#![allow(clippy::approx_constant)]
use approx::assert_abs_diff_eq;
use rtx_preprocessing::{InvertibleTransformer, PreprocessingError, RobustScaler, Transformer};
use rtx_tensor::{Device, Tensor};

/// Test fixture for RobustScaler tests
struct RobustScalerTestFixture {
    simple_data: Tensor,
    outlier_data: Tensor,
    multi_feature_data: Tensor,
    single_value_data: Tensor,
    constant_data: Tensor,
    symmetric_data: Tensor,
}

impl RobustScalerTestFixture {
    fn new() -> Self {
        // Simple data: [1, 2, 3, 4, 5] -> median=3, IQR=2
        let simple_data =
            Tensor::from_slice(&[1.0, 2.0, 3.0, 4.0, 5.0], &[5, 1], &Device::cpu()).unwrap();

        // Data with outliers: [1, 2, 3, 4, 100] -> median=3, should be robust to outlier
        let outlier_data =
            Tensor::from_slice(&[1.0, 2.0, 3.0, 4.0, 100.0], &[5, 1], &Device::cpu()).unwrap();

        // Multi-feature data
        let multi_feature_data = Tensor::from_slice(
            &[1.0, 10.0, 2.0, 20.0, 3.0, 30.0, 4.0, 40.0, 5.0, 50.0],
            &[5, 2],
            &Device::cpu(),
        )
        .unwrap();

        // Single value
        let single_value_data = Tensor::from_slice(&[5.0], &[1, 1], &Device::cpu()).unwrap();

        // Constant data
        let constant_data =
            Tensor::from_slice(&[3.0, 3.0, 3.0, 3.0], &[4, 1], &Device::cpu()).unwrap();

        // Symmetric data around zero: [-4, -2, 0, 2, 4]
        let symmetric_data =
            Tensor::from_slice(&[-4.0, -2.0, 0.0, 2.0, 4.0], &[5, 1], &Device::cpu()).unwrap();

        Self {
            simple_data,
            outlier_data,
            multi_feature_data,
            single_value_data,
            constant_data,
            symmetric_data,
        }
    }
}

#[test]
fn test_robust_scaler_creation() {
    // Default parameters
    let scaler = RobustScaler::new();
    assert!(!scaler.is_fitted());
    assert!(scaler.with_centering());
    assert!(scaler.with_scaling());
    assert_eq!(scaler.quantile_range(), (25.0, 75.0));

    // Custom parameters
    let scaler = RobustScaler::with_params(false, true, (10.0, 90.0));
    assert!(!scaler.is_fitted());
    assert!(!scaler.with_centering());
    assert!(scaler.with_scaling());
    assert_eq!(scaler.quantile_range(), (10.0, 90.0));
}

#[test]
fn test_robust_scaler_invalid_quantile_range() {
    // Should panic with invalid quantile range
    let result = std::panic::catch_unwind(|| RobustScaler::with_params(true, true, (75.0, 25.0)));
    assert!(result.is_err());

    let result = std::panic::catch_unwind(|| RobustScaler::with_params(true, true, (-5.0, 75.0)));
    assert!(result.is_err());

    let result = std::panic::catch_unwind(|| RobustScaler::with_params(true, true, (25.0, 105.0)));
    assert!(result.is_err());
}

#[test]
fn test_robust_scaler_fit_simple() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Should fit successfully
    let result = scaler.fit(&fixture.simple_data);
    assert!(result.is_ok());
    assert!(scaler.is_fitted());

    // Should have computed correct median and IQR
    assert_abs_diff_eq!(scaler.center()[0], 3.0, epsilon = 1e-5); // median
    assert_abs_diff_eq!(scaler.scale()[0], 2.0, epsilon = 1e-5); // IQR: Q3(4) - Q1(2) = 2
}

#[test]
fn test_robust_scaler_fit_outlier_data() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Should be robust to outliers
    scaler.fit(&fixture.outlier_data).unwrap();

    // Median should still be 3 (not affected by outlier)
    assert_abs_diff_eq!(scaler.center()[0], 3.0, epsilon = 1e-5);
    // IQR should still be 2 (Q1=2, Q3=4, outlier doesn't affect)
    assert_abs_diff_eq!(scaler.scale()[0], 2.0, epsilon = 1e-5);
}

#[test]
fn test_robust_scaler_fit_multi_feature() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Should fit successfully on multi-feature data
    let result = scaler.fit(&fixture.multi_feature_data);
    assert!(result.is_ok());
    assert!(scaler.is_fitted());

    // Should have computed correct median and IQR for each feature
    assert_eq!(scaler.center().len(), 2);
    assert_eq!(scaler.scale().len(), 2);

    // Feature 0: [1, 2, 3, 4, 5] -> median=3, IQR=2
    assert_abs_diff_eq!(scaler.center()[0], 3.0, epsilon = 1e-5);
    assert_abs_diff_eq!(scaler.scale()[0], 2.0, epsilon = 1e-5);

