/**
 * osm-pt-geojson web frontend
 * Handles map rendering, stop selection, segment preview and GeoJSON download.
 */

'use strict';

// ── Map setup ──────────────────────────────────────────────────────────────

const map = L.map('map').setView([20, 0], 2);

L.tileLayer('https://tile.openstreetmap.org/{z}/{x}/{y}.png', {
  attribution: '© <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
  maxZoom: 19,
}).addTo(map);

// Leaflet layers
let fullRouteLayer = null;   // thin grey polyline for the full route
let segmentLayer = null;     // bold coloured polyline for the selected segment
let markerLayer = null;      // all stop markers
let routeMasterLayers = [];  // coloured polylines when viewing a route_master

// ── State ─────────────────────────────────────────────────────────────────

const DEFAULT_TITLE = document.title;
let currentRelationId = RELATION_ID;  // tracks the currently loaded relation
let routeData = null;        // response from /api/route/
let segmentGeoJson = null;   // last response from /api/segment/ (always includes stops)
let activeSlot = 'from';     // 'from' | 'to' | null
let selectedFrom = null;     // stop name string or null
let selectedTo = null;       // stop name string or null

// ── Helpers ────────────────────────────────────────────────────────────────

/**
 * Show an error alert in the sidebar.
 * @param {string} msg
 */
function showError(msg) {
  const el = document.getElementById('js-alert');
  document.getElementById('js-alert-msg').textContent = msg;
  el.classList.remove('d-none');
}

/**
 * Trigger a file download of text content.
 * @param {string} content
 * @param {string} filename
 */
function downloadText(content, filename) {
  const blob = new Blob([content], { type: 'application/geo+json' });
  const url = URL.createObjectURL(blob);
  const a = document.createElement('a');
  a.href = url;
  a.download = filename;
  a.click();
  URL.revokeObjectURL(url);
}

/**
 * Return a safe filename fragment from a stop name.
 * @param {string} name
 * @returns {string}
 */
function safeName(name) {
  return name.replace(/[^a-zA-Z0-9_\-]/g, '_').replace(/_+/g, '_');
}

// ── Slot UI ────────────────────────────────────────────────────────────────

/**
 * Update the From/To slot boxes to reflect current state.
 */
function renderSlots() {
  const slots = { from: selectedFrom, to: selectedTo };
  for (const [id, value] of Object.entries(slots)) {
    const box = document.getElementById(`slot-${id}`);
    const text = document.getElementById(`slot-${id}-text`);
    const pencil = document.getElementById(`slot-${id}-pencil`);
    const isActive = activeSlot === id;

    box.classList.toggle('active', isActive);
    pencil.classList.toggle('d-none', !isActive);

    if (value) {
      text.textContent = value;
      text.classList.remove('placeholder');
    } else {
      text.textContent = 'Click a stop…';
      text.classList.add('placeholder');
    }
  }
}

/**
 * Set which slot is active. Pass null to deactivate both.
 * @param {'from'|'to'|null} slot
 */
function setActiveSlot(slot) {
  activeSlot = slot;
  renderSlots();
}

// ── Stop selection ─────────────────────────────────────────────────────────

/**
 * Handle a stop being selected (from list click or map marker click).
 * @param {string} name
 */
function selectStop(name) {
  if (activeSlot === 'from') {
    selectedFrom = name;
    setActiveSlot('to');
  } else if (activeSlot === 'to') {
    selectedTo = name;
    setActiveSlot(null);
  } else {
    // Neither slot active — do nothing, user must click a slot first.
    return;
  }
  renderStopList();
  updateMarkers();
  if (selectedFrom && selectedTo) {
    loadSegment();
  }
}

// ── Stop list ──────────────────────────────────────────────────────────────

/**
 * Render the sidebar stop list from routeData.
 */
function renderStopList() {
  if (!routeData) return;
  const list = document.getElementById('stop-list');
  document.getElementById('stop-count').textContent = `(${routeData.stops.length})`;
  list.innerHTML = '';
  for (const stop of routeData.stops) {
    const div = document.createElement('div');
    div.className = 'stop-item';
    div.textContent = stop.name;
    if (stop.name === selectedFrom) div.classList.add('is-from');
    if (stop.name === selectedTo) div.classList.add('is-to');
    div.addEventListener('click', () => selectStop(stop.name));
    list.appendChild(div);
  }
}

