Refactor code structure for improved readability and maintainability

app/api/chat/route.ts

@@ -1,14 +1,53 @@
 import { NextResponse } from "next/server";
 
+type ChatProvider = "groq" | "openai" | "ollama";
+
+type ChatRequestBody = {
+  provider?: ChatProvider;
+  apiKey?: string;
+  userMessageContent?: string;
+};
+
+type ProviderErrorResponse = {
+  error?: {
+    message?: string;
+  };
+};
+
+type ChatCompletionResponse = {
+  choices?: Array<{
+    message?: {
+      content?: string;
+    };
+  }>;
+};
+
+type OllamaResponse = {
+  response?: string;
+};
+
+function getErrorMessage(error: unknown) {
+  return error instanceof Error ? error.message : "Bilinmeyen sunucu hatası";
+}
+
 export async function POST(request: Request) {
   try {
-    const body = await request.json();
-    const { provider, apiKey, userMessageContent } = body;
+    const body = (await request.json()) as ChatRequestBody;
+    const provider = body.provider ?? "ollama";
+    const apiKey = body.apiKey ?? "";
+    const userMessageContent = body.userMessageContent?.trim();
+
+    if (!userMessageContent) {
+      return NextResponse.json(
+        { error: "Mesaj içeriği boş olamaz." },
+        { status: 400 },
+      );
+    }
 
     let assistantReply = "";
 
     if (provider === "groq") {
-      const res = await fetch(
+      const response = await fetch(
         "https://api.groq.com/openai/v1/chat/completions",
         {
           method: "POST",
@@ -30,14 +69,15 @@ export async function POST(request: Request) {
         },
       );
 
-      if (!res.ok) {
-        const errorData = await res.json();
-        throw new Error(errorData.error?.message || "Groq API Hatası");
+      if (!response.ok) {
+        const errorData = (await response.json()) as ProviderErrorResponse;
+        throw new Error(errorData.error?.message || "Groq API hatası");
       }
-      const data = await res.json();
-      assistantReply = data.choices[0].message.content;
+
+      const data = (await response.json()) as ChatCompletionResponse;
+      assistantReply = data.choices?.[0]?.message?.content ?? "";
     } else if (provider === "openai") {
-      const res = await fetch("https://api.openai.com/v1/chat/completions", {
+      const response = await fetch("https://api.openai.com/v1/chat/completions", {
         method: "POST",
         headers: {
           "Content-Type": "application/json",
@@ -55,32 +95,41 @@ export async function POST(request: Request) {
           ],
         }),
       });
-      if (!res.ok) throw new Error("OpenAI API Hatası");
-      const data = await res.json();
-      assistantReply = data.choices[0].message.content;
+
+      if (!response.ok) {
+        throw new Error("OpenAI API hatası");
+      }
+
+      const data = (await response.json()) as ChatCompletionResponse;
+      assistantReply = data.choices?.[0]?.message?.content ?? "";
     } else {
-      // Varsayılan: Yerel Ollama
-      const res = await fetch("http://127.0.0.1:11434/api/generate", {
+      const response = await fetch("http://127.0.0.1:11434/api/generate", {
         method: "POST",
         headers: { "Content-Type": "application/json" },
         body: JSON.stringify({
-          model: "llama3", // veya mistral
+          model: "llama3",
           prompt: `Sen MindSpace adlı kullanıcının kişisel yapay zeka terapistisin ve sırdaşısın. Şefkatli ve destekleyici cevap ver.\n\nKullanıcı: ${userMessageContent}\nTerapist:`,
           stream: false,
         }),
       });
 
-      if (!res.ok) throw new Error("Ollama API yanıt vermedi.");
-      const data = await res.json();
-      assistantReply = data.response;
+      if (!response.ok) {
+        throw new Error("Ollama API yanıt vermedi.");
+      }
+
+      const data = (await response.json()) as OllamaResponse;
+      assistantReply = data.response ?? "";
+    }
+
+    if (!assistantReply) {
+      throw new Error("Model geçerli bir yanıt üretmedi.");
     }
 
     return NextResponse.json({ reply: assistantReply });
-  } catch (error: any) {
-    console.error("API Route Hatası:", error);
-    return NextResponse.json(
-      { error: error.message || "Bilinmeyen Sunucu Hatası" },
-      { status: 500 },
-    );
+  } catch (error: unknown) {
+    const message = getErrorMessage(error);
+    console.error("API route hatası:", error);
+
+    return NextResponse.json({ error: message }, { status: 500 });
   }
 }