import { Injectable } from '@nestjs/common';

/** A single chat message in OpenAI chat-completions shape. */
export interface ChatMessage {
  role: string;
  content: string;
}

@Injectable()
export class LlmService {
  // read at construction, like other services' env config
  private readonly apiBase =
    process.env.LLM_API_BASE ?? 'http://192.168.1.70:1111/v1';
  private readonly model = process.env.LLM_MODEL ?? 'qwen3.8-27b';
  // local 27B model can be slow (uncontrollable reasoning tokens) — generous default: 3 min headroom for slow reasoning periods
  private readonly timeoutMs = parseInt(
    process.env.LLM_TIMEOUT_MS ?? '180000',
    10,
  );

  /** GET {base}/models → the `data[].id` strings. */
  async listModels(): Promise<string[]> {
    const res = await fetch(`${this.apiBase}/models`, {
      signal: AbortSignal.timeout(this.timeoutMs),
    });
    if (!res.ok) {
      throw new Error(
        `listModels failed: HTTP ${res.status} ${(await res.text()).slice(0, 200)}`,
      );
    }
    const body = (await res.json()) as { data?: { id: string }[] };
    return (body.data ?? []).map((m) => m.id);
  }

  /** POST {base}/chat/completions → `choices[0].message.content`. */
  async chat(
    messages: ChatMessage[],
    opts?: { maxTokens?: number; temperature?: number },
  ): Promise<string> {
    const res = await fetch(`${this.apiBase}/chat/completions`, {
      method: 'POST',
      headers: { 'content-type': 'application/json' },
      body: JSON.stringify({ model: this.model, messages, ...opts }),
      signal: AbortSignal.timeout(this.timeoutMs),
    });
    if (!res.ok) {
      throw new Error(
        `chat failed: HTTP ${res.status} ${(await res.text()).slice(0, 200)}`,
      );
    }
    const body = (await res.json()) as {
      choices?: { message?: { content?: string } }[];
    };
    const content = body.choices?.[0]?.message?.content;
    if (typeof content !== 'string') {
      throw new Error('chat failed: no choices[0].message.content in response');
    }
    return content;
  }

  /** Thin wrapper over chat(): the stated primary use of this service. */
  async summarize(text: string): Promise<string> {
    return this.chat([
      { role: 'system', content: 'Summarize the following text concisely.' },
      { role: 'user', content: text },
    ]);
  }
}