// Leaflet map: numbered markers for located stops, a polyline through them,
// per-leg km labels, and a leg-by-leg list. Graceful empty state when the
// trip has no located entries yet. Uses the /route response from tctx.route.
import { el } from '../dom.js';
import { typeInfo, entryIcon } from '../format.js';
import { api } from '../api.js';
import { STAY_PALETTE } from './stayBands.js';

// Each route leg gets its own colour from the same palette used for stay
// bands/area dots, so several ground legs (e.g. multiple car routes) read
// apart instead of blending into one generic "ground" colour.
function legColor(i) {
  return STAY_PALETTE[((i % STAY_PALETTE.length) + STAY_PALETTE.length) % STAY_PALETTE.length];
}

export function renderMap(tctx) {
  const route = tctx.route || { stops: [], legs: [], totalKm: 0 };
  const stops = route.stops || [];

  const section = el('section', { class: 'card map-section' });
  section.appendChild(
    el(
      'div',
      { class: 'section-head' },
      el('h2', {}, 'Map'),
      el('p', { class: 'muted' }, stops.length
        ? `${stops.length} located ${stops.length === 1 ? 'stop' : 'stops'} · ${fmtKm(route.totalKm)} km total`
        : 'Add a location to an entry to see it here.'),
    ),
  );

  if (!stops.length) {
    section.appendChild(
      el(
        'div',
        { class: 'map-empty' },
        el('div', { class: 'empty-icon' }, '🗺️'),
        el('p', {}, 'No located entries yet.'),
        el('p', { class: 'muted' }, 'Open a day, add an entry, and give it a location to plot it on the map.'),
      ),
    );
    return section;
  }

  const mapDiv = el('div', { class: 'leaflet-map', id: `map-${tctx.tripId}` });
  section.appendChild(mapDiv);

  // Legs and the "Legs" list below share the same filtered (leg, fromStop,
  // toStop) triples so the map's polylines/labels and the list rows stay in
  // lockstep by index.
  const legs = visibleLegs(route, stops);
  const { wrap: legListEl, kmEls } = legList(legs);
  section.appendChild(legListEl);

  // Leaflet needs the container attached with a real size, so init on the
  // next tick after this section is mounted into the page.
  setTimeout(() => initMap(mapDiv, stops, legs, kmEls), 0);

  return section;
}

// Consecutive non-coincident stop pairs (skip <0.05km, the server's rule),
// paired with their matching /route leg.
function visibleLegs(route, stops) {
  const legs = route.legs || [];
  const result = [];
  let li = 0;
  for (let i = 0; i < stops.length - 1 && li < legs.length; i++) {
    const a = stops[i];
    const b = stops[i + 1];
    if (haversineKm(a.lat, a.lng, b.lat, b.lng) < 0.05) continue;
    result.push({ leg: legs[li], a, b });
    li += 1;
  }
  return result;
}

function initMap(mapDiv, stops, legs, kmEls) {
  const L = window.L;
  if (!L) {
    mapDiv.appendChild(el('p', { class: 'muted' }, 'Map library failed to load.'));
    return;
  }

  const map = L.map(mapDiv, { scrollWheelZoom: true });
  L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
    attribution: '© OpenStreetMap contributors',
    maxZoom: 19,
  }).addTo(map);

  // Geometry is driven by stop ORDER, not entryId: a multi-leg flight expands
  // into several airport stops that all share the same entryId, so keying by
  // entryId would collapse them.
  const points = stops.map((s) => [s.lat, s.lng]);
  stops.forEach((stop, i) => {
    const info = typeInfo(stop.type);
    L.marker(points[i], { icon: numberedIcon(L, i + 1, info.color) })
      .addTo(map)
      .bindPopup(popupHtml(stop, info, entryIcon(stop)));
  });

  // One polyline per measured leg, each in its own colour from the shared
  // palette (air legs keep the dashed pattern), each with a km label at its
  // midpoint (straight great-circle line to start — the map is never empty
  // while road geometry loads).
  const legLayers = legs.map(({ leg, a, b }, i) => {
    const air = leg.mode === 'air';
    const color = legColor(i);
    const line = L.polyline([[a.lat, a.lng], [b.lat, b.lng]], {
      color,
      weight: 3,
      opacity: 0.75,
      dashArray: air ? '6 6' : null,
    }).addTo(map);
    const mid = [(a.lat + b.lat) / 2, (a.lng + b.lng) / 2];
    const label = L.marker(mid, { icon: kmLabel(L, leg.km, false, color), interactive: false }).addTo(map);
    // Scenic via-points (ground legs only) — small dots in the leg's colour,
    // with the waypoint name as a tooltip.
    (leg.waypoints || []).forEach((wp) => {
      // esc() the name: Leaflet renders a string tooltip as HTML, and wp.name
      // is user-typed, so a raw value is a stored-XSS sink for co-travellers.
      L.marker([wp.lat, wp.lng], { icon: waypointIcon(L, color), title: wp.name || '' })
        .bindTooltip(esc(wp.name || 'Waypoint'))
        .addTo(map);
    });
    return { leg, a, b, line, label, color };
  });

  if (points.length === 1) {
    map.setView(points[0], 10);
  } else {
    map.fitBounds(L.latLngBounds(points).pad(0.2));
  }
  map.invalidateSize();

