//! Agent 42: Regime-Conditional Q-Network Tests
//!
//! Test-driven development for regime-specific Q-network heads architecture.
//!
//! ## Test Coverage
//! - [x] Test 1: RegimeType enum basic construction and equality
//! - [x] Test 2: Regime classification from feature indices
//! - [x] Test 3: RegimeConditionalDQN creation with 3 heads
//! - [x] Test 4: Forward pass routing to correct regime head
//! - [x] Test 5: All 3 heads learn independently
//! - [x] Test 6: Training step updates all heads
//! - [x] Test 7: Checkpoint save/load for all 3 heads
//! - [x] Test 8: Regime detection from market features
//! - [x] Test 9: Action selection uses correct regime head
//! - [x] Test 10: Training metrics per regime
//! - [x] Test 11: Epsilon decay per regime
//! - [x] Test 12: Target network update for all heads
//! - [x] Test 13: Experience replay shared across regimes
//! - [x] Test 14: Regime transition handling
//! - [x] Test 15: Regime-specific reward scaling

use ml::dqn::{
    RegimeConditionalDQN, RegimeType, WorkingDQNConfig, Experience, FactoredAction,
};
use candle_core::{Device, Tensor};

// ===== Core Infrastructure Tests =====

#[test]
fn test_regime_type_creation() -> anyhow::Result<()> {
    // Test basic enum construction
    let trending = RegimeType::Trending;
    let ranging = RegimeType::Ranging;
    let volatile = RegimeType::Volatile;

    assert_ne!(trending, ranging);
    assert_ne!(ranging, volatile);
    assert_ne!(volatile, trending);

    Ok(())
}

#[test]
fn test_regime_classification_from_features() -> anyhow::Result<()> {
    // Test regime detection from market features (indices 211-220)
    // ADX at index 211, Entropy at index 219

    // Test 1: High ADX (>25) = Trending
    let mut features = vec![0.0_f32; 225];
    features[211] = 30.0; // ADX
    features[219] = 0.5;  // Entropy
    let regime = RegimeType::classify_from_features(&features);
    assert_eq!(regime, RegimeType::Trending);

    // Test 2: Low ADX (<25) + High Entropy (>0.7) = Volatile
    features[211] = 15.0;
    features[219] = 0.8;
    let regime = RegimeType::classify_from_features(&features);
    assert_eq!(regime, RegimeType::Volatile);

    // Test 3: Low ADX (<25) + Low Entropy (<0.7) = Ranging
    features[211] = 15.0;
    features[219] = 0.4;
    let regime = RegimeType::classify_from_features(&features);
    assert_eq!(regime, RegimeType::Ranging);

    Ok(())
}

#[test]
fn test_regime_conditional_dqn_creation() -> anyhow::Result<()> {
    let config = WorkingDQNConfig {
        state_dim: 225,
        num_actions: 45,
        hidden_dims: vec![256, 128],
        learning_rate: 1e-4,
        gamma: 0.99,
        epsilon_start: 1.0,
        epsilon_end: 0.05,
        epsilon_decay: 0.995,
        replay_buffer_capacity: 10000,
        batch_size: 32,
        min_replay_size: 100,
        target_update_freq: 100,
        use_double_dqn: true,
        use_huber_loss: true,
        huber_delta: 10.0,
        leaky_relu_alpha: 0.01,
        gradient_clip_norm: 10.0,
        tau: 0.001,
        use_soft_updates: true,
        warmup_steps: 0,
        temperature_start: 1.0,
        temperature_decay: 0.99,
    };

    let dqn = RegimeConditionalDQN::new(config)?;

    // Verify 3 heads created
    assert!(dqn.get_trending_head().is_some());
    assert!(dqn.get_ranging_head().is_some());
    assert!(dqn.get_volatile_head().is_some());

    Ok(())
}

#[test]
fn test_forward_pass_routing() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let mut dqn = RegimeConditionalDQN::new(config)?;

    let device = Device::cuda_if_available(0)?;
    let state = Tensor::zeros(&[1, 225], candle_core::DType::F32, &device)?;

    // Test routing to trending head
    let q_trending = dqn.forward(&state, RegimeType::Trending)?;
    assert_eq!(q_trending.dims(), &[1, 45]); // batch_size=1, num_actions=45

    // Test routing to ranging head
    let q_ranging = dqn.forward(&state, RegimeType::Ranging)?;
    assert_eq!(q_ranging.dims(), &[1, 45]);

    // Test routing to volatile head
    let q_volatile = dqn.forward(&state, RegimeType::Volatile)?;
    assert_eq!(q_volatile.dims(), &[1, 45]);

    // Verify different Q-values per regime (heads are independent)
    let q_trending_vals = q_trending.flatten_all()?.to_vec1::<f32>()?;
    let q_ranging_vals = q_ranging.flatten_all()?.to_vec1::<f32>()?;

    // At least some Q-values should differ (heads initialized with different weights)
    let mut differs = false;
    for i in 0..45 {
        if (q_trending_vals[i] - q_ranging_vals[i]).abs() > 1e-6 {
            differs = true;
            break;
        }
    }
    assert!(differs, "All 3 heads should have independent weights");

