# FarmaFinder — Feature Plan

## Overview

Three features in recommended implementation order. Each is self-contained and can be shipped independently.

---

## Step 1 — "Near Me" Sorting (~2 hrs)

### Goal
Sort pharmacy results by distance from user's current location. Works in browser today, same logic reusable in React Native later.

### Backend changes
None. `latitude` and `longitude` already returned by `GET /api/medicines/:nregistro/pharmacies`.

### Frontend changes

**`frontend/src/utils/geo.js`** (new)
```js
export function haversineKm(lat1, lon1, lat2, lon2) {
  const R = 6371;
  const dLat = ((lat2 - lat1) * Math.PI) / 180;
  const dLon = ((lon2 - lon1) * Math.PI) / 180;
  const a =
    Math.sin(dLat / 2) ** 2 +
    Math.cos((lat1 * Math.PI) / 180) *
      Math.cos((lat2 * Math.PI) / 180) *
      Math.sin(dLon / 2) ** 2;
  return R * 2 * Math.atan2(Math.sqrt(a), Math.sqrt(1 - a));
}

export function getUserPosition() {
  return new Promise((resolve, reject) => {
    if (!navigator.geolocation) return reject(new Error('Geolocation not supported'));
    navigator.geolocation.getCurrentPosition(
      pos => resolve({ lat: pos.coords.latitude, lon: pos.coords.longitude }),
      reject,
      { timeout: 8000 }
    );
  });
}
```

**`frontend/src/views/PublicView.jsx`**
- Add state: `userPosition` (null | { lat, lon }), `sortByDistance` (bool)
- Add "Sort by distance" button — on click calls `getUserPosition()`, sets `userPosition`, sets `sortByDistance = true`
- Before rendering pharmacies, if `sortByDistance && userPosition`:
  ```js
  const sorted = [...pharmacies].sort((a, b) => {
    if (!a.latitude) return 1;
    if (!b.latitude) return -1;
    return haversineKm(userPosition.lat, userPosition.lon, a.latitude, a.longitude)
         - haversineKm(userPosition.lat, userPosition.lon, b.latitude, b.longitude);
  });
  ```
- Pass `sorted` (or original `pharmacies`) to `PharmacyList` and `PharmacyMap`

**`frontend/src/components/PharmacyList.jsx`**
- Accept optional `userPosition` prop
- When present and pharmacy has lat/lng, show distance badge: `1.2 km` next to pharmacy name

### Verification
```bash
# Start app, search a medicine, click "Sort by distance", allow geolocation
# Pharmacies reorder, distance badges appear
```

---

## Step 2 — Pharmacy Hours (~3 hrs)

### Goal
Store structured opening hours per pharmacy. Show "Open now" / "Closed" / "Opens at HH:MM" badge on pharmacy cards.

### Data model

Store hours as JSON in a single column — structured enough to parse, simple enough to edit manually in admin:

```json
{
  "mon": ["09:00", "21:00"],
  "tue": ["09:00", "21:00"],
  "wed": ["09:00", "21:00"],
  "thu": ["09:00", "21:00"],
  "fri": ["09:00", "21:00"],
  "sat": ["09:00", "14:00"],
  "sun": null
}
```

`null` = closed that day. 24h format strings. Only one time range per day (no split shifts) — extend later if needed.

### Backend changes

**`backend/server.js`** — `initDatabase()`
```sql
ALTER TABLE pharmacies ADD COLUMN opening_hours TEXT;
```
Wrap in try/catch — `ALTER TABLE` throws if column already exists.

**`GET /api/medicines/:nregistro/pharmacies`** — already returns `SELECT *`, no change needed.

**`POST /api/admin/pharmacies`** and **`PUT /api/admin/pharmacies/:id`**
- Accept `opening_hours` in request body (JSON string or object)
- Serialize to string before INSERT/UPDATE: `JSON.stringify(opening_hours) || null`

