foxhunt/ml/tests/ppo_hyperopt_edge_cases.rs

//! PPO-Specific Edge Case Tests for Hyperparameter Optimization
//!
//! This test suite covers PPO-specific edge cases:
//! 1. Dual learning rate constraints (policy vs value)
//! 2. Clip epsilon boundaries
//! 3. Value loss coefficient edge cases
//! 4. Entropy coefficient constraints
//! 5. Synthetic trajectory generation edge cases
//!
//! Purpose: Ensure PPO adapter handles actor-critic specific edge cases robustly

use ml::hyperopt::adapters::ppo::{PPOParams, PPOTrainer};
use ml::hyperopt::traits::{HyperparameterOptimizable, ParameterSpace};

// ============================================================================
// DUAL LEARNING RATE CONSTRAINTS
// ============================================================================

#[test]
fn test_policy_lr_bounds() {
    let bounds = PPOParams::continuous_bounds();

    // Policy LR bounds: [ln(1e-6), ln(1e-3)]
    let min_lr = bounds[0].0.exp();
    let max_lr = bounds[0].1.exp();

    assert!((min_lr - 1e-6).abs() < 1e-10);
    assert!((max_lr - 1e-3).abs() < 1e-10);
}

#[test]
fn test_value_lr_bounds() {
    let bounds = PPOParams::continuous_bounds();

    // Value LR bounds: [ln(1e-5), ln(1e-3)]
    let min_lr = bounds[1].0.exp();
    let max_lr = bounds[1].1.exp();

    assert!((min_lr - 1e-5).abs() < 1e-10);
    assert!((max_lr - 1e-3).abs() < 1e-10);
}

#[test]
fn test_policy_value_lr_relationship() {
    // Typically policy_lr < value_lr, but not enforced
    let params = PPOParams::default();

    assert!(params.policy_learning_rate > 0.0);
    assert!(params.value_learning_rate > 0.0);
}

#[test]
fn test_extreme_lr_difference() {
    // Test very different learning rates
    let params = PPOParams {
        policy_learning_rate: 1e-6, // Very small
        value_learning_rate: 1e-3,   // Large
        ..Default::default()
    };

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Extreme LR difference should be valid");

    assert!((recovered.policy_learning_rate - 1e-6).abs() < 1e-10);
    assert!((recovered.value_learning_rate - 1e-3).abs() < 1e-10);
}

// ============================================================================
// CLIP EPSILON BOUNDARIES
// ============================================================================

#[test]
fn test_clip_epsilon_bounds() {
    let bounds = PPOParams::continuous_bounds();

    // Clip epsilon bounds: [0.1, 0.3]
    assert_eq!(bounds[2], (0.1, 0.3));
}

#[test]
fn test_clip_epsilon_min() {
    let mut params = PPOParams::default();
    params.clip_epsilon = 0.1; // Conservative clipping

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Min clip epsilon should be valid");

    assert!((recovered.clip_epsilon - 0.1).abs() < 1e-10);
}

#[test]
fn test_clip_epsilon_max() {
    let mut params = PPOParams::default();
    params.clip_epsilon = 0.3; // Aggressive clipping

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Max clip epsilon should be valid");

    assert!((recovered.clip_epsilon - 0.3).abs() < 1e-10);
}

#[test]
fn test_clip_epsilon_clamping() {
    // Test values outside [0.1, 0.3] are clamped
    let too_small = vec![
        (-5.0_f64).ln(), // policy_lr
        (-4.0_f64).ln(), // value_lr
        0.05,            // clip_epsilon (below min)
        1.0,             // value_loss_coeff
        (0.05_f64).ln(), // entropy_coeff
    ];

    let params_small = PPOParams::from_continuous(&too_small)
        .expect("Should clamp clip epsilon");
    assert!((params_small.clip_epsilon - 0.1).abs() < 1e-6, "Should clamp to 0.1");

    let too_large = vec![
        (-5.0_f64).ln(), // policy_lr
        (-4.0_f64).ln(), // value_lr
        0.5,             // clip_epsilon (above max)
        1.0,             // value_loss_coeff
        (0.05_f64).ln(), // entropy_coeff
    ];

    let params_large = PPOParams::from_continuous(&too_large)
        .expect("Should clamp clip epsilon");
    assert!((params_large.clip_epsilon - 0.3).abs() < 1e-6, "Should clamp to 0.3");
}

