interface Message {
  role: "system" | "user" | "assistant";
  content: string;
}

interface AskAIOptions {
  model?: string;
  temperature?: number;
  maxRetries?: number;
  maxTokens?: number;
}

export interface AskAIResult {
  text: string;
  cost: number;
}

function sleep(ms: number) {
  return new Promise((resolve) => setTimeout(resolve, ms));
}


export async function askAI(messages: Message[], options: AskAIOptions = {}): Promise<AskAIResult> {
  const config = useRuntimeConfig();
  const apiKey = config.openrouterApiKey;

  if (!apiKey) throw new Error("OPENROUTER_API_KEY is not set");

  const model = options.model ?? (config as any).openrouterModel ?? "anthropic/claude-sonnet-4-5";
  const maxRetries = options.maxRetries ?? 4;

  let lastError: any;

  for (let attempt = 0; attempt <= maxRetries; attempt++) {
    const label = attempt > 0 ? ` (attempt ${attempt + 1}/${maxRetries + 1})` : "";
    const promptPreview = messages[messages.length - 1]?.content?.slice(0, 120).replace(/\n/g, " ");
    console.log(`[openrouter] → ${model}${label} | prompt: "${promptPreview}…"`);
    const t0 = Date.now();

    try {
      const res = await $fetch<{ id?: string; choices: { message: { content: string } }[]; usage?: { prompt_tokens?: number; completion_tokens?: number; cost?: number } }>(
        "https://openrouter.ai/api/v1/chat/completions",
        {
          method: "POST",
          headers: {
            Authorization: `Bearer ${apiKey}`,
            "Content-Type": "application/json",
            "HTTP-Referer": "https://revisi.one",
            "X-Title": "Revisi.one",
          },
          body: {
            model,
            messages,
            temperature: options.temperature ?? 0.3,
            ...(options.maxTokens ? { max_tokens: options.maxTokens } : {}),
          },
        }
      );

      const elapsed = ((Date.now() - t0) / 1000).toFixed(1);
      const content = res.choices?.[0]?.message?.content;

      if (!content) {
        console.error(`[openrouter] ✗ empty response after ${elapsed}s — full response:`, JSON.stringify(res));
        throw new Error("Empty response from OpenRouter");
      }

      const usage = res.usage;
      const tokenInfo = usage ? ` | tokens: ${usage.prompt_tokens ?? "?"}→${usage.completion_tokens ?? "?"}` : "";
      console.log(`[openrouter] ✓ ${elapsed}s${tokenInfo} | reply: "${content.slice(0, 120).replace(/\n/g, " ")}…"`);

      const cost = usage?.cost ?? 0;

      return { text: content, cost };
    } catch (err: any) {
      lastError = err;
      const elapsed = ((Date.now() - t0) / 1000).toFixed(1);
      const status = err?.response?.status ?? err?.statusCode ?? err?.status;
      const body = err?.data ?? err?.response?._data ?? "(no body)";

      console.error(`[openrouter] ✗ ${elapsed}s — status: ${status ?? "unknown"} | error: ${err?.message}`);
      if (body && body !== "(no body)") {
        console.error(`[openrouter]   response body:`, JSON.stringify(body).slice(0, 400));
      }

      // 402 = insufficient credits — wait 60s and keep retrying indefinitely
      if (status === 402) {
        console.warn(`[openrouter] insufficient credits — waiting 60s before retry…`);
        await sleep(60_000);
        attempt--; // don't count against maxRetries
        continue;
      }

      // only retry on 429 and 5xx
      if (status !== 429 && (status < 500 || status > 599)) throw err;

      if (attempt < maxRetries) {
        const retryAfterHeader = err?.response?.headers?.get?.("retry-after");
        const retryAfterSec = retryAfterHeader ? parseInt(retryAfterHeader, 10) : NaN;
        const backoffMs = isNaN(retryAfterSec)
          ? Math.min(1000 * 2 ** attempt + Math.random() * 500, 30000)
          : retryAfterSec * 1000;

        console.warn(`[openrouter] retrying in ${Math.round(backoffMs)}ms…`);
        await sleep(backoffMs);
      }
    }
  }

  throw lastError;
}