import { NextRequest, NextResponse } from "next/server";
import { locationDb, userDb } from "@/lib/db";
import { auth } from "@/lib/auth";
import { calculateDistance, RateLimitedGeocoder } from "@/lib/geo-utils";

/**
 * GET /api/export/csv
 *
 * Export location data as CSV for Lexware digital logbook
 *
 * Query parameters:
 * - username: Filter by device tracker ID
 * - startTime: Custom range start (ISO string)
 * - endTime: Custom range end (ISO string)
 * - includeGeocoding: Whether to include addresses (default: false for preview)
 */
export async function GET(request: NextRequest) {
  try {
    // Check authentication
    const session = await auth();
    if (!session?.user) {
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }

    // Get user's allowed device IDs
    const userId = (session.user as any).id;
    const role = (session.user as any).role;
    const sessionUsername = session.user.name || '';

    const userDeviceIds = userDb.getAllowedDeviceIds(userId, role, sessionUsername);

    if (userDeviceIds.length === 0) {
      return new NextResponse("Keine Geräte verfügbar", { status: 403 });
    }

    const searchParams = request.nextUrl.searchParams;
    const username = searchParams.get('username') || undefined;
    const startTime = searchParams.get('startTime') || undefined;
    const endTime = searchParams.get('endTime') || undefined;
    const includeGeocoding = searchParams.get('includeGeocoding') === 'true';

    // Fetch locations from database
    let locations = locationDb.findMany({
      user_id: 0,
      username,
      startTime,
      endTime,
      limit: 10000, // High limit for exports
    });

    // Filter by user's allowed devices
    locations = locations.filter(loc => loc.username && userDeviceIds.includes(loc.username));

    if (locations.length === 0) {
      return new NextResponse("Keine Daten im gewählten Zeitraum", { status: 404 });
    }

    // Sort chronologically (oldest first) for proper distance calculation
    locations.sort((a, b) => new Date(a.timestamp).getTime() - new Date(b.timestamp).getTime());

    // Initialize geocoder if needed
    const geocoder = includeGeocoding ? new RateLimitedGeocoder() : null;

    // Build CSV
    const csvRows: string[] = [];

    // Header
    csvRows.push('Datum,Uhrzeit,Latitude,Longitude,Adresse,Distanz (km),Geschwindigkeit (km/h),Gerät');

    // Process each location
    for (let i = 0; i < locations.length; i++) {
      const loc = locations[i];
      const lat = Number(loc.latitude);
      const lon = Number(loc.longitude);

      // Calculate distance from previous point
      let distance = 0;
      if (i > 0) {
        const prevLoc = locations[i - 1];
        distance = calculateDistance(
          Number(prevLoc.latitude),
          Number(prevLoc.longitude),
          lat,
          lon
        );
      }

      // Geocode if requested
      let address = `${lat.toFixed(6)}, ${lon.toFixed(6)}`;
      if (geocoder) {
        address = await geocoder.geocode(lat, lon);
      }

      // Format timestamp (German format)
      const date = new Date(loc.timestamp);
      const dateStr = date.toLocaleDateString('de-DE', {
        year: 'numeric',
        month: '2-digit',
        day: '2-digit',
      });
      const timeStr = date.toLocaleTimeString('de-DE', {
        hour: '2-digit',
        minute: '2-digit',
        second: '2-digit',
      });

      // Speed (may be null)
      const speed = loc.speed != null ? Number(loc.speed).toFixed(1) : '';

      // Device name
      const deviceName = loc.username || 'Unbekannt';

      // Build CSV row - properly escape address field
      const escapedAddress = address.includes(',') ? `"${address}"` : address;
      const distanceStr = distance.toFixed(3).replace('.', ','); // German decimal separator

      csvRows.push(
        `${dateStr},${timeStr},${lat.toFixed(6)},${lon.toFixed(6)},${escapedAddress},${distanceStr},${speed},${deviceName}`
      );
    }

    const csv = csvRows.join('\n');

    // Return CSV with proper headers
    const filename = `fahrtenbuch_${startTime ? new Date(startTime).toISOString().split('T')[0] : 'alle'}_${endTime ? new Date(endTime).toISOString().split('T')[0] : 'alle'}.csv`;

    return new NextResponse(csv, {
      headers: {
        'Content-Type': 'text/csv; charset=utf-8',
        'Content-Disposition': `attachment; filename="${filename}"`,
      },
    });
  } catch (error) {
    console.error("Error exporting CSV:", error);
    return NextResponse.json(
      {
        error: "Failed to export CSV",
        details: error instanceof Error ? error.message : "Unknown error"
      },
      { status: 500 }
    );
  }
}