"""Tests for Alembic migration setup."""

import os
from pathlib import Path

import pytest
from alembic import command
from alembic.config import Config
from sqlalchemy import create_engine, inspect

# Resolve the repo root regardless of where pytest is invoked from.
_REPO_ROOT = Path(__file__).resolve().parents[2]


@pytest.fixture()
def alembic_cfg(tmp_path):
    """Create an Alembic config pointing at a temporary SQLite database."""
    db_path = tmp_path / "test.db"
    db_url = f"sqlite:///{db_path}"

    cfg = Config(str(_REPO_ROOT / "alembic.ini"))
    cfg.set_main_option("script_location", str(_REPO_ROOT / "alembic"))
    cfg.set_main_option("sqlalchemy.url", db_url)
    return cfg, db_url


def test_upgrade_head_creates_all_tables(alembic_cfg):
    """Running 'upgrade head' should create all expected tables."""
    cfg, db_url = alembic_cfg
    command.upgrade(cfg, "head")

    engine = create_engine(db_url)
    inspector = inspect(engine)
    tables = set(inspector.get_table_names())

    expected = {
        "alembic_version",
        "users",
        "projects",
        "experiments",
        "runs",
        "stage_results",
        "scores",
        "response_cache",
        "webhook_configs",
    }
    assert expected == tables


def test_downgrade_base_removes_all_tables(alembic_cfg):
    """Running 'downgrade base' should remove all application tables."""
    cfg, db_url = alembic_cfg
    command.upgrade(cfg, "head")
    command.downgrade(cfg, "base")

    engine = create_engine(db_url)
    inspector = inspect(engine)
    tables = set(inspector.get_table_names())

    # Only alembic_version should remain
    assert tables == {"alembic_version"}


def test_runs_table_has_expected_columns(alembic_cfg):
    """Spot-check that the runs table has key columns."""
    cfg, db_url = alembic_cfg
    command.upgrade(cfg, "head")

    engine = create_engine(db_url)
    inspector = inspect(engine)
    columns = {c["name"] for c in inspector.get_columns("runs")}

    assert "id" in columns
    assert "experiment_id" in columns
    assert "config_hash" in columns
    assert "status" in columns
    assert "cost_estimate" in columns


def test_indexes_created(alembic_cfg):
    """Verify key indexes exist after migration."""
    cfg, db_url = alembic_cfg
    command.upgrade(cfg, "head")

    engine = create_engine(db_url)
    inspector = inspect(engine)

    run_indexes = {idx["name"] for idx in inspector.get_indexes("runs")}
    assert "ix_runs_config_hash" in run_indexes
    assert "ix_runs_experiment_id" in run_indexes

    score_indexes = {idx["name"] for idx in inspector.get_indexes("scores")}
    assert "ix_scores_run_id" in score_indexes
    assert "ix_scores_scorer_name" in score_indexes


def test_foreign_keys_on_experiments(alembic_cfg):
    """Verify experiments table has FK to projects."""
    cfg, db_url = alembic_cfg
    command.upgrade(cfg, "head")

    engine = create_engine(db_url)
    inspector = inspect(engine)
    fks = inspector.get_foreign_keys("experiments")

    referred_tables = {fk["referred_table"] for fk in fks}
    assert "projects" in referred_tables