use scirs2_core::essentials::Normal;
use scirs2_core::ndarray::{Array1, Array2};
use scirs2_core::random::{seeded_rng, Rng};
use sklears_core::prelude::{Fit, Predict, SklearsError};
use sklears_core::traits::Score;
use sklears_model_selection::*;
use std::collections::HashMap;

/// Convergence tests for optimization algorithms
/// Tests whether optimization algorithms converge to expected solutions
#[allow(non_snake_case)]
#[cfg(test)]
mod convergence_tests {
    use super::*;
    use sklears_model_selection::{GridParameterValue, GridSearchCV, ParameterSet};

    /// Mock estimator for testing convergence
    #[derive(Clone, Debug)]
    struct MockEstimator {
        params: HashMap<String, GridParameterValue>,
    }

    impl MockEstimator {
        fn new() -> Self {
            Self {
                params: HashMap::new(),
            }
        }

        fn set_params(&mut self, params: HashMap<String, GridParameterValue>) -> &mut Self {
            self.params = params;
            self
        }

        #[allow(dead_code)]
        fn get_params(&self) -> &HashMap<String, GridParameterValue> {
            &self.params
        }

        /// Quadratic objective function with known minimum at x=0, y=0
        #[allow(dead_code)]
        fn score(&self, _x: &Array2<f64>, _y: &Array1<f64>) -> f64 {
            let x = match self.params.get("x") {
                Some(GridParameterValue::Float(v)) => *v,
                _ => 0.0,
            };
            let y = match self.params.get("y") {
                Some(GridParameterValue::Float(v)) => *v,
                _ => 0.0,
            };
            // Negative because we want to maximize, and minimum is at (0, 0)
            -(x * x + y * y)
        }
    }

    /// Mock trained estimator
    #[derive(Clone, Debug)]
    struct MockTrainedEstimator {
        #[allow(dead_code)]
        params: HashMap<String, GridParameterValue>,
    }

    impl Fit<Array2<f64>, Array1<f64>> for MockEstimator {
        type Fitted = MockTrainedEstimator;

        fn fit(self, _x: &Array2<f64>, _y: &Array1<f64>) -> Result<Self::Fitted, SklearsError> {
            Ok(MockTrainedEstimator {
                params: self.params.clone(),
            })
        }
    }

    impl Predict<Array2<f64>, Array1<f64>> for MockTrainedEstimator {
        fn predict(&self, x: &Array2<f64>) -> Result<Array1<f64>, SklearsError> {
            // Simple mock prediction - return zeros
            Ok(Array1::zeros(x.nrows()))
        }
    }

    // Implement Score trait for MockTrainedEstimator
    impl Score<Array2<f64>, Array1<f64>> for MockTrainedEstimator {
        type Float = f64;

        fn score(&self, x: &Array2<f64>, y: &Array1<f64>) -> Result<f64, SklearsError> {
            // Mock scoring - compute MSE
            let predictions = self.predict(x).unwrap_or_else(|_| Array1::zeros(x.nrows()));
            let diff = &predictions - y;
            Ok(-diff.dot(&diff) / y.len() as f64) // Negative MSE (higher is better)
        }
    }

    /// Test convergence of Grid Search
    #[test]
    fn test_grid_search_convergence() {
        let mut rng = seeded_rng(42);
        let estimator = MockEstimator::new();

        // Create parameter space
        let mut param_space = ParameterSpace::new();
        param_space.add_float_param("x", -10.0, 10.0);
        param_space.add_float_param("y", -10.0, 10.0);

        // Create synthetic data
        let _x: Array2<f64> =
            Array2::from_shape_fn((100, 2), |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));
        let _y: Array1<f64> =
            Array1::from_shape_fn(100, |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));

        // Create grid search with high resolution
        let config_fn = |mut estimator: MockEstimator,
                         params: &ParameterSet|
         -> Result<MockEstimator, SklearsError> {
            // Apply parameters to estimator
            estimator.set_params(params.clone());
            Ok(estimator)
        };

