import { serve } from 'https://deno.land/std@0.190.0/http/server.ts';
import { createEdgeFunction, type EdgeFunctionContext } from '../_shared/edgeFunctionWrapper.ts';
import { addSpanEvent } from '../_shared/logger.ts';
import { corsHeaders } from '../_shared/cors.ts';

interface MetricData {
  timestamp: string;
  metric_value: number;
}

interface AnomalyDetectionConfig {
  metric_name: string;
  metric_category: string;
  enabled: boolean;
  sensitivity: number;
  lookback_window_minutes: number;
  detection_algorithms: string[];
  min_data_points: number;
  alert_threshold_score: number;
  auto_create_alert: boolean;
}

interface AnomalyResult {
  isAnomaly: boolean;
  anomalyType: string;
  deviationScore: number;
  confidenceScore: number;
  algorithm: string;
  baselineValue: number;
  anomalyValue: number;
}

// Advanced ML-based anomaly detection algorithms
class AnomalyDetector {
  // Isolation Forest approximation: Detects outliers based on isolation score
  static isolationForest(data: number[], currentValue: number, sensitivity: number = 0.6): AnomalyResult {
    if (data.length < 10) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'isolation_forest', baselineValue: currentValue, anomalyValue: currentValue };
    }

    // Calculate isolation score (simplified version)
    // Based on how different the value is from random samples
    const samples = 20;
    let isolationScore = 0;
    
    for (let i = 0; i < samples; i++) {
      const randomSample = data[Math.floor(Math.random() * data.length)];
      const distance = Math.abs(currentValue - randomSample);
      isolationScore += distance;
    }
    
    isolationScore = isolationScore / samples;
    
    // Normalize by standard deviation
    const mean = data.reduce((sum, val) => sum + val, 0) / data.length;
    const variance = data.reduce((sum, val) => sum + Math.pow(val - mean, 2), 0) / data.length;
    const stdDev = Math.sqrt(variance);
    
    const normalizedScore = stdDev > 0 ? isolationScore / stdDev : 0;
    const isAnomaly = normalizedScore > (1 / sensitivity);
    
    return {
      isAnomaly,
      anomalyType: currentValue > mean ? 'outlier_high' : 'outlier_low',
      deviationScore: normalizedScore,
      confidenceScore: Math.min(normalizedScore / 5, 1),
      algorithm: 'isolation_forest',
      baselineValue: mean,
      anomalyValue: currentValue,
    };
  }

  // Seasonal decomposition: Detects anomalies considering seasonal patterns
  static seasonalDecomposition(data: number[], currentValue: number, sensitivity: number = 2.5, period: number = 24): AnomalyResult {
    if (data.length < period * 2) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'seasonal', baselineValue: currentValue, anomalyValue: currentValue };
    }

    // Calculate seasonal component (average of values at same position in period)
    const position = data.length % period;
    const seasonalValues: number[] = [];
    
    for (let i = position; i < data.length; i += period) {
      seasonalValues.push(data[i]);
    }
    
    const seasonalMean = seasonalValues.reduce((sum, val) => sum + val, 0) / seasonalValues.length;
    const seasonalStdDev = Math.sqrt(
      seasonalValues.reduce((sum, val) => sum + Math.pow(val - seasonalMean, 2), 0) / seasonalValues.length
    );
    
    if (seasonalStdDev === 0) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'seasonal', baselineValue: seasonalMean, anomalyValue: currentValue };
    }
    
    const deviationScore = Math.abs(currentValue - seasonalMean) / seasonalStdDev;
    const isAnomaly = deviationScore > sensitivity;
    
    return {
      isAnomaly,
      anomalyType: currentValue > seasonalMean ? 'seasonal_spike' : 'seasonal_drop',
      deviationScore,
      confidenceScore: Math.min(deviationScore / (sensitivity * 2), 1),
      algorithm: 'seasonal',
      baselineValue: seasonalMean,
      anomalyValue: currentValue,
    };
  }

  // LSTM-inspired prediction: Simple exponential smoothing with trend detection
  static predictiveAnomaly(data: number[], currentValue: number, sensitivity: number = 2.5): AnomalyResult {
    if (data.length < 5) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'predictive', baselineValue: currentValue, anomalyValue: currentValue };
    }

