const axios = require('axios');
const logger = require('../utils/logger');

// OSRM public demo server (free, rate-limited)
// For production, consider self-hosting OSRM or using a paid service
const OSRM_BASE_URL = 'https://router.project-osrm.org';

// Cache for routing results
const routeCache = new Map();
const CACHE_TTL = 30 * 60 * 1000; // 30 minutes

/**
 * Get driving directions between two points using OSRM
 * @param {number} startLat - Starting latitude
 * @param {number} startLng - Starting longitude
 * @param {number} endLat - Destination latitude
 * @param {number} endLng - Destination longitude
 * @param {string} profile - Routing profile: 'driving', 'walking', 'cycling'
 * @returns {Promise<Object>} Route with geometry and turn-by-turn instructions
 */
async function getDirections(startLat, startLng, endLat, endLng, profile = 'driving') {
  const cacheKey = `${startLat.toFixed(5)},${startLng.toFixed(5)}-${endLat.toFixed(5)},${endLng.toFixed(5)}-${profile}`;

  // Check cache
  const cached = routeCache.get(cacheKey);
  if (cached && Date.now() - cached.timestamp < CACHE_TTL) {
    logger.debug('Route cache hit');
    return cached.data;
  }

  try {
    // OSRM expects coordinates as lng,lat (GeoJSON order)
    const coordinates = `${startLng},${startLat};${endLng},${endLat}`;

    const response = await axios.get(
      `${OSRM_BASE_URL}/route/v1/${profile}/${coordinates}`,
      {
        params: {
          overview: 'full',           // Get full route geometry
          geometries: 'geojson',      // Return as GeoJSON
          steps: true,                // Include turn-by-turn steps
          annotations: 'duration,distance' // Include duration and distance
        },
        timeout: 15000,
        headers: {
          'User-Agent': 'FreeAlbertaFood/1.0'
        }
      }
    );

    if (response.data.code !== 'Ok') {
      throw new Error(`OSRM error: ${response.data.code}`);
    }

    const route = response.data.routes[0];
    const result = {
      distance: route.distance,           // meters
      duration: route.duration,           // seconds
      distanceText: formatDistance(route.distance),
      durationText: formatDuration(route.duration),
      geometry: route.geometry,           // GeoJSON LineString
      steps: formatSteps(route.legs[0].steps),
      bounds: calculateBounds(route.geometry.coordinates),
      waypoints: response.data.waypoints.map(wp => ({
        name: wp.name || 'Unknown',
        location: [wp.location[1], wp.location[0]] // Convert to [lat, lng]
      }))
    };

    // Cache result
    routeCache.set(cacheKey, { data: result, timestamp: Date.now() });

    return result;

  } catch (error) {
    logger.error('Routing error:', error.message);

    if (error.code === 'ECONNABORTED') {
      throw new Error('Routing service timeout');
    }
    if (error.response?.status === 429) {
      throw new Error('Rate limit exceeded. Please try again later.');
    }

    throw new Error('Could not calculate route');
  }
}

/**
 * Format turn-by-turn steps with icons and instructions
 */
function formatSteps(steps) {
  return steps.map((step, index) => {
    const maneuver = step.maneuver;

    return {
      number: index + 1,
      instruction: formatInstruction(step),
      distance: step.distance,
      duration: step.duration,
      distanceText: formatDistance(step.distance),
      durationText: formatDuration(step.duration),
      name: step.name || 'unnamed road',
      mode: step.mode,
      maneuver: {
        type: maneuver.type,
        modifier: maneuver.modifier || null,
        location: [maneuver.location[1], maneuver.location[0]], // [lat, lng]
        bearingBefore: maneuver.bearing_before,
        bearingAfter: maneuver.bearing_after,
        icon: getManeuverIcon(maneuver.type, maneuver.modifier)
      },
      geometry: step.geometry
    };
  });
}

