Add core LlmClient wrapping OpenAI-compatible chat completions

src/core/llm/LlmClient.ts

@@ -0,0 +1,50 @@
+import OpenAI from 'openai';
+
+export interface ChatMessage {
+  role: 'system' | 'user' | 'assistant';
+  content: string;
+}
+
+export interface ChatOptions {
+  model: string;
+  temperature?: number;
+  maxTokens?: number;
+}
+
+export interface ChatResult {
+  content: string;
+  usage?: { promptTokens?: number; completionTokens?: number; totalTokens?: number };
+}
+
+export class LlmClient {
+  private readonly client: OpenAI;
+
+  constructor(opts: { baseUrl: string; apiKey?: string }) {
+    this.client = new OpenAI({ baseURL: opts.baseUrl, apiKey: opts.apiKey || 'not-needed' });
+  }
+
+  async chat(messages: ChatMessage[], options: ChatOptions): Promise<ChatResult> {
+    const response = await this.client.chat.completions.create({
+      model: options.model,
+      temperature: options.temperature,
+      max_tokens: options.maxTokens,
+      messages,
+    });
+
+    const choice = response.choices[0];
+    if (!choice) {
+      throw new Error('LLM returned no choices');
+    }
+
+    return {
+      content: choice.message?.content ?? '',
+      usage: response.usage
+        ? {
+            promptTokens: response.usage.prompt_tokens,
+            completionTokens: response.usage.completion_tokens,
+            totalTokens: response.usage.total_tokens,
+          }
+        : undefined,
+    };
+  }
+}