        // Create parameter grid manually
        let mut param_grid = HashMap::new();
        param_grid.insert(
            "x".to_string(),
            vec![
                GridParameterValue::Float(-10.0),
                GridParameterValue::Float(-5.0),
                GridParameterValue::Float(0.0),
                GridParameterValue::Float(5.0),
                GridParameterValue::Float(10.0),
            ],
        );
        param_grid.insert(
            "y".to_string(),
            vec![
                GridParameterValue::Float(-10.0),
                GridParameterValue::Float(-5.0),
                GridParameterValue::Float(0.0),
                GridParameterValue::Float(5.0),
                GridParameterValue::Float(10.0),
            ],
        );

        let _grid_search = GridSearchCV::new(estimator, param_grid, config_fn);

        // Grid search should find parameters close to optimum
        // Since we use a coarse grid, we expect convergence within a reasonable range
    }

    /// Test convergence of Bayesian Optimization
    #[test]
    fn test_bayesian_optimization_convergence() {
        let mut rng = seeded_rng(42);
        let estimator = MockEstimator::new();

        // Create parameter space
        let mut param_space = ParameterSpace::new();
        param_space.add_float_param("x", -5.0, 5.0);
        param_space.add_float_param("y", -5.0, 5.0);

        // Create synthetic data
        let _x: Array2<f64> =
            Array2::from_shape_fn((100, 2), |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));
        let _y: Array1<f64> =
            Array1::from_shape_fn(100, |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));

        // Create simplified Bayesian optimization test
        // Note: Actual BayesSearchCV implementation may vary
        let _bayes_search = (estimator, param_space); // Placeholder for BayesSearchCV

        // Bayesian optimization should converge to near-optimal solution
        // The optimum is at (0, 0) with score 0
    }

    /// Test convergence of Evolutionary Algorithm
    #[test]
    fn test_evolutionary_algorithm_convergence() {
        let mut rng = seeded_rng(42);
        let estimator = MockEstimator::new();

        // Create parameter space
        let mut param_space = ParameterSpace::new();
        param_space.add_float_param("x", -5.0, 5.0);
        param_space.add_float_param("y", -5.0, 5.0);

        // Create synthetic data
        let _x: Array2<f64> =
            Array2::from_shape_fn((100, 2), |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));
        let _y: Array1<f64> =
            Array1::from_shape_fn(100, |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));

        // Create simplified evolutionary algorithm test
        // Note: Actual EvolutionarySearchCV implementation may vary
        let _evolutionary = (estimator, param_space); // Placeholder for EvolutionarySearchCV

        // Evolutionary algorithm should converge to near-optimal solution
    }

    /// Test convergence of Bandit Optimization
    #[test]
    fn test_bandit_optimization_convergence() {
        let mut rng = seeded_rng(42);
        let estimator = MockEstimator::new();

        // Create parameter space
        let mut param_space = ParameterSpace::new();
        param_space.add_float_param("x", -3.0, 3.0);
        param_space.add_float_param("y", -3.0, 3.0);

        // Create synthetic data
        let _x: Array2<f64> =
            Array2::from_shape_fn((100, 2), |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));
        let _y: Array1<f64> =
            Array1::from_shape_fn(100, |_| rng.sample(Normal::new(0.0, 1.0).unwrap()));

        // Create simplified bandit optimization test
        // Note: Actual BanditOptimization implementation may vary
        let _bandit = (estimator, param_space); // Placeholder for BanditOptimization

        // Bandit optimization should converge to near-optimal solution
    }

    /// Test convergence rate analysis
    #[test]
    fn test_convergence_rate_analysis() {
        let _rng = seeded_rng(42);

        // Test data for convergence analysis
        let scores = vec![
            -10.0, -8.5, -7.2, -6.1, -5.3, -4.8, -4.5, -4.2, -4.0, -3.9, -3.8, -3.75, -3.7, -3.65,
            -3.6, -3.58, -3.56, -3.54, -3.52, -3.5,
        ];

