//! ML-powered strategy execution engine for backtesting
//!
//! This module integrates the shared ML strategy from common crate to ensure
//! ONE SINGLE SYSTEM across trading and backtesting services.

use anyhow::Result;
use chrono::{DateTime, Utc};
use rust_decimal::{prelude::ToPrimitive, Decimal};
use serde::{Deserialize, Serialize};
use std::collections::HashMap;
use std::sync::Arc;
use tracing::{debug, info};

use crate::storage::StorageManager;
use crate::strategy_engine::{
    BacktestTrade, MarketData, Portfolio, StrategyExecutor, TradeSide, TradeSignal,
};
use config::structures::BacktestingStrategyConfig;

// Import shared ML strategy (ONE SINGLE SYSTEM)
use common::ml_strategy::{MLPrediction as CommonMLPrediction, SharedMLStrategy};


// Import UnifiedFeatureExtractor (256 features, production system)
use ml::features::unified::{FeatureExtractionConfig, UnifiedFeatureExtractor};
use ml::safety::{MLSafetyConfig, MLSafetyManager};

/// ML model prediction result for backtesting
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MLPrediction {
    /// Model identifier
    pub model_id: String,
    /// Prediction value (0.0-1.0)
    pub prediction_value: f64,
    /// Confidence score (0.0-1.0)
    pub confidence: f64,
    /// Features used for prediction
    pub features: Vec<f64>,
    /// Prediction timestamp
    pub timestamp: DateTime<Utc>,
    /// Inference latency in microseconds
    pub inference_latency_us: u64,
}

/// ML model performance tracking for backtesting
#[derive(Debug, Clone, Default, Serialize, Deserialize)]
pub struct MLModelPerformance {
    /// Model identifier
    pub model_id: String,
    /// Total predictions made
    pub total_predictions: u64,
    /// Correct predictions (when outcome is known)
    pub correct_predictions: u64,
    /// Average inference latency
    pub avg_latency_us: f64,
    /// Average confidence score
    pub avg_confidence: f64,
    /// Model accuracy percentage
    pub accuracy_percentage: f64,
    /// Returns generated when following this model
    pub returns: Vec<f64>,
    /// Sharpe ratio for this model
    pub sharpe_ratio: f64,
    /// Maximum drawdown when following this model
    pub max_drawdown: f64,
}

// NOTE: MLFeatureExtractor REMOVED - Replaced with UnifiedFeatureExtractor (256 features)
// Old implementation used only 8 features (price return, MA, volatility, volume, time).
// New implementation uses production-grade 256-feature extraction pipeline:
// - 5 OHLCV features
// - 10 technical indicators (RSI, MACD, Bollinger, ATR, EMA)
// - 60 price patterns
// - 40 volume patterns
// - 50 microstructure features
// - 10 time-based features
// - 81 statistical features
//
// This ensures backtesting uses the SAME features as live trading and model training.

/// ML-powered strategy for backtesting (uses shared ML strategy - ONE SINGLE SYSTEM)
pub struct MLPoweredStrategy {
    /// Strategy name
    name: String,
    /// Shared ML strategy (ONE SINGLE SYSTEM)
    strategy: Arc<SharedMLStrategy>,
    /// Unified feature extractor (256 features, production system)
    _feature_extractor: Arc<UnifiedFeatureExtractor>,
    /// Model performance tracking (local copy for backward compatibility)
    model_performance: HashMap<String, MLModelPerformance>,
    /// Current position size based on confidence
    confidence_based_sizing: bool,
    /// Minimum confidence threshold for trades
    min_confidence_threshold: f64,
}

// NOTE: Old model simulator implementations removed.
// We now use SharedMLStrategy from common crate (ONE SINGLE SYSTEM).
// This eliminates code duplication and ensures consistent ML predictions
// across trading and backtesting services.

impl std::fmt::Debug for MLPoweredStrategy {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        f.debug_struct("MLPoweredStrategy")
            .field("name", &self.name)
            .field("confidence_based_sizing", &self.confidence_based_sizing)
            .field("min_confidence_threshold", &self.min_confidence_threshold)
            .field("model_performance_count", &self.model_performance.len())
            .finish()
    }
}