### Frontend changes

**`frontend/src/utils/hours.js`** (new)
```js
const DAYS = ['sun', 'mon', 'tue', 'wed', 'thu', 'fri', 'sat'];

export function getOpenStatus(openingHoursJson) {
  if (!openingHoursJson) return null;
  let hours;
  try { hours = typeof openingHoursJson === 'string' ? JSON.parse(openingHoursJson) : openingHoursJson; }
  catch { return null; }

  const now = new Date();
  const day = DAYS[now.getDay()];
  const range = hours[day];

  if (!range) return { status: 'closed', label: 'Closed today' };

  const [openStr, closeStr] = range;
  const [oh, om] = openStr.split(':').map(Number);
  const [ch, cm] = closeStr.split(':').map(Number);
  const nowMins = now.getHours() * 60 + now.getMinutes();
  const openMins = oh * 60 + om;
  const closeMins = ch * 60 + cm;

  if (nowMins < openMins) return { status: 'closed', label: `Opens at ${openStr}` };
  if (nowMins >= closeMins) return { status: 'closed', label: `Closed · Opens ${getNextOpen(hours, now)}` };
  return { status: 'open', label: `Open · Closes at ${closeStr}` };
}
```

**`frontend/src/components/PharmacyList.jsx`**
- Import `getOpenStatus`, render status badge per pharmacy card
- CSS: `.badge-open { color: green }` / `.badge-closed { color: #999 }`

**`frontend/src/components/admin/PharmacyManagement.jsx`**
- Add hours editor: 7 rows (Mon–Sun), each with two time inputs (open/close) + "Closed" checkbox
- Serialize to JSON on save

### Verification
```bash
# Add pharmacy with hours via admin panel
# Search medicine linked to that pharmacy
# Card shows "Open · Closes at 21:00" or "Closed · Opens at 09:00"
# Change system clock or test at different times
```

---

## Step 3 — PWA + Push Notifications / Medicine Alerts (~1 day)

### Goal
User subscribes to a medicine. When any pharmacy links that medicine (via admin panel), the user receives a push notification in the browser. Foundation reusable for React Native (swap `web-push` for FCM).

### Architecture

```
User visits app
  → service worker registered (PWA)
  → user searches medicine, clicks "Notify me"
  → browser prompts for notification permission
  → browser generates push subscription (endpoint + keys)
  → POST /api/notifications/subscribe { medicine_nregistro, subscription }
  → stored in DB

Admin links medicine to pharmacy (POST /api/admin/pharmacy-medicines)
  → backend queries notifications table for medicine_nregistro
  → fires web-push to each subscription endpoint
  → user receives notification: "Ibuprofeno 400mg now available at Farmacia Sol"
```

### Backend changes

**Dependencies**
```bash
npm install web-push
```

Generate VAPID keys (one-time, store in `.env`):
```bash
node -e "const wp = require('web-push'); const k = wp.generateVAPIDKeys(); console.log(k)"
```
Add to `.env.example`:
```
VAPID_PUBLIC_KEY=
VAPID_PRIVATE_KEY=
VAPID_EMAIL=mailto:admin@example.com
```

**`backend/server.js`** — `initDatabase()`
```sql
CREATE TABLE IF NOT EXISTS push_subscriptions (
  id INTEGER PRIMARY KEY AUTOINCREMENT,
  medicine_nregistro TEXT NOT NULL,
  endpoint TEXT NOT NULL,
  p256dh TEXT NOT NULL,
  auth TEXT NOT NULL,
  created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
  UNIQUE(medicine_nregistro, endpoint)
);
```

**New routes**
```
POST /api/notifications/subscribe
  body: { medicine_nregistro, medicine_name, subscription: { endpoint, keys: { p256dh, auth } } }
  → upsert into push_subscriptions
  → 201

DELETE /api/notifications/unsubscribe
  body: { medicine_nregistro, endpoint }
  → delete from push_subscriptions
  → 204

GET /api/notifications/vapid-public-key
  → returns { publicKey: process.env.VAPID_PUBLIC_KEY }
```

**Hook into `POST /api/admin/pharmacy-medicines`**
After successful insert:
```js
const subs = await dbAll(
  'SELECT * FROM push_subscriptions WHERE medicine_nregistro = ?',
  [medicine_nregistro]
);
for (const sub of subs) {
  await webpush.sendNotification(
    { endpoint: sub.endpoint, keys: { p256dh: sub.p256dh, auth: sub.auth } },
    JSON.stringify({
      title: 'Medicine available',
      body: `${medicine_name} now available at ${pharmacyName}`,
      url: '/'
    })
  ).catch(() => {
    // subscription expired — delete it
    dbRun('DELETE FROM push_subscriptions WHERE id = ?', [sub.id]);
  });
}
```

