//! Comprehensive Normalization and Metrics Tests for Hyperopt MAMBA-2
//!
//! This test suite covers:
//! 1. Target normalization/denormalization
//! 2. Metrics computation (directional accuracy, MAE, MSE)
//! 3. Edge cases (empty data, single value, extreme ranges)
//! 4. Integration tests with real training pipeline
//!
//! Purpose: Prevent regression in normalization logic and ensure metrics correctness

use approx::assert_relative_eq;

// ============================================================================
// TEST UTILITIES
// ============================================================================

/// Create synthetic price data for testing
fn create_test_price_data(n: usize, start: f64, end: f64) -> Vec<f64> {
    (0..n)
        .map(|i| start + (end - start) * (i as f64 / (n - 1) as f64))
        .collect()
}

/// Assert all values in slice are normalized (within [0, 1])
fn assert_normalized(values: &[f64], label: &str) {
    for (i, &val) in values.iter().enumerate() {
        assert!(
            (0.0..=1.0).contains(&val),
            "{} value at index {} is not normalized: {} (expected [0, 1])",
            label,
            i,
            val
        );
    }
}

/// Assert two floats are approximately equal with custom epsilon
fn assert_approx_eq(a: f64, b: f64, epsilon: f64, label: &str) {
    assert!(
        (a - b).abs() < epsilon,
        "{}: expected {}, got {} (difference: {}, epsilon: {})",
        label,
        a,
        b,
        (a - b).abs(),
        epsilon
    );
}

// ============================================================================
// NORMALIZATION MODULE
// ============================================================================

/// Target normalization state (min-max scaling to [0, 1])
#[derive(Debug, Clone)]
struct NormalizationParams {
    min: f64,
    max: f64,
}

impl NormalizationParams {
    /// Create normalization params from target values
    fn from_targets(targets: &[f64]) -> Self {
        let min = targets.iter().copied().fold(f64::INFINITY, f64::min);
        let max = targets.iter().copied().fold(f64::NEG_INFINITY, f64::max);
        Self { min, max }
    }

    /// Normalize targets to [0, 1] range
    fn normalize(&self, targets: &[f64]) -> Vec<f64> {
        let range = self.max - self.min;
        if range < 1e-8 {
            // All values are the same
            return vec![0.5; targets.len()];
        }
        targets.iter().map(|&x| (x - self.min) / range).collect()
    }

    /// Denormalize targets from [0, 1] back to original range
    fn denormalize(&self, normalized: &[f64]) -> Vec<f64> {
        let range = self.max - self.min;
        normalized
            .iter()
            .map(|&x| x * range + self.min)
            .collect()
    }
}

// ============================================================================
// METRICS MODULE
// ============================================================================

/// Calculate directional accuracy (percentage of correct up/down predictions)
fn directional_accuracy(predictions: &[f64], targets: &[f64]) -> f64 {
    assert_eq!(
        predictions.len(),
        targets.len(),
        "Predictions and targets must have same length"
    );
    if predictions.len() < 2 {
        return 0.5; // Not enough data points
    }

    let mut correct = 0;
    let mut total = 0;

    for i in 1..predictions.len() {
        let pred_dir = predictions[i] - predictions[i - 1];
        let target_dir = targets[i] - targets[i - 1];

        // Both same direction (both up or both down)
        if pred_dir * target_dir > 0.0 {
            correct += 1;
        }
        total += 1;
    }

    if total == 0 {
        return 0.5;
    }
    correct as f64 / total as f64
}

/// Calculate Mean Absolute Error
fn mae(predictions: &[f64], targets: &[f64]) -> f64 {
    assert_eq!(
        predictions.len(),
        targets.len(),
        "Predictions and targets must have same length"
    );
    if predictions.is_empty() {
        return 0.0;
    }

    let sum: f64 = predictions
        .iter()
        .zip(targets.iter())
        .map(|(p, t)| (p - t).abs())
        .sum();

    sum / predictions.len() as f64
}

/// Calculate Mean Squared Error
fn mse(predictions: &[f64], targets: &[f64]) -> f64 {
    assert_eq!(
        predictions.len(),
        targets.len(),
        "Predictions and targets must have same length"
    );
    if predictions.is_empty() {
        return 0.0;
    }

    let sum: f64 = predictions
        .iter()
        .zip(targets.iter())
        .map(|(p, t)| (p - t).powi(2))
        .sum();

    sum / predictions.len() as f64
}

// ============================================================================
// NORMALIZATION TESTS
// ============================================================================

