import crypto from 'node:crypto';

function secureEqual(left, right) {
  const a = Buffer.from(String(left ?? ''));
  const b = Buffer.from(String(right ?? ''));
  return a.length === b.length && crypto.timingSafeEqual(a, b);
}

function normalizeMessages(value) {
  if (!Array.isArray(value) || !value.length || value.length > 20) return null;
  const messages = value.map((message) => ({
    role: ['system', 'user', 'assistant'].includes(message?.role) ? message.role : '',
    content: String(message?.content ?? '').trim(),
  }));
  if (messages.some((message) => !message.role || !message.content || message.content.length > 120_000)) {
    return null;
  }
  if (messages.reduce((total, message) => total + message.content.length, 0) > 150_000) return null;
  return messages;
}

export async function executeDeepSearchLlmGateway({
  llmProviderService,
  expectedSecret,
  providedSecret,
  input = {},
} = {}) {
  if (!expectedSecret || !secureEqual(expectedSecret, providedSecret)) {
    return { status: 401, body: { ok: false, message: 'Deep Search LLM gateway credential is invalid' } };
  }
  if (!llmProviderService?.createChatCompletion) {
    return { status: 503, body: { ok: false, message: 'LLM provider service is unavailable' } };
  }
  const providerKeyId = String(input.providerKeyId ?? '').trim();
  const model = String(input.model ?? '').trim();
  const messages = normalizeMessages(input.messages);
  if (!/^[a-zA-Z0-9._:-]{1,128}$/.test(providerKeyId) || !model || model.length > 200 || !messages) {
    return { status: 400, body: { ok: false, message: 'Invalid Deep Search LLM request' } };
  }
  const result = await llmProviderService.createChatCompletion({
    providerKeyId,
    model,
    messages,
    temperature: Math.max(0, Math.min(1, Number(input.temperature ?? 0.2) || 0.2)),
  });
  if (!result?.ok) {
    return {
      status: Number(result?.status) >= 400 ? Number(result.status) : 502,
      body: { ok: false, message: result?.message || 'Deep Search LLM request failed' },
    };
  }
  return {
    status: 200,
    body: {
      ok: true,
      reply: result.reply,
      providerKeyId: result.providerKeyId,
      providerId: result.providerId,
      model: result.model,
      usage: result.usage ?? null,
    },
  };
}