### Frontend changes

**Dependencies**
```bash
npm install vite-plugin-pwa
```

**`frontend/vite.config.js`**
```js
import { VitePWA } from 'vite-plugin-pwa';

// Add to plugins array:
VitePWA({
  registerType: 'autoUpdate',
  manifest: {
    name: 'FarmaFinder',
    short_name: 'FarmaFinder',
    theme_color: '#2563eb',
    icons: [{ src: '/icon-192.png', sizes: '192x192', type: 'image/png' }],
  },
  workbox: {
    globPatterns: ['**/*.{js,css,html,ico,png,svg}'],
  },
})
```

**`frontend/src/utils/notifications.js`** (new)
```js
export async function getVapidKey() {
  const res = await fetch('/api/notifications/vapid-public-key');
  const { publicKey } = await res.json();
  return publicKey;
}

export function urlBase64ToUint8Array(base64String) {
  const padding = '='.repeat((4 - (base64String.length % 4)) % 4);
  const base64 = (base64String + padding).replace(/-/g, '+').replace(/_/g, '/');
  return Uint8Array.from(atob(base64), c => c.charCodeAt(0));
}

export async function subscribeToPush(medicineNregistro, medicineName) {
  const reg = await navigator.serviceWorker.ready;
  const publicKey = await getVapidKey();
  const subscription = await reg.pushManager.subscribe({
    userVisibleOnly: true,
    applicationServerKey: urlBase64ToUint8Array(publicKey),
  });
  await fetch('/api/notifications/subscribe', {
    method: 'POST',
    headers: { 'Content-Type': 'application/json' },
    body: JSON.stringify({
      medicine_nregistro: medicineNregistro,
      medicine_name: medicineName,
      subscription,
    }),
  });
}
```

**`frontend/src/components/MedicineResults.jsx`**
- Add "Notify me" bell button per medicine result
- On click: call `subscribeToPush(medicine.id, medicine.name)`
- Toggle state: subscribed / not subscribed (persist in `localStorage`)

**Service worker push handler** — `vite-plugin-pwa` injects the SW; add a custom handler:
```js
// frontend/src/sw.js (custom SW additions via injectManifest mode)
self.addEventListener('push', event => {
  const data = event.data.json();
  event.waitUntil(
    self.registration.showNotification(data.title, {
      body: data.body,
      icon: '/icon-192.png',
      data: { url: data.url },
    })
  );
});

self.addEventListener('notificationclick', event => {
  event.notification.close();
  event.waitUntil(clients.openWindow(event.notification.data.url));
});
```

### React Native path (future)
- Replace `web-push` with Firebase Admin SDK (`firebase-admin`)
- Replace `push_subscriptions.endpoint/p256dh/auth` with `fcm_token`
- Frontend subscription logic moves to Expo `registerForPushNotificationsAsync()`
- Backend notification dispatch abstracted into `notify(medicineNregistro, message)` function — same interface, different transport

### Verification
```bash
# Start app over HTTPS (required for push — use ngrok or deploy)
# Search medicine, click bell icon
# Browser prompts notification permission — allow
# In admin: link that medicine to a pharmacy
# Browser notification fires: "Ibuprofeno 400mg now available at Farmacia Sol"
```

---

## Recommended Order

| Step | Time | Depends on |
|------|------|-----------|
| 1. Near me sorting | ~2 hrs | Nothing |
| 2. Pharmacy hours | ~3 hrs | Nothing (can run parallel with step 1) |
| 3. PWA + alerts | ~1 day | Steps 1 and 2 done (better UX in notification: "open now, 1.2 km away") |

---

## Notes

- Push notifications require HTTPS in production. In development use ngrok or set `CHROME_FLAGS=--unsafely-treat-insecure-origin-as-secure=http://localhost:3000` for testing.
- VAPID keys are per-environment — generate once, never rotate unless necessary (rotation invalidates all existing subscriptions).
- The `UNIQUE(medicine_nregistro, endpoint)` constraint on `push_subscriptions` prevents duplicate alerts if user clicks "Notify me" multiple times.