    // Triple exponential smoothing (Holt-Winters approximation)
    const alpha = 0.3; // Level smoothing
    const beta = 0.1;  // Trend smoothing
    
    let level = data[0];
    let trend = data[1] - data[0];
    
    // Calculate smoothed values
    for (let i = 1; i < data.length; i++) {
      const prevLevel = level;
      level = alpha * data[i] + (1 - alpha) * (level + trend);
      trend = beta * (level - prevLevel) + (1 - beta) * trend;
    }
    
    // Predict next value
    const prediction = level + trend;
    
    // Calculate prediction error
    const recentData = data.slice(-10);
    const predictionErrors: number[] = [];
    
    for (let i = 1; i < recentData.length; i++) {
      const simplePrediction = recentData[i - 1];
      predictionErrors.push(Math.abs(recentData[i] - simplePrediction));
    }
    
    const meanError = predictionErrors.reduce((sum, err) => sum + err, 0) / predictionErrors.length;
    const errorStdDev = Math.sqrt(
      predictionErrors.reduce((sum, err) => sum + Math.pow(err - meanError, 2), 0) / predictionErrors.length
    );
    
    const actualError = Math.abs(currentValue - prediction);
    const deviationScore = errorStdDev > 0 ? actualError / errorStdDev : 0;
    const isAnomaly = deviationScore > sensitivity;
    
    return {
      isAnomaly,
      anomalyType: currentValue > prediction ? 'unexpected_spike' : 'unexpected_drop',
      deviationScore,
      confidenceScore: Math.min(deviationScore / (sensitivity * 2), 1),
      algorithm: 'predictive',
      baselineValue: prediction,
      anomalyValue: currentValue,
    };
  }

  // Ensemble method: Combines multiple algorithms for better accuracy
  static ensemble(data: number[], currentValue: number, sensitivity: number = 2.5): AnomalyResult {
    const results: AnomalyResult[] = [
      this.zScore(data, currentValue, sensitivity),
      this.movingAverage(data, currentValue, sensitivity),
      this.rateOfChange(data, currentValue, sensitivity),
      this.isolationForest(data, currentValue, 0.6),
      this.predictiveAnomaly(data, currentValue, sensitivity),
    ];
    
    // Count how many algorithms detected an anomaly
    const anomalyCount = results.filter(r => r.isAnomaly).length;
    const anomalyRatio = anomalyCount / results.length;
    
    // Calculate average deviation and confidence
    const avgDeviation = results.reduce((sum, r) => sum + r.deviationScore, 0) / results.length;
    const avgConfidence = results.reduce((sum, r) => sum + r.confidenceScore, 0) / results.length;
    
    // Determine anomaly type based on most common classification
    const typeCount = new Map<string, number>();
    results.forEach(r => {
      typeCount.set(r.anomalyType, (typeCount.get(r.anomalyType) || 0) + 1);
    });
    
    let mostCommonType = 'none';
    let maxCount = 0;
    typeCount.forEach((count, type) => {
      if (count > maxCount) {
        maxCount = count;
        mostCommonType = type;
      }
    });
    
    const mean = data.reduce((sum, val) => sum + val, 0) / data.length;
    
    return {
      isAnomaly: anomalyRatio >= 0.4, // At least 40% of algorithms agree
      anomalyType: mostCommonType,
      deviationScore: avgDeviation,
      confidenceScore: Math.min(avgConfidence * anomalyRatio * 2, 1),
      algorithm: 'ensemble',
      baselineValue: mean,
      anomalyValue: currentValue,
    };
  }

  // Z-Score algorithm: Detects outliers based on standard deviation
  static zScore(data: number[], currentValue: number, sensitivity: number = 3.0): AnomalyResult {
    if (data.length < 2) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'z_score', baselineValue: currentValue, anomalyValue: currentValue };
    }

    const mean = data.reduce((sum, val) => sum + val, 0) / data.length;
    const variance = data.reduce((sum, val) => sum + Math.pow(val - mean, 2), 0) / data.length;
    const stdDev = Math.sqrt(variance);

    if (stdDev === 0) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'z_score', baselineValue: mean, anomalyValue: currentValue };
    }

    const zScore = Math.abs((currentValue - mean) / stdDev);
    const isAnomaly = zScore > sensitivity;
    
    return {
      isAnomaly,
      anomalyType: currentValue > mean ? 'spike' : 'drop',
      deviationScore: zScore,
      confidenceScore: Math.min(zScore / (sensitivity * 2), 1),
      algorithm: 'z_score',
      baselineValue: mean,
      anomalyValue: currentValue,
    };
  }

