feat: add auth and cache to currency route

app/api/currency/route.ts

@@ -1,3 +1,5 @@
+import { getSession } from "@/lib/auth"
+import { PoorManCache } from "@/lib/cache"
 import { format } from "date-fns"
 import { NextRequest, NextResponse } from "next/server"
 
@@ -7,7 +9,23 @@ type HistoricRate = {
   inverse: number
 }
 
+const currencyCache = new PoorManCache<number>(24 * 60 * 60 * 1000) // 24 hours
+
+function generateCacheKey(fromCurrency: string, toCurrency: string, date: string): string {
+  return `${fromCurrency},${toCurrency},${date}`
+}
+
+const CLEANUP_INTERVAL = 90 * 60 * 1000
+if (typeof setInterval !== "undefined") {
+  setInterval(() => currencyCache.cleanup(), CLEANUP_INTERVAL)
+}
+
 export async function GET(request: NextRequest) {
+  const session = await getSession()
+  if (!session || !session.user) {
+    return NextResponse.json({ error: "Unauthorized" }, { status: 401 })
+  }
+
   try {
     const searchParams = request.nextUrl.searchParams
     const fromCurrency = searchParams.get("from")
@@ -24,6 +42,15 @@ export async function GET(request: NextRequest) {
     }
 
     const formattedDate = format(date, "yyyy-MM-dd")
+
+    // Check cache first
+    const cacheKey = generateCacheKey(fromCurrency, toCurrency, formattedDate)
+    const cachedRate = currencyCache.get(cacheKey)
+
+    if (cachedRate !== undefined) {
+      return NextResponse.json({ rate: cachedRate, cached: true })
+    }
+
     const url = `https://www.xe.com/currencytables/?from=${fromCurrency}&date=${formattedDate}`
 
     const response = await fetch(url)
@@ -58,7 +85,10 @@ export async function GET(request: NextRequest) {
       return NextResponse.json({ error: `Currency rate not found for ${toCurrency}` }, { status: 404 })
     }
 
-    return NextResponse.json({ rate: rate.rate })
+    // Store in cache
+    currencyCache.set(cacheKey, rate.rate)
+
+    return NextResponse.json({ rate: rate.rate, cached: false })
   } catch (error) {
     console.error("Currency API error:", error)
     return NextResponse.json({ error: "Internal server error" }, { status: 500 })