// ── Map rendering ──────────────────────────────────────────────────────────

/** Marker colours for stop states. */
const MARKER_COLOURS = {
  from:    '#198754',  // green
  to:      '#dc3545',  // red
  segment: '#0d6efd',  // blue
  default: '#6c757d',  // grey
};

/**
 * Create a small circular Leaflet marker.
 * @param {number} lat
 * @param {number} lon
 * @param {string} colour  hex colour
 * @param {string} title
 * @returns {L.CircleMarker}
 */
function makeMarker(lat, lon, colour, title) {
  return L.circleMarker([lat, lon], {
    radius: 6,
    color: colour,
    fillColor: colour,
    fillOpacity: 0.9,
    weight: 2,
  }).bindTooltip(title);
}

/**
 * Determine which stops fall within the current segment (by index).
 * Returns a Set of stop names.
 * @returns {Set<string>}
 */
function segmentStopNames() {
  if (!segmentGeoJson) return new Set();
  return new Set(
    segmentGeoJson.features
      .filter(f => f.geometry.type === 'Point')
      .map(f => f.properties.name)
  );
}

/**
 * Redraw all stop markers to reflect current selection state.
 */
function updateMarkers() {
  if (!routeData) return;
  if (markerLayer) markerLayer.remove();
  markerLayer = L.layerGroup();
  const inSegment = segmentStopNames();

  for (const stop of routeData.stops) {
    let colour;
    if (stop.name === selectedFrom)       colour = MARKER_COLOURS.from;
    else if (stop.name === selectedTo)    colour = MARKER_COLOURS.to;
    else if (inSegment.has(stop.name))    colour = MARKER_COLOURS.segment;
    else                                  colour = MARKER_COLOURS.default;

    const marker = makeMarker(stop.lat, stop.lon, colour, stop.name);
    marker.on('click', () => selectStop(stop.name));
    markerLayer.addLayer(marker);
  }
  markerLayer.addTo(map);
}

/**
 * Draw or redraw the segment layer from segmentGeoJson, respecting the stops toggle.
 */
function renderSegment() {
  if (segmentLayer) segmentLayer.remove();
  if (!segmentGeoJson) return;

  const includeStops = document.getElementById('include-stops').checked;

  // Build a filtered GeoJSON: always keep LineString, conditionally keep Points.
  const filtered = {
    type: 'FeatureCollection',
    features: segmentGeoJson.features.filter(f =>
      f.geometry.type === 'LineString' || (f.geometry.type === 'Point' && includeStops)
    ),
  };

  segmentLayer = L.geoJSON(filtered, {
    style: { color: '#0d6efd', weight: 5, opacity: 0.85 },
    pointToLayer: (feature, latlng) =>
      makeMarker(latlng.lat, latlng.lng, MARKER_COLOURS.segment, feature.properties.name),
  }).addTo(map);

  updateMarkers();
  updateDownloadButtons();
}

// ── Download buttons ───────────────────────────────────────────────────────

/**
 * Enable/disable the segment download button and wire up both download buttons.
 */
function updateDownloadButtons() {
  const btn = document.getElementById('btn-download-segment');
  if (segmentGeoJson && selectedFrom && selectedTo) {
    btn.classList.remove('disabled');
  } else {
    btn.classList.add('disabled');
  }
}

document.getElementById('btn-download-segment').addEventListener('click', () => {
  if (!segmentGeoJson || !selectedFrom || !selectedTo) return;
  const includeStops = document.getElementById('include-stops').checked;
  const geojson = {
    type: 'FeatureCollection',
    features: segmentGeoJson.features.filter(f =>
      f.geometry.type === 'LineString' || (f.geometry.type === 'Point' && includeStops)
    ),
  };
  const ref = routeData.ref || 'route';
  const filename = `${safeName(ref)}-${safeName(selectedFrom)}-${safeName(selectedTo)}.geojson`;
  downloadText(JSON.stringify(geojson, null, 2), filename);
});

