(function (ns, $) {
  'use strict';

  const state = {
    routes: [],
    route: null,
    position: null,
    triggered: new Set(),
    tracking: false,
    activePage: null
  };

  function escapeHtml(value) {
    return $('<div>').text(value ?? '').html();
  }

  function navigate(pageSelector, options = {}) {
    const target = $(pageSelector);
    if (!target.length) throw new Error(`Unbekannte Ansicht: ${pageSelector}`);

    const previous = state.activePage;
    $('.app-page').attr('hidden', true).removeClass('is-active');
    target.removeAttr('hidden').addClass('is-active');
    state.activePage = pageSelector;
    window.scrollTo({ top: 0, behavior: options.instant ? 'auto' : 'smooth' });

    if (options.updateHistory === false) return;
    const historyState = { page: pageSelector, previous };
    if (options.replace) history.replaceState(historyState, '', pageSelector);
    else if (previous !== pageSelector) history.pushState(historyState, '', pageSelector);
  }

  function renderRoutes() {
    const list = $('#route-list').empty();
    if (!state.routes.length) {
      list.append('<li class="empty-list">Keine Route in der Nähe gefunden.</li>');
      return;
    }

    state.routes.forEach(route => {
      const proximity = route.proximityM == null
        ? ''
        : `<span class="route-distance">${escapeHtml(ns.Distance.format(route.proximityM))} entfernt</span>`;
      list.append(`
        <li>
          <button class="card-link" type="button" data-route-id="${route.id}">
            <span class="card-title">${escapeHtml(route.name)}</span>
            <span class="card-description">${escapeHtml(route.schoolName || route.description || '')}</span>
            ${proximity}
          </button>
        </li>
      `);
    });
  }

  function renderRoute(route) {
    state.route = route;
    state.triggered.clear();
    $('#route-title').text(route.name);
    $('#route-description').text(route.description || '');
    $('#route-distance').text(ns.Distance.format(route.distanceM));
    $('#route-elevation').text(`${Math.round(route.elevationGainM)} m`);
    $('#route-poi-count').text(route.pois.length);

    const list = $('#poi-list').empty();
    if (!route.pois.length) {
      list.append('<li class="empty-list">Diese Route enthält noch keine Stationen.</li>');
      return;
    }

    route.pois.forEach(poi => {
      list.append(`
        <li>
          <button class="card-link" type="button" data-poi-id="${poi.id}">
            <span class="card-title">${escapeHtml(poi.title)}</span>
            <span class="card-description">${escapeHtml(poi.description || '')}</span>
          </button>
        </li>
      `);
    });
  }

  function showPoi(poi, automatic) {
    $('#poi-title').text(poi.title);
    $('#poi-description').text(poi.description || '');
    ns.Slideshow.show(poi.images);
    ns.AudioPlayer.load(poi.audioUrl);
    navigate('#poi-page');
    if (automatic && poi.audioUrl) ns.AudioPlayer.play().catch(() => {});
  }

  function evaluatePosition(position) {
    state.position = position;
    if (!state.route || !state.tracking) return;

    let nearest = null;
    state.route.pois.forEach(poi => {
      if (state.triggered.has(poi.id)) return;
      const distance = ns.Distance.meters(position, poi);
      if (!nearest || distance < nearest.distance) nearest = { poi, distance };
    });

    $('#tracking-status').text(
      `GPS aktiv · Genauigkeit ${Math.round(position.accuracy)} m` +
      (nearest ? ` · nächste Station ${Math.round(nearest.distance)} m` : '')
    );

    if (nearest && nearest.distance <= nearest.poi.triggerRadiusM) {
      state.triggered.add(nearest.poi.id);
      if (navigator.vibrate) navigator.vibrate([120, 80, 120]);
      showPoi(nearest.poi, true);
    }
  }

  function updateTrackingButton() {
    const button = $('#start-tracking');
    button.button('option', {
      label: state.tracking ? 'GPS-Begleitung stoppen' : 'GPS-Begleitung starten',
      icon: state.tracking ? 'ui-icon-stop' : 'ui-icon-pin-s'
    });
  }

  function bindEvents() {
    $(document).on('click', '[data-route-id]', async function () {
      const button = $(this);
      button.prop('disabled', true);
      try {
        const route = await ns.Api.route(button.data('route-id'));
        renderRoute(route);
        navigate('#route-page');
      } catch (error) {
        alert(error.responseJSON?.message || error.statusText || error.message);
      } finally {
        button.prop('disabled', false);
      }
    });

    $(document).on('click', '[data-poi-id]', function () {
      const poi = state.route?.pois.find(item => item.id === Number($(this).data('poi-id')));
      if (poi) showPoi(poi, false);
    });

    $(document).on('click', '[data-page-target]', function () {
      const target = $(this).data('page-target');
      if (history.state?.previous === target) history.back();
      else navigate(target, { replace: true });
    });

    $(document).on('click', '#start-tracking', function () {
      state.tracking = !state.tracking;
      updateTrackingButton();
      $('#tracking-status').toggle(state.tracking);
      if (state.tracking) {
        ns.Geo.start(evaluatePosition, error => $('#tracking-status').text(`GPS-Fehler: ${error.message}`));
      } else {
        ns.Geo.stop();
      }
    });

    window.addEventListener('popstate', event => {
      const page = event.state?.page || '#routes-page';
      navigate(page, { updateHistory: false, instant: true });
    });
  }

  ns.App = {
    navigate,

    async initialize(context) {
      bindEvents();
      await ns.Api.health();
      context.markStep('server', 'done');

      const response = await ns.Api.routes(null);
      state.routes = response.routes;
      context.markStep('routes', 'done');

      try {
        const position = await ns.Geo.current();
        state.position = position;
        $('#location-hint').text(`Standort ermittelt (Genauigkeit ${Math.round(position.accuracy)} m).`);
        state.routes = state.routes
          .map(route => ({
            ...route,
            proximityM: route.start ? ns.Distance.meters(position, route.start) : null
          }))
          .filter(route => route.proximityM == null || route.proximityM <= ns.Config.routeRadiusKm * 1000)
          .sort((a, b) => (a.proximityM ?? Number.MAX_VALUE) - (b.proximityM ?? Number.MAX_VALUE));
      } catch (error) {
        $('#location-hint').text(`Standort nicht verfügbar: ${error.message}. Es werden alle Routen angezeigt.`);
      }

      context.markStep('location', 'done');
      renderRoutes();
      updateTrackingButton();
    }
  };
}(window.Wegwichtel, window.jQuery));