// Graph-based Trend Visualization with Offline Charts
// Comprehensive charting system using Chart.js for environmental data visualization

import { Chart, ChartConfiguration, ChartData, ChartOptions } from 'chart.js';

interface ChartDataPoint {
  x: number | string | Date;
  y: number;
  label?: string;
  metadata?: Record<string, any>;
}

interface TrendAnalysis {
  slope: number;
  correlation: number;
  trend: 'increasing' | 'decreasing' | 'stable';
  confidence: number;
  forecast?: ChartDataPoint[];
}

interface ChartTheme {
  primary: string;
  secondary: string;
  accent: string;
  background: string;
  text: string;
  grid: string;
}

class ChartVisualizer {
  private readonly indianTheme: ChartTheme = {
    primary: '#FF6B35', // Saffron
    secondary: '#2E8B57', // Sea Green  
    accent: '#4169E1', // Royal Blue
    background: '#FFFEF7', // Cream
    text: '#2F4F4F', // Dark Slate Gray
    grid: '#E6E6FA' // Lavender
  };

  // Time Series Chart for Environmental Parameters
  createTimeSeriesChart(
    canvasId: string,
    data: ChartDataPoint[],
    options: {
      title: string;
      yAxisLabel: string;
      parameter: string;
      unit: string;
      showTrend?: boolean;
      thresholds?: { value: number; label: string; color: string }[];
    }
  ): Chart {
    try {
      if (!data || data.length === 0) {
        throw new Error('Chart data is required and cannot be empty');
      }

      this.validateChartData(data);

      const canvas = document.getElementById(canvasId) as HTMLCanvasElement;
      if (!canvas) {
        throw new Error(`Canvas element with ID '${canvasId}' not found`);
      }

      // Sort data by time
      const sortedData = [...data].sort((a, b) => {
        const timeA = new Date(a.x).getTime();
        const timeB = new Date(b.x).getTime();
        return timeA - timeB;
      });

      const datasets: any[] = [{
        label: `${options.parameter} (${options.unit})`,
        data: sortedData.map(point => ({ x: point.x, y: point.y })),
        borderColor: this.indianTheme.primary,
        backgroundColor: this.indianTheme.primary + '20',
        tension: 0.4,
        fill: true,
        pointBackgroundColor: this.indianTheme.primary,
        pointBorderColor: '#fff',
        pointBorderWidth: 2,
        pointRadius: 4
      }];

      // Add trend line if requested
      if (options.showTrend && sortedData.length > 2) {
        const trendData = this.calculateTrendLine(sortedData);
        datasets.push({
          label: 'Trend',
          data: trendData,
          borderColor: this.indianTheme.accent,
          backgroundColor: 'transparent',
          borderDash: [5, 5],
          pointRadius: 0,
          tension: 0
        });
      }

      // Add threshold lines
      if (options.thresholds) {
        options.thresholds.forEach((threshold, index) => {
          datasets.push({
            label: threshold.label,
            data: sortedData.map(point => ({ x: point.x, y: threshold.value })),
            borderColor: threshold.color,
            backgroundColor: 'transparent',
            borderDash: [10, 5],
            pointRadius: 0,
            tension: 0
          });
        });
      }

      const config: ChartConfiguration = {
        type: 'line',
        data: { datasets },
        options: {
          responsive: true,
          maintainAspectRatio: false,
          plugins: {
            title: {
              display: true,
              text: options.title,
              font: { size: 16, weight: 'bold' },
              color: this.indianTheme.text
            },
            legend: {
              display: true,
              position: 'top',
              labels: {
                color: this.indianTheme.text,
                usePointStyle: true
              }
            },
            tooltip: {
              mode: 'index',
              intersect: false,
              backgroundColor: this.indianTheme.background,
              titleColor: this.indianTheme.text,
              bodyColor: this.indianTheme.text,
              borderColor: this.indianTheme.primary,
              borderWidth: 1
            }
          },
          scales: {
            x: {
              type: 'time',
              display: true,
              title: {
                display: true,
                text: 'Time',
                color: this.indianTheme.text
              },
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              }
            },
            y: {
              display: true,
              title: {
                display: true,
                text: options.yAxisLabel,
                color: this.indianTheme.text
              },
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              }
            }
          },
          interaction: {
            mode: 'nearest',
            axis: 'x',
            intersect: false
          }
        }
      };

