"""Tests for train_baseline() — fits one LightGBM regressor per target.

train_baseline produces the baseline metrics (MAPE + R^2) and dumps per-target
feature-importance JSON to storage. This is the only stage that pulls in
LightGBM + sklearn; downstream training repos read the metrics + parquet only.
"""

import json
from pathlib import Path

import numpy as np
import pandas as pd

from ml_training_data.storage import LocalStorage
from ml_training_data.train_baseline import train_baseline


def _synthetic_dataset(n: int = 200, seed: int = 0) -> pd.DataFrame:
    rng = np.random.default_rng(seed)
    floor_area = rng.uniform(40, 200, size=n)
    walls = rng.integers(1, 5, size=n)
    # sap_score correlates with floor_area + walls, plus noise.
    sap_score = (100 - 0.2 * floor_area + 3 * walls + rng.normal(0, 2, size=n)).astype(int)
    return pd.DataFrame(
        {
            "certificate_number": [f"CN-{i:04d}" for i in range(n)],
            "total_floor_area_m2": floor_area,
            "wall_count": walls,
            "sap_score": sap_score,
        }
    )


def test_train_baseline_returns_mape_and_r2_per_target(tmp_path: Path) -> None:
    # Arrange
    storage = LocalStorage(root=tmp_path)
    df = _synthetic_dataset()

    # Act
    metrics = train_baseline(
        df=df,
        targets=["sap_score"],
        storage=storage,
        run_key="runs/2026-05-16/",
        seed=42,
    )

    # Assert
    assert "sap_score" in metrics
    assert "mape" in metrics["sap_score"]
    assert "r2" in metrics["sap_score"]
    assert metrics["sap_score"]["r2"] > 0.0  # learns something on a correlated signal


def test_train_baseline_writes_feature_importance_per_target(tmp_path: Path) -> None:
    # Arrange
    storage = LocalStorage(root=tmp_path)
    df = _synthetic_dataset()

    # Act
    train_baseline(
        df=df,
        targets=["sap_score"],
        storage=storage,
        run_key="runs/2026-05-16/",
        seed=42,
    )

    # Assert
    importance = json.loads(storage.read_bytes("runs/2026-05-16/importance_sap_score.json"))
    assert set(importance.keys()) == {"total_floor_area_m2", "wall_count"}
    assert all(isinstance(v, (int, float)) for v in importance.values())


def test_train_baseline_handles_multiple_targets_independently(tmp_path: Path) -> None:
    # Arrange
    storage = LocalStorage(root=tmp_path)
    df = _synthetic_dataset()
    df["co2_emissions"] = df["sap_score"] * 0.1 + 1.0  # second correlated target

    # Act
    metrics = train_baseline(
        df=df,
        targets=["sap_score", "co2_emissions"],
        storage=storage,
        run_key="runs/2026-05-16/",
        seed=42,
    )

    # Assert
    assert set(metrics.keys()) == {"sap_score", "co2_emissions"}
    assert storage.exists("runs/2026-05-16/importance_sap_score.json")
    assert storage.exists("runs/2026-05-16/importance_co2_emissions.json")
    assert storage.exists("runs/2026-05-16/metrics.json")