/**
 * LeafletMapInner Component
 * Internal Leaflet map implementation (client-side only)
 */

'use client';

import { useEffect, useRef, useState } from 'react';
import L from 'leaflet';
import 'leaflet/dist/leaflet.css';
import type { School } from '@/lib/types';
import { schoolUrl, isSpecialSchool, buildOfstedListBadge, listRwmValue } from '@/lib/utils';

interface LeafletMapInnerProps {
  schools: School[];
  center: [number, number];
  zoom: number;
  referencePoint?: [number, number];
  /** Search radius in miles. Drawn as a dashed circle the view fits to. */
  radiusMiles?: number;
  /** The school whose pin is highlighted and, on wide screens, whose card is open. */
  selectedUrn?: number | null;
  onMarkerClick?: (school: School) => void;
  /** The open card was closed from the map itself (its × or a click elsewhere). */
  onDeselect?: () => void;
  onAddToCompare?: (school: School) => void;
  compareUrns?: number[];
  nationalAvgRwm?: number | null;
  laAverages?: Record<string, number | null>;
}

const METRES_PER_MILE = 1609.344;

/*
 * Wide screens show the selected school as a card on the map. Narrow ones do
 * not: HomeView shows the same card as a bottom sheet there, and a popup on a
 * 390px map would cover most of it.
 */
const CARD_ON_MAP_QUERY = '(min-width: 769px)';

// ---------------------------------------------------------------------------
// Card helpers (must work in plain JS string templates — no React / CSS Modules)
// Class names are global and styled in SchoolMap.module.css.
// ---------------------------------------------------------------------------

function escapeHtml(s: string): string {
  return s.replace(/&/g, '&amp;').replace(/</g, '&lt;').replace(/>/g, '&gt;').replace(/"/g, '&quot;');
}

function pinIcon(selected: boolean): L.DivIcon {
  const size = selected ? 32 : 22;
  return L.divIcon({
    className: selected ? 'sc-pin sc-pin--selected' : 'sc-pin',
    html: '',
    iconSize: [size, size],
    iconAnchor: [size / 2, size / 2],
  });
}

interface CardContext {
  inCompare: boolean;
  nationalAvgRwm?: number | null;
  laAverages?: Record<string, number | null>;
}

/** The headline figure and its comparison, the same rule as the list rows. */
function metricHtml(school: School, { nationalAvgRwm, laAverages }: CardContext): string {
  const special = isSpecialSchool(school);
  if (school.attainment_8_score != null) {
    const score = school.attainment_8_score;
    const laAvg = school.local_authority ? (laAverages?.[school.local_authority] ?? null) : null;
    let delta = '';
    if (!special && laAvg != null) {
      const diff = Math.round((score - laAvg) * 10) / 10;
      // Att8 runs 0–90 in 0.1 steps; ±0.5 is meaningful, where RWM needs ±2.
      const cls = diff >= 0.5 ? 'sc-up' : diff <= -0.5 ? 'sc-down' : '';
      delta = ` <span class="${cls}">${diff >= 0 ? '+' : ''}${diff} vs LA</span>`;
    }
    return `<strong>${score.toFixed(1)}</strong> Att 8${delta}`;
  }
  const rwm = listRwmValue(school);
  if (rwm != null) {
    let delta = '';
    if (!special && nationalAvgRwm != null) {
      const diff = Math.round(rwm - nationalAvgRwm);
      const cls = diff >= 2 ? 'sc-up' : diff <= -2 ? 'sc-down' : '';
      const text = diff >= 2 ? `+${diff} pts` : diff <= -2 ? `${diff} pts` : '≈ national';
      delta = ` <span class="${cls}">${text}</span>`;
    }
    return `<strong>${rwm}%</strong> RWM${delta}`;
  }
  return '';
}

