mqtt-ingest draft

app/src/helpers/parse.ts

@@ -0,0 +1,20 @@
+export function parseUtf8(payload: Buffer): string {
+  return payload.toString('utf8')
+}
+
+export function parseJson<T = unknown>(payload: Buffer): T {
+  const text = parseUtf8(payload)
+  return JSON.parse(text) as T
+}
+
+export function parseJsonArray(payload: Buffer): unknown[] {
+  const value = parseJson(payload)
+  if (!Array.isArray(value)) {
+    throw new Error('Expected JSON array')
+  }
+  return value
+}
+
+export function decodeBase64(payload: Buffer): Buffer {
+  return Buffer.from(payload.toString('utf8'), 'base64')
+}

app/src/helpers/validate.ts

@@ -0,0 +1,39 @@
+const EXPECTED_CHUNK_LENGTH = 125
+
+export function isNonEmptyString(value: unknown): value is string {
+  return typeof value === 'string' && value.length > 0
+}
+
+export function isFiniteNumber(value: unknown): value is number {
+  return typeof value === 'number' && Number.isFinite(value)
+}
+
+export function isArrayOfLength(
+  value: unknown,
+  length: number,
+): value is unknown[] {
+  return Array.isArray(value) && value.length === length
+}
+
+export function isArrayOfLength125(value: unknown): value is unknown[] {
+  return isArrayOfLength(value, EXPECTED_CHUNK_LENGTH)
+}
+
+export function isArrayOfChunks125(
+  value: unknown,
+): value is unknown[][] {
+  if (!Array.isArray(value)) {
+    return false
+  }
+  return value.every((chunk) => isArrayOfLength125(chunk))
+}
+
+export function assertValid<T>(
+  value: unknown,
+  guard: (v: unknown) => v is T,
+  label: string,
+): asserts value is T {
+  if (!guard(value)) {
+    throw new Error(`Invalid payload: ${label}`)
+  }
+}