feat: implement /v1/translate and /v1/explain routes and preserve legacy / endpoint

backend/src/index.ts

@@ -4,51 +4,95 @@ export interface Env {
 	GEMINI_API_KEY: string;
 }
 
+const corsHeaders = {
+	'Access-Control-Allow-Origin': '*',
+	'Access-Control-Allow-Methods': 'POST, OPTIONS',
+	'Access-Control-Allow-Headers': 'Content-Type',
+};
+
+async function handleTranslate(request: Request, model: ReturnType<GoogleGenerativeAI['getGenerativeModel']>) {
+	const { code, targetLanguage } = await request.json<{ code: string; targetLanguage: string }>();
+
+	if (!code || !targetLanguage) {
+		return new Response(JSON.stringify({ error: "Missing 'code' or 'targetLanguage' in request body." }), {
+			status: 400,
+			headers: { ...corsHeaders, 'Content-Type': 'application/json' },
+		});
+	}
+
+	const prompt = `Translate the following code snippet to ${targetLanguage}.
+Do not add any explanation, commentary, or markdown formatting like \`\`\` around the code.
+**IMPORTANT: Preserve all original comments and their exact placement in the translated code. Do not add extra spaces in between.**
+Only provide the raw, translated code itself.
+
+Original Code:
+${code}`;
+
+	const result = await model.generateContent(prompt);
+	const translatedCode = result.response.text();
+
+	return new Response(JSON.stringify({ translation: translatedCode }), {
+		status: 200,
+		headers: { ...corsHeaders, 'Content-Type': 'application/json' },
+	});
+}
+
+async function handleExplain(request: Request, model: ReturnType<GoogleGenerativeAI['getGenerativeModel']>) {
+	const { code } = await request.json<{ code: string }>();
+
+	if (!code) {
+		return new Response(JSON.stringify({ error: "Missing 'code' in request body." }), {
+			status: 400,
+			headers: { ...corsHeaders, 'Content-Type': 'application/json' },
+		});
+	}
+
+	const prompt = `Explain the following code snippet in detail:
+1. Provide a clear breakdown of what each part (functions, variables, logic blocks) does.
+2. If applicable, describe the overall purpose or intent of the code.
+3. Offer a step-by-step explanation of how the code executes.
+4. If the code is executable, show a sample input and the corresponding output.
+5. Keep the explanation beginner-friendly but technically accurate.
+
+Code:
+${code}`;
+
+	const result = await model.generateContent(prompt);
+	const explanation = result.response.text();
+
+	return new Response(JSON.stringify({ explanation }), {
+		status: 200,
+		headers: { ...corsHeaders, 'Content-Type': 'application/json' },
+	});
+}
+
 export default {
 	async fetch(request: Request, env: Env, ctx: ExecutionContext): Promise<Response> {
-		const corsHeaders = {
-			'Access-Control-Allow-Origin': '*',
-			'Access-Control-Allow-Methods': 'POST, OPTIONS',
-			'Access-Control-Allow-Headers': 'Content-Type',
-		};
-
 		if (request.method === 'OPTIONS') {
 			return new Response(null, { headers: corsHeaders });
 		}
 
 		try {
-			const { code, targetLanguage } = await request.json<{ code: string; targetLanguage: string }>();
-
-			if (!code || !targetLanguage) {
-				return new Response(JSON.stringify({ error: "Missing 'code' or 'targetLanguage' in request body." }), {
-					status: 400,
-					headers: { ...corsHeaders, 'Content-Type': 'application/json' },
-				});
-			}
-
+			const url = new URL(request.url);
+			const path = url.pathname;
 			const genAI = new GoogleGenerativeAI(env.GEMINI_API_KEY);
-
 			const model = genAI.getGenerativeModel({ model: 'gemini-2.0-flash' });
 
-			const prompt = `Translate the following code snippet to ${targetLanguage}.
-Do not add any explanation, commentary, or markdown formatting like \`\`\` around the code.
-**IMPORTANT: Preserve all original comments and their exact placement in the translated code. do not add extra spaces in between.**
-Only provide the raw, translated code itself.
-
-Original Code:
-${code}`;
+			if (path === '/' || path === '/v1/translate') {
+				return await handleTranslate(request, model);
+			}
 
-			const result = await model.generateContent(prompt);
-			const geminiResponse = result.response;
-			const translatedCode = geminiResponse.text();
+			if (path === '/v1/explain') {
+				return await handleExplain(request, model);
+			}
 
-			return new Response(JSON.stringify({ translation: translatedCode }), {
-				status: 200,
+			return new Response(JSON.stringify({ error: 'Route not found.' }), {
+				status: 404,
 				headers: { ...corsHeaders, 'Content-Type': 'application/json' },
 			});
 		} catch (error) {
-			console.error('Error during translation:', error);
-			return new Response(JSON.stringify({ error: 'An error occurred while translating the code.' }), {
+			console.error('Error during request:', error);
+			return new Response(JSON.stringify({ error: 'An internal error occurred.' }), {
 				status: 500,
 				headers: { ...corsHeaders, 'Content-Type': 'application/json' },
 			});