  // Moving Average algorithm: Detects deviation from trend
  static movingAverage(data: number[], currentValue: number, sensitivity: number = 2.5, window: number = 10): AnomalyResult {
    if (data.length < window) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'moving_average', baselineValue: currentValue, anomalyValue: currentValue };
    }

    const recentData = data.slice(-window);
    const ma = recentData.reduce((sum, val) => sum + val, 0) / recentData.length;
    
    const mad = recentData.reduce((sum, val) => sum + Math.abs(val - ma), 0) / recentData.length;
    
    if (mad === 0) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'moving_average', baselineValue: ma, anomalyValue: currentValue };
    }

    const deviation = Math.abs(currentValue - ma) / mad;
    const isAnomaly = deviation > sensitivity;

    return {
      isAnomaly,
      anomalyType: currentValue > ma ? 'spike' : 'drop',
      deviationScore: deviation,
      confidenceScore: Math.min(deviation / (sensitivity * 2), 1),
      algorithm: 'moving_average',
      baselineValue: ma,
      anomalyValue: currentValue,
    };
  }

  // Rate of Change algorithm: Detects sudden changes
  static rateOfChange(data: number[], currentValue: number, sensitivity: number = 3.0): AnomalyResult {
    if (data.length < 2) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'rate_of_change', baselineValue: currentValue, anomalyValue: currentValue };
    }

    const previousValue = data[data.length - 1];
    
    if (previousValue === 0) {
      return { isAnomaly: false, anomalyType: 'none', deviationScore: 0, confidenceScore: 0, algorithm: 'rate_of_change', baselineValue: previousValue, anomalyValue: currentValue };
    }

    const percentChange = Math.abs((currentValue - previousValue) / previousValue) * 100;
    const isAnomaly = percentChange > (sensitivity * 10); // sensitivity * 10 = % threshold

    return {
      isAnomaly,
      anomalyType: currentValue > previousValue ? 'trend_change' : 'drop',
      deviationScore: percentChange / 10,
      confidenceScore: Math.min(percentChange / (sensitivity * 20), 1),
      algorithm: 'rate_of_change',
      baselineValue: previousValue,
      anomalyValue: currentValue,
    };
  }
}

const handler = async (req: Request, { supabase, span, requestId }: EdgeFunctionContext) => {
  addSpanEvent(span, 'starting_anomaly_detection', { requestId });

    // Get all enabled anomaly detection configurations
    const { data: configs, error: configError } = await supabase
      .from('anomaly_detection_config')
      .select('*')
      .eq('enabled', true);

    if (configError) {
      addSpanEvent(span, 'error_fetching_configs', { error: configError.message });
      throw configError;
    }

    addSpanEvent(span, 'processing_metric_configs', { count: configs?.length || 0 });

    const anomaliesDetected: any[] = [];

    for (const config of (configs as AnomalyDetectionConfig[])) {
      try {
        // Fetch historical data for this metric
        const windowStart = new Date(Date.now() - config.lookback_window_minutes * 60 * 1000);
        
        const { data: metricData, error: metricError } = await supabase
          .from('metric_time_series')
          .select('timestamp, metric_value')
          .eq('metric_name', config.metric_name)
          .gte('timestamp', windowStart.toISOString())
          .order('timestamp', { ascending: true });

        if (metricError) {
          addSpanEvent(span, 'error_fetching_metric_data', { 
            metric: config.metric_name, 
            error: metricError.message 
          });
          continue;
        }

        const data = metricData as MetricData[];

        if (!data || data.length < config.min_data_points) {
          addSpanEvent(span, 'insufficient_data', {
            metric: config.metric_name,
            points: data?.length || 0
          });
          continue;
        }

        // Get current value (most recent)
        const currentValue = data[data.length - 1].metric_value;
        const historicalValues = data.slice(0, -1).map(d => d.metric_value);

