/// Bug #8: Action Selection Frequency Test Suite
///
/// **Bug Description**:
/// Experience collection in DQN training incorrectly executes portfolio actions
/// for ALL training samples (16,819 samples/epoch), causing 522,713 total actions
/// in 1 epoch instead of expected 0 actions during training.
///
/// **Root Cause**:
/// Line 928 of trainers/dqn.rs calls `portfolio_tracker.execute_action()` during
/// experience collection phase. Experience collection should SIMULATE rewards
/// without executing portfolio actions.
///
/// **Expected Behavior**:
/// - Experience collection: 0 portfolio executions (simulation only)
/// - Evaluation/Backtesting: N portfolio executions (actual trading simulation)

use anyhow::Result;
use ml::trainers::dqn::{DQNTrainer, DQNHyperparameters};
use ml::trainers::TargetUpdateMode;
use std::path::PathBuf;

/// Helper: Get path to ES.FUT test data
fn get_test_data_dir() -> Result<String> {
    let workspace_root = PathBuf::from(env!("CARGO_MANIFEST_DIR"))
        .parent()
        .ok_or_else(|| anyhow::anyhow!("Failed to get workspace root"))?
        .to_path_buf();

    let data_dir = workspace_root.join("test_data/real/databento/ml_training_small");

    if !data_dir.exists() {
        anyhow::bail!(
            "ES.FUT data directory not found: {}. Skipping Bug #8 tests.",
            data_dir.display()
        );
    }

    Ok(data_dir.to_string_lossy().to_string())
}

/// Helper: Create checkpoint directory for tests
fn create_checkpoint_dir() -> Result<PathBuf> {
    let checkpoint_dir = PathBuf::from("/tmp/bug8_checkpoints");
    std::fs::create_dir_all(&checkpoint_dir)?;
    Ok(checkpoint_dir)
}

/// Helper: Create test hyperparameters for Bug #8 validation
fn create_test_hyperparams(epochs: usize) -> DQNHyperparameters {
    DQNHyperparameters {
        learning_rate: 0.0001,
        batch_size: 32,
        gamma: 0.99,
        epsilon_start: 1.0,
        epsilon_end: 0.05,
        epsilon_decay: 0.995,
        buffer_size: 1000,
        min_replay_size: 32,
        epochs,
        checkpoint_frequency: 10,
        early_stopping_enabled: false,
        q_value_floor: 0.5,
        min_loss_improvement_pct: 0.1,
        plateau_window: 30,
        min_epochs_before_stopping: 50,
        hold_penalty: 0.01,
        use_huber_loss: true,
        huber_delta: 1.0,
        use_double_dqn: true,
        gradient_clip_norm: Some(10.0),
        hold_penalty_weight: 1.0,
        movement_threshold: 0.02,
        enable_preprocessing: false,
        preprocessing_window: 50,
        preprocessing_clip_sigma: 5.0,
        target_update_mode: TargetUpdateMode::Hard,
        target_update_frequency: 1000,
        tau: 0.005,
        warmup_steps: 0,                    // No warmup for fast testing
        initial_capital: 100_000.0,          // $100K initial capital
        cash_reserve_percent: 0.0,           // No reserve requirement
    }
}

#[tokio::test]
async fn test_no_transaction_costs_during_training() -> Result<()> {
    // Test: Transaction costs are NOT charged during training experience collection
    // Expected: transaction_costs() remains 0.0 after training
    // Bug Scenario: With bug, 522K actions × ~0.15% fee = massive cost inflation

    let data_dir = match get_test_data_dir() {
        Ok(dir) => dir,
        Err(e) => {
            eprintln!("⚠️  Skipping Bug #8 test - data not available: {}", e);
            return Ok(());
        }
    };

    let checkpoint_dir = create_checkpoint_dir()?;
    let hyperparams = create_test_hyperparams(1);

    let mut trainer = DQNTrainer::new(hyperparams)
        .expect("Failed to create DQN trainer");

    // Get initial fees via accessor method (Wave 8 API change)
    let initial_fees = trainer.portfolio_tracker.transaction_costs();

    // Run training
    let _metrics = trainer
        .train(&data_dir, |epoch, checkpoint_data, _is_best| {
            let path = checkpoint_dir.join(format!("test_checkpoint_{}.safetensors", epoch));
            std::fs::write(&path, checkpoint_data)?;
            Ok(path.to_string_lossy().to_string())
        })
        .await
        .expect("Training failed");