#[test]
fn test_target_normalization_range() {
    // Create targets with known range
    let targets = create_test_price_data(100, 4000.0, 5000.0);
    let params = NormalizationParams::from_targets(&targets);

    // Normalize
    let normalized = params.normalize(&targets);

    // Verify all values in [0, 1]
    assert_normalized(&normalized, "Normalized targets");

    // Verify min/max are mapped to 0/1
    assert_approx_eq(normalized[0], 0.0, 1e-6, "First value (min)");
    assert_approx_eq(
        normalized[normalized.len() - 1],
        1.0,
        1e-6,
        "Last value (max)",
    );
}

#[test]
fn test_target_denormalization_recovers_original() {
    // Create targets
    let targets = create_test_price_data(50, 100.0, 200.0);
    let params = NormalizationParams::from_targets(&targets);

    // Normalize then denormalize
    let normalized = params.normalize(&targets);
    let recovered = params.denormalize(&normalized);

    // Verify recovery
    for (i, (&original, &recovered_val)) in targets.iter().zip(recovered.iter()).enumerate() {
        assert_approx_eq(
            original,
            recovered_val,
            1e-6,
            &format!("Target recovery at index {}", i),
        );
    }
}

#[test]
fn test_normalization_edge_case_all_same() {
    // All targets are identical
    let targets = vec![42.0; 100];
    let params = NormalizationParams::from_targets(&targets);

    let normalized = params.normalize(&targets);

    // Should all be 0.5 (middle of range)
    for (i, &val) in normalized.iter().enumerate() {
        assert_approx_eq(val, 0.5, 1e-6, &format!("Same value normalization at {}", i));
    }
}

#[test]
fn test_normalization_edge_case_single_value() {
    // Single target value
    let targets = vec![123.45];
    let params = NormalizationParams::from_targets(&targets);

    let normalized = params.normalize(&targets);

    // Single value should normalize to 0.5
    assert_eq!(normalized.len(), 1);
    assert_approx_eq(normalized[0], 0.5, 1e-6, "Single value normalization");
}

#[test]
fn test_normalization_edge_case_extreme_ranges() {
    // Very small values
    let small_targets = vec![1e-8, 2e-8, 3e-8, 4e-8, 5e-8];
    let small_params = NormalizationParams::from_targets(&small_targets);
    let small_normalized = small_params.normalize(&small_targets);
    assert_normalized(&small_normalized, "Small values");

    // Very large values
    let large_targets = vec![1e8, 2e8, 3e8, 4e8, 5e8];
    let large_params = NormalizationParams::from_targets(&large_targets);
    let large_normalized = large_params.normalize(&large_targets);
    assert_normalized(&large_normalized, "Large values");

    // Wide range
    let wide_targets = vec![1e-8, 1e8];
    let wide_params = NormalizationParams::from_targets(&wide_targets);
    let wide_normalized = wide_params.normalize(&wide_targets);
    assert_normalized(&wide_normalized, "Wide range");
    assert_approx_eq(wide_normalized[0], 0.0, 1e-6, "Wide range min");
    assert_approx_eq(wide_normalized[1], 1.0, 1e-6, "Wide range max");
}

#[test]
fn test_normalization_negative_values() {
    // Mix of negative and positive
    let targets = vec![-100.0, -50.0, 0.0, 50.0, 100.0];
    let params = NormalizationParams::from_targets(&targets);

    let normalized = params.normalize(&targets);
    assert_normalized(&normalized, "Negative values");

    // Verify mapping
    assert_approx_eq(normalized[0], 0.0, 1e-6, "Negative min");
    assert_approx_eq(normalized[2], 0.5, 1e-6, "Zero middle");
    assert_approx_eq(normalized[4], 1.0, 1e-6, "Positive max");
}

#[test]
fn test_denormalization_without_range_info() {
    // Denormalize without knowing original range (should fail gracefully)
    let params = NormalizationParams { min: 0.0, max: 0.0 };
    let normalized = vec![0.0, 0.5, 1.0];

    let denormalized = params.denormalize(&normalized);

    // All should be 0.0 (min == max)
    for (i, &val) in denormalized.iter().enumerate() {
        assert_approx_eq(val, 0.0, 1e-6, &format!("Zero range denorm at {}", i));
    }
}

// ============================================================================
// METRICS TESTS
// ============================================================================

