"""Tests for Flow Matching training pipeline."""
from __future__ import annotations

import json
import math
from pathlib import Path

import numpy as np
import pytest

from ai_mouse.trainer import load_and_prepare_data, train, _augment


def _make_synthetic_trace(start, end, n_moves=30):
    """Create a synthetic trace dict mimicking real JSONL format."""
    sx, sy = start
    ex, ey = end
    dist = math.hypot(ex - sx, ey - sy)
    angle = math.degrees(math.atan2(ey - sy, ex - sx))

    events = []
    for i in range(n_moves):
        t_frac = i / (n_moves - 1)
        x = int(sx + (ex - sx) * t_frac + np.random.normal(0, 3))
        y = int(sy + (ey - sy) * t_frac + np.random.normal(0, 3))
        t = int(t_frac * 500 + np.random.normal(0, 5))
        events.append({"type": "move", "x": x, "y": y, "t": max(0, t)})

    events.sort(key=lambda e: e["t"])
    events[0]["t"] = 0

    last_t = events[-1]["t"]
    events.append({"type": "down", "x": ex, "y": ey, "t": last_t + 50})
    events.append({"type": "up", "x": ex, "y": ey, "t": last_t + 130})

    return {
        "meta": {"start": [sx, sy], "end": [ex, ey], "dist": int(dist), "angle": round(angle, 1)},
        "events": events,
    }


@pytest.fixture
def synthetic_traces_file(tmp_path):
    """Create a temp JSONL file with 25 synthetic traces."""
    traces_path = tmp_path / "traces.jsonl"
    rng = np.random.default_rng(42)
    lines = []
    for _ in range(25):
        sx, sy = int(rng.integers(50, 750)), int(rng.integers(50, 750))
        angle = rng.uniform(0, 2 * math.pi)
        dist = int(rng.integers(100, 500))
        ex = int(sx + dist * math.cos(angle))
        ey = int(sy + dist * math.sin(angle))
        ex = max(0, min(800, ex))
        ey = max(0, min(600, ey))
        trace = _make_synthetic_trace((sx, sy), (ex, ey))
        lines.append(json.dumps(trace))
    traces_path.write_text("\n".join(lines), encoding="utf-8")
    return traces_path


class TestLoadAndPrepare:
    def test_returns_correct_shapes(self, synthetic_traces_file):
        seq, cond, click_durs = load_and_prepare_data(synthetic_traces_file, seq_len=64)
        assert seq.shape[1] == 64
        assert seq.shape[2] == 3
        assert cond.shape[1] == 3
        assert len(seq) > 0

    def test_forward_starts_near_zero(self, synthetic_traces_file):
        seq, cond, _ = load_and_prepare_data(synthetic_traces_file, seq_len=64)
        assert abs(seq[:, 0, 0].mean()) < 0.15

    def test_forward_ends_near_one(self, synthetic_traces_file):
        seq, cond, _ = load_and_prepare_data(synthetic_traces_file, seq_len=64)
        assert abs(seq[:, -1, 0].mean() - 1.0) < 0.15


class TestAugment:
    def test_augmentation_multiplies_data(self, synthetic_traces_file):
        seq, cond, _ = load_and_prepare_data(synthetic_traces_file, seq_len=64)
        n_orig = len(seq)
        seq_aug, cond_aug = _augment(seq, cond)
        assert len(seq_aug) == n_orig * 6
        assert len(cond_aug) == n_orig * 6


class TestTrain:
    def test_train_produces_model_files(self, synthetic_traces_file, tmp_path):
        output_dir = tmp_path / "models"
        train(
            data_path=synthetic_traces_file,
            output_dir=output_dir,
            epochs=3,
            batch_size=8,
            seq_len=64,
        )
        assert (output_dir / "flow_model.pt").exists()
        assert (output_dir / "click_dist.json").exists()
        assert (output_dir / "duration_dist.json").exists()
        assert (output_dir / "train_config.json").exists()

    def test_train_loss_decreases(self, synthetic_traces_file, tmp_path):
        output_dir = tmp_path / "models"
        losses = []

        def cb(msg):
            if "loss" in msg:
                losses.append(msg["loss"])

        train(
            data_path=synthetic_traces_file,
            output_dir=output_dir,
            epochs=20,
            batch_size=8,
            seq_len=64,
            progress_callback=cb,
        )
        first_half = np.mean(losses[:10])
        second_half = np.mean(losses[10:])
        assert second_half < first_half


class TestTrajectoryDataset:
    def test_dataset_length_with_augmentation(self):
        """Dataset length = N * 6 when augment=True."""
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((10, 64, 3), dtype=np.float32)
        cond = np.zeros((10, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        assert len(ds) == 60

    def test_dataset_length_without_augmentation(self):
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((10, 64, 3), dtype=np.float32)
        cond = np.zeros((10, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=False)
        assert len(ds) == 10

    def test_getitem_returns_tensors(self):
        from ai_mouse.trainer import TrajectoryDataset
        import torch
        seq = np.random.randn(5, 64, 3).astype(np.float32)
        cond = np.random.randn(5, 3).astype(np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s, c = ds[0]
        assert isinstance(s, torch.Tensor)
        assert isinstance(c, torch.Tensor)
        assert s.shape == (64, 3)
        assert c.shape == (3,)

    def test_aug_id_zero_returns_original(self):
        """Aug id 0 (idx=0 % 6 == 0) should return the original sample unchanged."""
        from ai_mouse.trainer import TrajectoryDataset
        import torch
        seq = np.array([[[0.5, 0.7, 0.3]] * 64] * 3, dtype=np.float32)
        cond = np.array([[1.0, 2.0, 3.0]] * 3, dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s0, c0 = ds[0]
        np.testing.assert_allclose(s0.numpy(), seq[0], rtol=1e-5)
        np.testing.assert_allclose(c0.numpy(), cond[0], rtol=1e-5)