function cardHtml(school: School, ctx: CardContext): string {
  const badge = buildOfstedListBadge(school);
  const href = schoolUrl(school.urn, school.school_name);
  const distance = school.distance != null
    ? `<span class="sc-dist">${school.distance.toFixed(1)} mi</span>` : '';
  const type = school.school_type
    ? `<span class="sc-tag">${escapeHtml(school.school_type)}</span>` : '';
  const metric = metricHtml(school, ctx);
  const pupils = school.total_pupils != null
    ? `${metric ? ' · ' : ''}${school.total_pupils.toLocaleString('en-GB')} pupils` : '';
  return `<div class="sc-card">
  <div class="sc-card-head"><a class="sc-card-name" href="${href}">${escapeHtml(school.school_name)}</a>${distance}</div>
  <div class="sc-card-tags"><span class="sc-ofsted sc-${badge.cssClass}">${escapeHtml(badge.label)}</span>${type}</div>
  ${metric || pupils ? `<div class="sc-card-metric">${metric}${pupils}</div>` : ''}
  <div class="sc-card-actions">
    <a class="btn btn-tertiary btn-sm" href="${href}">View</a>
    <button type="button" class="btn ${ctx.inCompare ? 'btn-active' : 'btn-secondary'} btn-sm" data-compare>${ctx.inCompare ? '✓ Comparing' : '+ Compare'}</button>
  </div>
</div>`;
}

export default function LeafletMapInner({
  schools, center, zoom, referencePoint, radiusMiles, selectedUrn,
  onMarkerClick, onDeselect, onAddToCompare, compareUrns,
  nationalAvgRwm, laAverages,
}: LeafletMapInnerProps) {
  const mapRef = useRef<L.Map | null>(null);
  const mapContainerRef = useRef<HTMLDivElement>(null);
  const markersRef = useRef<Map<number, L.Marker>>(new Map());
  const overlayRef = useRef<L.LayerGroup | null>(null);
  const popupRef = useRef<L.Popup | null>(null);
  const selectedRef = useRef<number | null>(null);
  // Bumped whenever the pins are rebuilt, for any reason, so the selection
  // effect puts the card back on the new pin rather than only when the
  // selection or the school list changes.
  const [pinsVersion, setPinsVersion] = useState(0);

  // The popup is plain HTML outside React, so its handlers read the latest
  // props through a ref rather than closing over the render they were made in.
  const latest = useRef({ onMarkerClick, onDeselect, onAddToCompare, compareUrns, nationalAvgRwm, laAverages });
  latest.current = { onMarkerClick, onDeselect, onAddToCompare, compareUrns, nationalAvgRwm, laAverages };

  const cardHtmlFor = (school: School) => cardHtml(school, {
    inCompare: !!latest.current.compareUrns?.includes(school.urn),
    nationalAvgRwm: latest.current.nationalAvgRwm,
    laAverages: latest.current.laAverages,
  });

  // Map, tiles and controls: once.
  useEffect(() => {
    if (!mapContainerRef.current || mapRef.current) return;
    const map = L.map(mapContainerRef.current, { zoomControl: false }).setView(center, zoom);
    L.control.zoom({ position: 'topright' }).addTo(map);
    L.tileLayer('https://{s}.tile.openstreetmap.org/{z}/{x}/{y}.png', {
      attribution: '&copy; <a href="https://www.openstreetmap.org/copyright">OpenStreetMap</a> contributors',
      maxZoom: 19,
    }).addTo(map);
    overlayRef.current = L.layerGroup().addTo(map);
    mapRef.current = map;
    // center/zoom only seed the first view; later changes go through the
    // markers effect, which fits the view to the results.
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, []);

  // Search location, radius and school pins.
  useEffect(() => {
    const map = mapRef.current;
    const overlay = overlayRef.current;
    if (!map || !overlay) return;

    // Forget the open card before closing it, so its close handler does not
    // read this rebuild as the reader deselecting; the selection effect below
    // reopens it on the new pin.
    popupRef.current = null;
    map.closePopup();
    overlay.clearLayers();
    markersRef.current.clear();

