const https = require('https');
const http = require('http');
const { URL } = require('url');
const logger = require('./logger');

function normalizeBaseURL(baseURL) {
  let url = (baseURL || '').trim().replace(/\/+$/, '');
  if (/\/chat\/completions$/.test(url)) {
    url = url.replace(/\/chat\/completions$/, '');
  }
  return url;
}

function buildChatURL(baseURL) {
  return normalizeBaseURL(baseURL) + '/chat/completions';
}

function buildModelsURL(baseURL) {
  return normalizeBaseURL(baseURL) + '/models';
}

async function fetchModels({ baseURL, apiKey }) {
  const url = buildModelsURL(baseURL);
  logger.log('FETCH_MODELS_START', { url });
  const res = await fetch(url, {
    method: 'GET',
    headers: { Authorization: 'Bearer ' + apiKey, 'Content-Type': 'application/json' },
  });
  if (!res.ok) {
    const text = await res.text().catch(() => '');
    logger.log('FETCH_MODELS_FAIL', { status: res.status, body: text.slice(0, 300) });
    throw new Error('获取模型列表失败 (HTTP ' + res.status + '): ' + text.slice(0, 300));
  }
  const json = await res.json();
  const data = json.data || json.models || [];
  const models = data.map((m) => (typeof m === 'string' ? m : m.id || m.name)).filter(Boolean);
  logger.log('FETCH_MODELS_OK', { count: models.length });
  return models;
}

function doRequest(url, { method, headers, bodyStr, signal }) {
  return new Promise((resolve, reject) => {
    const u = new URL(url);
    const lib = u.protocol === 'https:' ? https : http;
    const opts = {
      hostname: u.hostname,
      port: u.port || (u.protocol === 'https:' ? 443 : 80),
      path: u.pathname + u.search,
      method,
      headers: Object.assign({}, headers, { 'Content-Length': Buffer.byteLength(bodyStr) }),
    };
    const req = lib.request(opts, (res) => resolve(res));

    if (signal) {
      if (signal.aborted) {
        req.destroy();
        reject(Object.assign(new Error('Aborted'), { name: 'AbortError' }));
        return;
      }
      signal.addEventListener('abort', () => {
        try { req.destroy(); } catch { /* ignore */ }
      });
    }
    req.on('error', (err) => {
      if (signal && signal.aborted) reject(Object.assign(new Error('Aborted'), { name: 'AbortError' }));
      else reject(err);
    });
    req.write(bodyStr);
    req.end();
  });
}

function readAll(stream) {
  return new Promise((resolve) => {
    const chunks = [];
    stream.on('data', (c) => chunks.push(c));
    stream.on('end', () => resolve(Buffer.concat(chunks).toString('utf8')));
    stream.on('error', () => resolve(Buffer.concat(chunks).toString('utf8')));
  });
}

async function streamChat({ baseURL, apiKey, model, messages, enableThinking, reasoningEffort, maxTokens, signal, onChunk, onUsage }) {
  const url = buildChatURL(baseURL);
  let currentMessages = messages;
  let accumulated = '';
  const MAX_ITER = 12;
  const CONTINUE_PROMPT = '继续，请从刚才中断的地方直接接着输出，不要重复已经输出的任何内容。';

  for (let iter = 0; iter < MAX_ITER; iter++) {
    const body = { model, messages: currentMessages, stream: true };
    if (enableThinking) {
      body.thinking = { type: 'enabled' };
      if (reasoningEffort) body.reasoning_effort = reasoningEffort;
    }
    if (maxTokens && maxTokens > 0) body.max_tokens = maxTokens;
    const bodyStr = JSON.stringify(body);

    logger.log('REQUEST', { iter, model, msgCount: currentMessages.length, thinking: !!enableThinking, effort: reasoningEffort || null, maxTokens: maxTokens || null, url });

    let res;
    try {
      res = await doRequest(url, {
        method: 'POST',
        headers: { 'Content-Type': 'application/json', 'Authorization': 'Bearer ' + apiKey },
        bodyStr,
        signal,
      });
    } catch (e) {
      if (e && e.name === 'AbortError') { logger.log('ABORTED_AT_REQUEST', { iter }); throw e; }
      logger.log('REQUEST_ERROR', { iter, error: e.message, code: e.code });
      throw e;
    }

    logger.log('RESPONSE_STATUS', { iter, status: res.statusCode });

    if (res.statusCode !== 200) {
      const text = await readAll(res);
      logger.log('HTTP_ERROR', { iter, status: res.statusCode, body: text.slice(0, 500) });
      throw new Error('请求失败 (HTTP ' + res.statusCode + '): ' + text.slice(0, 500));
    }

    const decoder = new TextDecoder('utf-8');
    let buffer = '';
    let finishReason = null;
    let sawDone = false;
    let chunkCount = 0;
    let gotContentThisIter = false;

    try {
      for await (const chunk of res) {
        buffer += decoder.decode(chunk, { stream: true });
        const lines = buffer.split('\n');
        buffer = lines.pop() || '';
        for (const raw of lines) {
          const line = raw.trim();
          if (!line || !line.startsWith('data:')) continue;
          const data = line.slice(5).trim();
          if (data === '[DONE]') { sawDone = true; break; }
          try {
            const json = JSON.parse(data);
            chunkCount++;
            if (json.usage && onUsage) onUsage(json.usage);
            const choice = (json.choices && json.choices[0]) || {};
            const delta = choice.delta || {};
            const content = delta.content || '';
            const reasoning = delta.reasoning_content || delta.reasoning || '';
            if (content) { accumulated += content; gotContentThisIter = true; onChunk({ content, reasoning: '' }); }
            if (reasoning) { onChunk({ content: '', reasoning }); }
            if (choice.finish_reason) finishReason = choice.finish_reason;
          } catch {
            /* ignore malformed lines */
          }
        }
        if (sawDone) break;
      }
    } catch (e) {
      if (e && e.name === 'AbortError') { logger.log('ABORTED_IN_STREAM', { iter }); throw e; }
      logger.log('STREAM_ERROR', { iter, error: e.message, code: e.code, stack: e.stack });
      throw e;
    }

    try { res.destroy(); } catch { /* ignore */ }

    logger.log('SEGMENT_END', { iter, finishReason: finishReason || null, sawDone, chunkCount, accumulatedLen: accumulated.length, gotContent: gotContentThisIter });

    if (signal && signal.aborted) { logger.log('SIGNAL_ABORTED_AFTER', { iter }); throw Object.assign(new Error('Aborted'), { name: 'AbortError' }); }

    const truncated = finishReason === 'length' || (!finishReason && !sawDone && gotContentThisIter);

    if (truncated && iter < MAX_ITER - 1 && accumulated.length > 0) {
      logger.log('AUTO_CONTINUE', { iter, reason: finishReason === 'length' ? 'length' : 'abrupt', accumulatedLen: accumulated.length });
      currentMessages = messages.concat([
        { role: 'assistant', content: accumulated },
        { role: 'user', content: CONTINUE_PROMPT },
      ]);
      continue;
    }
    if (iter === MAX_ITER - 1 && truncated) {
      logger.log('MAX_ITER_REACHED', { accumulatedLen: accumulated.length });
    }
    break;
  }

  logger.log('STREAM_COMPLETE', { totalAccumulatedLen: accumulated.length });
}

module.exports = { fetchModels, streamChat, buildChatURL };