feat(*): Add AI functionality to grading endpoint

src/routes/api/grade/+server.ts

@@ -1,25 +1,40 @@
 import type { RequestHandler } from '@sveltejs/kit';
 import type { RequestEvent } from '@sveltejs/kit';
+import { gradeWithOpenAI } from '$lib/utils/ai';
 
-// TODO - don't just mock the grading logic
 export const POST: RequestHandler = async (event: RequestEvent) => {
-  const data = await event.request.formData();
-  const file = data.get('file');
-  const text = data.get('text');
+  try {
+    const data = await event.request.formData();
+    const file = data.get('file');
+    const text = data.get('text');
+    let submission = '';
 
-  // Simulation of grading and feedback
-  let feedback = '';
-  if (file) {
-    feedback = 'Received file: ' + (file as File).name + '. [AI feedback coming soon]';
-  } else if (typeof text === 'string' && text.trim().length > 0) {
-    feedback = 'Received text submission. [AI feedback coming soon]';
-  } else {
-    return new Response(JSON.stringify({ error: 'No valid input provided.' }), { status: 400 });
+    if (file && typeof file === 'object' && 'arrayBuffer' in file && 'name' in file) {
+      // Only support .txt for now for hackathon speed
+      const fileObj = file as File;
+      if (!fileObj.name.endsWith('.txt')) {
+        return new Response(JSON.stringify({ error: 'Only .txt files are supported at this time.' }), { status: 400 });
+      }
+      const buffer = await fileObj.arrayBuffer();
+      submission = new TextDecoder('utf-8').decode(buffer);
+    } else if (typeof text === 'string' && text.trim().length > 0) {
+      submission = text.trim();
+    } else {
+      return new Response(JSON.stringify({ error: 'No valid input provided.' }), { status: 400 });
+    }
+
+    // Call the AI grading agent
+    const aiResult = await gradeWithOpenAI(submission);
+
+    return new Response(JSON.stringify({
+      success: true,
+      feedback: `Grade: ${aiResult.grade}\nStrengths: ${aiResult.strengths}\nWeaknesses: ${aiResult.weaknesses}\nIndividualized Activity: ${aiResult.individualized_activity}\nReasoning: ${aiResult.reasoning}`,
+      ...aiResult
+    }), {
+      status: 200,
+      headers: { 'Content-Type': 'application/json' }
+    });
+  } catch (err: any) {
+    return new Response(JSON.stringify({ error: err.message || 'Internal server error.' }), { status: 500 });
   }
-
-  // Return mock feedback for now
-  return new Response(JSON.stringify({ success: true, feedback }), {
-    status: 200,
-    headers: { 'Content-Type': 'application/json' }
-  });
 };