    let radiusBounds: L.LatLngBounds | null = null;
    if (referencePoint) {
      if (radiusMiles) {
        const circle = L.circle(referencePoint, {
          radius: radiusMiles * METRES_PER_MILE,
          className: 'sc-radius',
          interactive: false,
        }).addTo(overlay);
        radiusBounds = circle.getBounds();
        const label = radiusMiles === 1 ? '1 mile' : `${radiusMiles} miles`;
        L.marker([radiusBounds.getNorth(), referencePoint[1]], {
          icon: L.divIcon({ className: 'sc-radius-label', html: label, iconSize: undefined }),
          interactive: false,
          keyboard: false,
        }).addTo(overlay);
      }
      L.marker(referencePoint, {
        icon: L.divIcon({ className: 'sc-home', html: '', iconSize: [16, 16], iconAnchor: [8, 8] }),
        zIndexOffset: 500,
        title: 'Search location',
        alt: 'Search location',
      }).addTo(overlay);
    }

    for (const school of schools) {
      if (!school.latitude || !school.longitude) continue;
      const selected = school.urn === selectedRef.current;
      const marker = L.marker([school.latitude, school.longitude], {
        icon: pinIcon(selected),
        zIndexOffset: selected ? 1000 : 0,
        title: school.school_name,
        alt: school.school_name,
        riseOnHover: true,
      }).addTo(overlay);
      marker.on('click', () => latest.current.onMarkerClick?.(school));
      markersRef.current.set(school.urn, marker);
    }

    // Fit the search radius when there is one: every result lies inside it,
    // and it keeps the view the same shape whatever the pins happen to be.
    if (radiusBounds) {
      map.fitBounds(radiusBounds, { padding: [16, 16] });
    } else if (schools.length > 1) {
      const points = schools
        .filter(s => s.latitude && s.longitude)
        .map(s => [s.latitude!, s.longitude!] as [number, number]);
      if (points.length) map.fitBounds(L.latLngBounds(points), { padding: [50, 50] });
    } else {
      map.setView(center, zoom);
    }
    setPinsVersion(v => v + 1);
  }, [schools, center, zoom, referencePoint, radiusMiles]);

  // Selection: restyle the pin, and on wide screens open its card.
  useEffect(() => {
    const map = mapRef.current;
    if (!map) return;
    const previous = selectedRef.current;
    selectedRef.current = selectedUrn ?? null;

    if (previous != null && previous !== selectedUrn) {
      const old = markersRef.current.get(previous);
      old?.setIcon(pinIcon(false));
      old?.setZIndexOffset(0);
    }

    const marker = selectedUrn != null ? markersRef.current.get(selectedUrn) : undefined;
    const school = selectedUrn != null ? schools.find(s => s.urn === selectedUrn) : undefined;
    if (!marker || !school) {
      popupRef.current = null;
      map.closePopup();
      return;
    }
    marker.setIcon(pinIcon(true));
    marker.setZIndexOffset(1000);

    if (!window.matchMedia(CARD_ON_MAP_QUERY).matches) {
      if (!map.getBounds().contains(marker.getLatLng())) map.panTo(marker.getLatLng());
      return;
    }

    const popup = L.popup({
      className: 'sc-popup',
      maxWidth: 300,
      minWidth: 260,
      offset: [0, -12],
      autoPanPadding: [24, 24],
    }).setLatLng(marker.getLatLng()).setContent(cardHtmlFor(school));
    popup.on('remove', () => {
      // Closed from the map, not replaced by another selection.
      if (popupRef.current === popup) {
        popupRef.current = null;
        latest.current.onDeselect?.();
      }
    });
    popupRef.current = popup;
    popup.openOn(map);
    // One listener on the card's shell: it outlives the content swaps below.
    popup.getElement()?.addEventListener('click', (e) => {
      if ((e.target as HTMLElement).closest('[data-compare]')) latest.current.onAddToCompare?.(school);
    });
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [selectedUrn, pinsVersion]);

  // The open card follows the compare basket and the averages as they arrive.
  useEffect(() => {
    const popup = popupRef.current;
    if (!popup || selectedUrn == null) return;
    const school = schools.find(s => s.urn === selectedUrn);
    if (school) popup.setContent(cardHtmlFor(school));
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [compareUrns, nationalAvgRwm, laAverages]);

  // Cleanup map on unmount
  useEffect(() => {
    return () => {
      if (mapRef.current) {
        mapRef.current.remove();
        mapRef.current = null;
      }
    };
  }, []);

  return <div ref={mapContainerRef} style={{ width: '100%', height: '100%' }} />;
}