impl MLPoweredStrategy {
    /// Create new ML-powered strategy (uses shared strategy - ONE SINGLE SYSTEM)
    /// # Errors
    /// Returns error if ML model adapter construction fails.
    pub fn new(name: String, _lookback_periods: usize) -> Result<Self> {
        // Use shared ML strategy (ONE SINGLE SYSTEM) with ProductionFeatureExtractorAdapter (225 features).
        //
        // `build_production_strategy` now takes a Vec of real per-model inference
        // adapters. The backtesting service has no checkpoint-loader wired at this
        // layer, so we pass an empty vec: the resulting `SharedMLStrategy` honestly
        // reports "no models loaded" (empty prediction list) instead of the prior
        // ghost behaviour where 10 stub adapters all returned confidence=0.0 and
        // were silently filtered by the threshold.
        //
        // When the backtesting service grows a model-loader, it should build the
        // appropriate `DqnInferenceAdapter::from_checkpoint(..)` / `PpoInferenceAdapter::new(..)`
        // / etc. adapters and pass them in here with their ensemble ids.
        let min_confidence_threshold = 0.6;
        let strategy = Arc::new(ml::ensemble::build_production_strategy(
            min_confidence_threshold,
            Vec::new(),
        ));

        // Initialize UnifiedFeatureExtractor (256 features)
        let feature_config = FeatureExtractionConfig::default();
        let safety_config = MLSafetyConfig::default();
        let safety_manager = Arc::new(MLSafetyManager::new(safety_config));
        let feature_extractor =
            Arc::new(UnifiedFeatureExtractor::new(feature_config, safety_manager));

        Ok(Self {
            name,
            strategy,
            _feature_extractor: feature_extractor,
            model_performance: HashMap::new(),
            confidence_based_sizing: true,
            min_confidence_threshold,
        })
    }

    /// Get ensemble prediction from all models (delegates to shared strategy)
    pub async fn get_ensemble_prediction(
        &mut self,
        market_data: &MarketData,
    ) -> Result<Vec<MLPrediction>> {
        // Use shared ML strategy (ONE SINGLE SYSTEM)
        let price = market_data.close.to_f64().unwrap_or(0.0);
        let volume = market_data.volume.to_f64().unwrap_or(0.0);
        let timestamp = market_data.timestamp;

        // Get predictions from shared strategy
        let common_predictions = self
            .strategy
            .get_ensemble_prediction(price, volume, timestamp)
            .await?;

        // Convert to local type for backward compatibility
        let predictions = common_predictions
            .iter()
            .map(|p| MLPrediction {
                model_id: p.model_id.clone(),
                prediction_value: p.prediction_value,
                confidence: p.confidence,
                features: p.features.clone(),
                timestamp: p.timestamp,
                inference_latency_us: p.inference_latency_us,
            })
            .collect();

        Ok(predictions)
    }

    /// Calculate weighted ensemble prediction
    pub fn calculate_ensemble_vote(&self, predictions: &[MLPrediction]) -> Option<(f64, f64)> {
        if predictions.is_empty() {
            return None;
        }

        let total_confidence: f64 = predictions.iter().map(|p| p.confidence).sum();
        if total_confidence == 0.0 {
            return None;
        }

        // Weighted average by confidence
        let weighted_prediction: f64 = predictions
            .iter()
            .map(|p| p.prediction_value * p.confidence)
            .sum::<f64>()
            / total_confidence;

        let average_confidence: f64 =
            predictions.iter().map(|p| p.confidence).sum::<f64>() / predictions.len() as f64;

        Some((weighted_prediction, average_confidence))
    }

    /// Validate predictions against actual market outcomes (delegates to shared strategy)
    pub async fn validate_predictions(&mut self, predictions: &[MLPrediction], actual_return: f64) {
        // Convert to common predictions
        let common_predictions: Vec<CommonMLPrediction> = predictions
            .iter()
            .map(|p| CommonMLPrediction {
                model_id: p.model_id.clone(),
                prediction_value: p.prediction_value,
                confidence: p.confidence,
                features: p.features.clone(),
                timestamp: p.timestamp,
                inference_latency_us: p.inference_latency_us,
            })
            .collect();

        // Delegate to shared strategy (ONE SINGLE SYSTEM)
        self.strategy
            .validate_predictions(&common_predictions, actual_return)
            .await;

        // Update local performance tracking for backward compatibility
        let shared_performance = self.strategy.get_performance_summary().await;
        for (model_id, perf) in shared_performance {
            self.model_performance.insert(
                model_id.clone(),
                MLModelPerformance {
                    model_id: model_id.clone(),
                    total_predictions: perf.total_predictions,
                    correct_predictions: perf.correct_predictions,
                    avg_latency_us: perf.avg_latency_us,
                    avg_confidence: perf.avg_confidence,
                    accuracy_percentage: perf.accuracy_percentage,
                    returns: perf.returns,
                    sharpe_ratio: perf.sharpe_ratio,
                    max_drawdown: perf.max_drawdown,
                },
            );
        }
    }

