"""Tests for multi-pair G10 pipeline (Option C).

Tests the prepare_multipair.py merge logic and train.py multipair build().
Run: cd ~/dev/AI/jepa-fx-risk && .venv/bin/python -m pytest tests/test_multipair.py -v
"""
import importlib.util
import numpy as np
import pandas as pd
import pytest
import os


def _import_mp():
    spec = importlib.util.spec_from_file_location("prepare_multipair", "scripts/prepare_multipair.py")
    mod = importlib.util.module_from_spec(spec)
    spec.loader.exec_module(mod)
    return mod


@pytest.fixture(scope="module")
def mp():
    return _import_mp()


def _pair_df(start: str, n_hours: int, seed: int) -> pd.DataFrame:
    """Synthetic single-pair hourly parquet (same schema as prepare_hourly output)."""
    rng = np.random.default_rng(seed)
    dts = pd.date_range(start, periods=n_hours, freq="h")
    closes = 1.1 + np.cumsum(rng.normal(0, 0.001, n_hours))
    return pd.DataFrame({
        "datetime":     dts,
        "close":        closes,
        "ret":          rng.normal(0, 0.001, n_hours),
        "realized_vol": np.abs(rng.normal(0.0005, 0.0001, n_hours)),
    })


# 1. merge_pair_parquets returns inner join on datetime
def test_merge_inner_join(mp):
    eur = _pair_df("2020-01-01 00:00", 100, seed=1)  # t0 to t0+99h
    gbp = _pair_df("2020-01-01 20:00", 60, seed=2)   # t0+20 to t0+79h → 60 common
    result = mp.merge_pair_parquets({"eurusd": eur, "gbpusd": gbp})
    assert len(result) == 60, f"expected 60 (inner join), got {len(result)}"


# 2. merge_pair_parquets prefixes columns with pair name
def test_merge_column_prefixes(mp):
    eur = _pair_df("2020-01-01 00:00", 50, seed=1)
    gbp = _pair_df("2020-01-01 00:00", 50, seed=2)
    result = mp.merge_pair_parquets({"eurusd": eur, "gbpusd": gbp})
    assert "datetime" in result.columns, "datetime column missing"
    assert "eurusd_ret" in result.columns
    assert "eurusd_rv" in result.columns
    assert "gbpusd_ret" in result.columns
    assert "gbpusd_rv" in result.columns
    # raw pair columns should not leak through unprefixed
    assert "ret" not in result.columns
    assert "realized_vol" not in result.columns


# 3. No NaN in merged output
def test_merge_no_nan(mp):
    eur = _pair_df("2020-01-01 00:00", 50, seed=1)
    gbp = _pair_df("2020-01-01 00:00", 50, seed=2)
    result = mp.merge_pair_parquets({"eurusd": eur, "gbpusd": gbp})
    nan_count = result.isnull().sum().sum()
    assert nan_count == 0, f"{nan_count} NaN values in merged output"


# 4. PAIRS constant is a non-empty list starting with eurusd
def test_pairs_constant(mp):
    assert hasattr(mp, "PAIRS"), "PAIRS constant missing from prepare_multipair.py"
    assert len(mp.PAIRS) >= 2, "PAIRS must have at least 2 pairs"
    assert mp.PAIRS[0] == "eurusd", "first pair must be eurusd (target pair)"


# 5. merge target column is eurusd_rv (for build() target selection)
def test_merge_has_eurusd_rv_as_target(mp):
    eur = _pair_df("2020-01-01 00:00", 50, seed=1)
    gbp = _pair_df("2020-01-01 00:00", 50, seed=2)
    result = mp.merge_pair_parquets({"eurusd": eur, "gbpusd": gbp})
    assert "eurusd_rv" in result.columns, "eurusd_rv (target) missing from merged output"
    assert (result["eurusd_rv"] > 0).all(), "eurusd_rv should be positive"


# 6. train.py recognises JEPA_USE_MULTIPAIR env var
def test_use_multipair_knob():
    import importlib.util as ilu
    spec = ilu.spec_from_file_location(f"train_mp_{id(None)}", "train.py")
    mod = ilu.module_from_spec(spec)
    saved = os.environ.get("JEPA_USE_MULTIPAIR")
    os.environ["JEPA_USE_MULTIPAIR"] = "1"
    try:
        spec.loader.exec_module(mod)
    finally:
        if saved is None:
            os.environ.pop("JEPA_USE_MULTIPAIR", None)
        else:
            os.environ["JEPA_USE_MULTIPAIR"] = saved
    assert hasattr(mod, "USE_MULTIPAIR"), "USE_MULTIPAIR knob missing from train.py"
    assert mod.USE_MULTIPAIR is True


# 7. build() uses n_pairs*2 channels when multipair parquet present
def test_build_uses_multipair_channels():
    import importlib.util as ilu
    multipair_path = "data/processed/eurusd_multipair.parquet"
    if not os.path.exists(multipair_path):
        pytest.skip("eurusd_multipair.parquet not present — run data:prepare:multipair first")
    saved = os.environ.get("JEPA_USE_MULTIPAIR")
    os.environ["JEPA_USE_MULTIPAIR"] = "1"
    try:
        spec = ilu.spec_from_file_location(f"train_mp2_{id(None)}", "train.py")
        mod = ilu.module_from_spec(spec)
        spec.loader.exec_module(mod)
        (Xtr, _), _ = mod.build()
    finally:
        if saved is None:
            os.environ.pop("JEPA_USE_MULTIPAIR", None)
        else:
            os.environ["JEPA_USE_MULTIPAIR"] = saved
    mp = _import_mp()
    expected_ch = len(mp.PAIRS) * 2
    assert Xtr.shape[2] == expected_ch, (
        f"expected {expected_ch} channels (n_pairs={len(mp.PAIRS)}×2), got {Xtr.shape[2]}"
    )