import { useState, useEffect, useCallback } from 'react';

// Default location: Phoenix, AZ (fallback if all else fails)
const DEFAULT_LOCATION = {
  lat: 33.4484,
  lng: -112.0740,
  city: 'Phoenix',
  state: 'AZ'
};

const LOCATION_STORAGE_KEY = 'findagram_location';
const SESSION_ID_KEY = 'findagram_session_id';
const API_BASE_URL = process.env.REACT_APP_API_URL || '';

/**
 * Get or create session ID
 */
function getSessionId() {
  let sessionId = sessionStorage.getItem(SESSION_ID_KEY);
  if (!sessionId) {
    sessionId = `${Date.now()}-${Math.random().toString(36).substr(2, 9)}`;
    sessionStorage.setItem(SESSION_ID_KEY, sessionId);
  }
  return sessionId;
}

/**
 * Get cached location from sessionStorage
 */
function getCachedLocation() {
  try {
    const cached = sessionStorage.getItem(LOCATION_STORAGE_KEY);
    if (cached) {
      return JSON.parse(cached);
    }
  } catch (err) {
    console.error('Error reading cached location:', err);
  }
  return null;
}

/**
 * Save location to sessionStorage
 */
function cacheLocation(location) {
  try {
    sessionStorage.setItem(LOCATION_STORAGE_KEY, JSON.stringify(location));
  } catch (err) {
    console.error('Error caching location:', err);
  }
}

/**
 * Track visitor and get location from our backend API
 * This logs the visit for analytics and returns location from IP
 */
async function trackVisitorAndGetLocation() {
  try {
    const response = await fetch(`${API_BASE_URL}/api/v1/visitor/track`, {
      method: 'POST',
      headers: {
        'Content-Type': 'application/json',
      },
      body: JSON.stringify({
        domain: 'findagram.co',
        page_path: window.location.pathname,
        session_id: getSessionId(),
        referrer: document.referrer || null,
      }),
    });

    const data = await response.json();

    if (data.success && data.location) {
      return {
        lat: data.location.lat,
        lng: data.location.lng,
        city: data.location.city,
        state: data.location.state,
        stateCode: data.location.stateCode,
        source: 'api'
      };
    }
  } catch (err) {
    console.error('Visitor tracking error:', err);
  }
  return null;
}

/**
 * Custom hook for getting user's geolocation
 *
 * @param {Object} options
 * @param {boolean} options.autoRequest - Whether to request location automatically on mount
 * @param {boolean} options.useIPFallback - Whether to use IP geolocation as fallback (default: true)
 * @param {Object} options.defaultLocation - Default location if all methods fail
 * @returns {Object} { location, loading, error, requestLocation, hasPermission }
 */
export function useGeolocation(options = {}) {
  const {
    autoRequest = false,
    useIPFallback = true,
    defaultLocation = DEFAULT_LOCATION
  } = options;

  const [location, setLocation] = useState(null);
  const [loading, setLoading] = useState(false);
  const [error, setError] = useState(null);
  const [hasPermission, setHasPermission] = useState(null);
  const [locationSource, setLocationSource] = useState(null); // 'gps', 'ip', or 'default'

  // Try IP geolocation first (no permission needed)
  const getIPLocation = useCallback(async () => {
    if (!useIPFallback) return null;

    const ipLoc = await getLocationFromIP();
    if (ipLoc) {
      setLocation(ipLoc);
      setLocationSource('ip');
      return ipLoc;
    }
    return null;
  }, [useIPFallback]);

  // Request precise GPS location (requires permission)
  const requestLocation = useCallback(async () => {
    setLoading(true);
    setError(null);

    // First try browser geolocation
    if (navigator.geolocation) {
      return new Promise(async (resolve) => {
        navigator.geolocation.getCurrentPosition(
          (position) => {
            const { latitude, longitude } = position.coords;
            const loc = { lat: latitude, lng: longitude, source: 'gps' };
            setLocation(loc);
            setLocationSource('gps');
            setHasPermission(true);
            setLoading(false);
            resolve(loc);
          },
          async (err) => {
            console.error('Geolocation error:', err);

            if (err.code === err.PERMISSION_DENIED) {
              setHasPermission(false);
            }

            // Fall back to IP geolocation
            if (useIPFallback) {
              const ipLoc = await getLocationFromIP();
              if (ipLoc) {
                setLocation(ipLoc);
                setLocationSource('ip');
                setLoading(false);
                resolve(ipLoc);
                return;
              }
            }