  fetchRoadGeometry(L, map, mapDiv, legLayers, kmEls);
}

// Async road-following geometry for ground legs, per the /api/directions
// "Consumer contract (map)" in docs/API.md. Straight great-circle lines are
// already drawn, so a slow/failed fetch just leaves those in place — no
// error UI. Each leg fetches (and fails) independently.
function fetchRoadGeometry(L, map, mapDiv, legLayers, kmEls) {
  legLayers.forEach(({ leg, a, b, line, label, color }, i) => {
    if (leg.mode !== 'ground') return;
    api.directions({ lat: a.lat, lng: a.lng }, { lat: b.lat, lng: b.lng }, leg.waypoints || [])
      .then((res) => {
        // The trip view may have been re-rendered (refreshTrip) while this
        // was in flight — the old map/section is detached from the DOM and
        // its layers must not be touched. Only latlngs/label are swapped —
        // the polyline keeps its per-leg colour/style from creation.
        if (!mapDiv.isConnected || !map.hasLayer(line) || !map.hasLayer(label)) return;
        line.setLatLngs(res.geometry);
        label.setLatLng(pathMidpoint(res.geometry) || label.getLatLng());
        label.setIcon(kmLabel(L, res.km, true, color));
        const kmEl = kmEls[i];
        if (kmEl) kmEl.textContent = `${fmtKm(res.km)} km · road`;
      })
      .catch(() => {});
  });
}

function pathMidpoint(coords) {
  if (!coords || !coords.length) return null;
  return coords[Math.floor(coords.length / 2)];
}

// Great-circle km — mirrors the server rule for skipping zero-distance legs.
function haversineKm(lat1, lng1, lat2, lng2) {
  const R = 6371;
  const toRad = (d) => (d * Math.PI) / 180;
  const dLat = toRad(lat2 - lat1);
  const dLng = toRad(lng2 - lng1);
  const a = Math.sin(dLat / 2) ** 2 +
    Math.cos(toRad(lat1)) * Math.cos(toRad(lat2)) * Math.sin(dLng / 2) ** 2;
  return 2 * R * Math.asin(Math.min(1, Math.sqrt(a)));
}

function numberedIcon(L, n, color) {
  return L.divIcon({
    className: 'map-pin-wrap',
    html: `<span class="map-pin" style="background:${color}">${n}</span>`,
    iconSize: [26, 26],
    iconAnchor: [13, 26],
    popupAnchor: [0, -24],
  });
}

function waypointIcon(L, color) {
  return L.divIcon({
    className: 'wp-dot-wrap',
    html: `<span class="wp-dot" style="--wp-color:${color}"></span>`,
    iconSize: [10, 10],
    iconAnchor: [5, 5],
  });
}

function kmLabel(L, km, road, color) {
  const accent = color ? ` style="--leg-accent:${color}"` : '';
  return L.divIcon({
    className: 'km-label-wrap',
    html: `<span class="km-label"${accent}>${fmtKm(km)} km${road ? ' · road' : ''}</span>`,
    iconSize: [0, 0],
  });
}

// Built from server-provided fields; escape to keep the popup injection-safe.
function popupHtml(stop, info, icon) {
  const isAirport = stop.kind === 'airport' && stop.code;
  const heading = isAirport ? `${icon} ${esc(stop.code)}` : `${icon} ${esc(stop.title)}`;
  const sub = isAirport
    ? `${esc(info.label)} · ${esc(stop.date)}${stop.title ? ` · ${esc(stop.title)}` : ''}`
    : `${esc(info.label)} · ${esc(stop.date)}`;
  const locIcon = isAirport ? '✈️' : '📍';
  return (
    `<div class="map-popup">` +
    `<strong>${heading}</strong>` +
    `<div class="map-popup-sub">${sub}</div>` +
    (stop.location_name ? `<div class="map-popup-loc">${locIcon} ${esc(stop.location_name)}</div>` : '') +
    `</div>`
  );
}

function stopLabel(stop) {
  if (stop.kind === 'airport' && stop.code) return stop.code;
  return stop.location_name || stop.title || '?';
}

// legs: [{ leg, a, b }, …] from visibleLegs — same order/filtering the map
// polylines use. Returns the list element plus the per-row km <span>s (by
// the same index) so fetchRoadGeometry can update them once routed km lands.
function legList(legs) {
  if (!legs.length) {
    return {
      wrap: el('div', { class: 'leg-list-empty muted' }, 'A single stop — no legs to measure yet.'),
      kmEls: [],
    };
  }

  const wrap = el('div', { class: 'leg-list' }, el('h3', {}, 'Legs'));
  const kmEls = [];
  legs.forEach(({ leg, a, b }, i) => {
    const air = leg.mode === 'air';
    const kmEl = el('span', { class: 'leg-km' }, `${fmtKm(leg.km)} km`);
    kmEls.push(kmEl);
    wrap.appendChild(
      el(
        'div',
        { class: 'leg-row' },
        // Dark text, not white: the palette's mid-tone hues (amber, lime, …)
        // don't clear AA contrast with white at full strength — the same
        // reason stay bands use dark text on these colours (see stayBands.js).
        el('span', { class: 'leg-index', style: { background: legColor(i), color: '#334155' } }, String(i + 1)),
        el('span', { class: 'leg-mode', title: air ? 'Flight' : 'Ground' }, air ? '✈️' : '🚗'),
        el('span', { class: 'leg-path' }, stopLabel(a), ' → ', stopLabel(b)),
        kmEl,
      ),
    );
  });
  return { wrap, kmEls };
}

function fmtKm(n) {
  return (Math.round((Number(n) || 0) * 10) / 10).toLocaleString();
}

function esc(str) {
  return String(str == null ? '' : str)
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;');
}