Test setup for Paddle currency detection

site/config/config.getkirby.com.php

@@ -5,5 +5,6 @@
 	'cdn' => [
 		'domain' => 'https://assets.getkirby.com',
 	],
+	'cloudflare' => true,
 	'debug' => false
 ];

site/config/routes.php

@@ -59,6 +59,25 @@
 			]);
 		}
 	],
+	[
+		// TODO: Temporary test, remove this route again
+		'pattern' => 'buy/currency-test',
+		'action'  => function () {
+			$visitor = \Buy\Paddle::visitor();
+			$rates = Data::read(dirname(__DIR__) . '/plugins/buy/rates.json');
+
+			$body = 'Detected IP:       ' . (\Buy\Visitor::ip() ?? 'N/A') . "\n" .
+				'Detected country:  ' . ($visitor->country() ?? 'N/A') . "\n" .
+				'Detected currency: ' . $visitor->currency() . "\n" .
+				'Detected rate:     ' . $visitor->conversionRate() . ' (hardcoded for this currency: ' . $rates[$visitor->currency()] . ")\n" .
+				'Status:            ' . ($visitor->error() ?? 'OK') . "\n\n" .
+				'Example price:     ' . $visitor->currencySign() . "123\n" .
+				'Revenue limit:     ' . $visitor->revenueLimit(1000000);
+
+
+			return new \Kirby\Http\Response($body, 'text/plain');
+		}
+	],
 	[
 		'pattern' => 'buy/(:any)/(:any?)',
 		'action' => function (string $product, string $currency = 'EUR') {

site/plugins/buy/Paddle.php

@@ -0,0 +1,124 @@
+<?php
+
+namespace Buy;
+
+use Exception;
+use Kirby\Http\Remote;
+use Throwable;
+
+class Paddle
+{
+	// cache
+	protected static Visitor $visitor;
+
+	/**
+	 * Generates a custom checkout link and returns the checkout URL
+	 *
+	 * @throws \Exception On request errors or Paddle API errors
+	 */
+	public static function checkout(string $product, array $payload = []): string
+	{
+		$data = [
+			'vendor_id'         => option('keys.paddle.id'),
+			'vendor_auth_code'  => option('keys.paddle.auth'),
+			'product_id'        => $product,
+			'expires'           => date('Y-m-d', strtotime('+1 day')),
+			'quantity_variable' => false,
+			'quantity'          => 1,
+			...$payload
+		];
+
+		$response = static::request('POST', 'vendors', 'product/generate_pay_link', compact('data'));
+		return $response['url'];
+	}
+
+	/**
+	 * Performs a request to the Paddle API
+	 *
+	 * @param 'GET'|'POST' $method HTTP method
+	 *
+	 * @throws \Exception On request errors or Paddle API errors
+	 */
+	public static function request(string $method, string $subdomain, string $endpoint, array $options = []): array
+	{
+		// GET requests need the data as query params
+		$method = strtoupper($method);
+		$query  = '';
+		if ($method === 'GET' && isset($options['data']) === true) {
+			$query = '?' . http_build_query($options['data']);
+		}
+
+		$response = new Remote(
+			'https://' . $subdomain . '.paddle.com/api/2.0/' . $endpoint . $query,
+			[
+				'method' => $method,
+				...$options
+			]
+		);
+
+		$data = $response->json();
+
+		if (isset($data['success']) === true && $data['success'] === true) {
+			return $data['response'];
+		}
+
+		throw new Exception($data['error']['message'] ?? 'Unknown error');
+	}
+
+	/**
+	 * Determines the country, currency and conversion rate information
+	 * for the visitor via the Paddle price API
+	 *
+	 * @param string|null $country Override for a country code (used for testing)
+	 */
+	public static function visitor(string|null $country = null): Visitor
+	{
+		// cache for the entire request as the IP won't change
+		if (isset(static::$visitor) === true) {
+			return static::$visitor;
+		}
+
+		try {
+			$product = Product::Basic;
+
+			$options = [
+				'data' => [
+					'product_ids' => $product->productId()
+				],
+
+				// fast timeout to avoid letting the user wait too long
+				'timeout' => 1
+			];
+
+			if ($country !== null) {
+				$options['data']['customer_country'] = $country;
+			} else {
+				$ip = Visitor::ip();
+
+				// if we only have a local IP, don't bother
+				// requesting dynamic information from Paddle
+				if ($ip === null) {
+					return static::$visitor = Visitor::createFromError('No visitor IP available');
+				}
+
+				$options['data']['customer_ip'] = $ip;
+			}
+
+			$response      = static::request('GET', 'checkout', 'prices', $options);
+			$paddleProduct = $response['products'][0];
+
+			return static::$visitor = Visitor::create(
+				country: $response['customer_country'],
+				currency: $paddleProduct['currency'],
+
+				// calculate conversion rate from the EUR price;
+				// requires that the EUR price matches between the site and Paddle admin
+				conversionRate: $paddleProduct['list_price']['net'] / $product->rawPrice()
+			);
+		} catch (Throwable $e) {
+			// on any kind of error, use the EUR prices as a fallback
+			// to avoid a broken buy page
+			return static::$visitor = Visitor::createFromError($e->getMessage());
+		}
+	}
+}