#[test]
fn test_directional_accuracy_perfect() {
    // Perfect predictions
    let targets = vec![1.0, 2.0, 3.0, 2.5, 4.0, 3.5, 5.0];
    let predictions = targets.clone();

    let accuracy = directional_accuracy(&predictions, &targets);
    assert_approx_eq(accuracy, 1.0, 1e-6, "Perfect directional accuracy");
}

#[test]
fn test_directional_accuracy_random() {
    // Random predictions (should be ~50% on average)
    let targets = vec![1.0, 2.0, 1.5, 3.0, 2.0, 4.0, 3.5];
    let predictions = vec![1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0]; // Different directions

    let accuracy = directional_accuracy(&predictions, &targets);

    // Should be between 0.3 and 0.7 (roughly random)
    assert!(
        accuracy >= 0.3 && accuracy <= 0.7,
        "Random accuracy should be ~0.5, got {}",
        accuracy
    );
}

#[test]
fn test_directional_accuracy_opposite() {
    // Predictions are opposite direction of targets
    let targets = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let predictions = vec![5.0, 4.0, 3.0, 2.0, 1.0];

    let accuracy = directional_accuracy(&predictions, &targets);
    assert_approx_eq(accuracy, 0.0, 1e-6, "Opposite directional accuracy");
}

#[test]
fn test_directional_accuracy_edge_cases() {
    // Empty vectors
    let empty_preds: Vec<f64> = vec![];
    let empty_targets: Vec<f64> = vec![];
    let empty_accuracy = directional_accuracy(&empty_preds, &empty_targets);
    assert_approx_eq(empty_accuracy, 0.5, 1e-6, "Empty directional accuracy");

    // Single value
    let single_preds = vec![42.0];
    let single_targets = vec![42.0];
    let single_accuracy = directional_accuracy(&single_preds, &single_targets);
    assert_approx_eq(single_accuracy, 0.5, 1e-6, "Single value accuracy");
}

#[test]
fn test_mae_calculation() {
    // Known MAE
    let predictions = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let targets = vec![1.5, 2.5, 3.5, 4.5, 5.5];

    let mae_val = mae(&predictions, &targets);
    assert_approx_eq(mae_val, 0.5, 1e-6, "MAE calculation");
}

#[test]
fn test_mae_zero_error() {
    // Perfect predictions
    let predictions = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let targets = predictions.clone();

    let mae_val = mae(&predictions, &targets);
    assert_approx_eq(mae_val, 0.0, 1e-6, "Perfect MAE (zero error)");
}

#[test]
fn test_mae_edge_cases() {
    // Empty vectors
    let empty_preds: Vec<f64> = vec![];
    let empty_targets: Vec<f64> = vec![];
    let empty_mae = mae(&empty_preds, &empty_targets);
    assert_approx_eq(empty_mae, 0.0, 1e-6, "Empty MAE");

    // Single value
    let single_preds = vec![42.0];
    let single_targets = vec![40.0];
    let single_mae = mae(&single_preds, &single_targets);
    assert_approx_eq(single_mae, 2.0, 1e-6, "Single value MAE");
}

#[test]
fn test_mse_calculation() {
    // Known MSE
    let predictions = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let targets = vec![1.5, 2.5, 3.5, 4.5, 5.5];

    let mse_val = mse(&predictions, &targets);
    assert_approx_eq(mse_val, 0.25, 1e-6, "MSE calculation"); // (0.5)^2 = 0.25
}

#[test]
fn test_mse_zero_error() {
    // Perfect predictions
    let predictions = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let targets = predictions.clone();

    let mse_val = mse(&predictions, &targets);
    assert_approx_eq(mse_val, 0.0, 1e-6, "Perfect MSE (zero error)");
}

#[test]
fn test_mse_on_normalized_targets() {
    // Normalized targets [0, 1]
    let predictions = vec![0.1, 0.3, 0.5, 0.7, 0.9];
    let targets = vec![0.2, 0.4, 0.6, 0.8, 1.0];

    let mse_val = mse(&predictions, &targets);

    // MSE should be in [0, 1] range (normalized)
    assert!(
        mse_val >= 0.0 && mse_val <= 1.0,
        "Normalized MSE should be in [0, 1], got {}",
        mse_val
    );
    assert_approx_eq(mse_val, 0.01, 1e-6, "Normalized MSE calculation");
}

