// prompt-analysis.js —— 图片反推生图提示词（移植自「提示词提取」项目）
// LLM 通道走本应用的 router 分组（直接读中转分组列表），与 team.js 同模式。
"use strict";
const router = require("./router");
const { SYSTEM_PROMPT, USER_INSTRUCTION } = require("./team-prompt");

// ============================================================================
//  以下 <CORE> 自 提示词提取/server.js 原样提取（extractJson / callChat），未改动逻辑。
// ============================================================================

function extractJson(text) {
  if (!text) throw new Error('模型返回为空');
  let t = text.trim();
  const fence = t.match(/```(?:json)?\s*([\s\S]*?)```/i);
  if (fence) t = fence[1].trim();
  const start = t.indexOf('{');
  const end = t.lastIndexOf('}');
  if (start !== -1 && end !== -1 && end > start) t = t.slice(start, end + 1);

  const tryParse = (s) => { try { return JSON.parse(s); } catch (_) { return undefined; } };
  let r = tryParse(t);
  if (r !== undefined) return r;
  r = tryParse(t.replace(/,\s*([}\]])/g, '$1'));
  if (r !== undefined) return r;
  throw new Error('模型输出的 JSON 格式有误，请重试');
}

// 流式调用：空闲超时——120 秒收不到任何数据就判定挂起并中止
const CHAT_IDLE_MS = 120000;
function chatTimeoutError() {
  return Object.assign(new Error('模型长时间无响应（可能渠道不稳或模型太慢），请重试或换个更快的模型'), { status: 504 });
}
async function callChat(gwBase, apiKey, model, messages, maxTokens) {
  const ctrl = new AbortController();
  let idle;
  const resetIdle = () => { clearTimeout(idle); idle = setTimeout(() => ctrl.abort(), CHAT_IDLE_MS); };
  resetIdle();

  let upstream;
  try {
    upstream = await fetch(`${gwBase}/chat/completions`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json', Authorization: `Bearer ${apiKey}` },
      body: JSON.stringify({ model, temperature: 0.4, max_tokens: maxTokens, messages, stream: true }),
      signal: ctrl.signal,
    });
  } catch (e) {
    clearTimeout(idle);
    if (e.name === 'AbortError') throw chatTimeoutError();
    throw e;
  }
  if (!upstream.ok) {
    clearTimeout(idle);
    const detail = await upstream.text().catch(() => '');
    const err = new Error(`上游模型调用失败 (${upstream.status})`);
    err.status = upstream.status === 401 ? 401 : 502;
    err.detail = detail.slice(0, 300);
    throw err;
  }

  const reader = upstream.body.getReader();
  const decoder = new TextDecoder();
  let buf = '';
  let content = '';
  try {
    while (true) {
      const { done, value } = await reader.read();
      if (done) break;
      resetIdle();
      buf += decoder.decode(value, { stream: true });
      let nl;
      while ((nl = buf.indexOf('\n')) >= 0) {
        const line = buf.slice(0, nl).trim();
        buf = buf.slice(nl + 1);
        if (!line.startsWith('data:')) continue;
        const data = line.slice(5).trim();
        if (!data || data === '[DONE]') continue;
        try {
          const j = JSON.parse(data);
          const delta = j.choices?.[0]?.delta;
          if (delta?.content) content += delta.content;
          else if (j.choices?.[0]?.message?.content) content += j.choices[0].message.content;
        } catch (_) { /* 跳过 keep-alive / 非 JSON 行 */ }
      }
    }
  } catch (e) {
    if (e.name === 'AbortError') throw chatTimeoutError();
    throw e;
  } finally {
    clearTimeout(idle);
  }
  if (!content) throw new Error('模型未返回内容（可能超时或渠道异常）');
  return content;
}

// ============================================================================
//  适配层：LLM 走 router 分组
// ============================================================================

// 把分组 baseUrl 归一成「+ /chat/completions 即正确」的基址（对齐 team.js）
function chatBase(baseUrl) {
  const base = String(baseUrl || "").replace(/\/+$/, "");
  if (/\/chat\/completions$/.test(base)) return base.replace(/\/chat\/completions$/, "");
  if (/\/v\d+$/.test(base)) return base;
  return base + "/v1";
}

// 取分组：优先按 id，否则用默认 LLM 分组
function resolveGroup(groupId) {
  let g = null;
  if (groupId != null && groupId !== "" && typeof router.groupById === "function") {
    g = router.groupById(groupId);
  }
  if (!g && typeof router.llmGroup === "function") g = router.llmGroup();
  if (!g) throw new Error("没有可用的中转分组，请先在「路由」里配置好带 baseUrl 和密钥的分组");
  if (!g.baseUrl || !g.key) throw new Error(`分组「${g.name || g.id}」缺少 baseUrl 或密钥`);
  return g;
}

// 获取所有可用分组列表（给前端下拉用）
function listGroups() {
  try {
    return router.usableGroups().map((g) => ({
      id: g.id,
      name: g.name || g.id,
      host: (() => { try { return new (require("url").URL)(g.baseUrl).host; } catch (_) { return ""; } })(),
      mode: g.mode || "chat",
    }));
  } catch (_) {
    return [];
  }
}

// 拉取指定分组的模型列表
async function listModels(groupId) {
  const g = resolveGroup(groupId);
  const models = await router.fetchModels(g.baseUrl, g.key);
  return models;
}

// 核心：图片 → 提示词分析
async function analyze({ image, model, groupId } = {}) {
  if (!image || typeof image !== "string") throw new Error("缺少图片数据");
  if (!model) throw new Error("未选择模型");
  const g = resolveGroup(groupId);
  const gwBase = chatBase(g.baseUrl);

  const content = await callChat(gwBase, g.key, model, [
    { role: "system", content: SYSTEM_PROMPT },
    {
      role: "user",
      content: [
        { type: "text", text: USER_INSTRUCTION },
        { type: "image_url", image_url: { url: image } },
      ],
    },
  ], 2000);

  return { result: extractJson(content), model };
}

module.exports = { analyze, listGroups, listModels };