site/plugins/buy/Visitor.php

@@ -0,0 +1,200 @@
+<?php
+
+namespace Buy;
+
+use Exception;
+use Kirby\Cms\App;
+use Kirby\Toolkit\Str;
+
+class Visitor
+{
+	/**
+	 * Supported currencies with their currency sign (prefixed to the amount);
+	 * currencies not listed here will automatically fall back to EUR
+	 */
+	const CURRENCIES = [
+		'ARS' => 'ARS ',
+		'AUD' => 'A$',
+		'BRL' => 'R$',
+		'CAD' => 'CA$',
+		'CHF' => 'CHF ',
+		'CNY' => 'CN¥',
+		'COP' => 'COP ',
+		'CZK' => 'CZK ',
+		'DKK' => 'DKK ',
+		'EUR' => '€',
+		'GBP' => '£',
+		'HKD' => 'HK$',
+		'HUF' => 'HUF ',
+		'ILS' => '₪',
+		'INR' => '₹',
+		'JPY' => '¥',
+		'KRW' => '₩',
+		'MXN' => 'MX$',
+		'NOK' => 'NOK ',
+		'NZD' => 'NZ$',
+		'PLN' => 'PLN ',
+		'SEK' => 'SEK ',
+		'SGD' => 'SGD ',
+		'THB' => 'THB ',
+		'TRY' => 'TRY ',
+		'TWD' => 'NT$',
+		'UAH' => 'UAH ',
+		'USD' => '$',
+		'ZAR' => 'ZAR ',
+	];
+
+	protected function __construct(
+		protected string $currency,
+		protected float $conversionRate,
+		protected string|null $country = null,
+		protected string|null $error = null
+	) {
+	}
+
+	/**
+	 * Creates a new instance (with validation)
+	 *
+	 * @param string $currency Currency code
+	 * @param float $conversionRate Currency conversion rate from EUR
+	 * @param string|null $country Two-character ISO country code if available
+	 * @param string|null $error Error message if an error occurred during currency detection
+	 */
+	public static function create(
+		string $currency,
+		float $conversionRate,
+		string|null $country = null,
+		string|null $error = null
+	): static {
+		// fall back to EUR if the user currency is not supported
+		if (isset(static::CURRENCIES[$currency]) !== true) {
+			$error          = 'Invalid currency "' . $currency . '"';
+			$currency       = 'EUR';
+			$conversionRate = 1.0;
+		}
+
+		// the conversion rate of EUR always needs to be 1
+		if ($currency === 'EUR' && $conversionRate !== 1.0) {
+			$conversionRate = 1.0;
+			$error          = 'Invalid conversion rate "' . $conversionRate . '" for currency EUR';
+		}
+
+		return new static($currency, $conversionRate, $country, $error);
+	}
+
+	/**
+	 * Creates a fallback EUR instance if an error occurred
+	 * during currency detection
+	 */
+	public static function createFromError(string $error): static
+	{
+		return static::create(
+			currency: 'EUR',
+			conversionRate: 1.0,
+			error: $error
+		);
+	}
+
+	/**
+	 * Returns the dynamic conversion rate from EUR based
+	 * on the chosen user currency
+	 */
+	public function conversionRate(): float
+	{
+		return $this->conversionRate;
+	}
+
+	/**