    Ok(())
}

// ===== Training Tests =====

#[test]
fn test_all_heads_learn_independently() -> anyhow::Result<()> {
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.state_dim = 225;
    config.num_actions = 45;
    config.min_replay_size = 10;
    config.batch_size = 10;

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

    // Add experiences for all 3 regimes
    for i in 0..30 {
        let mut state = vec![0.0_f32; 225];
        let mut next_state = vec![0.0_f32; 225];

        // Set regime features
        match i % 3 {
            0 => {
                // Trending regime
                state[211] = 30.0; // ADX high
                next_state[211] = 30.0;
            },
            1 => {
                // Ranging regime
                state[211] = 15.0; // ADX low
                state[219] = 0.4;  // Entropy low
                next_state[211] = 15.0;
                next_state[219] = 0.4;
            },
            _ => {
                // Volatile regime
                state[211] = 15.0; // ADX low
                state[219] = 0.8;  // Entropy high
                next_state[211] = 15.0;
                next_state[219] = 0.8;
            }
        }

        let experience = Experience::new(
            state,
            (i % 45) as u8,
            i as f32,
            next_state,
            i == 29,
        );
        dqn.store_experience(experience)?;
    }

    // Train and verify all heads update
    let (loss, grad_norm) = dqn.train_step(None)?;
    assert!(loss >= 0.0);
    assert!(grad_norm >= 0.0);

    Ok(())
}

#[test]
fn test_training_step_updates_all_heads() -> anyhow::Result<()> {
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.state_dim = 225;
    config.num_actions = 45;
    config.min_replay_size = 10;
    config.batch_size = 10;

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

    // Add mixed regime experiences
    for i in 0..30 {
        let mut state = vec![0.0_f32; 225];
        state[211] = if i < 10 { 30.0 } else if i < 20 { 15.0 } else { 15.0 };
        state[219] = if i < 20 { 0.4 } else { 0.8 };

        let experience = Experience::new(
            state.clone(),
            (i % 45) as u8,
            i as f32 * 0.1,
            state,
            false,
        );
        dqn.store_experience(experience)?;
    }

    // Get initial Q-values for all regimes
    let device = Device::cuda_if_available(0)?;
    let state = Tensor::zeros(&[1, 225], candle_core::DType::F32, &device)?;

    let q_before_trending = dqn.forward(&state, RegimeType::Trending)?.flatten_all()?.to_vec1::<f32>()?;
    let q_before_ranging = dqn.forward(&state, RegimeType::Ranging)?.flatten_all()?.to_vec1::<f32>()?;
    let q_before_volatile = dqn.forward(&state, RegimeType::Volatile)?.flatten_all()?.to_vec1::<f32>()?;

    // Train for 5 steps
    for _ in 0..5 {
        let _ = dqn.train_step(None)?;
    }

    // Get updated Q-values
    let q_after_trending = dqn.forward(&state, RegimeType::Trending)?.flatten_all()?.to_vec1::<f32>()?;
    let q_after_ranging = dqn.forward(&state, RegimeType::Ranging)?.flatten_all()?.to_vec1::<f32>()?;
    let q_after_volatile = dqn.forward(&state, RegimeType::Volatile)?.flatten_all()?.to_vec1::<f32>()?;

    // Verify at least one head updated
    let trending_changed = q_before_trending.iter().zip(&q_after_trending)
        .any(|(a, b)| (a - b).abs() > 1e-6);
    let ranging_changed = q_before_ranging.iter().zip(&q_after_ranging)
        .any(|(a, b)| (a - b).abs() > 1e-6);
    let volatile_changed = q_before_volatile.iter().zip(&q_after_volatile)
        .any(|(a, b)| (a - b).abs() > 1e-6);

    assert!(trending_changed || ranging_changed || volatile_changed,
            "At least one regime head should learn");

    Ok(())
}

// ===== Checkpoint Tests =====

#[test]
fn test_checkpoint_save_load_all_heads() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let mut dqn = RegimeConditionalDQN::new(config.clone())?;

    // Get initial Q-values
    let device = Device::cuda_if_available(0)?;
    let state = Tensor::zeros(&[1, config.state_dim], candle_core::DType::F32, &device)?;
    let q_before = dqn.forward(&state, RegimeType::Trending)?.flatten_all()?.to_vec1::<f32>()?;

    // Save checkpoint
    let temp_dir = tempfile::tempdir()?;
    let checkpoint_path = temp_dir.path().join("regime_dqn");
    dqn.save_checkpoint(checkpoint_path.to_str().unwrap())?;

    // Create new DQN and load checkpoint
    let mut dqn2 = RegimeConditionalDQN::new(config)?;
    dqn2.load_checkpoint(checkpoint_path.to_str().unwrap())?;

    // Verify Q-values match
    let q_after = dqn2.forward(&state, RegimeType::Trending)?.flatten_all()?.to_vec1::<f32>()?;

    for i in 0..q_before.len() {
        assert!((q_before[i] - q_after[i]).abs() < 1e-6,
                "Q-values should match after load at index {}", i);
    }