      return new Chart(canvas, config);
    } catch (error) {
      throw new Error(`Failed to create time series chart: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Bar Chart for Comparative Analysis
  createBarChart(
    canvasId: string,
    data: { label: string; value: number; color?: string }[],
    options: {
      title: string;
      yAxisLabel: string;
      horizontal?: boolean;
    }
  ): Chart {
    try {
      if (!data || data.length === 0) {
        throw new Error('Chart data is required and cannot be empty');
      }

      const canvas = document.getElementById(canvasId) as HTMLCanvasElement;
      if (!canvas) {
        throw new Error(`Canvas element with ID '${canvasId}' not found`);
      }

      const colors = data.map((item, index) => 
        item.color || this.getColorByIndex(index)
      );

      const config: ChartConfiguration = {
        type: options.horizontal ? 'bar' : 'bar',
        data: {
          labels: data.map(item => item.label),
          datasets: [{
            label: options.yAxisLabel,
            data: data.map(item => item.value),
            backgroundColor: colors.map(color => color + '80'),
            borderColor: colors,
            borderWidth: 2
          }]
        },
        options: {
          indexAxis: options.horizontal ? 'y' : 'x',
          responsive: true,
          maintainAspectRatio: false,
          plugins: {
            title: {
              display: true,
              text: options.title,
              font: { size: 16, weight: 'bold' },
              color: this.indianTheme.text
            },
            legend: {
              display: false
            },
            tooltip: {
              backgroundColor: this.indianTheme.background,
              titleColor: this.indianTheme.text,
              bodyColor: this.indianTheme.text,
              borderColor: this.indianTheme.primary,
              borderWidth: 1
            }
          },
          scales: {
            x: {
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              }
            },
            y: {
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              },
              title: {
                display: true,
                text: options.yAxisLabel,
                color: this.indianTheme.text
              }
            }
          }
        }
      };

      return new Chart(canvas, config);
    } catch (error) {
      throw new Error(`Failed to create bar chart: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Scatter Plot for Correlation Analysis
  createScatterPlot(
    canvasId: string,
    data: { x: number; y: number; label?: string }[],
    options: {
      title: string;
      xAxisLabel: string;
      yAxisLabel: string;
      showTrendLine?: boolean;
    }
  ): Chart {
    try {
      if (!data || data.length === 0) {
        throw new Error('Chart data is required and cannot be empty');
      }

      data.forEach((point, index) => {
        if (typeof point.x !== 'number' || typeof point.y !== 'number') {
          throw new Error(`Invalid data point at index ${index}: x and y must be numbers`);
        }
        if (isNaN(point.x) || isNaN(point.y)) {
          throw new Error(`Invalid data point at index ${index}: x and y cannot be NaN`);
        }
      });

      const canvas = document.getElementById(canvasId) as HTMLCanvasElement;
      if (!canvas) {
        throw new Error(`Canvas element with ID '${canvasId}' not found`);
      }

      const datasets: any[] = [{
        label: 'Data Points',
        data: data,
        backgroundColor: this.indianTheme.primary + '80',
        borderColor: this.indianTheme.primary,
        pointRadius: 6,
        pointHoverRadius: 8
      }];

      // Add trend line if requested
      if (options.showTrendLine && data.length > 2) {
        const correlation = this.calculateCorrelation(data);
        const trendLine = this.calculateLinearRegression(data);
        
        datasets.push({
          label: `Trend Line (r = ${correlation.toFixed(3)})`,
          data: trendLine,
          type: 'line',
          backgroundColor: 'transparent',
          borderColor: this.indianTheme.accent,
          borderDash: [5, 5],
          pointRadius: 0,
          tension: 0
        });
      }