+	 * Returns the user's two-character ISO country code if available
+	 */
+	public function country(): string|null
+	{
+		return $this->country;
+	}
+
+	/**
+	 * Returns the currency code chosen for the user
+	 */
+	public function currency(): string
+	{
+		return $this->currency;
+	}
+
+	/**
+	 * Returns the currency sign prefix chosen for the user
+	 */
+	public function currencySign(): string
+	{
+		return static::CURRENCIES[$this->currency];
+	}
+
+	/**
+	 * If there was an error during currency detection,
+	 * it will be returned here
+	 */
+	public function error(): string|null
+	{
+		return $this->error;
+	}
+
+	/**
+	 * Determines the user IP address depending on the setup
+	 * @internal
+	 */
+	public static function ip(): string|null
+	{
+		$env = App::instance()->environment();
+
+		// if the site is served via Cloudflare, use the proxied IP header
+		if (option('cloudflare', false) === true) {
+			return $env->get('CF_CONNECTING_IP', '');
+		}
+
+		// otherwise use the direct IP header
+		$ip = $env->get('REMOTE_ADDR', '');
+
+		// ignore local IPs as we cannot determine the country from them
+		if (
+			Str::startsWith($ip, '0.') === true ||
+			Str::startsWith($ip, '10.') === true ||
+			Str::startsWith($ip, '127.') === true ||
+			Str::startsWith($ip, '192.') === true ||
+			Str::startsWith($ip, 'fe80::') === true ||
+			$ip === '::1'
+		) {
+			return null;
+		}
+
+		return $ip;
+	}
+
+	/**
+	 * Returns the formatted approximate revenue limit
+	 * in the user's currency
+	 *
+	 * @param int $revenueLimit Limit in EUR to convert
+	 */
+	public function revenueLimit(int $revenueLimit): string
+	{
+		$converted = $revenueLimit * $this->conversionRate;
+
+		// shorten to three digits with K/M/B suffix
+		$suffix = '';
+		if ($converted >= 1000000000) {
+			$converted /= 1000000000;
+			$suffix = 'B';
+		} elseif ($converted >= 1000000) {
+			$converted /= 1000000;
+			$suffix = 'M';
+		} elseif ($converted >= 1000) {
+			$converted /= 1000;
+			$suffix = 'K';
+		}
+
+		// use two significant digits because it's just an approximation
+		$digits    = strlen(round($converted));
+		$converted = round($converted, -$digits + 2);
+
+		return '~ ' . $this->currencySign() . $converted . $suffix;
+	}
+}

site/plugins/buy/index.php

@@ -3,10 +3,12 @@
 use Kirby\Cms\App;
 
 load([
+	'Buy\Paddle'  => __DIR__ . '/Paddle.php',
 	'Buy\Price'   => __DIR__ . '/Price.php',
 	'Buy\Product' => __DIR__ . '/Product.php',
 	'Buy\Sale'    => __DIR__ . '/Sale.php',
 	'Buy\Upgrade' => __DIR__ . '/Upgrade.php',
+	'Buy\Visitor' => __DIR__ . '/Visitor.php',
 ]);
 
 App::plugin('getkirby/buy', []);