feat: add contact form with SMS OTP verification

server/utils/rate-limiter.js

@@ -0,0 +1,33 @@
+// A shared, in-memory store for tracking submission timestamps.
+const submissionTimestamps = new Map();
+
+// The rate-limiting period (1 week in milliseconds).
+const ONE_WEEK_IN_MS = 7 * 24 * 60 * 60 * 1000;
+
+/**
+ * Checks if a given phone number is currently rate-limited.
+ * A phone number is considered rate-limited if a successful submission
+ * was recorded within the last week.
+ *
+ * @param {string} phoneNumber The phone number to check.
+ * @returns {boolean} True if the number is rate-limited, false otherwise.
+ */
+export function isRateLimited(phoneNumber) {
+  const lastSubmissionTime = submissionTimestamps.get(phoneNumber);
+  if (!lastSubmissionTime) {
+    return false; // Not in the map, so not rate-limited.
+  }
+
+  // Check if the time elapsed since the last submission is less than one week.
+  return Date.now() - lastSubmissionTime < ONE_WEEK_IN_MS;
+}
+
+/**
+ * Records a successful submission for a given phone number by setting
+ * the current timestamp. This will start the 1-week rate-limiting period.
+ *
+ * @param {string} phoneNumber The phone number to record the submission for.
+ */
+export function recordSubmission(phoneNumber) {
+  submissionTimestamps.set(phoneNumber, Date.now());
+}