curl -X POST 
  'https://graph.facebook.com/v20.0/{PHONE_NUMBER_ID}/messages' 
  -H 'Authorization: Bearer {ACCESS_TOKEN}' 
  -H 'Content-Type: application/json' 
  -d '{
    "messaging_product": "whatsapp",
    "to": "919876543210",
    "type": "template",
    "template": {
      "name": "hello_world",
      "language": { "code": "en_US" }
    }
  }'

function sendWhatsApp($to, $templateName, $params = []) {
    $url = "https://graph.facebook.com/v20.0/" . getenv('WA_PHONE_ID') . "/messages";
    $body = [
        'messaging_product' => 'whatsapp',
        'to' => $to,
        'type' => 'template',
        'template' => [
            'name' => $templateName,
            'language' => ['code' => 'en_IN'],
            'components' => $params,
        ],
    ];
    $ch = curl_init($url);
    curl_setopt_array($ch, [
        CURLOPT_POST => true,
        CURLOPT_POSTFIELDS => json_encode($body),
        CURLOPT_HTTPHEADER => [
            'Authorization: Bearer ' . getenv('WA_ACCESS_TOKEN'),
            'Content-Type: application/json',
        ],
        CURLOPT_RETURNTRANSFER => true,
    ]);
    return json_decode(curl_exec($ch), true);
}

// Order confirmation
sendWhatsApp('919876543210', 'order_confirmation', [
    [
        'type' => 'body',
        'parameters' => [
            ['type' => 'text', 'text' => 'Rajesh'],       // {{1}}
            ['type' => 'text', 'text' => 'ORD-1234'],     // {{2}}
            ['type' => 'text', 'text' => '₹1,500'],        // {{3}}
        ],
    ],
]);

import axios from 'axios';

async function sendWhatsApp(to, template, params) {
  const resp = await axios.post(
    `https://graph.facebook.com/v20.0/${process.env.WA_PHONE_ID}/messages`,
    {
      messaging_product: 'whatsapp',
      to,
      type: 'template',
      template: {
        name: template,
        language: { code: 'en_IN' },
        components: params,
      },
    },
    { headers: { Authorization: `Bearer ${process.env.WA_ACCESS_TOKEN}` } }
  );
  return resp.data;
}

// Verification (GET) — Meta verifies endpoint
app.get('/webhook/whatsapp', (req, res) => {
  const mode = req.query['hub.mode'];
  const token = req.query['hub.verify_token'];
  const challenge = req.query['hub.challenge'];
  if (mode === 'subscribe' && token === process.env.WA_VERIFY_TOKEN) {
    return res.send(challenge);
  }
  res.sendStatus(403);
});

// Event receiver (POST)
app.post('/webhook/whatsapp', express.json(), async (req, res) => {
  const entry = req.body.entry?.[0];
  const changes = entry?.changes?.[0];
  const value = changes?.value;

  // Incoming message
  if (value?.messages) {
    for (const msg of value.messages) {
      const from = msg.from;
      const text = msg.text?.body;
      console.log(`${from}: ${text}`);
      // Process — maybe auto-reply, create ticket, etc.
      await handleIncomingMessage(from, text);
    }
  }

  // Delivery/read receipts
  if (value?.statuses) {
    for (const s of value.statuses) {
      await updateDeliveryStatus(s.id, s.status);
    }
  }

  res.sendStatus(200);
});

{
  "type": "interactive",
  "interactive": {
    "type": "button",
    "body": { "text": "Did your package arrive?" },
    "action": {
      "buttons": [
        { "type": "reply", "reply": { "id": "yes", "title": "Yes" } },
        { "type": "reply", "reply": { "id": "no", "title": "No, issues" } }
      ]
    }
  }
}

{
  "type": "interactive",
  "interactive": {
    "type": "product_list",
    "header": { "type": "text", "text": "Today's Deals" },
    "action": {
      "catalog_id": "YOUR_CATALOG_ID",
      "sections": [...]
    }
  }
}

Your verification code is {{1}}. It expires in 10 minutes. Do not share this code.

const otp = generate6DigitOTP();
await redis.setex(`otp:${phone}`, 600, otp);

await sendWhatsApp(phone, 'otp_login', [
  { type: 'body', parameters: [{ type: 'text', text: otp }] },
]);