        // Run detection algorithms
        const results: AnomalyResult[] = [];

        for (const algorithm of config.detection_algorithms) {
          let result: AnomalyResult;

          switch (algorithm) {
            case 'z_score':
              result = AnomalyDetector.zScore(historicalValues, currentValue, config.sensitivity);
              break;
            case 'moving_average':
              result = AnomalyDetector.movingAverage(historicalValues, currentValue, config.sensitivity);
              break;
            case 'rate_of_change':
              result = AnomalyDetector.rateOfChange(historicalValues, currentValue, config.sensitivity);
              break;
            case 'isolation_forest':
              result = AnomalyDetector.isolationForest(historicalValues, currentValue, 0.6);
              break;
            case 'seasonal':
              result = AnomalyDetector.seasonalDecomposition(historicalValues, currentValue, config.sensitivity, 24);
              break;
            case 'predictive':
              result = AnomalyDetector.predictiveAnomaly(historicalValues, currentValue, config.sensitivity);
              break;
            case 'ensemble':
              result = AnomalyDetector.ensemble(historicalValues, currentValue, config.sensitivity);
              break;
            default:
              continue;
          }

          if (result.isAnomaly && result.deviationScore >= config.alert_threshold_score) {
            results.push(result);
          }
        }

        // If any algorithm detected an anomaly
        if (results.length > 0) {
          // Use the result with highest confidence
          const bestResult = results.reduce((best, current) => 
            current.confidenceScore > best.confidenceScore ? current : best
          );

          // Determine severity based on deviation score
          const severity = 
            bestResult.deviationScore >= 5 ? 'critical' :
            bestResult.deviationScore >= 4 ? 'high' :
            bestResult.deviationScore >= 3 ? 'medium' : 'low';

          // Insert anomaly detection record
          const { data: anomaly, error: anomalyError } = await supabase
            .from('anomaly_detections')
            .insert({
              metric_name: config.metric_name,
              metric_category: config.metric_category,
              anomaly_type: bestResult.anomalyType,
              severity,
              baseline_value: bestResult.baselineValue,
              anomaly_value: bestResult.anomalyValue,
              deviation_score: bestResult.deviationScore,
              confidence_score: bestResult.confidenceScore,
              detection_algorithm: bestResult.algorithm,
              time_window_start: windowStart.toISOString(),
              time_window_end: new Date().toISOString(),
              metadata: {
                algorithms_run: config.detection_algorithms,
                total_data_points: data.length,
                sensitivity: config.sensitivity,
              },
            })
            .select()
            .single();

          if (anomalyError) {
            addSpanEvent(span, 'error_inserting_anomaly', { 
              metric: config.metric_name, 
              error: anomalyError.message 
            });
            continue;
          }

          anomaliesDetected.push(anomaly);

          // Auto-create alert if configured
          if (config.auto_create_alert && severity in ['critical', 'high']) {
            const { data: alert, error: alertError } = await supabase
              .from('system_alerts')
              .insert({
                alert_type: 'anomaly_detected',
                severity,
                message: `Anomaly detected in ${config.metric_name}: ${bestResult.anomalyType} (${bestResult.deviationScore.toFixed(2)}σ deviation)`,
                metadata: {
                  anomaly_id: anomaly.id,
                  metric_name: config.metric_name,
                  baseline_value: bestResult.baselineValue,
                  anomaly_value: bestResult.anomalyValue,
                  algorithm: bestResult.algorithm,
                },
              })
              .select()
              .single();

            if (!alertError && alert) {
              // Update anomaly with alert_id
              await supabase
                .from('anomaly_detections')
                .update({ alert_created: true, alert_id: alert.id })
                .eq('id', anomaly.id);

              addSpanEvent(span, 'alert_created', { 
                metric: config.metric_name,
                alertId: alert.id 
              });
            }
          }

          addSpanEvent(span, 'anomaly_detected', { 
            metric: config.metric_name, 
            type: bestResult.anomalyType, 
            deviation: bestResult.deviationScore.toFixed(2) 
          });
        }
      } catch (error) {
        addSpanEvent(span, 'error_processing_metric', { 
          metric: config.metric_name, 
          error: error instanceof Error ? error.message : String(error) 
        });
      }
    }

    addSpanEvent(span, 'anomaly_detection_complete', { detected: anomaliesDetected.length });

    return new Response(
      JSON.stringify({
        success: true,
        anomalies_detected: anomaliesDetected.length,
        anomalies: anomaliesDetected,
      }),
      {
        status: 200,
        headers: { 'Content-Type': 'application/json' },
      }
    );
};

serve(createEdgeFunction({
  name: 'detect-anomalies',
  requireAuth: false,
  corsHeaders,
  enableTracing: true,
}, handler));