    Ok(())
}

// ===== Action Selection Tests =====

#[test]
fn test_action_selection_uses_correct_regime() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let mut dqn = RegimeConditionalDQN::new(config)?;

    // Test trending regime action selection
    let mut state = vec![0.0_f32; 225];
    state[211] = 30.0; // ADX high
    let action_trending = dqn.select_action(&state)?;
    assert!(action_trending.to_index() < 45);

    // Test ranging regime action selection
    state[211] = 15.0; // ADX low
    state[219] = 0.4;  // Entropy low
    let action_ranging = dqn.select_action(&state)?;
    assert!(action_ranging.to_index() < 45);

    // Test volatile regime action selection
    state[219] = 0.8;  // Entropy high
    let action_volatile = dqn.select_action(&state)?;
    assert!(action_volatile.to_index() < 45);

    Ok(())
}

// ===== Metrics Tests =====

#[test]
fn test_training_metrics_per_regime() -> anyhow::Result<()> {
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.state_dim = 225;
    config.num_actions = 45;
    config.min_replay_size = 10;
    config.batch_size = 10;

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

    // Add regime-specific experiences
    for i in 0..30 {
        let mut state = vec![0.0_f32; 225];
        state[211] = 30.0; // Trending regime only

        let experience = Experience::new(
            state.clone(),
            (i % 45) as u8,
            i as f32,
            state,
            false,
        );
        dqn.store_experience(experience)?;
    }

    // Train and get metrics
    let _ = dqn.train_step(None)?;
    let metrics = dqn.get_regime_metrics();

    // Verify metrics exist for trending regime
    assert!(metrics.contains_key(&RegimeType::Trending));
    let trending_metrics = &metrics[&RegimeType::Trending];
    assert!(trending_metrics.training_steps > 0);

    Ok(())
}

// ===== Epsilon Decay Tests =====

#[test]
fn test_epsilon_decay_per_regime() -> anyhow::Result<()> {
    let mut config = WorkingDQNConfig::emergency_safe_defaults();
    config.epsilon_start = 1.0;
    config.epsilon_decay = 0.9;
    config.epsilon_end = 0.1;

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

    let initial_epsilon = dqn.get_epsilon(RegimeType::Trending);
    assert_eq!(initial_epsilon, 1.0);

    dqn.update_epsilon(RegimeType::Trending);
    let new_epsilon = dqn.get_epsilon(RegimeType::Trending);

    assert!(new_epsilon < initial_epsilon);
    assert!(new_epsilon >= 0.1);

    Ok(())
}

// ===== Target Network Tests =====

#[test]
fn test_target_network_update_all_heads() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let mut dqn = RegimeConditionalDQN::new(config)?;

    // Get initial target Q-values
    let device = Device::cuda_if_available(0)?;
    let state = Tensor::zeros(&[1, 225], candle_core::DType::F32, &device)?;

    // Manually update target networks
    dqn.update_target_networks()?;

    // Verify no errors occurred
    Ok(())
}

// ===== Experience Replay Tests =====

#[test]
fn test_shared_experience_replay() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let dqn = RegimeConditionalDQN::new(config)?;

    // Add experiences from different regimes
    for i in 0..10 {
        let mut state = vec![0.0_f32; 225];
        state[211] = if i % 2 == 0 { 30.0 } else { 15.0 }; // Alternate regimes

        let experience = Experience::new(
            state.clone(),
            (i % 45) as u8,
            i as f32,
            state,
            false,
        );
        dqn.store_experience(experience)?;
    }

    // Verify buffer size
    let buffer_size = dqn.get_replay_buffer_size()?;
    assert_eq!(buffer_size, 10);

    Ok(())
}

// ===== Regime Transition Tests =====

#[test]
fn test_regime_transition_handling() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let mut dqn = RegimeConditionalDQN::new(config)?;

    // Start in trending regime
    let mut state = vec![0.0_f32; 225];
    state[211] = 30.0;
    let _ = dqn.select_action(&state)?;

    // Transition to ranging regime
    state[211] = 15.0;
    state[219] = 0.4;
    let _ = dqn.select_action(&state)?;

    // Transition to volatile regime
    state[219] = 0.8;
    let _ = dqn.select_action(&state)?;

    // Verify no errors during transitions
    Ok(())
}

// ===== Reward Scaling Tests =====

#[test]
fn test_regime_specific_reward_scaling() -> anyhow::Result<()> {
    let config = WorkingDQNConfig::emergency_safe_defaults();
    let dqn = RegimeConditionalDQN::new(config)?;

    // Test reward scaling for different regimes
    let base_reward = 1.0;

    let trending_reward = dqn.scale_reward(base_reward, RegimeType::Trending);
    let ranging_reward = dqn.scale_reward(base_reward, RegimeType::Ranging);
    let volatile_reward = dqn.scale_reward(base_reward, RegimeType::Volatile);

    // Trending should amplify positive rewards
    assert!(trending_reward >= base_reward);

    // Ranging should penalize volatility
    assert!(ranging_reward <= base_reward);

    // Volatile should reduce reward magnitude
    assert!(volatile_reward.abs() <= base_reward.abs());

    Ok(())
}