    // Verify zero transaction costs (use method, not field)
    let final_fees = trainer.portfolio_tracker.transaction_costs();
    assert_eq!(
        final_fees,
        initial_fees,
        "Bug #8: Training should NOT charge transaction costs (experience collection is simulation only). \
         Got {} fees (expected {})",
        final_fees,
        initial_fees
    );

    Ok(())
}

#[tokio::test]
async fn test_no_portfolio_execution_during_training() -> Result<()> {
    // Test: Portfolio position is NOT modified during training
    // Expected: current_position() remains 0.0 after training
    // Bug Scenario: With bug, executes 16,819 actions per epoch

    let data_dir = match get_test_data_dir() {
        Ok(dir) => dir,
        Err(e) => {
            eprintln!("⚠️  Skipping Bug #8 test - data not available: {}", e);
            return Ok(());
        }
    };

    let checkpoint_dir = create_checkpoint_dir()?;
    let hyperparams = create_test_hyperparams(1);

    let mut trainer = DQNTrainer::new(hyperparams)
        .expect("Failed to create DQN trainer");

    // Get initial position via accessor method (Wave 8 API change)
    let initial_position = trainer.portfolio_tracker.current_position();

    // Run training
    let _metrics = trainer
        .train(&data_dir, |epoch, checkpoint_data, _is_best| {
            let path = checkpoint_dir.join(format!("test_checkpoint_{}.safetensors", epoch));
            std::fs::write(&path, checkpoint_data)?;
            Ok(path.to_string_lossy().to_string())
        })
        .await
        .expect("Training failed");

    // Verify zero position change (use method, not field)
    let final_position = trainer.portfolio_tracker.current_position();
    assert_eq!(
        final_position,
        initial_position,
        "Bug #8: Training should NOT modify portfolio position. Got position={}, expected={}",
        final_position,
        initial_position
    );

    Ok(())
}

#[tokio::test]
async fn test_integration_1epoch_small_dataset() -> Result<()> {
    // Integration Test: Complete 1-epoch training with verification
    // Dataset: ES.FUT test data (DBN format)
    // Expected:
    // - 0 portfolio executions
    // - 0 transaction costs
    // - Valid training metrics
    // - No circuit breaker triggers

    let data_dir = match get_test_data_dir() {
        Ok(dir) => dir,
        Err(e) => {
            eprintln!("⚠️  Skipping Bug #8 test - data not available: {}", e);
            return Ok(());
        }
    };

    let checkpoint_dir = create_checkpoint_dir()?;
    let hyperparams = create_test_hyperparams(1);

    let mut trainer = DQNTrainer::new(hyperparams)
        .expect("Failed to create DQN trainer");

    // Capture initial state (Wave 8 API: use methods, not fields)
    let initial_fees = trainer.portfolio_tracker.transaction_costs();
    let initial_position = trainer.portfolio_tracker.current_position();

    let metrics = trainer
        .train(&data_dir, |epoch, checkpoint_data, _is_best| {
            let path = checkpoint_dir.join(format!("test_checkpoint_integration_{}.safetensors", epoch));
            std::fs::write(&path, checkpoint_data)?;
            Ok(path.to_string_lossy().to_string())
        })
        .await
        .expect("Training failed");

    // Comprehensive verification
    assert_eq!(metrics.epochs_trained, 1, "Should complete 1 epoch");
    
    // Bug #8 validation: Zero portfolio actions during training
    assert_eq!(
        trainer.portfolio_tracker.transaction_costs(),
        initial_fees,
        "Zero transaction costs during training"
    );
    assert_eq!(
        trainer.portfolio_tracker.current_position(),
        initial_position,
        "Zero portfolio position changes during training"
    );
    
    // Training metrics sanity checks
    assert!(
        metrics.loss.is_finite(),
        "Loss should be finite, got: {}",
        metrics.loss
    );

    println!("✅ Bug #8 Integration Test PASSED:");
    println!("   - 0 transaction costs (initial={}, final={})", 
        initial_fees, trainer.portfolio_tracker.transaction_costs());
    println!("   - 0 position changes (initial={}, final={})", 
        initial_position, trainer.portfolio_tracker.current_position());
    println!("   - Final loss: {:.6}", metrics.loss);

    Ok(())
}