import { useState, useEffect } from 'react';
import { logNonAbortError } from '../lib/api';
import type { TransportMode } from './useTravelTime';

interface TravelModeInfo {
  mode: TransportMode;
  destinations: number;
}

/** Fetches which transport modes have precomputed travel time data. */
export function useTravelModes() {
  const [availableModes, setAvailableModes] = useState<Set<TransportMode> | null>(null);

  useEffect(() => {
    const controller = new AbortController();

    fetch('/api/travel-modes', { signal: controller.signal })
      .then((res) => {
        if (!res.ok) throw new Error(`HTTP ${res.status}`);
        return res.json();
      })
      .then((data: { modes: TravelModeInfo[] }) => {
        const modes = new Set<TransportMode>(
          data.modes.filter((m) => m.destinations > 0).map((m) => m.mode)
        );
        setAvailableModes(modes);
      })
      .catch((err) => logNonAbortError('travel modes', err));

    return () => controller.abort();
  }, []);

  return availableModes;
}