Defines PayPal util logic

1 files changed, 114 insertions, 0 deletions

diff --git a/api/_paypal.ts b/api/_paypal.ts
new file mode 100644
index 0000000..348c972
--- /dev/null
+++ b/api/_paypal.ts
@@ -0,0 +1,114 @@
+import type Order from './Order';
+import env from './_env';
+
+export async function paypalCreateOrder(order: Order) {
+  const accessToken = await getLazyAccessToken();
+  const url = `${PAYPAL_URL}/v2/checkout/orders`;
+  const response = await fetch(url, {
+    method: 'POST',
+    headers: paypalCreateOrderRequestHeaders(accessToken),
+    body: paypalCreateOrderRequestBody(order),
+  });
+  return await handle(response);
+}
+
+export async function paypalCaptureOrder(orderId: string) {
+  const accessToken = await getLazyAccessToken();
+  const url = `${PAYPAL_URL}/v2/checkout/orders/${orderId}/capture`;
+  const response = await fetch(url, {
+    method: 'POST',
+    headers: paypalCaptureOrderRequestHeaders(accessToken),
+  });
+  return await handle(response);
+}
+
+async function handle(response: Response) {
+  if (response.ok) {
+    return await response.json();
+  }
+  throw new Error('Failed to communicate with PayPal. ' + await response.text());
+}
+
+function paypalCreateOrderRequestBody(order: Order) {
+  const body = JSON.stringify({
+    intent: 'CAPTURE',
+    purchase_units: [
+      {
+        description: order.productDescription,
+        soft_descriptor: order.shortDescription,
+        amount: {
+          currency_code: 'GBP',
+          value: order.totalPrice.toFixed(2),
+        },
+      },
+    ],
+  });
+  return body;
+}
+
+function paypalCreateOrderRequestHeaders(accessToken: string) {
+  return {
+    'Content-Type': 'application/json',
+    Authorization: `Bearer ${accessToken}`,
+  };
+}
+
+function paypalCaptureOrderRequestHeaders(accessToken: string) {
+  return {
+    Authorization: `Bearer ${accessToken}`,
+  };
+}
+
+const getLazyAccessToken = (() => {
+  let accessToken: string;
+  let timeRequested: number;
+  let timeExpires: number;
+  return async function (): Promise<string> {
+    const isNearlyExpired = timeExpires - Date.now() < 10_000;
+    if (!accessToken || isNearlyExpired) {
+      timeRequested = Date.now();
+      let secondsUntilExpires: number;
+      ({ accessToken, secondsUntilExpires } = await generateAccessToken());
+      const msUntilExpires = secondsUntilExpires * 1000;
+      timeExpires = timeRequested + msUntilExpires;
+    }
+    return accessToken;
+  };
+})();
+
+async function generateAccessToken(): Promise<AccessTokenResponse> {
+  const auth = Buffer.from(PAYPAL_CLIENT_ID + ':' + PAYPAL_SECRET).toString('base64');
+  const response = await fetch(`${PAYPAL_URL}/v1/oauth2/token`, {
+    method: 'POST',
+    body: 'grant_type=client_credentials',
+    headers: {
+      Authorization: `Basic ${auth}`,
+    },
+  });
+  const { access_token, expires_in } = await response.json();
+  if (access_token && expires_in) {
+    return {
+      accessToken: access_token,
+      secondsUntilExpires: expires_in,
+    };
+  }
+  throw new Error('Could not fetch access token from PayPal.');
+}
+
+type AccessTokenResponse = {
+  accessToken: string;
+  secondsUntilExpires: number;
+};
+
+const PAYPAL_CLIENT_ID =
+    env.ENVIRONMENT === 'prod'
+    ? env.PAYPAL_LIVE_CLIENT_ID
+    : env.PAYPAL_SANDBOX_CLIENT_ID;
+const PAYPAL_SECRET =
+    env.ENVIRONMENT === 'prod'
+    ? env.PAYPAL_LIVE_SECRET
+    : env.PAYPAL_SANDBOX_SECRET;
+const PAYPAL_URL =
+    env.ENVIRONMENT === 'prod'
+    ? 'https://api-m.paypal.com'
+    : 'https://api-m.sandbox.paypal.com'
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