/**
 * Analytics Export API
 * Exports analytics data in various formats (CSV, JSON)
 */

import type { NextApiRequest, NextApiResponse } from 'next';
import {
  getAnalyticsOverview,
  getPlantAnalytics,
  getTransportAnalytics,
  getFarmAnalytics,
  getSustainabilityAnalytics,
  TimeRange,
  AnalyticsFilters,
} from '../../../lib/analytics';
import { format } from 'date-fns';

interface ExportData {
  overview?: any;
  plants?: any;
  transport?: any;
  farms?: any;
  sustainability?: any;
}

function convertToCSV(data: any[], headers: string[]): string {
  const headerRow = headers.join(',');
  const rows = data.map(item =>
    headers.map(header => {
      const value = item[header];
      if (value === null || value === undefined) return '';
      if (typeof value === 'string' && value.includes(',')) {
        return `"${value.replace(/"/g, '""')}"`;
      }
      return String(value);
    }).join(',')
  );
  return [headerRow, ...rows].join('\n');
}

function generatePlantCSV(plantData: any): string {
  const speciesData = plantData.plantsBySpecies.map((s: any) => ({
    species: s.species,
    count: s.count,
    percentage: s.percentage,
    trend: s.trend,
  }));
  return convertToCSV(speciesData, ['species', 'count', 'percentage', 'trend']);
}

function generateTransportCSV(transportData: any): string {
  const methodData = transportData.eventsByMethod.map((m: any) => ({
    method: m.method,
    count: m.count,
    distanceKm: m.distanceKm,
    carbonKg: m.carbonKg,
    efficiency: m.efficiency,
  }));
  return convertToCSV(methodData, ['method', 'count', 'distanceKm', 'carbonKg', 'efficiency']);
}

function generateSustainabilityCSV(sustainData: any): string {
  const goalsData = sustainData.goals.map((g: any) => ({
    name: g.name,
    target: g.target,
    current: g.current,
    unit: g.unit,
    progress: g.progress,
    status: g.status,
  }));
  return convertToCSV(goalsData, ['name', 'target', 'current', 'unit', 'progress', 'status']);
}

export default async function handler(
  req: NextApiRequest,
  res: NextApiResponse
) {
  if (req.method !== 'GET') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  try {
    const exportFormat = (req.query.format as string) || 'json';
    const timeRange = (req.query.timeRange as TimeRange) || '30d';
    const sections = req.query.sections
      ? (req.query.sections as string).split(',')
      : ['overview', 'plants', 'transport', 'farms', 'sustainability'];

    const filters: AnalyticsFilters = { timeRange };
    const exportData: ExportData = {};

    // Fetch requested sections
    if (sections.includes('overview')) {
      exportData.overview = await getAnalyticsOverview(filters);
    }
    if (sections.includes('plants')) {
      exportData.plants = await getPlantAnalytics(filters);
    }
    if (sections.includes('transport')) {
      exportData.transport = await getTransportAnalytics(filters);
    }
    if (sections.includes('farms')) {
      exportData.farms = await getFarmAnalytics(filters);
    }
    if (sections.includes('sustainability')) {
      exportData.sustainability = await getSustainabilityAnalytics(filters);
    }

    const timestamp = format(new Date(), 'yyyy-MM-dd_HH-mm-ss');

    if (exportFormat === 'csv') {
      // Generate combined CSV
      let csvContent = '';

      if (exportData.plants) {
        csvContent += '# Plant Analytics - Species Distribution\n';
        csvContent += generatePlantCSV(exportData.plants);
        csvContent += '\n\n';
      }

      if (exportData.transport) {
        csvContent += '# Transport Analytics - By Method\n';
        csvContent += generateTransportCSV(exportData.transport);
        csvContent += '\n\n';
      }

      if (exportData.sustainability) {
        csvContent += '# Sustainability Goals\n';
        csvContent += generateSustainabilityCSV(exportData.sustainability);
      }

      res.setHeader('Content-Type', 'text/csv');
      res.setHeader('Content-Disposition', `attachment; filename=analytics_export_${timestamp}.csv`);
      return res.status(200).send(csvContent);
    }

    // Default: JSON format
    res.setHeader('Content-Type', 'application/json');
    res.setHeader('Content-Disposition', `attachment; filename=analytics_export_${timestamp}.json`);

    return res.status(200).json({
      exportedAt: new Date().toISOString(),
      timeRange,
      sections,
      data: exportData,
    });

  } catch (error) {
    console.error('Analytics export error:', error);
    res.status(500).json({
      success: false,
      error: 'Failed to export analytics data',
    });
  }
}