create_fixture_function(
            registry=registry,
            fixture_name=fixture.name,
            dependencies=pytest_deps,
            strategy=strategy,
        )

        # Apply pytest.fixture decorator
        decorated = pytest.fixture(fixture_func)

        # Add to namespace
        namespace[fixture_name] = decorated
        created_fixtures.append(fixture_name)

    return created_fixtures


def _create_fixture_function(
    registry: FixtureRegistry,
    fixture_name: str,
    dependencies: list[str],
    strategy: LoadStrategy,
) -> Callable[..., Any]:
    """Create a fixture function with the correct signature.

    The function signature must include all dependencies as parameters
    for pytest to resolve them correctly.
    """
    # Get the fixture definition
    fixture_def = registry.get(fixture_name)

    # Build the function dynamically with correct parameters
    # We need the session as first param, then all dependencies
    async def fixture_func(**kwargs: Any) -> Sequence[DeclarativeBase]:
        # Get session from kwargs (first dependency)
        session: AsyncSession = kwargs[dependencies[0]]

        # Load the fixture data
        instances = list(fixture_def.func())

        if not instances:
            return []

        loaded: list[DeclarativeBase] = []

        async with get_transaction(session):
            for instance in instances:
                if strategy == LoadStrategy.INSERT:
                    session.add(instance)
                    loaded.append(instance)
                elif strategy == LoadStrategy.MERGE:
                    merged = await session.merge(instance)
                    loaded.append(merged)
                elif strategy == LoadStrategy.SKIP_EXISTING:  # pragma: no branch
                    pk = _get_primary_key(instance)
                    if pk is not None:
                        existing = await session.get(type(instance), pk)
                        if existing is None:
                            session.add(instance)
                            loaded.append(instance)
                        else:
                            loaded.append(existing)
                    else:
                        session.add(instance)
                        loaded.append(instance)

        if loaded:  # pragma: no branch
            load_options = _relationship_load_options(type(loaded[0]))
            if load_options:
                return await _reload_with_relationships(session, loaded, load_options)

        return loaded

    # Update function signature to include dependencies
    # This is needed for pytest to inject the right fixtures
    params = ", ".join(dependencies)
    code = f"async def {fixture_name}_fixture({params}):\n    return await _impl({', '.join(f'{d}={d}' for d in dependencies)})"

    local_ns: dict[str, Any] = {"_impl": fixture_func}
    exec(code, local_ns)  # noqa: S102

    created_func = local_ns[f"{fixture_name}_fixture"]
    created_func.__doc__ = f"Load {fixture_name} fixture data."

    return created_func


def _relationship_load_options(model: type[DeclarativeBase]) -> list[ExecutableOption]:
    """Build selectinload options for all direct relationships on a model."""
    return [
        selectinload(getattr(model, rel.key)) for rel in model.__mapper__.relationships
    ]


async def _reload_with_relationships(
    session: AsyncSession,
    instances: list[DeclarativeBase],
    load_options: list[ExecutableOption],
) -> list[DeclarativeBase]:
    """Reload instances in a single bulk query with relationship eager-loading.

    Uses one SELECT … WHERE pk IN (…) so selectinload can batch all relationship
    queries — 1 + N_relationships round-trips regardless of how many instances
    there are, instead of one session.get() per instance.

    Preserves the original insertion order.
    """
    model = type(instances[0])
    mapper = model.__mapper__
    pk_cols = mapper.primary_key

    if len(pk_cols) == 1:
        pk_attr = getattr(model, pk_cols[0].key)
        pks = [getattr(inst, pk_cols[0].key) for inst in instances]
        result = await session.execute(
            select(model).where(pk_attr.in_(pks)).options(*load_options)
        )
        by_pk = {getattr(row, pk_cols[0].key): row for row in result.unique().scalars()}
        return [by_pk[pk] for pk in pks]

    # Composite PK: fall back to per-instance reload
    reloaded: list[DeclarativeBase] = []
    for instance in instances:
        pk = _get_primary_key(instance)
        refreshed = await session.get(
            model,
            pk,
            options=cast(list[ORMOption], load_options),
            populate_existing=True,
        )
        if refreshed is not None:  # pragma: no branch
            reloaded.append(refreshed)
    return reloaded


def _get_primary_key(instance: DeclarativeBase) -> Any | None:
    """Get the primary key value of a model instance."""
    mapper = instance.__class__.__mapper__
    pk_cols = mapper.primary_key

    if len(pk_cols) == 1:
        return getattr(instance, pk_cols[0].name, None)

    pk_values = tuple(getattr(instance, col.name, None) for col in pk_cols)
    if all(v is not None for v in pk_values):
        return pk_values
    return None