document.getElementById('btn-download-full').addEventListener('click', () => {
  if (!routeData) return;
  const includeStops = document.getElementById('include-stops').checked;
  const geojson = {
    type: 'FeatureCollection',
    features: routeData.geojson.features.filter(f =>
      f.geometry.type === 'LineString' || (f.geometry.type === 'Point' && includeStops)
    ),
  };
  const ref = routeData.ref || 'route';
  downloadText(JSON.stringify(geojson, null, 2), `${safeName(ref)}-full.geojson`);
});

// ── Clear button ───────────────────────────────────────────────────────────

document.getElementById('btn-clear').addEventListener('click', () => {
  selectedFrom = null;
  selectedTo = null;
  segmentGeoJson = null;
  if (segmentLayer) { segmentLayer.remove(); segmentLayer = null; }
  setActiveSlot('from');
  renderStopList();
  updateMarkers();
  updateDownloadButtons();
});

// ── Stops toggle ───────────────────────────────────────────────────────────

document.getElementById('include-stops').addEventListener('change', () => {
  renderSegment();   // re-filters existing data, no network request
});

// ── Slot click handlers ────────────────────────────────────────────────────

document.getElementById('slot-from').addEventListener('click', () => setActiveSlot('from'));
document.getElementById('slot-to').addEventListener('click', () => setActiveSlot('to'));

// ── Navigation ─────────────────────────────────────────────────────────────

/**
 * Load a relation without a full page reload, updating the browser URL.
 * Allows middle-click / ctrl-click to still open in a new tab via the href.
 * @param {number} id
 * @param {MouseEvent} e
 */
function navigateTo(id, e) {
  if (e.metaKey || e.ctrlKey || e.shiftKey || e.button !== 0) return;
  e.preventDefault();
  history.pushState(null, '', URLS.routePage + id);
  loadRoute(id);
}

// ── API calls ──────────────────────────────────────────────────────────────

/**
 * Fetch the full route and render it on the map.
 * @param {number} relationId
 */
async function loadRoute(relationId) {
  try {
    const resp = await fetch(URLS.routeApi + relationId);
    const data = await resp.json();
    if (!resp.ok) {
      if (data.error === 'is_route_master') {
        await loadRouteMaster(relationId);
        return;
      }
      showError(data.message || `Error loading relation ${relationId}.`);
      return;
    }
    routeData = data;
    currentRelationId = relationId;
    // Clean up any previous route_master view
    for (const l of routeMasterLayers) l.remove();
    routeMasterLayers = [];
    document.getElementById('route-master-panel').classList.add('d-none');
    selectedFrom = null;
    selectedTo = null;
    segmentGeoJson = null;
    setActiveSlot('from');

    // Show route panel
    document.getElementById('route-panel').classList.remove('d-none');
    document.getElementById('route-name').textContent = data.name;
    document.title = `${data.name} – ${DEFAULT_TITLE}`;
    document.getElementById('route-osm-link').href =
      `https://www.openstreetmap.org/relation/${relationId}`;

    // Draw full route in grey
    if (fullRouteLayer) fullRouteLayer.remove();
    fullRouteLayer = L.geoJSON(data.geojson, {
      style: { color: '#adb5bd', weight: 3, opacity: 0.7 },
      pointToLayer: () => null,   // don't render stop points here
      filter: f => f.geometry.type === 'LineString',
    }).addTo(map);

    map.fitBounds(fullRouteLayer.getBounds(), { padding: [20, 20] });

    renderStopList();
    updateMarkers();
    updateDownloadButtons();

    // Other directions (sibling routes from the same route_master)
    const dirPanel = document.getElementById('other-directions-panel');
    const dirList = document.getElementById('other-directions-list');
    dirList.innerHTML = '';
    if (data.other_directions && data.other_directions.length > 0) {
      dirPanel.classList.remove('d-none');
      for (const dir of data.other_directions) {
        const a = document.createElement('a');
        a.href = URLS.routePage + dir.id;
        a.className = 'stop-item d-block text-decoration-none';
        a.textContent = dir.name;
        a.addEventListener('click', (e) => navigateTo(dir.id, e));
        dirList.appendChild(a);
      }
    } else {
      dirPanel.classList.add('d-none');
    }
  } catch (e) {
    showError('Network error loading route.');
  }
}