    // Feature 1: [10, 20, 30, 40, 50] -> median=30, IQR=20
    assert_abs_diff_eq!(scaler.center()[1], 30.0, epsilon = 1e-5);
    assert_abs_diff_eq!(scaler.scale()[1], 20.0, epsilon = 1e-5);
}

#[test]
fn test_robust_scaler_fit_empty_data() {
    let empty_data = Tensor::zeros(&[0, 1], &Device::cpu()).unwrap();
    let mut scaler = RobustScaler::new();

    // Should fail on empty data
    let result = scaler.fit(&empty_data);
    assert!(result.is_err());
    assert!(matches!(
        result.unwrap_err(),
        PreprocessingError::EmptyDataset
    ));
    assert!(!scaler.is_fitted());
}

#[test]
fn test_robust_scaler_fit_single_value() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Should handle single value
    let result = scaler.fit(&fixture.single_value_data);
    assert!(result.is_ok());
    assert!(scaler.is_fitted());

    // Center should be the value, scale should be 1.0
    assert_abs_diff_eq!(scaler.center()[0], 5.0, epsilon = 1e-5);
    assert_abs_diff_eq!(scaler.scale()[0], 1.0, epsilon = 1e-5);
}

#[test]
fn test_robust_scaler_fit_constant_data() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Should handle constant data
    let result = scaler.fit(&fixture.constant_data);
    assert!(result.is_ok());
    assert!(scaler.is_fitted());

    // Center should be the constant value, scale should be 1.0 (IQR=0)
    assert_abs_diff_eq!(scaler.center()[0], 3.0, epsilon = 1e-5);
    assert_abs_diff_eq!(scaler.scale()[0], 1.0, epsilon = 1e-5);
}

#[test]
fn test_robust_scaler_transform_not_fitted() {
    let fixture = RobustScalerTestFixture::new();
    let scaler = RobustScaler::new();

    // Should fail when not fitted
    let result = scaler.transform(&fixture.simple_data);
    assert!(result.is_err());
    assert!(matches!(result.unwrap_err(), PreprocessingError::NotFitted));
}

#[test]
fn test_robust_scaler_transform_simple() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Fit first
    scaler.fit(&fixture.simple_data).unwrap();

    // Transform: (x - median) / IQR = (x - 3) / 2
    let transformed = scaler.transform(&fixture.simple_data).unwrap();
    assert_eq!(transformed.shape(), &[5, 1]);

    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let expected = vec![-1.0, -0.5, 0.0, 0.5, 1.0]; // (1-3)/2, (2-3)/2, etc.

    for (actual, expected) in values.iter().zip(expected.iter()) {
        assert_abs_diff_eq!(actual, expected, epsilon = 1e-5);
    }
}

#[test]
fn test_robust_scaler_transform_outlier_robustness() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Fit on data with outliers
    scaler.fit(&fixture.outlier_data).unwrap();

    // Transform should handle outliers gracefully
    let transformed = scaler.transform(&fixture.outlier_data).unwrap();
    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    // First 4 values should be scaled normally, outlier will be far but not break scaling
    assert_abs_diff_eq!(values[0], -1.0, epsilon = 1e-5); // (1-3)/2
    assert_abs_diff_eq!(values[1], -0.5, epsilon = 1e-5); // (2-3)/2
    assert_abs_diff_eq!(values[2], 0.0, epsilon = 1e-5); // (3-3)/2
    assert_abs_diff_eq!(values[3], 0.5, epsilon = 1e-5); // (4-3)/2
    assert_abs_diff_eq!(values[4], 48.5, epsilon = 1e-5); // (100-3)/2 = 48.5
}

#[test]
fn test_robust_scaler_transform_without_centering() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::with_params(false, true, (25.0, 75.0));

    // Should scale but not center
    scaler.fit(&fixture.simple_data).unwrap();
    let transformed = scaler.transform(&fixture.simple_data).unwrap();

    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let expected = vec![0.5, 1.0, 1.5, 2.0, 2.5]; // x / IQR = x / 2

    for (actual, expected) in values.iter().zip(expected.iter()) {
        assert_abs_diff_eq!(actual, expected, epsilon = 1e-5);
    }
}

#[test]
fn test_robust_scaler_transform_without_scaling() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::with_params(true, false, (25.0, 75.0));

    // Should center but not scale
    scaler.fit(&fixture.simple_data).unwrap();
    let transformed = scaler.transform(&fixture.simple_data).unwrap();

    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let expected = vec![-2.0, -1.0, 0.0, 1.0, 2.0]; // x - median = x - 3

    for (actual, expected) in values.iter().zip(expected.iter()) {
        assert_abs_diff_eq!(actual, expected, epsilon = 1e-5);
    }
}

