feat: improve compare API route with searching stage and validation

src/app/api/compare/route.ts

@@ -18,6 +18,10 @@ function slugify(text: string): string {
     .slice(0, 200);
 }
 
+// TODO: Implement rate limiting per IP/user
+// Example: Use Upstash Ratelimit or a simple in-memory counter
+// const ratelimit = new Ratelimit({ redis, limiter: slidingWindow(5, "1m") })
+
 export async function POST(request: Request) {
   const body: { query?: string; items?: string[]; dimensions?: string[] } =
     await request.json();
@@ -25,7 +29,21 @@ export async function POST(request: Request) {
 
   if (!items || items.length < 2) {
     return Response.json(
-      { error: "At least 2 items are required" },
+      { error: "At least 2 items are required for comparison" },
+      { status: 400 }
+    );
+  }
+
+  if (items.length > 10) {
+    return Response.json(
+      { error: "Maximum 10 items allowed per comparison" },
+      { status: 400 }
+    );
+  }
+
+  if (items.some((item) => item.trim().length === 0)) {
+    return Response.json(
+      { error: "Item names cannot be empty" },
       { status: 400 }
     );
   }
@@ -70,6 +88,20 @@ export async function POST(request: Request) {
             );
           }
 
+          if (progress.stage === "searching") {
+            controller.enqueue(
+              encoder.encode(
+                serializeSSE("progress", {
+                  status: "researching",
+                  message: `Searching the web for ${progress.item}... (${progress.results} results found)`,
+                  itemsCompleted,
+                  totalItems: items.length,
+                  currentStep: `Searching ${progress.item}`,
+                })
+              )
+            );
+          }
+
           if (progress.stage === "researching") {
             itemsCompleted++;
             controller.enqueue(
@@ -102,7 +134,17 @@ export async function POST(request: Request) {
           if (progress.stage === "complete") {
             const result = progress.result;
 
-            const comparisonData: Omit<ComparisonData, "id" | "userId" | "slug" | "tags" | "isPublic" | "viewCount" | "createdAt" | "updatedAt"> = {
+            const comparisonData: Omit<
+              ComparisonData,
+              | "id"
+              | "userId"
+              | "slug"
+              | "tags"
+              | "isPublic"
+              | "viewCount"
+              | "createdAt"
+              | "updatedAt"
+            > = {
               title,
               query: query || "",
               status: "completed",
@@ -177,7 +219,7 @@ export async function POST(request: Request) {
               encoder.encode(
                 serializeSSE("progress", {
                   status: "failed",
-                  message: progress.error,
+                  message: `Comparison failed: ${progress.error}`,
                   itemsCompleted,
                   totalItems: items.length,
                   currentStep: "Failed",
@@ -192,11 +234,16 @@ export async function POST(request: Request) {
           .set({ status: "failed", updatedAt: new Date() })
           .where(eq(comparisons.id, id));
 
+        const message =
+          error instanceof Error
+            ? error.message
+            : "An unexpected error occurred during research";
+
         controller.enqueue(
           encoder.encode(
             serializeSSE("progress", {
               status: "failed",
-              message: error instanceof Error ? error.message : "Unknown error",
+              message: `Comparison failed: ${message}`,
               itemsCompleted,
               totalItems: items.length,
               currentStep: "Failed",