//! Unit tests for Performance-Based Adaptive Temperature Decay
//!
//! Tests the adaptive temperature strategy where:
//! - Temperature decays faster when validation loss improves (>0.1% change)
//! - Temperature decays slower when validation loss plateaus (<0.1% change)
//! - Temperature increases when stuck in local optimum (10+ epochs without improvement)

use ml::dqn::{WorkingDQN, WorkingDQNConfig};

#[test]
fn test_temperature_adaptive_improving_loss() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature enabled
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = true;
    config.loss_improvement_threshold = 0.999; // 0.1% improvement
    config.plateau_window = 10;
    config.temp_increase_factor = 1.05;
    config.temperature_start = 1.0;
    config.temperature_min = 0.1;
    config.temperature_decay = 0.99; // Fast decay
    config.temperature_slow_decay = 0.998; // Slow decay

    let mut dqn = WorkingDQN::new(config)?;

    // Simulate improving loss over 6 epochs (first is baseline)
    let losses = vec![1.0, 0.95, 0.90, 0.85, 0.80, 0.75];
    let initial_temp = dqn.get_temperature();

    for loss in losses {
        dqn.update_temperature_adaptive(loss);
    }

    // Temperature should decay faster (loss improved)
    // First update establishes baseline, next 5 trigger fast decay
    // Expected: temp * 0.99^5 ≈ 0.9509 (close to 0.95)
    let final_temp = dqn.get_temperature();
    assert!(
        final_temp < initial_temp * 0.952, // Slightly relaxed for floating point
        "Temperature should decay significantly when loss improves: {} -> {}",
        initial_temp,
        final_temp
    );

    // Plateau counter should be reset
    assert_eq!(
        dqn.get_plateau_count(),
        0,
        "Plateau count should reset on improvement"
    );

    Ok(())
}

#[test]
fn test_temperature_adaptive_plateaued_loss() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature enabled
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = true;
    config.loss_improvement_threshold = 0.999; // 0.1% improvement
    config.plateau_window = 10;
    config.temp_increase_factor = 1.05;
    config.temperature_start = 1.0;
    config.temperature_min = 0.1;
    config.temperature_decay = 0.99; // Fast decay
    config.temperature_slow_decay = 0.998; // Slow decay

    let mut dqn = WorkingDQN::new(config)?;

    // Simulate plateaued loss (no improvement)
    // First call establishes baseline, next 5 trigger plateau detection
    let initial_temp = dqn.get_temperature();
    for _ in 0..6 {
        dqn.update_temperature_adaptive(1.0); // Same loss value
    }

    // Temperature should decay slowly (loss plateaued)
    let final_temp = dqn.get_temperature();
    assert!(
        final_temp < initial_temp,
        "Temperature should decay slowly when loss plateaus: {} -> {}",
        initial_temp,
        final_temp
    );
    assert!(
        final_temp > initial_temp * 0.98,
        "Slow decay should be minimal: {} -> {}",
        initial_temp,
        final_temp
    );

    // Plateau counter should increase (5 epochs after baseline)
    assert_eq!(
        dqn.get_plateau_count(),
        5,
        "Plateau count should track epochs without improvement"
    );

    Ok(())
}

#[test]
fn test_temperature_adaptive_stuck_recovery() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature enabled
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = true;
    config.loss_improvement_threshold = 0.999; // 0.1% improvement
    config.plateau_window = 10;
    config.temp_increase_factor = 1.05;
    config.temperature_start = 1.0;
    config.temperature_min = 0.1;
    config.temperature_decay = 0.99; // Fast decay
    config.temperature_slow_decay = 0.998; // Slow decay

    let mut dqn = WorkingDQN::new(config)?;

    // Simulate stuck in local optimum (13 epochs: 1 baseline + 12 plateau)
    // After 11 plateau epochs (window=10), temperature should increase and reset counter
    let initial_temp = dqn.get_temperature();
    for _ in 0..13 {
        dqn.update_temperature_adaptive(1.0); // Same loss value
    }