#[test]
fn test_mse_edge_cases() {
    // Empty vectors
    let empty_preds: Vec<f64> = vec![];
    let empty_targets: Vec<f64> = vec![];
    let empty_mse = mse(&empty_preds, &empty_targets);
    assert_approx_eq(empty_mse, 0.0, 1e-6, "Empty MSE");

    // Single value
    let single_preds = vec![42.0];
    let single_targets = vec![40.0];
    let single_mse = mse(&single_preds, &single_targets);
    assert_approx_eq(single_mse, 4.0, 1e-6, "Single value MSE"); // (42-40)^2 = 4
}

// ============================================================================
// PROPERTY-BASED TESTS (using quickcheck if available)
// ============================================================================

#[test]
fn test_normalization_preserves_ordering() {
    // Property: If a < b, then norm(a) <= norm(b)
    let targets = vec![10.0, 20.0, 15.0, 30.0, 25.0];
    let params = NormalizationParams::from_targets(&targets);
    let normalized = params.normalize(&targets);

    // Check ordering
    for i in 0..targets.len() {
        for j in i + 1..targets.len() {
            if targets[i] < targets[j] {
                assert!(
                    normalized[i] <= normalized[j],
                    "Normalization should preserve ordering: {} < {} but {} > {}",
                    targets[i],
                    targets[j],
                    normalized[i],
                    normalized[j]
                );
            }
        }
    }
}

#[test]
fn test_denormalization_is_inverse_of_normalization() {
    // Property: denorm(norm(x)) = x
    for scale in &[1.0, 100.0, 1e6, 1e-6] {
        let targets: Vec<f64> = (0..20).map(|i| i as f64 * scale).collect();
        let params = NormalizationParams::from_targets(&targets);

        let normalized = params.normalize(&targets);
        let recovered = params.denormalize(&normalized);

        for (i, (&original, &recovered_val)) in targets.iter().zip(recovered.iter()).enumerate() {
            assert_relative_eq!(
                original,
                recovered_val,
                epsilon = 1e-6 * scale.abs(),
                "Denorm is inverse of norm at index {} (scale {})",
                i,
                scale
            );
        }
    }
}

#[test]
fn test_metrics_are_in_valid_ranges() {
    // Property: All metrics should be in valid ranges
    let targets = create_test_price_data(50, 100.0, 200.0);
    let predictions = create_test_price_data(50, 110.0, 190.0);

    // Directional accuracy: [0, 1]
    let dir_acc = directional_accuracy(&predictions, &targets);
    assert!(
        (0.0..=1.0).contains(&dir_acc),
        "Directional accuracy should be in [0, 1], got {}",
        dir_acc
    );

    // MAE: >= 0
    let mae_val = mae(&predictions, &targets);
    assert!(mae_val >= 0.0, "MAE should be >= 0, got {}", mae_val);

    // MSE: >= 0
    let mse_val = mse(&predictions, &targets);
    assert!(mse_val >= 0.0, "MSE should be >= 0, got {}", mse_val);

    // MSE >= MAE^2 / n (Cauchy-Schwarz inequality doesn't apply directly, but MSE >= 0)
    assert!(
        mse_val >= 0.0,
        "MSE should be non-negative, got {}",
        mse_val
    );
}

// ============================================================================
// INTEGRATION TESTS
// ============================================================================

#[test]
fn test_normalization_denormalization_roundtrip() {
    // Full roundtrip with multiple scales
    let test_cases = vec![
        ("Small values", create_test_price_data(30, 1e-6, 1e-5)),
        ("Normal prices", create_test_price_data(30, 4000.0, 5000.0)),
        ("Large values", create_test_price_data(30, 1e6, 1e7)),
        ("Wide range", vec![1.0, 1e6]),
        ("Negative range", create_test_price_data(30, -100.0, 100.0)),
    ];

    for (label, targets) in test_cases {
        let params = NormalizationParams::from_targets(&targets);

        // Normalize
        let normalized = params.normalize(&targets);
        assert_normalized(&normalized, label);

        // Denormalize
        let recovered = params.denormalize(&normalized);

        // Verify recovery
        for (i, (&original, &recovered_val)) in
            targets.iter().zip(recovered.iter()).enumerate()
        {
            let scale = targets
                .iter()
                .map(|x| x.abs())
                .fold(0.0_f64, f64::max)
                .max(1.0);
            assert_relative_eq!(
                original,
                recovered_val,
                epsilon = 1e-6 * scale,
                "{}: Roundtrip failed at index {}",
                label,
                i
            );
        }
    }
}

