import { claudeToOpenAIRequest } from "../translator/request/claude-to-openai.js";
import { openaiToClaudeRequest } from "../translator/request/openai-to-claude.js";

const DEFAULT_TIMEOUT_MS = 3000;

// POST messages to Headroom /v1/compress; returns compressed messages + stats or null.
async function callCompress(url, messages, model, timeoutMs, compressUserMessages) {
  const endpoint = `${String(url).replace(/\/$/, "")}/v1/compress`;
  const payload = { messages, model };
  if (compressUserMessages) payload.config = { compress_user_messages: true };
  const res = await fetch(endpoint, {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(payload),
    signal: AbortSignal.timeout(timeoutMs),
  });
  if (!res.ok) return null;
  const data = await res.json();
  if (!Array.isArray(data?.messages)) return null;
  return data;
}

// Compress request body via Headroom proxy. Fail-open: returns null on any error.
// /v1/compress only understands OpenAI shape, so Claude bodies are translated
// to OpenAI, compressed, then translated back using 9Router's own translators.
export async function compressWithHeadroom(body, { enabled, url, model, format, compressUserMessages, timeoutMs = DEFAULT_TIMEOUT_MS } = {}) {
  if (!enabled || !url || !body) return null;

  try {
    // Claude shape: translate → OpenAI → compress → translate back.
    if (format === "claude") {
      const oai = claudeToOpenAIRequest(model, body, false);
      if (!Array.isArray(oai?.messages)) return null;
      const data = await callCompress(url, oai.messages, model, timeoutMs, compressUserMessages);
      if (!data) return null;
      const claudeBody = openaiToClaudeRequest(model, { ...oai, messages: data.messages }, false);
      if (Array.isArray(claudeBody?.messages)) body.messages = claudeBody.messages;
      if (claudeBody?.system !== undefined) body.system = claudeBody.system;
      return data;
    }

    // OpenAI shape: messages/input go straight to the proxy.
    const key = Array.isArray(body.messages) ? "messages"
      : Array.isArray(body.input) ? "input"
      : null;
    if (!key) return null;
    const data = await callCompress(url, body[key], model, timeoutMs, compressUserMessages);
    if (!data) return null;
    body[key] = data.messages;
    return data;
  } catch {
    return null;
  }
}

export function formatHeadroomLog(stats) {
  if (!stats) return null;
  const before = stats.tokens_before || 0;
  const after = stats.tokens_after || 0;
  const saved = stats.tokens_saved || 0;
  const pct = before > 0 ? ((saved / before) * 100).toFixed(1) : "0";
  return `saved ${saved} tokens / ${before} (${pct}%) ${after ? `after=${after}` : ""}`.trim();
}