more functional design principles

server/utils/cotParser.js

@@ -15,21 +15,20 @@ const TRADITIONAL_DELIMITER = Buffer.from('</event>', 'utf8')
 /**
  * @param {Buffer} buf
  * @param {number} offset
+ * @param {number} value - Accumulated value
+ * @param {number} shift - Current bit shift
+ * @param {number} bytesRead - Bytes consumed so far
  * @returns {{ value: number, bytesRead: number }} Decoded varint and bytes consumed.
  */
-function readVarint(buf, offset) {
-  let value = 0
-  let shift = 0
-  let bytesRead = 0
-  while (offset + bytesRead < buf.length) {
-    const b = buf[offset + bytesRead]
-    bytesRead += 1
-    value += (b & 0x7F) << shift
-    if ((b & 0x80) === 0) return { value, bytesRead }
-    shift += 7
-    if (shift > 28) return { value: 0, bytesRead: 0 }
-  }
-  return { value, bytesRead }
+function readVarint(buf, offset, value = 0, shift = 0, bytesRead = 0) {
+  if (offset + bytesRead >= buf.length) return { value, bytesRead }
+  const b = buf[offset + bytesRead]
+  const newValue = value + ((b & 0x7F) << shift)
+  const newBytesRead = bytesRead + 1
+  if ((b & 0x80) === 0) return { value: newValue, bytesRead: newBytesRead }
+  const newShift = shift + 7
+  if (newShift > 28) return { value: 0, bytesRead: 0 }
+  return readVarint(buf, offset, newValue, newShift, newBytesRead)
 }
 
 /**
@@ -127,12 +126,14 @@ export function parseCotPayload(payload) {
     const uid = String(event['@_uid'] ?? event.uid ?? '')
     const eventType = String(event['@_type'] ?? event.type ?? '')
     const point = findInObject(parsed, 'point') ?? findInObject(event, 'point')
-    let lat = Number.NaN
-    let lng = Number.NaN
-    if (point && typeof point === 'object') {
-      lat = Number(point['@_lat'] ?? point.lat)
-      lng = Number(point['@_lon'] ?? point.lon ?? point['@_lng'] ?? point.lng)
+    const extractCoords = (pt) => {
+      if (!pt || typeof pt !== 'object') return { lat: Number.NaN, lng: Number.NaN }
+      return {
+        lat: Number(pt['@_lat'] ?? pt.lat),
+        lng: Number(pt['@_lon'] ?? pt.lon ?? pt['@_lng'] ?? pt.lng),
+      }
     }
+    const { lat, lng } = extractCoords(point)
     if (!Number.isFinite(lat) || !Number.isFinite(lng)) return null
 
     const detail = findInObject(parsed, 'detail')