more functional design principles

test/helpers/fakeAtakClient.js

@@ -1,3 +1,18 @@
+/**
+ * Encode a number as varint bytes (little-endian, continuation bit).
+ * @param {number} value - Value to encode
+ * @param {number[]} bytes - Accumulated bytes (default empty)
+ * @returns {number[]} Varint bytes
+ */
+const encodeVarint = (value, bytes = []) => {
+  const byte = value & 0x7F
+  const remaining = value >>> 7
+  if (remaining === 0) {
+    return [...bytes, byte]
+  }
+  return encodeVarint(remaining, [...bytes, byte | 0x80])
+}
+
 /**
  * Build a TAK Protocol stream frame: 0xBF, varint payload length, payload.
  * @param {string|Buffer} payload - UTF-8 payload (e.g. CoT XML)
@@ -5,17 +20,7 @@
  */
 export function buildTakFrame(payload) {
   const buf = Buffer.isBuffer(payload) ? payload : Buffer.from(payload, 'utf8')
-  let n = buf.length
-  const varint = []
-  while (true) {
-    const byte = n & 0x7F
-    n >>>= 7
-    if (n === 0) {
-      varint.push(byte)
-      break
-    }
-    varint.push(byte | 0x80)
-  }
+  const varint = encodeVarint(buf.length)
   return Buffer.concat([Buffer.from([0xBF]), Buffer.from(varint), buf])
 }