feat: display friendly error messages on API failure

closes #34

Add user-friendly error messages when GitHub API calls fail:
- ErrorMessage component with error type detection (rate limit/not found/network)
- Retry button for transient errors
- Replaces generic red error box with proper Alert component

Signed-off-by: Ai-chan-0411 <ai-chan-0411@users.noreply.github.com>

Author: Ai-chan-0411

app/api/compare/route.ts

@@ -36,10 +36,15 @@ export async function GET(request: Request) {
     return NextResponse.json({ success: true, users: results });
   } catch (error: any) {
     console.error("GitHub score error:", error);
-    const message =
-      error?.message === "User not found"
-        ? "GitHub user not found"
-        : "Failed to calculate score";
+    let message = "Failed to calculate score";
+    if (error?.message === "User not found") {
+      message = "User not found";
+    } else if (
+      error?.message?.toLowerCase().includes("rate limit") ||
+      error?.status === 403
+    ) {
+      message = "GitHub API rate limit exceeded. Please try again later.";
+    }
     return NextResponse.json(
       { success: false, error: message },
       { status: 500 }

app/page.tsx

@@ -2,6 +2,7 @@
 
 import { useMemo, useState } from "react";
 import { CompareForm } from "../components/compare-form";
+import { ErrorMessage } from "../components/error-message";
 import { ResultDashboard } from "../components/result-dashboard";
 import { DashboardSkeleton } from "../components/skeletons";
 import { UserResult } from "@/types/user-result";
@@ -65,7 +66,7 @@ export default function HomePage() {
     console.log("Swapped users", data);
   };
   return (
-    <main className="min-h-screen">
+    <main className="min-h-screen flex flex-col">
       {" "}
       <header className="sticky top-0 z-50 w-full border-b bg-background/95 backdrop-blur supports-[backdrop-filter]:bg-background/60">
         <div className="container flex h-16 max-w-7xl items-center justify-between m-auto px-4">
@@ -74,10 +75,10 @@ export default function HomePage() {
               DevImpact
             </span>
           </div>
-       
+
         </div>
       </header>
-      <div className="max-w-6xl mx-auto px-4 py-10 space-y-6">
+      <div className="flex-1 max-w-6xl mx-auto px-4 py-10 space-y-6 w-full">
         <CompareForm
           onSubmit={handleCompare}
           loading={loading}
@@ -88,9 +89,7 @@ export default function HomePage() {
 
         {loading && skeleton}
         {error && (
-          <div className="card p-4 text-sm text-red-600 bg-red-50 border border-red-100">
-            {error}
-          </div>
+          <ErrorMessage error={error} onRetry={() => setError(null)} />
         )}
         {data && <ResultDashboard user1={data.user1} user2={data.user2} />}
         {!loading && !error && !data && (

components/error-message.tsx

@@ -0,0 +1,61 @@
+import { AlertCircle } from "lucide-react";
+import { Alert, AlertDescription, AlertTitle } from "./ui/alert";
+
+type ErrorMessageProps = {
+  error: string;
+  onRetry?: () => void;
+};
+
+function getErrorDetails(error: string): {
+  title: string;
+  description: string;
+} {
+  const lower = error.toLowerCase();
+  if (lower.includes("not found") || lower.includes("user not found")) {
+    return {
+      title: "User not found",
+      description:
+        "The GitHub username you entered does not exist. Please check the spelling and try again.",
+    };
+  }
+  if (lower.includes("rate limit") || lower.includes("rate_limit")) {
+    return {
+      title: "Rate limit exceeded",
+      description:
+        "GitHub API rate limit has been reached. Please wait a few minutes and try again.",
+    };
+  }
+  if (lower.includes("network") || lower.includes("failed to fetch")) {
+    return {
+      title: "Network error",
+      description:
+        "Could not connect to the server. Check your internet connection and try again.",
+    };
+  }
+  return {
+    title: "Something went wrong",
+    description: error || "An unexpected error occurred. Please try again.",
+  };
+}
+
+export function ErrorMessage({ error, onRetry }: ErrorMessageProps) {
+  const { title, description } = getErrorDetails(error);
+
+  return (
+    <Alert variant="destructive">
+      <AlertCircle className="h-4 w-4" />
+      <AlertTitle>{title}</AlertTitle>
+      <AlertDescription>
+        <p>{description}</p>
+        {onRetry && (
+          <button
+            onClick={onRetry}
+            className="mt-2 text-sm underline underline-offset-2 hover:no-underline"
+          >
+            Try again
+          </button>
+        )}
+      </AlertDescription>
+    </Alert>
+  );
+}