<?php
/**
 * WhatsApp Business API (Cloud API) — PHP Starter Script
 * Source: https://michaelclaudiu.com/resources/whatsapp-business-api-php-integration
 *
 * Combines a template-message sender and a basic webhook receiver in one file.
 * Replace the placeholder values below with your own Meta credentials before use.
 */

// ---------------------------------------------------------------------------
// 1) SEND A TEMPLATE MESSAGE
// ---------------------------------------------------------------------------
function sendWhatsAppTemplateMessage(string $token, string $phoneNumberId, string $recipient, string $templateName, string $languageCode = 'en_US'): string
{
    $url = "https://graph.facebook.com/v17.0/$phoneNumberId/messages";

    $data = [
        'messaging_product' => 'whatsapp',
        'to' => $recipient, // E.164 format without the leading +
        'type' => 'template',
        'template' => [
            'name' => $templateName,
            'language' => ['code' => $languageCode],
        ],
    ];

    $ch = curl_init($url);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
    curl_setopt($ch, CURLOPT_POST, true);
    curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($data));
    curl_setopt($ch, CURLOPT_HTTPHEADER, [
        'Authorization: Bearer ' . $token,
        'Content-Type: application/json',
    ]);

    $response = curl_exec($ch);
    curl_close($ch);

    return $response;
}

// Example usage (uncomment and fill in your credentials):
// echo sendWhatsAppTemplateMessage('YOUR_ACCESS_TOKEN', 'YOUR_PHONE_NUMBER_ID', '1234567890', 'hello_world');

// ---------------------------------------------------------------------------
// 2) WEBHOOK RECEIVER (handles verification + incoming messages)
// ---------------------------------------------------------------------------
// Point your Meta App's webhook URL at this script (or a route that calls
// handleWhatsAppWebhook()) to receive messages and verification challenges.

function handleWhatsAppWebhook(string $verifyToken): void
{
    // Webhook verification (GET request from Meta)
    if ($_SERVER['REQUEST_METHOD'] === 'GET' && isset($_GET['hub_mode']) && $_GET['hub_mode'] === 'subscribe') {
        if ($_GET['hub_verify_token'] === $verifyToken) {
            echo $_GET['hub_challenge'];
            http_response_code(200);
            exit;
        }

        http_response_code(403);
        exit;
    }

    // Incoming message (POST request)
    $input = file_get_contents('php://input');
    $data = json_decode($input, true);

    if (isset($data['entry'][0]['changes'][0]['value']['messages'])) {
        $message = $data['entry'][0]['changes'][0]['value']['messages'][0];
        $from = $message['from'];
        $text = $message['text']['body'] ?? '';

        // Replace with your own storage/processing logic (database, queue, CRM, etc.)
        file_put_contents('whatsapp_log.txt', "Received from $from: $text\n", FILE_APPEND);
    }

    http_response_code(200);
}

// Uncomment to activate this script as your webhook endpoint:
// handleWhatsAppWebhook('YOUR_VERIFY_TOKEN');