    /// Get performance summary for all models
    pub fn get_performance_summary(&self) -> HashMap<String, MLModelPerformance> {
        self.model_performance.clone()
    }
}

impl StrategyExecutor for MLPoweredStrategy {
    fn execute(
        &self,
        market_data: &MarketData,
        _portfolio: &Portfolio,
        parameters: &HashMap<String, String>,
    ) -> Result<Vec<TradeSignal>> {
        // NOTE: This method has &self (immutable), but we need mutable access to extract features.
        // In production, consider using interior mutability (RefCell/Mutex) or redesigning the trait.
        // For now, use async runtime to call SharedMLStrategy which handles this internally.

        let mut signals = Vec::new();

        // Use shared ML strategy for ensemble prediction (handles feature extraction internally)
        let price = market_data.close.to_f64().unwrap_or(0.0);
        let volume = market_data.volume.to_f64().unwrap_or(0.0);
        let timestamp = market_data.timestamp;

        // Create tokio runtime for async calls
        let runtime = tokio::runtime::Runtime::new()?;
        let predictions = runtime.block_on(async {
            self.strategy
                .get_ensemble_prediction(price, volume, timestamp)
                .await
        })?;

        // Convert to local MLPrediction type
        let local_predictions: Vec<MLPrediction> = predictions
            .iter()
            .map(|p| MLPrediction {
                model_id: p.model_id.clone(),
                prediction_value: p.prediction_value,
                confidence: p.confidence,
                features: p.features.clone(),
                timestamp: p.timestamp,
                inference_latency_us: p.inference_latency_us,
            })
            .collect();

        // Calculate ensemble vote
        if let Some((ensemble_prediction, ensemble_confidence)) =
            self.calculate_ensemble_vote(&local_predictions)
        {
            let min_confidence = parameters
                .get("min_confidence")
                .and_then(|s| s.parse::<f64>().ok())
                .unwrap_or(self.min_confidence_threshold);

            if ensemble_confidence >= min_confidence {
                let quantity = if self.confidence_based_sizing {
                    Decimal::try_from(ensemble_confidence * 1000.0).unwrap_or(Decimal::from(100))
                } else {
                    Decimal::from(100)
                };

                if ensemble_prediction > 0.6 {
                    signals.push(TradeSignal {
                        symbol: market_data.symbol.clone(),
                        side: TradeSide::Buy,
                        quantity,
                        reason: format!(
                            "ML ensemble prediction: {:.3} (confidence: {:.3})",
                            ensemble_prediction, ensemble_confidence
                        ),
                    });
                } else if ensemble_prediction < 0.4 {
                    signals.push(TradeSignal {
                        symbol: market_data.symbol.clone(),
                        side: TradeSide::Sell,
                        quantity,
                        reason: format!(
                            "ML ensemble prediction: {:.3} (confidence: {:.3})",
                            ensemble_prediction, ensemble_confidence
                        ),
                    });
                }
            }
        }

        Ok(signals)
    }
}

/// ML Strategy Engine with model performance tracking
pub struct MLStrategyEngine {
    /// Base strategy engine
    base_engine: crate::strategy_engine::StrategyEngine,
    /// ML-powered strategies
    ml_strategies: HashMap<String, MLPoweredStrategy>,
    /// Model performance tracking across backtests
    global_model_performance: HashMap<String, MLModelPerformance>,
}

impl MLStrategyEngine {
    /// Create new ML strategy engine
    pub async fn new(
        config: &BacktestingStrategyConfig,
        storage_manager: Arc<StorageManager>,
    ) -> Result<Self> {
        // Create repositories from storage manager
        let repositories =
            Arc::new(crate::repository_impl::create_repositories(storage_manager).await?);
        let base_engine = crate::strategy_engine::StrategyEngine::new(config, repositories).await?;

        let mut ml_strategies = HashMap::new();

        // Add ML-powered strategies
        ml_strategies.insert(
            "ml_momentum".to_string(),
            MLPoweredStrategy::new("ml_momentum".to_string(), 20)?,
        );

        ml_strategies.insert(
            "ml_ensemble".to_string(),
            MLPoweredStrategy::new("ml_ensemble".to_string(), 50)?,
        );

        Ok(Self {
            base_engine,
            ml_strategies,
            global_model_performance: HashMap::new(),
        })
    }

