//! Test suite for DQNTrainer PortfolioTracker initialization (Bug #2 fix)
//!
//! This test validates that PortfolioTracker is correctly initialized in DQNTrainer
//! and properly configured with starting capital and spread parameters.
//!
//! Bug #2 Context: Portfolio features were hardcoded as empty vector [0.0, 0.0, 0.0]
//! at ml/src/trainers/dqn.rs:1528. PortfolioTracker module exists (9/9 tests passing)
//! but was NOT USED by DQNTrainer.
//!
//! Test Strategy (TDD):
//! 1. Write tests first (expect failures)
//! 2. Implement PortfolioTracker field in DQNTrainer struct
//! 3. Initialize in constructor with $100k cash and 1bp spread
//! 4. Watch tests pass

use anyhow::Result;
use ml::trainers::dqn::{DQNHyperparameters, DQNTrainer};

/// Test 1: Verify PortfolioTracker is initialized with correct cash ($100,000)
///
/// Expected behavior:
/// - DQNTrainer should have a portfolio_tracker field
/// - Initial capital should be $100,000
/// - Portfolio value should equal cash when no positions are open
#[tokio::test]
async fn test_portfolio_tracker_initialized_with_correct_cash() -> Result<()> {
    // Create DQN trainer with conservative hyperparameters
    let hyperparams = DQNHyperparameters::conservative();
    let trainer = DQNTrainer::new(hyperparams)?;

    // Verify portfolio_tracker is initialized with $100,000
    let features = trainer.portfolio_tracker.get_portfolio_features(100.0);

    assert_eq!(
        features[0], 100_000.0,
        "Portfolio value should be $100,000 at initialization"
    );

    Ok(())
}

/// Test 2: Verify spread is set correctly (0.0001 = 1 basis point)
///
/// Expected behavior:
/// - PortfolioTracker should be initialized with 1 basis point spread
/// - Spread should be 0.0001 (as a fraction)
#[tokio::test]
async fn test_portfolio_tracker_spread_initialization() -> Result<()> {
    // Create DQN trainer
    let hyperparams = DQNHyperparameters::conservative();
    let trainer = DQNTrainer::new(hyperparams)?;

    // Verify spread is 1 basis point (0.0001)
    let features = trainer.portfolio_tracker.get_portfolio_features(100.0);

    assert_eq!(
        features[2], 0.0001,
        "Spread should be 1 basis point (0.0001)"
    );

    Ok(())
}

/// Test 3: Verify portfolio features are extracted correctly
///
/// Expected behavior:
/// - get_portfolio_features() should return [value, position, spread]
/// - Initial state: [100_000.0, 0.0, 0.0001]
#[tokio::test]
async fn test_portfolio_features_extraction() -> Result<()> {
    // Create DQN trainer
    let hyperparams = DQNHyperparameters::conservative();
    let trainer = DQNTrainer::new(hyperparams)?;

    // Verify all portfolio features are correctly initialized
    let features = trainer.portfolio_tracker.get_portfolio_features(100.0);

    assert_eq!(
        features[0], 100_000.0,
        "Portfolio value should be $100k (cash, no positions)"
    );
    assert_eq!(features[1], 0.0, "Position size should be 0 (flat)");
    assert_eq!(features[2], 0.0001, "Spread should be 1 basis point");

    Ok(())
}

/// Test 4: Verify PortfolioTracker survives across training loop initialization
///
/// This test ensures that portfolio_tracker is properly initialized before
/// the training loop begins, preventing the Bug #2 scenario where portfolio
/// features were always [0.0, 0.0, 0.0].
#[tokio::test]
async fn test_portfolio_tracker_persists_through_initialization() -> Result<()> {
    // Create DQN trainer
    let hyperparams = DQNHyperparameters::conservative();
    let trainer = DQNTrainer::new(hyperparams)?;

    // Verify PortfolioTracker is initialized (not the bug scenario of [0, 0, 0])
    let features = trainer.portfolio_tracker.get_portfolio_features(100.0);

    // Bug #2 would have resulted in [0.0, 0.0, 0.0]
    // Verify we get the correct initial values instead
    assert_ne!(
        features[0], 0.0,
        "Portfolio value should NOT be 0 (Bug #2 scenario)"
    );
    assert_eq!(features[0], 100_000.0, "Portfolio value should be $100k");

    Ok(())
}

/// Test 5: Verify PortfolioTracker can be reset for new epochs
///
/// Expected behavior:
/// - After execute_action(), portfolio state changes
/// - After reset(), portfolio state returns to initial values
#[tokio::test]
async fn test_portfolio_tracker_reset_capability() -> Result<()> {
    use ml::dqn::agent::TradingAction;

    // Create DQN trainer
    let hyperparams = DQNHyperparameters::conservative();
    let mut trainer = DQNTrainer::new(hyperparams)?;

    // Execute a buy action to change portfolio state
    trainer
        .portfolio_tracker
        .execute_action(TradingAction::Buy, 100.0, 10.0);

    // Verify portfolio state changed
    let features_after_trade = trainer.portfolio_tracker.get_portfolio_features(100.0);
    assert_eq!(
        features_after_trade[1], 10.0,
        "Position size should be 10.0 after buy"
    );

    // Reset portfolio for new epoch
    trainer.portfolio_tracker.reset();

    // Verify portfolio state returned to initial values
    let features_after_reset = trainer.portfolio_tracker.get_portfolio_features(100.0);
    assert_eq!(
        features_after_reset[0], 100_000.0,
        "Portfolio value should be $100k after reset"
    );
    assert_eq!(
        features_after_reset[1], 0.0,
        "Position size should be 0 after reset"
    );
    assert_eq!(
        features_after_reset[2], 0.0001,
        "Spread should remain 1 basis point after reset"
    );

    Ok(())
}