feat: add sort by distance and directions to ProductView

- Added sort by distance functionality (same as SearchView)
- Added PharmacyList component with distance display
- Added 'Cómo llegar' button in map popup (Google Maps directions)
- Uses haversineKm for distance calculation

apps/frontend/src/components/PharmacyMap.jsx

@@ -34,6 +34,15 @@ function PharmacyMap({ pharmacies }) {
               <strong>{pharmacy.name}</strong><br />
               {pharmacy.address}
               {pharmacy.phone && <><br />{pharmacy.phone}</>}
+              <br />
+              <a
+                href={`https://www.google.com/maps/dir/?api=1&destination=${pharmacy.latitude},${pharmacy.longitude}`}
+                target="_blank"
+                rel="noopener noreferrer"
+                style={{ color: '#2563eb', marginTop: '8px', display: 'inline-block' }}
+              >
+                📍 Cómo llegar
+              </a>
             </Popup>
           </Marker>
         ))}

apps/frontend/src/views/ProductView.jsx

@@ -1,5 +1,7 @@
-import React, { useState, useEffect } from 'react';
+import React, { useState, useEffect, useMemo } from 'react';
 import PharmacyMap from '../components/PharmacyMap';
+import PharmacyList from '../components/PharmacyList';
+import { haversineKm, getUserPosition, hasCachedPosition } from '../utils/geo';
 import './ProductView.css';
 
 export default function ProductView({ source, id, onBack }) {
@@ -8,6 +10,50 @@ export default function ProductView({ source, id, onBack }) {
   const [error, setError] = useState(null);
   const [pharmacies, setPharmacies] = useState([]);
   const [loadingPharmacies, setLoadingPharmacies] = useState(false);
+  const [sortByDistance, setSortByDistance] = useState(false);
+  const [userPosition, setUserPosition] = useState(null);
+  const [positionSource, setPositionSource] = useState(null);
+  const [locating, setLocating] = useState(false);
+  const [locationError, setLocationError] = useState('');
+
+  const hasSavedCoords = product?.latitude != null && product?.longitude != null;
+
+  const displayedPharmacies = useMemo(() => {
+    if (!sortByDistance || !userPosition) return pharmacies;
+    return [...pharmacies].sort((a, b) => {
+      if (a.latitude == null || a.longitude == null) return 1;
+      if (b.latitude == null || b.longitude == null) return -1;
+      return (
+        haversineKm(userPosition.lat, userPosition.lon, a.latitude, a.longitude) -
+        haversineKm(userPosition.lat, userPosition.lon, b.latitude, b.longitude)
+      );
+    });
+  }, [pharmacies, sortByDistance, userPosition]);
+
+  const handleSortByDistance = async () => {
+    if (sortByDistance) {
+      setSortByDistance(false);
+      return;
+    }
+    setLocationError('');
+    setLocating(true);
+    try {
+      const pos = await getUserPosition();
+      setUserPosition(pos);
+      setPositionSource('browser');
+      setSortByDistance(true);
+    } catch (err) {
+      let msg = 'No se pudo obtener tu ubicación';
+      if (err && typeof err.code === 'number') {
+        if (err.code === 1) msg = 'Permiso de ubicación denegado.';
+        else if (err.code === 2) msg = 'Ubicación no disponible.';
+        else if (err.code === 3) msg = 'La ubicación tardó demasiado.';
+      }
+      setLocationError(msg);
+    } finally {
+      setLocating(false);
+    }
+  };
 
   useEffect(() => {
     loadProduct();
@@ -152,31 +198,38 @@ export default function ProductView({ source, id, onBack }) {
               Disponible en {pharmacies.length} {pharmacies.length === 1 ? 'farmacia' : 'farmacias'}
             </h3>
 
-            <PharmacyMap pharmacies={pharmacies} />
+            <div className="pharmacy-controls">
-
+              <button
-            <div className="pharmacies-grid">
+                className={`sort-distance-button ${sortByDistance ? 'active' : ''}`}
-              {pharmacies.map((pharmacy) => (
+                onClick={handleSortByDistance}
-                <div key={pharmacy.id} className="product-pharmacy-card">
+                disabled={locating}
-                  <h4 className="product-pharmacy-name">{pharmacy.name}</h4>
+              >
-                  <p className="product-pharmacy-address">{pharmacy.address}</p>
+                {locating
-                  {pharmacy.phone && (
+                  ? '📍 Localizando…'
-                    <p className="product-pharmacy-phone">{pharmacy.phone}</p>
+                  : sortByDistance
-                  )}
+                    ? '📍 Ordenado por distancia · Reset'
-                  <div className="product-pharmacy-status">
+                    : '📍 Ordenar por distancia'}
-                    {pharmacy.price && (
+              </button>
-                      <span className="product-pharmacy-price">
+              {sortByDistance && positionSource && (
-                        {parseFloat(pharmacy.price).toFixed(2)} &euro;
+                <span className="location-source">Usando tu ubicación</span>
-                      </span>
+              )}
-                    )}
+              {locationError && (
-                    {pharmacy.stock !== undefined && (
+                <span className="location-error">
-                      <span className={`product-pharmacy-stock ${pharmacy.stock > 20 ? 'in-stock' : pharmacy.stock > 0 ? 'low-stock' : 'out-of-stock'}`}>
+                  {locationError}
-                        {pharmacy.stock > 20 ? 'En Stock' : pharmacy.stock > 0 ? `Stock Bajo (${pharmacy.stock})` : 'Sin Stock'}
+                  <button className="retry-location-btn" onClick={handleSortByDistance}>
-                      </span>
+                    Reintentar
-                    )}
+                  </button>
-                  </div>
+                </span>
-                </div>
+              )}
-              ))}
             </div>
+
+            <PharmacyMap pharmacies={displayedPharmacies} />
+
+            <PharmacyList
+              pharmacies={displayedPharmacies}
+              loading={loadingPharmacies}
+              userPosition={sortByDistance ? userPosition : null}
+            />
           </>
         ) : null}
       </div>