HOA_Financial_Platform/backend/src/common/utils/ai-caller.ts

/**
 * Shared utility for calling OpenAI-compatible chat completion APIs.
 * Used by both production AI features and shadow AI benchmarking.
 */

export interface AICallerParams {
  apiUrl: string;
  apiKey: string;
  model: string;
  messages: Array<{ role: string; content: string }>;
  temperature: number;
  maxTokens: number;
  timeoutMs?: number;
}

export interface AICallerResult {
  content: string;
  usage?: { prompt_tokens: number; completion_tokens: number; total_tokens: number };
  responseTimeMs: number;
  rawResponse: string;
}

export async function callOpenAICompatible(params: AICallerParams): Promise<AICallerResult> {
  const { apiUrl, apiKey, model, messages, temperature, maxTokens, timeoutMs = 600000 } = params;

  const requestBody = {
    model,
    messages,
    temperature,
    max_tokens: maxTokens,
  };

  const bodyString = JSON.stringify(requestBody);
  const startTime = Date.now();

  const { URL } = await import('url');
  const https = await import('https');

  const aiResult = await new Promise<{ status: number; body: string }>((resolve, reject) => {
    // Normalize: strip trailing slash and /chat/completions if user included it
    let baseUrl = apiUrl.replace(/\/+$/, '');
    if (baseUrl.endsWith('/chat/completions')) {
      baseUrl = baseUrl.slice(0, -'/chat/completions'.length);
    }
    const url = new URL(`${baseUrl}/chat/completions`);

    const options = {
      hostname: url.hostname,
      port: url.port || 443,
      path: url.pathname,
      method: 'POST',
      headers: {
        'Authorization': `Bearer ${apiKey}`,
        'Content-Type': 'application/json',
        'Content-Length': Buffer.byteLength(bodyString, 'utf-8'),
      },
      timeout: timeoutMs,
    };

    const req = https.request(options, (res) => {
      let data = '';
      res.on('data', (chunk) => { data += chunk; });
      res.on('end', () => {
        resolve({ status: res.statusCode!, body: data });
      });
    });

    req.on('error', (err) => reject(err));
    req.on('timeout', () => {
      req.destroy();
      reject(new Error(`Request timed out after ${timeoutMs / 1000}s`));
    });

    req.write(bodyString);
    req.end();
  });

  const responseTimeMs = Date.now() - startTime;

  if (aiResult.status >= 400) {
    throw new Error(`AI API returned ${aiResult.status}: ${aiResult.body}`);
  }

  const data = JSON.parse(aiResult.body);
  const content = data.choices?.[0]?.message?.content || null;

  if (!content) {
    throw new Error('AI model returned empty content');
  }

  // Clean response: strip markdown fences and thinking blocks
  let cleaned = content.trim();
  if (cleaned.startsWith('```')) {
    cleaned = cleaned.replace(/^```(?:json)?\s*\n?/, '').replace(/\n?```\s*$/, '');
  }
  cleaned = cleaned.replace(/<think>[\s\S]*?<\/think>\s*/g, '').trim();

  const usage = data.usage || undefined;

  return {
    content: cleaned,
    usage,
    responseTimeMs,
    rawResponse: content,
  };
}