      const config: ChartConfiguration = {
        type: 'scatter',
        data: { datasets },
        options: {
          responsive: true,
          maintainAspectRatio: false,
          plugins: {
            title: {
              display: true,
              text: options.title,
              font: { size: 16, weight: 'bold' },
              color: this.indianTheme.text
            },
            legend: {
              display: true,
              position: 'top',
              labels: {
                color: this.indianTheme.text
              }
            },
            tooltip: {
              backgroundColor: this.indianTheme.background,
              titleColor: this.indianTheme.text,
              bodyColor: this.indianTheme.text,
              borderColor: this.indianTheme.primary,
              borderWidth: 1,
              callbacks: {
                label: function(context: any) {
                  const point = context.parsed;
                  return `(${point.x.toFixed(2)}, ${point.y.toFixed(2)})`;
                }
              }
            }
          },
          scales: {
            x: {
              type: 'linear',
              position: 'bottom',
              title: {
                display: true,
                text: options.xAxisLabel,
                color: this.indianTheme.text
              },
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              }
            },
            y: {
              title: {
                display: true,
                text: options.yAxisLabel,
                color: this.indianTheme.text
              },
              grid: {
                color: this.indianTheme.grid
              },
              ticks: {
                color: this.indianTheme.text
              }
            }
          }
        }
      };

      return new Chart(canvas, config);
    } catch (error) {
      throw new Error(`Failed to create scatter plot: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Pie Chart for Distribution Analysis
  createPieChart(
    canvasId: string,
    data: { label: string; value: number; color?: string }[],
    options: {
      title: string;
      showPercentages?: boolean;
    }
  ): Chart {
    try {
      if (!data || data.length === 0) {
        throw new Error('Chart data is required and cannot be empty');
      }

      data.forEach((item, index) => {
        if (typeof item.value !== 'number' || item.value < 0) {
          throw new Error(`Invalid value at index ${index}: must be a non-negative number`);
        }
      });

      const canvas = document.getElementById(canvasId) as HTMLCanvasElement;
      if (!canvas) {
        throw new Error(`Canvas element with ID '${canvasId}' not found`);
      }

      const total = data.reduce((sum, item) => sum + item.value, 0);
      if (total === 0) {
        throw new Error('Total of all values cannot be zero');
      }

      const colors = data.map((item, index) => 
        item.color || this.getColorByIndex(index)
      );

      const config: ChartConfiguration = {
        type: 'pie',
        data: {
          labels: data.map(item => item.label),
          datasets: [{
            data: data.map(item => item.value),
            backgroundColor: colors.map(color => color + '80'),
            borderColor: colors,
            borderWidth: 2
          }]
        },
        options: {
          responsive: true,
          maintainAspectRatio: false,
          plugins: {
            title: {
              display: true,
              text: options.title,
              font: { size: 16, weight: 'bold' },
              color: this.indianTheme.text
            },
            legend: {
              display: true,
              position: 'right',
              labels: {
                color: this.indianTheme.text,
                usePointStyle: true
              }
            },
            tooltip: {
              backgroundColor: this.indianTheme.background,
              titleColor: this.indianTheme.text,
              bodyColor: this.indianTheme.text,
              borderColor: this.indianTheme.primary,
              borderWidth: 1,
              callbacks: {
                label: function(context: any) {
                  const value = context.parsed;
                  const percentage = ((value / total) * 100).toFixed(1);
                  return options.showPercentages 
                    ? `${context.label}: ${value} (${percentage}%)`
                    : `${context.label}: ${value}`;
                }
              }
            }
          }
        }
      };

      return new Chart(canvas, config);
    } catch (error) {
      throw new Error(`Failed to create pie chart: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Trend Analysis
  analyzeTrend(data: ChartDataPoint[]): TrendAnalysis {
    try {
      if (!data || data.length < 3) {
        throw new Error('At least 3 data points are required for trend analysis');
      }

      this.validateChartData(data);

      // Convert to numeric format for analysis
      const numericData = data.map((point, index) => ({
        x: index,
        y: point.y
      }));

      const correlation = this.calculateCorrelation(numericData);
      const regression = this.calculateLinearRegression(numericData);
      const slope = this.calculateSlope(numericData);

      let trend: 'increasing' | 'decreasing' | 'stable';
      if (Math.abs(slope) < 0.01) {
        trend = 'stable';
      } else if (slope > 0) {
        trend = 'increasing';
      } else {
        trend = 'decreasing';
      }

      // Calculate confidence based on correlation strength
      const confidence = Math.min(95, Math.abs(correlation) * 100);