            // Last resort: default location
            setError('Unable to determine location');
            setLocation(defaultLocation);
            setLocationSource('default');
            setLoading(false);
            resolve(defaultLocation);
          },
          {
            enableHighAccuracy: false,
            timeout: 5000,
            maximumAge: 600000 // Cache for 10 minutes
          }
        );
      });
    }

    // No browser geolocation, try IP
    if (useIPFallback) {
      const ipLoc = await getLocationFromIP();
      if (ipLoc) {
        setLocation(ipLoc);
        setLocationSource('ip');
        setLoading(false);
        return ipLoc;
      }
    }

    // Fallback to default
    setLocation(defaultLocation);
    setLocationSource('default');
    setLoading(false);
    return defaultLocation;
  }, [defaultLocation, useIPFallback]);

  // Auto-request location on mount if enabled
  useEffect(() => {
    if (autoRequest) {
      const init = async () => {
        // Check for cached location first
        const cached = getCachedLocation();
        if (cached) {
          setLocation(cached);
          setLocationSource(cached.source || 'api');
          setLoading(false);
          return;
        }

        setLoading(true);

        // Track visitor and get location from our backend API
        const apiLoc = await trackVisitorAndGetLocation();
        if (apiLoc) {
          setLocation(apiLoc);
          setLocationSource('api');
          cacheLocation(apiLoc); // Save for session
        } else {
          // Fallback to default
          setLocation(defaultLocation);
          setLocationSource('default');
        }

        setLoading(false);
      };

      init();
    }
  }, [autoRequest, defaultLocation]);

  return {
    location,
    loading,
    error,
    requestLocation,
    hasPermission,
    locationSource,
    isDefault: locationSource === 'default',
    isFromIP: locationSource === 'ip',
    isFromGPS: locationSource === 'gps'
  };
}

/**
 * Calculate distance between two points using Haversine formula
 *
 * @param {number} lat1 - First point latitude
 * @param {number} lng1 - First point longitude
 * @param {number} lat2 - Second point latitude
 * @param {number} lng2 - Second point longitude
 * @returns {number} Distance in miles
 */
export function calculateDistance(lat1, lng1, lat2, lng2) {
  const R = 3959; // Earth's radius in miles
  const dLat = toRad(lat2 - lat1);
  const dLng = toRad(lng2 - lng1);
  const a =
    Math.sin(dLat / 2) * Math.sin(dLat / 2) +
    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) *
    Math.sin(dLng / 2) * Math.sin(dLng / 2);
  const c = 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
  return R * c;
}

function toRad(deg) {
  return deg * (Math.PI / 180);
}

/**
 * Sort items by distance from a location
 *
 * @param {Array} items - Array of items with location data
 * @param {Object} userLocation - User's location { lat, lng }
 * @param {Function} getItemLocation - Function to extract lat/lng from item
 * @returns {Array} Items sorted by distance with distance property added
 */
export function sortByDistance(items, userLocation, getItemLocation = (item) => item.location) {
  if (!userLocation || !items?.length) return items;

  return items
    .map(item => {
      const itemLoc = getItemLocation(item);
      if (!itemLoc?.latitude || !itemLoc?.longitude) {
        return { ...item, distance: null };
      }
      const distance = calculateDistance(
        userLocation.lat,
        userLocation.lng,
        itemLoc.latitude,
        itemLoc.longitude
      );
      return { ...item, distance: Math.round(distance * 10) / 10 };
    })
    .sort((a, b) => {
      if (a.distance === null) return 1;
      if (b.distance === null) return -1;
      return a.distance - b.distance;
    });
}

/**
 * Filter items within a radius from user location
 *
 * @param {Array} items - Array of items with location data
 * @param {Object} userLocation - User's location { lat, lng }
 * @param {number} radiusMiles - Max distance in miles
 * @param {Function} getItemLocation - Function to extract lat/lng from item
 * @returns {Array} Items within radius, sorted by distance
 */
export function filterByRadius(items, userLocation, radiusMiles = 50, getItemLocation = (item) => item.location) {
  const sorted = sortByDistance(items, userLocation, getItemLocation);
  return sorted.filter(item => item.distance !== null && item.distance <= radiusMiles);
}

export default useGeolocation;