// ============================================================================
// VALUE LOSS COEFFICIENT EDGE CASES
// ============================================================================

#[test]
fn test_value_loss_coeff_bounds() {
    let bounds = PPOParams::continuous_bounds();

    // Value loss coeff bounds: [0.5, 2.0]
    assert_eq!(bounds[3], (0.5, 2.0));
}

#[test]
fn test_value_loss_coeff_min() {
    let mut params = PPOParams::default();
    params.value_loss_coeff = 0.5; // Minimal value loss weight

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Min value loss coeff should be valid");

    assert!((recovered.value_loss_coeff - 0.5).abs() < 1e-10);
}

#[test]
fn test_value_loss_coeff_max() {
    let mut params = PPOParams::default();
    params.value_loss_coeff = 2.0; // High value loss weight

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Max value loss coeff should be valid");

    assert!((recovered.value_loss_coeff - 2.0).abs() < 1e-10);
}

// ============================================================================
// ENTROPY COEFFICIENT CONSTRAINTS
// ============================================================================

#[test]
fn test_entropy_coeff_bounds() {
    let bounds = PPOParams::continuous_bounds();

    // Entropy coeff bounds: [ln(0.001), ln(0.1)]
    let min_entropy = bounds[4].0.exp();
    let max_entropy = bounds[4].1.exp();

    assert!((min_entropy - 0.001).abs() < 1e-6);
    assert!((max_entropy - 0.1).abs() < 1e-6);
}

#[test]
fn test_entropy_coeff_min() {
    let mut params = PPOParams::default();
    params.entropy_coeff = 0.001; // Minimal exploration

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Min entropy coeff should be valid");

    assert!((recovered.entropy_coeff - 0.001).abs() < 1e-6);
}

#[test]
fn test_entropy_coeff_max() {
    let mut params = PPOParams::default();
    params.entropy_coeff = 0.1; // High exploration

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Max entropy coeff should be valid");

    assert!((recovered.entropy_coeff - 0.1).abs() < 1e-6);
}

// ============================================================================
// PARAMETER ROUNDTRIP TESTS
// ============================================================================

#[test]
fn test_ppo_params_roundtrip() {
    let params = PPOParams {
        policy_learning_rate: 3e-5,
        value_learning_rate: 1e-4,
        clip_epsilon: 0.2,
        value_loss_coeff: 1.0,
        entropy_coeff: 0.05,
    };

    let continuous = params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Roundtrip should succeed");

    assert!((recovered.policy_learning_rate - params.policy_learning_rate).abs() < 1e-10);
    assert!((recovered.value_learning_rate - params.value_learning_rate).abs() < 1e-10);
    assert!((recovered.clip_epsilon - params.clip_epsilon).abs() < 1e-10);
    assert!((recovered.value_loss_coeff - params.value_loss_coeff).abs() < 1e-10);
    assert!((recovered.entropy_coeff - params.entropy_coeff).abs() < 1e-10);
}

#[test]
fn test_extreme_values_roundtrip() {
    // Test boundary values
    let extreme_params = PPOParams {
        policy_learning_rate: 1e-6,
        value_learning_rate: 1e-5,
        clip_epsilon: 0.1,
        value_loss_coeff: 0.5,
        entropy_coeff: 0.001,
    };

    let continuous = extreme_params.to_continuous();
    let recovered = PPOParams::from_continuous(&continuous)
        .expect("Extreme values should roundtrip");

    assert!((recovered.policy_learning_rate - extreme_params.policy_learning_rate).abs() < 1e-10);
    assert!((recovered.value_learning_rate - extreme_params.value_learning_rate).abs() < 1e-10);
}

// ============================================================================
// PARAMETER NAMES
// ============================================================================