/**
 * Generate human-readable instruction from step
 */
function formatInstruction(step) {
  const maneuver = step.maneuver;
  const name = step.name || 'the road';
  const distance = formatDistance(step.distance);

  switch (maneuver.type) {
    case 'depart':
      return `Start on ${name} heading ${getCardinalDirection(maneuver.bearing_after)}`;

    case 'arrive':
      return 'Arrive at your destination';

    case 'turn':
      return `Turn ${maneuver.modifier || ''} onto ${name}`;

    case 'continue':
      return `Continue on ${name} for ${distance}`;

    case 'merge':
      return `Merge ${maneuver.modifier || ''} onto ${name}`;

    case 'on ramp':
    case 'off ramp':
      return `Take the ramp onto ${name}`;

    case 'fork':
      return `Keep ${maneuver.modifier || 'straight'} at the fork onto ${name}`;

    case 'end of road':
      return `At the end of the road, turn ${maneuver.modifier || ''} onto ${name}`;

    case 'new name':
      return `Continue onto ${name}`;

    case 'roundabout':
      const exit = step.maneuver.exit || '';
      return `Enter the roundabout and take exit ${exit} onto ${name}`;

    case 'rotary':
      return `Enter the rotary and take the exit onto ${name}`;

    case 'roundabout turn':
      return `At the roundabout, take the ${maneuver.modifier || ''} exit onto ${name}`;

    case 'notification':
      return step.name || 'Continue';

    default:
      if (maneuver.modifier) {
        return `Go ${maneuver.modifier} on ${name}`;
      }
      return `Continue on ${name}`;
  }
}

/**
 * Get icon class for maneuver type
 */
function getManeuverIcon(type, modifier) {
  const icons = {
    'depart': 'start',
    'arrive': 'destination',
    'turn': modifier?.includes('left') ? 'turn-left' : modifier?.includes('right') ? 'turn-right' : 'straight',
    'continue': 'straight',
    'merge': modifier?.includes('left') ? 'merge-left' : 'merge-right',
    'on ramp': 'ramp',
    'off ramp': 'ramp',
    'fork': modifier?.includes('left') ? 'fork-left' : 'fork-right',
    'end of road': modifier?.includes('left') ? 'turn-left' : 'turn-right',
    'roundabout': 'roundabout',
    'rotary': 'roundabout'
  };

  return icons[type] || 'straight';
}

/**
 * Get cardinal direction from bearing
 */
function getCardinalDirection(bearing) {
  const directions = ['north', 'northeast', 'east', 'southeast', 'south', 'southwest', 'west', 'northwest'];
  const index = Math.round(bearing / 45) % 8;
  return directions[index];
}

/**
 * Format distance in metric/imperial
 */
function formatDistance(meters) {
  if (meters < 1000) {
    return `${Math.round(meters)} m`;
  }
  return `${(meters / 1000).toFixed(1)} km`;
}

/**
 * Format duration in human readable format
 */
function formatDuration(seconds) {
  if (seconds < 60) {
    return `${Math.round(seconds)} sec`;
  }
  if (seconds < 3600) {
    const mins = Math.round(seconds / 60);
    return `${mins} min`;
  }
  const hours = Math.floor(seconds / 3600);
  const mins = Math.round((seconds % 3600) / 60);
  return `${hours} hr ${mins} min`;
}

/**
 * Calculate bounding box for route
 */
function calculateBounds(coordinates) {
  let minLat = Infinity, maxLat = -Infinity;
  let minLng = Infinity, maxLng = -Infinity;

  coordinates.forEach(coord => {
    const [lng, lat] = coord;
    minLat = Math.min(minLat, lat);
    maxLat = Math.max(maxLat, lat);
    minLng = Math.min(minLng, lng);
    maxLng = Math.max(maxLng, lng);
  });

  return [[minLat, minLng], [maxLat, maxLng]];
}

/**
 * Clear routing cache
 */
function clearCache() {
  routeCache.clear();
}

module.exports = {
  getDirections,
  formatDistance,
  formatDuration,
  clearCache
};