/**
 * React Hook for fetching country boundaries with institution counts from the Geo API
 * 
 * This hook fetches country polygons for low-zoom map views where individual
 * institution points would be too dense to display meaningfully.
 * 
 * API Endpoint:
 * - GET /api/geo/countries - Returns country polygons with institution counts
 */

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

// API base URL
const GEO_API_BASE = '/api/geo';

/**
 * Country data from the Geo API
 */
export interface CountryData {
  iso_a2: string;
  iso_a3: string | null;
  name: string;
  institution_count: number;
  centroid: [number | null, number | null]; // [lon, lat]
  area_km2: number | null;
}

/**
 * GeoJSON Feature for a country
 */
export interface CountryFeature {
  type: 'Feature';
  id: string;
  geometry: GeoJSON.Geometry;
  properties: CountryData;
}

export interface CountriesGeoJSON {
  type: 'FeatureCollection';
  features: CountryFeature[];
  metadata: {
    count: number;
    total_institutions: number;
    countries_with_data: number;
    type_filter: string | null;
    simplified: boolean;
  };
}

export interface UseGeoApiCountriesReturn {
  geojson: CountriesGeoJSON | null;
  isLoading: boolean;
  error: Error | null;
  refresh: (typeFilter?: string | string[]) => Promise<void>;
  countriesWithData: CountryData[];
  totalInstitutions: number;
}

/**
 * React hook to fetch country boundaries with institution counts
 * 
 * @param typeFilter - Optional institution type filter (single type or array of types)
 * @returns Country GeoJSON with institution counts
 */
export function useGeoApiCountries(typeFilter?: string | string[]): UseGeoApiCountriesReturn {
  const [geojson, setGeojson] = useState<CountriesGeoJSON | null>(null);
  const [isLoading, setIsLoading] = useState(true);
  const [error, setError] = useState<Error | null>(null);

  const refresh = useCallback(async (filter?: string | string[]) => {
    const activeFilter = filter !== undefined ? filter : typeFilter;
    
    setIsLoading(true);
    setError(null);

    try {
      const url = new URL(`${GEO_API_BASE}/countries`, window.location.origin);
      url.searchParams.set('simplified', 'true');
      url.searchParams.set('with_counts', 'true');
      
      // Support single type or array of types
      if (activeFilter) {
        if (Array.isArray(activeFilter)) {
          // Pass multiple types as comma-separated
          url.searchParams.set('type', activeFilter.join(','));
        } else {
          url.searchParams.set('type', activeFilter);
        }
      }

      console.log(`[GeoAPI Countries] Fetching from ${url.toString()}`);

      const response = await fetch(url.toString(), {
        headers: {
          'Accept': 'application/json',
        },
      });

      if (!response.ok) {
        throw new Error(`Geo API request failed: ${response.status} ${response.statusText}`);
      }

      const data: CountriesGeoJSON = await response.json();
      
      console.log(`[GeoAPI Countries] Loaded ${data.features.length} countries, ${data.metadata.total_institutions} institutions`);
      
      setGeojson(data);
    } catch (err) {
      console.error('[GeoAPI Countries] Failed to load countries:', err);
      setError(err instanceof Error ? err : new Error('Failed to load country boundaries'));
    } finally {
      setIsLoading(false);
    }
  }, [typeFilter]);

  // Initial load
  useEffect(() => {
    refresh();
  }, [refresh]);

  // Computed values
  const countriesWithData = geojson?.features
    .filter(f => f.properties.institution_count > 0)
    .map(f => f.properties)
    .sort((a, b) => b.institution_count - a.institution_count) || [];

  const totalInstitutions = geojson?.metadata.total_institutions || 0;

  return {
    geojson,
    isLoading,
    error,
    refresh,
    countriesWithData,
    totalInstitutions,
  };
}

/**
 * Hook to get country detail with institution breakdown by type
 */
export function useGeoApiCountryDetail(isoA2: string | null) {
  const [data, setData] = useState<CountryFeature | null>(null);
  const [isLoading, setIsLoading] = useState(false);
  const [error, setError] = useState<Error | null>(null);

  useEffect(() => {
    if (!isoA2) {
      setData(null);
      return;
    }

    async function fetchDetail() {
      setIsLoading(true);
      setError(null);

      try {
        const url = `${GEO_API_BASE}/countries/${isoA2}`;
        const response = await fetch(url);

        if (!response.ok) {
          throw new Error(`Failed to load country detail: ${response.status}`);
        }

        const result = await response.json();
        setData(result);
      } catch (err) {
        setError(err instanceof Error ? err : new Error('Failed to load country detail'));
      } finally {
        setIsLoading(false);
      }
    }

    fetchDetail();
  }, [isoA2]);

  return { data, isLoading, error };
}