      // Generate forecast for next 3 points
      const forecast: ChartDataPoint[] = [];
      const lastIndex = numericData.length - 1;
      
      for (let i = 1; i <= 3; i++) {
        const futureX = lastIndex + i;
        const futureY = slope * futureX + this.getYIntercept(numericData);
        forecast.push({
          x: futureX,
          y: Math.max(0, futureY), // Ensure non-negative forecast
          label: `Forecast ${i}`
        });
      }

      return {
        slope,
        correlation,
        trend,
        confidence,
        forecast
      };
    } catch (error) {
      throw new Error(`Failed to analyze trend: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Export chart as image
  exportChart(chart: Chart, filename: string = 'chart'): void {
    try {
      if (!chart || !chart.canvas) {
        throw new Error('Invalid chart object');
      }

      const canvas = chart.canvas;
      const url = canvas.toDataURL('image/png');
      
      const link = document.createElement('a');
      link.download = `${filename}.png`;
      link.href = url;
      document.body.appendChild(link);
      link.click();
      document.body.removeChild(link);
    } catch (error) {
      throw new Error(`Failed to export chart: ${error instanceof Error ? error.message : 'Unknown error'}`);
    }
  }

  // Private helper methods
  private validateChartData(data: ChartDataPoint[]): void {
    data.forEach((point, index) => {
      if (typeof point.y !== 'number') {
        throw new Error(`Invalid y value at index ${index}: must be a number`);
      }
      if (isNaN(point.y) || !isFinite(point.y)) {
        throw new Error(`Invalid y value at index ${index}: must be a finite number`);
      }
    });
  }

  private calculateTrendLine(data: ChartDataPoint[]): { x: string | number | Date; y: number }[] {
    const numericData = data.map((point, index) => ({ x: index, y: point.y }));
    const regression = this.calculateLinearRegression(numericData);
    
    return [
      { x: data[0].x, y: regression[0].y },
      { x: data[data.length - 1].x, y: regression[regression.length - 1].y }
    ];
  }

  private calculateCorrelation(data: { x: number; y: number }[]): number {
    const n = data.length;
    const sumX = data.reduce((sum, point) => sum + point.x, 0);
    const sumY = data.reduce((sum, point) => sum + point.y, 0);
    const sumXY = data.reduce((sum, point) => sum + point.x * point.y, 0);
    const sumX2 = data.reduce((sum, point) => sum + point.x * point.x, 0);
    const sumY2 = data.reduce((sum, point) => sum + point.y * point.y, 0);

    const numerator = n * sumXY - sumX * sumY;
    const denominator = Math.sqrt((n * sumX2 - sumX * sumX) * (n * sumY2 - sumY * sumY));

    return denominator === 0 ? 0 : numerator / denominator;
  }

  private calculateLinearRegression(data: { x: number; y: number }[]): { x: number; y: number }[] {
    const slope = this.calculateSlope(data);
    const yIntercept = this.getYIntercept(data);

    return data.map(point => ({
      x: point.x,
      y: slope * point.x + yIntercept
    }));
  }

  private calculateSlope(data: { x: number; y: number }[]): number {
    const n = data.length;
    const sumX = data.reduce((sum, point) => sum + point.x, 0);
    const sumY = data.reduce((sum, point) => sum + point.y, 0);
    const sumXY = data.reduce((sum, point) => sum + point.x * point.y, 0);
    const sumX2 = data.reduce((sum, point) => sum + point.x * point.x, 0);

    const denominator = n * sumX2 - sumX * sumX;
    return denominator === 0 ? 0 : (n * sumXY - sumX * sumY) / denominator;
  }

  private getYIntercept(data: { x: number; y: number }[]): number {
    const n = data.length;
    const sumX = data.reduce((sum, point) => sum + point.x, 0);
    const sumY = data.reduce((sum, point) => sum + point.y, 0);
    const slope = this.calculateSlope(data);

    return (sumY - slope * sumX) / n;
  }

  private getColorByIndex(index: number): string {
    const colors = [
      this.indianTheme.primary,
      this.indianTheme.secondary,
      this.indianTheme.accent,
      '#FF4500', // Orange Red
      '#32CD32', // Lime Green
      '#6A5ACD', // Slate Blue
      '#FF69B4', // Hot Pink
      '#20B2AA', // Light Sea Green
      '#FFD700', // Gold
      '#DC143C'  // Crimson
    ];
    return colors[index % colors.length];
  }
}

export const chartVisualizer = new ChartVisualizer();
export { ChartDataPoint, TrendAnalysis, ChartTheme };