phase-8f: persistant cache locally

server/services/BenchmarkProvider.ts

@@ -1,9 +1,16 @@
+import { readFileSync, writeFileSync, existsSync } from 'fs';
 import { YahooFinanceClient } from '../clients/YahooFinanceClient';
 import { REGIME } from '../config/constants';
 import type { MarketContext, Logger, BenchmarkProviderOptions } from '../types';
 
+interface CacheFile {
+  data: MarketContext;
+  expiresAt: number;
+}
+
 export class BenchmarkProvider {
   private static readonly TTL_MS = 60 * 60 * 1000;
+  private static readonly CACHE_PATH = '.benchmark-cache.json';
 
   private static readonly DEFAULTS: MarketContext = {
     sp500Price: 5000,
@@ -32,10 +39,33 @@ export class BenchmarkProvider {
     private readonly client: YahooFinanceClient,
     { logger }: BenchmarkProviderOptions = {},
   ) {
-    this.cache = { data: null, expiresAt: 0 };
+    this.cache = this.loadDiskCache();
     this.logger = logger ?? (console as unknown as Logger);
   }
 
+  private loadDiskCache(): { data: MarketContext | null; expiresAt: number } {
+    try {
+      if (!existsSync(BenchmarkProvider.CACHE_PATH)) return { data: null, expiresAt: 0 };
+      const file = JSON.parse(readFileSync(BenchmarkProvider.CACHE_PATH, 'utf8')) as CacheFile;
+      if (Date.now() < file.expiresAt) return { data: file.data, expiresAt: file.expiresAt };
+    } catch {
+      // corrupt or missing — ignore
+    }
+    return { data: null, expiresAt: 0 };
+  }
+
+  private saveDiskCache(data: MarketContext, expiresAt: number): void {
+    try {
+      writeFileSync(
+        BenchmarkProvider.CACHE_PATH,
+        JSON.stringify({ data, expiresAt } satisfies CacheFile, null, 2),
+        'utf8',
+      );
+    } catch {
+      // non-fatal — in-memory cache still works
+    }
+  }
+
   async getMarketContext(): Promise<MarketContext> {
     if (this.cache.data && Date.now() < this.cache.expiresAt) return this.cache.data;
 
@@ -75,7 +105,9 @@ export class BenchmarkProvider {
         },
       };
 
-      this.cache = { data: context, expiresAt: Date.now() + BenchmarkProvider.TTL_MS };
+      const expiresAt = Date.now() + BenchmarkProvider.TTL_MS;
+      this.cache = { data: context, expiresAt };
+      this.saveDiskCache(context, expiresAt);
       return context;
     } catch (err) {
       this.logger.warn('Market data fetch failed, using defaults:', (err as Error).message);