    /// Execute backtest with ML model validation
    pub async fn execute_ml_backtest(
        &mut self,
        context: &crate::service::BacktestContext,
    ) -> Result<(Vec<BacktestTrade>, HashMap<String, MLModelPerformance>)> {
        info!(
            "Executing ML-powered backtest {} for strategy {}",
            context.id, context.strategy_name
        );

        // Check if this is an ML strategy
        let is_ml_strategy = self.ml_strategies.contains_key(&context.strategy_name);

        if is_ml_strategy {
            // Execute ML-powered backtest with model validation
            self.execute_ml_strategy_backtest(context).await
        } else {
            // Fall back to base strategy engine
            let trades = self.base_engine.execute_backtest(context).await?;
            Ok((trades, HashMap::new()))
        }
    }

    /// Execute backtest for ML strategy with model performance tracking
    async fn execute_ml_strategy_backtest(
        &mut self,
        context: &crate::service::BacktestContext,
    ) -> Result<(Vec<BacktestTrade>, HashMap<String, MLModelPerformance>)> {
        // Load market data for the backtest period
        let market_data = self
            .base_engine
            .load_market_data(
                &context.symbols,
                context.started_at,
                context
                    .completed_at
                    .unwrap_or(chrono::Utc::now().timestamp_nanos_opt().unwrap_or(0)),
            )
            .await?;

        let trades = Vec::new();
        let mut previous_price = None;
        let total_data_points = market_data.len();

        // Get ML strategy reference
        let ml_strategy = self
            .ml_strategies
            .get_mut(&context.strategy_name)
            .ok_or_else(|| anyhow::anyhow!("ML strategy {} not found", context.strategy_name))?;

        // Process each data point with ML predictions
        for (i, data_point) in market_data.into_iter().enumerate() {
            // Get ML predictions (async call to shared strategy)
            let predictions = ml_strategy.get_ensemble_prediction(&data_point).await?;

            // Calculate ensemble vote
            if let Some((ensemble_prediction, ensemble_confidence)) =
                ml_strategy.calculate_ensemble_vote(&predictions)
            {
                debug!(
                    "Ensemble prediction: {:.3} (confidence: {:.3})",
                    ensemble_prediction, ensemble_confidence
                );

                // Validate predictions against future returns if we have next price
                if let Some(prev_price) = previous_price {
                    let current_price = data_point.close.to_f64().unwrap_or(prev_price);
                    let actual_return = (current_price - prev_price) / prev_price;
                    ml_strategy
                        .validate_predictions(&predictions, actual_return)
                        .await;
                }
            }

            previous_price = Some(data_point.close.to_f64().unwrap_or(0.0));

            // Generate and execute trades using base strategy logic
            // (This would integrate with the existing strategy execution logic)
            if i % 100 == 0 {
                let progress = (i as f64 / total_data_points as f64) * 100.0;
                debug!("ML backtest progress: {:.1}%", progress);
            }
        }

        // Get final model performance
        let model_performance = ml_strategy.get_performance_summary();

        // Update global performance tracking
        for (model_id, perf) in &model_performance {
            self.global_model_performance
                .insert(model_id.clone(), perf.clone());
        }

        info!(
            "ML backtest completed with {} trades and {} model evaluations",
            trades.len(),
            model_performance.len()
        );

        Ok((trades, model_performance))
    }

    /// Get model performance across all backtests
    pub fn get_global_model_performance(&self) -> &HashMap<String, MLModelPerformance> {
        &self.global_model_performance
    }

    /// Generate model performance report
    pub fn generate_performance_report(&self) -> String {
        let mut report = String::new();
        report.push_str("=== ML Model Performance Report ===\n\n");

        for (model_id, performance) in &self.global_model_performance {
            report.push_str(&format!("Model: {}\n", model_id));
            report.push_str(&format!(
                "  Total Predictions: {}\n",
                performance.total_predictions
            ));
            report.push_str(&format!(
                "  Accuracy: {:.2}%\n",
                performance.accuracy_percentage
            ));
            report.push_str(&format!(
                "  Average Confidence: {:.3}\n",
                performance.avg_confidence
            ));
            report.push_str(&format!(
                "  Average Latency: {:.1}μs\n",
                performance.avg_latency_us
            ));
            if performance.sharpe_ratio != 0.0 {
                report.push_str(&format!(
                    "  Sharpe Ratio: {:.3}\n",
                    performance.sharpe_ratio
                ));
            }
            if performance.max_drawdown != 0.0 {
                report.push_str(&format!(
                    "  Max Drawdown: {:.2}%\n",
                    performance.max_drawdown * 100.0
                ));
            }
            report.push('\n');
        }

        report
    }
}