/**
 * Fetch the segment GeoJSON and render it.
 */
async function loadSegment() {
  if (!selectedFrom || !selectedTo || !routeData) return;
  const rid = currentRelationId;
  const params = new URLSearchParams({ from: selectedFrom, to: selectedTo, stops: '1' });
  try {
    const resp = await fetch(URLS.segmentApi + rid + '?' + params);
    const data = await resp.json();
    if (!resp.ok) {
      showError(data.message || 'Error loading segment.');
      return;
    }
    segmentGeoJson = data;
    renderSegment();
  } catch (e) {
    showError('Network error loading segment.');
  }
}

/**
 * Fetch and display all member routes of a route_master relation.
 * @param {number} relationId
 */
async function loadRouteMaster(relationId) {
  try {
    const resp = await fetch(URLS.routeMasterApi + relationId);
    const data = await resp.json();
    if (!resp.ok) {
      showError(data.message || `Error loading route master ${relationId}.`);
      return;
    }

    // Clear individual route state
    routeData = null;
    selectedFrom = null;
    selectedTo = null;
    segmentGeoJson = null;
    if (fullRouteLayer) { fullRouteLayer.remove(); fullRouteLayer = null; }
    if (segmentLayer) { segmentLayer.remove(); segmentLayer = null; }
    if (markerLayer) { markerLayer.remove(); markerLayer = null; }
    for (const l of routeMasterLayers) l.remove();
    routeMasterLayers = [];

    // Hide individual route panel, show route_master panel
    document.getElementById('route-panel').classList.add('d-none');
    document.getElementById('route-master-panel').classList.remove('d-none');
    document.getElementById('route-master-name').textContent = data.name;
    document.title = `${data.name} – ${DEFAULT_TITLE}`;
    document.getElementById('route-master-osm-link').href =
      `https://www.openstreetmap.org/relation/${relationId}`;

    const colours = ['#0d6efd', '#dc3545', '#198754', '#fd7e14', '#6f42c1'];
    const list = document.getElementById('route-master-list');
    list.innerHTML = '';

    data.routes.forEach((route, i) => {
      const colour = colours[i % colours.length];

      if (route.geojson) {
        const layer = L.geoJSON(route.geojson, {
          style: { color: colour, weight: 4, opacity: 0.85 },
        }).addTo(map);
        routeMasterLayers.push(layer);
      }

      const div = document.createElement('div');
      div.className = 'stop-item d-flex align-items-center gap-2';

      const dot = document.createElement('span');
      dot.style.cssText =
        `display:inline-block;width:10px;height:10px;border-radius:50%;` +
        `background:${colour};flex-shrink:0`;

      const a = document.createElement('a');
      a.href = URLS.routePage + route.id;
      a.className = 'text-decoration-none text-reset flex-grow-1';
      a.textContent = route.name;
      a.addEventListener('click', (e) => navigateTo(route.id, e));

      div.appendChild(dot);
      div.appendChild(a);
      list.appendChild(div);
    });

    if (routeMasterLayers.length > 0) {
      let bounds = routeMasterLayers[0].getBounds();
      for (const l of routeMasterLayers.slice(1)) bounds = bounds.extend(l.getBounds());
      map.fitBounds(bounds, { padding: [20, 20] });
    }
  } catch (e) {
    showError('Network error loading route master.');
  }
}

// ── Init ───────────────────────────────────────────────────────────────────

window.addEventListener('popstate', () => {
  const prefix = URLS.routePage;
  if (location.pathname.startsWith(prefix)) {
    const id = parseInt(location.pathname.slice(prefix.length), 10);
    if (id) loadRoute(id);
  }
});

if (RELATION_ID) {
  loadRoute(RELATION_ID);
}