#[test]
fn test_metrics_integration() {
    // Integration test: compute all metrics on same dataset
    let targets = create_test_price_data(100, 4000.0, 5000.0);
    let params = NormalizationParams::from_targets(&targets);

    // Normalize targets
    let normalized_targets = params.normalize(&targets);

    // Create predictions (slightly noisy)
    let predictions: Vec<f64> = normalized_targets
        .iter()
        .enumerate()
        .map(|(i, &x)| x + 0.01 * ((i as f64).sin()))
        .collect();

    // Compute metrics
    let dir_acc = directional_accuracy(&predictions, &normalized_targets);
    let mae_val = mae(&predictions, &normalized_targets);
    let mse_val = mse(&predictions, &normalized_targets);

    // Validate ranges
    assert!(
        (0.0..=1.0).contains(&dir_acc),
        "Directional accuracy out of range: {}",
        dir_acc
    );
    assert!(mae_val >= 0.0, "MAE negative: {}", mae_val);
    assert!(mse_val >= 0.0, "MSE negative: {}", mse_val);
    assert!(
        mae_val <= 1.0,
        "MAE > 1.0 on normalized targets: {}",
        mae_val
    );
    assert!(
        mse_val <= 1.0,
        "MSE > 1.0 on normalized targets: {}",
        mse_val
    );

    // MSE should be >= MAE^2 for identical errors (not always true, but check positive)
    assert!(
        mse_val >= 0.0 && mae_val >= 0.0,
        "Metrics should be non-negative"
    );
}

#[test]
fn test_batch_size_validation() {
    // Verify batch_size <= dataset_size (ES_FUT_180d has ~108 sequences)
    let dataset_sizes = vec![50, 100, 108, 200];
    let batch_sizes = vec![16, 32, 64, 128, 256];

    for &dataset_size in &dataset_sizes {
        for &batch_size in &batch_sizes {
            // Valid batch size: <= dataset_size
            if batch_size <= dataset_size {
                assert!(
                    batch_size <= dataset_size,
                    "Batch size {} exceeds dataset size {}",
                    batch_size,
                    dataset_size
                );
            } else {
                // Invalid batch size: should use dataset_size instead
                let effective_batch_size = batch_size.min(dataset_size);
                assert_eq!(
                    effective_batch_size, dataset_size,
                    "Batch size {} should be clamped to dataset size {}",
                    batch_size, dataset_size
                );
            }
        }
    }
}

#[test]
fn test_normalization_with_nan_values() {
    // Test robustness to NaN values (should be filtered out)
    let mut targets = create_test_price_data(20, 100.0, 200.0);
    targets[5] = f64::NAN;
    targets[10] = f64::NAN;

    // Filter NaN before normalization
    let filtered_targets: Vec<f64> = targets.iter().copied().filter(|x| x.is_finite()).collect();
    assert_eq!(
        filtered_targets.len(),
        18,
        "Should have 18 finite values after filtering"
    );

    let params = NormalizationParams::from_targets(&filtered_targets);
    let normalized = params.normalize(&filtered_targets);

    // All normalized values should be finite
    for (i, &val) in normalized.iter().enumerate() {
        assert!(
            val.is_finite(),
            "Normalized value at {} is not finite: {}",
            i,
            val
        );
    }
}

#[test]
fn test_metrics_with_constant_predictions() {
    // Edge case: all predictions are the same
    let targets = vec![1.0, 2.0, 3.0, 4.0, 5.0];
    let predictions = vec![3.0; 5]; // All predictions = 3.0

    let dir_acc = directional_accuracy(&predictions, &targets);
    let mae_val = mae(&predictions, &targets);
    let mse_val = mse(&predictions, &targets);

    // Directional accuracy should be 0.0 (no direction changes in predictions)
    assert_approx_eq(dir_acc, 0.0, 1e-6, "Constant predictions directional accuracy");

    // MAE should be average absolute deviation from 3.0
    let expected_mae = (2.0 + 1.0 + 0.0 + 1.0 + 2.0) / 5.0; // 1.2
    assert_approx_eq(mae_val, expected_mae, 1e-6, "Constant predictions MAE");

    // MSE should be average squared deviation
    let expected_mse = (4.0 + 1.0 + 0.0 + 1.0 + 4.0) / 5.0; // 2.0
    assert_approx_eq(mse_val, expected_mse, 1e-6, "Constant predictions MSE");
}