    // Temperature should increase (escape local optimum)
    // First update: baseline (temp=1.0)
    // Next 10 updates: slow decay (temp = 1.0 * 0.998^10 ≈ 0.980)
    // Update 12: triggers increase (temp = 0.980 * 1.05 ≈ 1.029, plateau resets)
    // Update 13: slow decay again (temp = 1.029 * 0.998 ≈ 1.027)
    let final_temp = dqn.get_temperature();
    assert!(
        final_temp > initial_temp * 1.02, // Should be ~1.027 (relaxed for floating point)
        "Temperature should increase when stuck: {} -> {} (expected >{})",
        initial_temp,
        final_temp,
        initial_temp * 1.02
    );

    // Plateau counter should reset after temperature increase
    // 13 total - 1 baseline - 11 that triggered increase = 1 remaining
    assert_eq!(
        dqn.get_plateau_count(),
        1,
        "Plateau count should reset after temperature increase"
    );

    Ok(())
}

#[test]
fn test_temperature_adaptive_bounds() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature enabled
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = true;
    config.temperature_start = 1.0;
    config.temperature_min = 0.1;
    config.temperature_decay = 0.99;

    let mut dqn = WorkingDQN::new(config)?;

    // Decay temperature many times
    for _ in 0..1000 {
        dqn.update_temperature_adaptive(0.5); // Improving loss
    }

    // Temperature should not go below minimum
    assert!(
        dqn.get_temperature() >= 0.1,
        "Temperature should respect minimum bound: {}",
        dqn.get_temperature()
    );

    // Try to increase temperature many times
    for _ in 0..100 {
        // Simulate stuck condition (plateau_window reached)
        for _ in 0..11 {
            dqn.update_temperature_adaptive(1.0); // Same loss
        }
    }

    // Temperature should not exceed start value
    assert!(
        dqn.get_temperature() <= 1.0,
        "Temperature should not exceed start value: {}",
        dqn.get_temperature()
    );

    Ok(())
}

#[test]
fn test_temperature_adaptive_disabled() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature DISABLED
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = false; // Disabled
    config.temperature_start = 1.0;
    config.temperature_decay = 0.995;

    let mut dqn = WorkingDQN::new(config)?;

    // Simulate improving loss
    let initial_temp = dqn.get_temperature();
    for _ in 0..5 {
        dqn.update_temperature_adaptive(0.5); // Improving loss
    }

    // Temperature should use fixed decay (not adaptive)
    let expected_temp = initial_temp * 0.995_f64.powi(5);
    let actual_temp = dqn.get_temperature();
    assert!(
        (actual_temp - expected_temp).abs() < 0.001,
        "Fixed decay should be used when adaptive disabled: {} vs {}",
        actual_temp,
        expected_temp
    );

    Ok(())
}

#[test]
fn test_temperature_adaptive_loss_window_averaging() -> anyhow::Result<()> {
    // Create DQN with adaptive temperature enabled
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.use_adaptive_temperature = true;
    config.loss_improvement_threshold = 0.999; // 0.1% improvement
    config.plateau_window = 10;

    let mut dqn = WorkingDQN::new(config)?;

    // Simulate noisy loss (oscillating but overall improving)
    let noisy_losses = vec![1.0, 1.1, 0.9, 1.0, 0.8, 0.9, 0.7, 0.85, 0.65, 0.8];
    let initial_temp = dqn.get_temperature();

    for loss in noisy_losses {
        dqn.update_temperature_adaptive(loss);
    }

    // Temperature should decay (loss averaged over window shows improvement)
    let final_temp = dqn.get_temperature();
    assert!(
        final_temp < initial_temp,
        "Temperature should decay despite noisy loss: {} -> {}",
        initial_temp,
        final_temp
    );

    // Plateau counter should be low (averaging smooths noise)
    assert!(
        dqn.get_plateau_count() < 5,
        "Plateau count should be low with noisy but improving loss: {}",
        dqn.get_plateau_count()
    );

    Ok(())
}