#[test]
fn test_param_names() {
    let names = PPOParams::param_names();

    assert_eq!(names.len(), 5);
    assert_eq!(names[0], "policy_learning_rate");
    assert_eq!(names[1], "value_learning_rate");
    assert_eq!(names[2], "clip_epsilon");
    assert_eq!(names[3], "value_loss_coeff");
    assert_eq!(names[4], "entropy_coeff");
}

// ============================================================================
// TRAINER CREATION
// ============================================================================

#[test]
fn test_ppo_trainer_creation() {
    let result = PPOTrainer::new(1000);

    assert!(
        result.is_ok(),
        "PPOTrainer creation should succeed"
    );
}

#[test]
fn test_ppo_trainer_zero_episodes() {
    let result = PPOTrainer::new(0);

    // Zero episodes should either error or handle gracefully
    assert!(result.is_ok(), "Should handle zero episodes");
}

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

#[test]
fn test_default_params_valid() {
    let params = PPOParams::default();

    // Verify default values are reasonable
    assert!(params.policy_learning_rate > 0.0);
    assert!(params.value_learning_rate > 0.0);
    assert!(params.clip_epsilon > 0.0 && params.clip_epsilon < 1.0);
    assert!(params.value_loss_coeff > 0.0);
    assert!(params.entropy_coeff > 0.0);
}

#[test]
fn test_parameter_space_coverage() {
    let bounds = PPOParams::continuous_bounds();

    // Sample midpoint of parameter space
    let midpoint: Vec<f64> = bounds
        .iter()
        .map(|(min, max)| (min + max) / 2.0)
        .collect();

    let params = PPOParams::from_continuous(&midpoint)
        .expect("Midpoint should be valid");

    // Verify all params are in valid ranges
    assert!(params.policy_learning_rate > 0.0);
    assert!(params.value_learning_rate > 0.0);
    assert!(params.clip_epsilon >= 0.1 && params.clip_epsilon <= 0.3);
    assert!(params.value_loss_coeff >= 0.5 && params.value_loss_coeff <= 2.0);
    assert!(params.entropy_coeff > 0.0);
}

#[test]
fn test_log_scale_parameters() {
    // Verify learning rates and entropy use log scale
    let params1 = PPOParams {
        policy_learning_rate: 1e-6,
        value_learning_rate: 1e-5,
        entropy_coeff: 0.001,
        ..Default::default()
    };

    let params2 = PPOParams {
        policy_learning_rate: 1e-3,
        value_learning_rate: 1e-3,
        entropy_coeff: 0.1,
        ..Default::default()
    };

    let cont1 = params1.to_continuous();
    let cont2 = params2.to_continuous();

    // Log scale differences should be consistent
    assert!(cont1[0] < cont2[0]); // policy_lr
    assert!(cont1[1] < cont2[1]); // value_lr
    assert!(cont1[4] < cont2[4]); // entropy_coeff
}

#[test]
fn test_combined_loss_calculation() {
    // Test that combined loss formula is correct
    let params = PPOParams::default();

    let policy_loss = 0.5;
    let value_loss = 0.3;

    let combined_loss = policy_loss + params.value_loss_coeff * value_loss;

    // Verify formula
    let expected = policy_loss + params.value_loss_coeff * value_loss;
    assert!((combined_loss - expected).abs() < 1e-10);
}

#[test]
fn test_all_params_positive() {
    // All PPO parameters should be positive
    let params = PPOParams::default();

    assert!(params.policy_learning_rate > 0.0);
    assert!(params.value_learning_rate > 0.0);
    assert!(params.clip_epsilon > 0.0);
    assert!(params.value_loss_coeff > 0.0);
    assert!(params.entropy_coeff > 0.0);
}

#[test]
fn test_parameter_relationships() {
    // Test that parameter relationships make sense
    let params = PPOParams::default();

    // Clip epsilon should be reasonable (typically 0.1-0.3)
    assert!(params.clip_epsilon >= 0.1 && params.clip_epsilon <= 0.3);

    // Value loss coeff should be reasonable (typically 0.5-2.0)
    assert!(params.value_loss_coeff >= 0.5 && params.value_loss_coeff <= 2.0);

    // Entropy coeff should be small (typically 0.001-0.1)
    assert!(params.entropy_coeff >= 0.001 && params.entropy_coeff <= 0.1);
}