add mapper. add v2 handler. add tag description short and full versions. delete topic[1-5].

app/src/mapping.ts

@@ -0,0 +1,110 @@
+import { readFileSync } from 'node:fs'
+import { isAbsolute, resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+export type MappedMetric = {
+  edge: string
+  timestamp: number
+  tag: string
+  value: number
+}
+
+type MappingTagEntry = string | { tag: string } | { key: string }
+
+type MappingConfig = {
+  edge: string
+  tags: MappingTagEntry[]
+}
+
+export type MetricMapper = {
+  edge: string
+  tagCount: number
+  mapValues: (values: number[], timestamp: number) => MappedMetric[]
+}
+
+type MetricMapperOptions = {
+  filePath: string | URL
+}
+
+function resolveMappingPath(filePath: string | URL): string {
+  if (filePath instanceof URL) {
+    return fileURLToPath(filePath)
+  }
+
+  return isAbsolute(filePath) ? filePath : resolve(process.cwd(), filePath)
+}
+
+function readMappingConfig(filePath: string | URL): MappingConfig {
+  const resolvedPath = resolveMappingPath(filePath)
+  let raw: unknown
+
+  try {
+    raw = JSON.parse(readFileSync(resolvedPath, 'utf8')) as unknown
+  } catch (err) {
+    throw new Error(`Failed to read mapping file ${resolvedPath}: ${String(err)}`)
+  }
+
+  if (!isMappingConfig(raw)) {
+    throw new Error(`Invalid mapping file ${resolvedPath}`)
+  }
+
+  return raw
+}
+
+function isMappingConfig(value: unknown): value is MappingConfig {
+  if (!value || typeof value !== 'object') {
+    return false
+  }
+
+  const candidate = value as Partial<MappingConfig>
+
+  return (
+    typeof candidate.edge === 'string' &&
+    candidate.edge.length > 0 &&
+    Array.isArray(candidate.tags) &&
+    candidate.tags.length > 0 &&
+    candidate.tags.every(isMappingTagEntry)
+  )
+}
+
+function isMappingTagEntry(value: unknown): value is MappingTagEntry {
+  return (
+    (typeof value === 'string' && value.length > 0) ||
+    (Boolean(value) &&
+      typeof value === 'object' &&
+      ((typeof (value as { tag?: unknown }).tag === 'string' &&
+        (value as { tag: string }).tag.length > 0) ||
+        (typeof (value as { key?: unknown }).key === 'string' &&
+          (value as { key: string }).key.length > 0)))
+  )
+}
+
+function getTag(entry: MappingTagEntry): string {
+  if (typeof entry === 'string') {
+    return entry
+  }
+
+  return 'tag' in entry ? entry.tag : entry.key
+}
+
+export function createMetricMapper(options: MetricMapperOptions): MetricMapper {
+  const config = readMappingConfig(options.filePath)
+  const tags = config.tags.map(getTag)
+
+  return {
+    edge: config.edge,
+    tagCount: tags.length,
+    mapValues: (values, timestamp) => {
+      if (values.length !== tags.length) {
+        throw new Error(`Expected ${tags.length} values, got ${values.length}`)
+      }
+
+      return values.map((value, index) => ({
+        edge: config.edge,
+        timestamp,
+        tag: tags[index],
+        value,
+      }))
+    },
+  }
+}