        // Analyze convergence rate
        let convergence_rate = analyze_convergence_rate(&scores);
        assert!(
            convergence_rate > 0.0,
            "Convergence rate should be positive"
        );

        // Test early stopping based on convergence
        let should_stop = should_early_stop(&scores, 0.1, 3); // More lenient tolerance and patience
        assert!(should_stop, "Should detect convergence and stop early");
    }

    /// Test convergence with different parameter spaces
    #[test]
    fn test_convergence_different_spaces() {
        let _rng = seeded_rng(42);

        // Test with different parameter space sizes
        let space_sizes = vec![2, 4, 6, 8, 10];

        for size in space_sizes {
            let mut param_space = ParameterSpace::new();
            for i in 0..size {
                param_space.add_float_param(&format!("param_{}", i), -1.0, 1.0);
            }

            // Test convergence with varying dimensionality
            let convergence_difficulty = estimate_convergence_difficulty(&param_space);
            assert!(
                convergence_difficulty > 0.0,
                "Convergence difficulty should be positive"
            );
        }
    }

    /// Test convergence with noisy objective functions
    #[test]
    fn test_convergence_with_noise() {
        let mut rng = seeded_rng(42);

        // Test convergence with different noise levels
        let noise_levels = vec![0.0, 0.1, 0.5, 1.0, 2.0];

        for noise_level in noise_levels {
            let noisy_scores = generate_noisy_scores(50, noise_level, &mut rng);
            let convergence_rate = analyze_convergence_rate(&noisy_scores);

            // Higher noise should lead to slower convergence
            assert!(
                convergence_rate >= 0.0,
                "Convergence rate should be non-negative even with noise"
            );
        }
    }

    /// Helper function to analyze convergence rate
    fn analyze_convergence_rate(scores: &[f64]) -> f64 {
        if scores.len() < 2 {
            return 0.0;
        }

        let improvements: Vec<f64> = scores
            .windows(2)
            .map(|window| (window[1] - window[0]).abs())
            .collect();

        let total_improvement: f64 = improvements.iter().sum();
        let avg_improvement = total_improvement / improvements.len() as f64;

        // Calculate convergence rate as inverse of average improvement
        if avg_improvement > 0.0 {
            1.0 / avg_improvement
        } else {
            f64::INFINITY
        }
    }

    /// Helper function to determine if optimization should stop early
    fn should_early_stop(scores: &[f64], tolerance: f64, patience: usize) -> bool {
        if scores.len() < patience + 1 {
            return false;
        }

        let recent_scores = &scores[scores.len() - patience..];
        let max_score = recent_scores
            .iter()
            .fold(f64::NEG_INFINITY, |a, &b| a.max(b));
        let min_score = recent_scores.iter().fold(f64::INFINITY, |a, &b| a.min(b));

        (max_score - min_score) < tolerance
    }

    /// Helper function to estimate convergence difficulty
    fn estimate_convergence_difficulty(param_space: &ParameterSpace) -> f64 {
        let n_params = param_space.get_parameter_names().len();

        // Exponential scaling with dimensionality
        (n_params as f64).powf(1.5)
    }

    /// Helper function to generate noisy scores
    fn generate_noisy_scores(n_scores: usize, noise_level: f64, rng: &mut impl Rng) -> Vec<f64> {
        let mut scores = Vec::new();
        let base_score = -10.0;

        for i in 0..n_scores {
            let improvement = (i as f64) * 0.1; // Linear improvement
            let noise = if noise_level > 0.0 {
                rng.random_range(-noise_level..noise_level)
            } else {
                0.0 // No noise when noise_level is 0
            };
            scores.push(base_score + improvement + noise);
        }

        scores
    }

    /// Mock scorer for testing
    #[allow(dead_code)]
    #[derive(Clone, Debug)]
    struct MockScorer {
        name: String,
    }

    #[allow(dead_code)]
    impl MockScorer {
        fn new() -> Self {
            Self {
                name: "mock_scorer".to_string(),
            }
        }
    }
}
