refactor(shared): extract shared cache factory to deduplicate cache patterns

src/shared/json-file-cache-store.ts

@@ -0,0 +1,98 @@
+import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs"
+import { join } from "node:path"
+
+import { log } from "./logger"
+
+type JsonFileCacheStoreOptions<TValue> = {
+	getCacheDir: () => string
+	filename: string
+	logPrefix: string
+	cacheLabel: string
+	describe: (value: TValue) => Record<string, unknown>
+	serialize?: (value: TValue) => string
+}
+
+type JsonFileCacheStore<TValue> = {
+	read: () => TValue | null
+	has: () => boolean
+	write: (value: TValue) => void
+	resetMemory: () => void
+}
+
+function toLogLabel(cacheLabel: string): string {
+	return cacheLabel.toLowerCase()
+}
+
+export function createJsonFileCacheStore<TValue>(
+	options: JsonFileCacheStoreOptions<TValue>,
+): JsonFileCacheStore<TValue> {
+	let memoryValue: TValue | null | undefined
+
+	function getCacheFilePath(): string {
+		return join(options.getCacheDir(), options.filename)
+	}
+
+	function ensureCacheDir(): void {
+		const cacheDir = options.getCacheDir()
+		if (!existsSync(cacheDir)) {
+			mkdirSync(cacheDir, { recursive: true })
+		}
+	}
+
+	function read(): TValue | null {
+		if (memoryValue !== undefined) {
+			return memoryValue
+		}
+
+		const cacheFile = getCacheFilePath()
+		if (!existsSync(cacheFile)) {
+			memoryValue = null
+			log(`[${options.logPrefix}] ${options.cacheLabel} file not found`, { cacheFile })
+			return null
+		}
+
+		try {
+			const content = readFileSync(cacheFile, "utf-8")
+			const value = JSON.parse(content) as TValue
+			memoryValue = value
+			log(`[${options.logPrefix}] Read ${toLogLabel(options.cacheLabel)}`, options.describe(value))
+			return value
+		} catch (error) {
+			memoryValue = null
+			log(`[${options.logPrefix}] Error reading ${toLogLabel(options.cacheLabel)}`, {
+				error: String(error),
+			})
+			return null
+		}
+	}
+
+	function has(): boolean {
+		return existsSync(getCacheFilePath())
+	}
+
+	function write(value: TValue): void {
+		ensureCacheDir()
+		const cacheFile = getCacheFilePath()
+
+		try {
+			writeFileSync(cacheFile, options.serialize?.(value) ?? JSON.stringify(value, null, 2))
+			memoryValue = value
+			log(`[${options.logPrefix}] ${options.cacheLabel} written`, options.describe(value))
+		} catch (error) {
+			log(`[${options.logPrefix}] Error writing ${toLogLabel(options.cacheLabel)}`, {
+				error: String(error),
+			})
+		}
+	}
+
+	function resetMemory(): void {
+		memoryValue = undefined
+	}
+
+	return {
+		read,
+		has,
+		write,
+		resetMemory,
+	}
+}