#[test]
fn test_robust_scaler_transform_custom_quantiles() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::with_params(true, true, (10.0, 90.0));

    // Should use 10th and 90th percentiles instead of 25th and 75th
    scaler.fit(&fixture.simple_data).unwrap();
    let transformed = scaler.transform(&fixture.simple_data).unwrap();

    // For [1,2,3,4,5]: 10th percentile ≈ 1.4, 90th percentile ≈ 4.6
    // IQR = 4.6 - 1.4 = 3.2, median = 3
    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    // Values should be different from standard 25-75 percentile scaling
    // Just check that transformation occurred
    assert_ne!(values[0], -1.0); // Should be different from 25-75 scaling
}

#[test]
fn test_robust_scaler_transform_dimension_mismatch() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Fit on simple data (1 feature)
    scaler.fit(&fixture.simple_data).unwrap();

    // Try to transform multi-feature data (2 features)
    let result = scaler.transform(&fixture.multi_feature_data);
    assert!(result.is_err());
    assert!(matches!(
        result.unwrap_err(),
        PreprocessingError::DimensionMismatch {
            expected: 1,
            actual: 2
        }
    ));
}

#[test]
fn test_robust_scaler_inverse_transform() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Fit and transform
    scaler.fit(&fixture.simple_data).unwrap();
    let transformed = scaler.transform(&fixture.simple_data).unwrap();

    // Inverse transform should recover original data
    let recovered = scaler.inverse_transform(&transformed).unwrap();
    assert_eq!(recovered.shape(), fixture.simple_data.shape());

    let original_values = fixture
        .simple_data
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let recovered_values = recovered
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    for (orig, rec) in original_values.iter().zip(recovered_values.iter()) {
        assert_abs_diff_eq!(orig, rec, epsilon = 1e-5);
    }
}

#[test]
fn test_robust_scaler_fit_transform() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // fit_transform should be equivalent to fit + transform
    let result1 = scaler.fit_transform(&fixture.simple_data).unwrap();

    let mut scaler2 = RobustScaler::new();
    scaler2.fit(&fixture.simple_data).unwrap();
    let result2 = scaler2.transform(&fixture.simple_data).unwrap();

    assert_eq!(result1.shape(), result2.shape());
    let values1 = result1
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let values2 = result2
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    for (v1, v2) in values1.iter().zip(values2.iter()) {
        assert_abs_diff_eq!(v1, v2, epsilon = 1e-5);
    }
}

#[test]
fn test_robust_scaler_reset() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Fit scaler
    scaler.fit(&fixture.simple_data).unwrap();
    assert!(scaler.is_fitted());

    // Reset should make it unfitted
    scaler.reset();
    assert!(!scaler.is_fitted());

    // Should fail to transform after reset
    let result = scaler.transform(&fixture.simple_data);
    assert!(result.is_err());
    assert!(matches!(result.unwrap_err(), PreprocessingError::NotFitted));
}

#[test]
fn test_robust_scaler_symmetric_data() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::new();

    // Test with symmetric data around zero
    scaler.fit(&fixture.symmetric_data).unwrap();
    let transformed = scaler.transform(&fixture.symmetric_data).unwrap();

    let values = transformed
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    // Should be centered around zero and scaled by IQR
    let mean: f32 = values.iter().sum::<f32>() / values.len() as f32;
    assert_abs_diff_eq!(mean, 0.0, epsilon = 1e-5);
}

#[test]
fn test_robust_scaler_serialization() {
    let fixture = RobustScalerTestFixture::new();
    let mut scaler = RobustScaler::with_params(true, true, (10.0, 90.0));

    // Fit scaler
    scaler.fit(&fixture.simple_data).unwrap();

    // Should be serializable and deserializable
    let serialized = bincode::serialize(&scaler).unwrap();
    let deserialized: RobustScaler = bincode::deserialize(&serialized).unwrap();

    // Should maintain fitted state and parameters
    assert!(deserialized.is_fitted());
    assert_eq!(scaler.with_centering(), deserialized.with_centering());
    assert_eq!(scaler.with_scaling(), deserialized.with_scaling());
    assert_eq!(scaler.quantile_range(), deserialized.quantile_range());
    assert_eq!(scaler.center(), deserialized.center());
    assert_eq!(scaler.scale(), deserialized.scale());

    // Should produce same transform results
    let original_result = scaler.transform(&fixture.simple_data).unwrap();
    let deserialized_result = deserialized.transform(&fixture.simple_data).unwrap();

    let orig_values = original_result
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();
    let deser_values = deserialized_result
        .to_cpu()
        .unwrap()
        .iter()
        .copied()
        .collect::<Vec<f32>>();

    for (orig, deser) in orig_values.iter().zip(deser_values.iter()) {
        assert_abs_diff_eq!(orig, deser, epsilon = 1e-5);
    }
}