    def test_aug_id_one_flips_lateral(self):
        """Aug id 1 should flip the sign of the lateral channel (index 1)."""
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((1, 64, 3), dtype=np.float32)
        seq[0, :, 1] = 0.5  # lateral all positive
        cond = np.zeros((1, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        # idx=1 → base_idx=0, aug_id=1 → flip
        s1, _ = ds[1]
        assert (s1[:, 1] < 0).all()

    def test_aug_id_two_slows_speed(self):
        """Aug id 2 should add log(1.25) to log_dt channel and cond[2]."""
        import math
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((1, 64, 3), dtype=np.float32)
        cond = np.zeros((1, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s2, c2 = ds[2]  # idx=2 → base=0, aug_id=2
        expected_delta = math.log(1.25)
        np.testing.assert_allclose(s2[1:, 2].numpy(), expected_delta, rtol=1e-5)
        assert abs(c2[2].item() - expected_delta) < 1e-5

    def test_aug_id_three_speeds_up(self):
        """Aug id 3 should add log(1/1.2) to log_dt channel and cond[2]."""
        import math
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((1, 64, 3), dtype=np.float32)
        cond = np.zeros((1, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s3, c3 = ds[3]  # idx=3 → base=0, aug_id=3
        expected_delta = math.log(1.0 / 1.2)
        np.testing.assert_allclose(s3[1:, 2].numpy(), expected_delta, rtol=1e-5)
        assert abs(c3[2].item() - expected_delta) < 1e-5

    def test_aug_id_four_adds_temporal_noise(self):
        """Aug id 4 should add Gaussian noise to log_dt (channel 2), leaving other channels unchanged."""
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((1, 64, 3), dtype=np.float32)
        cond = np.zeros((1, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s4, c4 = ds[4]  # idx=4 → base=0, aug_id=4
        # Channels 0 and 1 should be unchanged (still 0)
        np.testing.assert_allclose(s4[:, 0].numpy(), 0.0, atol=1e-6)
        np.testing.assert_allclose(s4[:, 1].numpy(), 0.0, atol=1e-6)
        # Channel 2 (log_dt) at position 0 is unchanged; positions 1+ have noise
        assert s4[0, 2].item() == 0.0
        # Noise should be non-zero (with overwhelming probability for 63 samples)
        assert not np.allclose(s4[1:, 2].numpy(), 0.0)
        # cond is unchanged for aug_id 4
        np.testing.assert_allclose(c4.numpy(), cond[0], atol=1e-6)

    def test_aug_id_five_flips_and_slows(self):
        """Aug id 5 should flip lateral and add log(1/0.9) to log_dt and cond[2]."""
        import math
        from ai_mouse.trainer import TrajectoryDataset
        seq = np.zeros((1, 64, 3), dtype=np.float32)
        seq[0, :, 1] = 0.5  # lateral positive
        cond = np.zeros((1, 3), dtype=np.float32)
        ds = TrajectoryDataset(seq, cond, augment=True)
        s5, c5 = ds[5]  # idx=5 → base=0, aug_id=5
        # Lateral flipped
        assert (s5[:, 1] < 0).all()
        # log_dt shifted
        expected_delta = math.log(1.0 / 0.9)
        np.testing.assert_allclose(s5[1:, 2].numpy(), expected_delta, rtol=1e-5)
        assert abs(c5[2].item() - expected_delta) < 1e-5


class TestResumeFrom:
    def test_resume_from_loads_checkpoint(self, synthetic_traces_file, tmp_path):
        """train() with resume_from should load weights from given checkpoint dir."""
        import torch
        from ai_mouse.trainer import train
        from ai_mouse.models import TrajectoryFlowModel

        # First, train an initial model and save it
        ckpt_dir = tmp_path / "pretrain"
        train(
            data_path=synthetic_traces_file,
            output_dir=ckpt_dir,
            epochs=2,
            batch_size=8,
            seq_len=64,
        )
        assert (ckpt_dir / "flow_model.pt").exists()

        # Read its weights to compare later
        m_pretrain = TrajectoryFlowModel(seq_len=64)
        m_pretrain.load_state_dict(torch.load(ckpt_dir / "flow_model.pt", weights_only=True))
        first_param_pre = next(m_pretrain.parameters()).clone()

        # Now train with resume_from for 1 epoch — weights should still be loaded
        out_dir = tmp_path / "finetune"
        train(
            data_path=synthetic_traces_file,
            output_dir=out_dir,
            epochs=1,
            batch_size=8,
            seq_len=64,
            resume_from=ckpt_dir,
        )

        m_after = TrajectoryFlowModel(seq_len=64)
        m_after.load_state_dict(torch.load(out_dir / "flow_model.pt", weights_only=True))
        first_param_after = next(m_after.parameters())

        # After 1 epoch, weights should be close to pre-train, not random init
        # (random init would be O(1) magnitude apart; 1 epoch on small data shifts O(0.1))
        diff = (first_param_pre - first_param_after).abs().mean().item()
        assert diff < 0.5, f"Resume_from weights diverged too much: {diff}"

    def test_resume_from_missing_path_raises(self, synthetic_traces_file, tmp_path):
        from ai_mouse.trainer import train

        with pytest.raises(FileNotFoundError):
            train(
                data_path=synthetic_traces_file,
                output_dir=tmp_path / "out",
                epochs=1,
                batch_size=8,
                seq_len=64,
                resume_from=tmp_path / "nonexistent",
            )