const net = require('net');
const fs = require('fs');
const path = require('path');
const iconv = require('iconv-lite');

const {
  extractFramesFromUtf16leBuffer,
  guessTextEncodingFromBuffer,
} = require('./framing');

function parseArgs(argv) {
  const args = {
    host: '127.0.0.1',
    port: 3021,
    interval: 1000,
    once: false,
    mode: 'frames', // frames | bytes
    chunk: 0, // when mode=bytes: bytes per write; 0 = one write
    jitter: 0, // optional random jitter ms added to interval
    fromHexFile: null,
    fromBinFile: null,
    encoding: null, // utf16le | utf8 | null(auto)
    debug: false,
  };

  // Collect positional args too (in case caller passes: host port hexFile interval)
  const positional = [];

  for (let i = 2; i < argv.length; i++) {
    const a = argv[i];
    const next = argv[i + 1];

    if (a && !a.startsWith('-')) {
      positional.push(a);
      continue;
    }

    if (a === '--host' && next) { args.host = next; i++; continue; }
    if (a === '--port' && next) { args.port = Number(next); i++; continue; }
    if (a === '--interval' && next) { args.interval = Number(next); i++; continue; }
    if (a === '--jitter' && next) { args.jitter = Number(next); i++; continue; }
    if (a === '--once') { args.once = true; continue; }

    if (a === '--mode' && next) { args.mode = next; i++; continue; }
    if (a === '--chunk' && next) { args.chunk = Number(next); i++; continue; }

    if (a === '--hex-file' && next) { args.fromHexFile = next; i++; continue; }
    if (a === '--bin-file' && next) { args.fromBinFile = next; i++; continue; }
    if (a === '--utf16le') { args.encoding = 'utf16le'; continue; }
    if (a === '--utf8') { args.encoding = 'utf8'; continue; }

    if (a === '--debug') { args.debug = true; continue; }
    if (a === '--help' || a === '-h') { args.help = true; continue; }
  }

  // Fallback positional mapping (only when flags are not provided)
  // node sim_server.js 127.0.0.1 39023 .\结果全部.txt 200
  if (positional.length) {
    const [pHost, pPort, pFile, pInterval] = positional;

    if (pHost && args.host === '127.0.0.1') args.host = pHost;
    if (pPort && args.port === 3021) {
      const n = Number(pPort);
      if (!Number.isNaN(n) && n > 0) args.port = n;
    }

    if (pFile && !args.fromHexFile && !args.fromBinFile) {
      // Assume it's a hex dump text file like 结果全部.txt
      args.fromHexFile = pFile;
    }

    if (pInterval && args.interval === 1000) {
      const n = Number(pInterval);
      if (!Number.isNaN(n) && n >= 0) args.interval = n;
    }
  }

  return args;
}

function usage() {
  // eslint-disable-next-line no-console
  console.log(`\n用法: node .\\sim_server.js [options]\n\n常用:（从你抓到的透析机 hex 数据里取帧并发送）\n  node .\\sim_server.js --port 3021 --hex-file .\\结果全部.txt --interval 1000\n\n选项:\n  --host <ip>          监听地址 (默认 127.0.0.1)\n  --port <n>           监听端口 (默认 3021)\n  --interval <ms>      每帧发送间隔 (默认 1000)\n  --jitter <ms>        每帧额外随机抖动 (0~jitter)\n  --once               只发送一轮后停止\n\n  --hex-file <path>    输入：hex 文本（可含空格/换行，或 RTF 包裹）\n  --bin-file <path>    输入：原始二进制（抓包 .bin / payload.bin）\n  --utf16le/--utf8     强制输入编码（默认自动猜测）\n\n  --mode frames        按“帧”发送（默认）：每次 write 一整帧（可能粘包取决于系统）\n  --mode bytes         按“字节流”发送：把整段 bytes 拆成小块写出，模拟半包/粘包\n  --chunk <n>          mode=bytes 时每次写出 n 字节；0=一次性写出\n\n  --debug              打印发送日志\n`);
}

function stripNonHex(text) {
  return text
    .replace(/0x/gi, '')
    .replace(/\\x/gi, '')
    .replace(/[^0-9a-fA-F]/g, '');
}

function extractLikelyHexBytesFromText(text) {
  const candidates = text.match(/[0-9A-Fa-f]{2}(?:\s+[0-9A-Fa-f]{2}){40,}/g);
  if (candidates && candidates.length) {
    let best = candidates[0];
    for (const c of candidates) if (c.length > best.length) best = c;
    return best.split(/\s+/g).filter(Boolean).join('');
  }
  return stripNonHex(text);
}

function decodeHexTextToBytes(text) {
  let cleaned = extractLikelyHexBytesFromText(text);
  if (!cleaned || cleaned.length < 40) {
    throw new Error('未在 hex-file 中提取到足够的 hex 字节');
  }
  if (cleaned.length % 2 !== 0) {
    // eslint-disable-next-line no-console
    console.warn('⚠️ hex 长度不是偶数，已丢弃最后 1 个半字节继续');
    cleaned = cleaned.slice(0, -1);
  }
  return Buffer.from(cleaned, 'hex');
}

function loadBytes(args) {
  if (args.fromBinFile) {
    const p = path.resolve(process.cwd(), args.fromBinFile);
    return fs.readFileSync(p);
  }

  if (args.fromHexFile) {
    const p = path.resolve(process.cwd(), args.fromHexFile);
    const text = fs.readFileSync(p, 'utf8');
    return decodeHexTextToBytes(text);
  }

  // default: a tiny demo ORU_R31 frame in UTF-16LE
  const demoXml = `<?xml version="1.0" encoding="UTF-8"?>\n<ORU_R31>\n  <MSH><MSH.18>UNICODE</MSH.18></MSH>\n  <ORU_R31.OBSERVATION>\n    <OBX>\n      <OBX.3><CE.1>13</CE.1><CE.2>Venous Pressure</CE.2></OBX.3>\n      <OBX.5><FN.1>150</FN.1></OBX.5>\n      <OBX.6><CE.1>mmHg</CE.1></OBX.6>\n    </OBX>\n  </ORU_R31.OBSERVATION>\n</ORU_R31>`;
  return iconv.encode(demoXml, 'utf16le');
}

function splitBytes(bytes, chunkSize) {
  if (!chunkSize || chunkSize <= 0) return [bytes];
  const chunks = [];
  for (let i = 0; i < bytes.length; i += chunkSize) {
    chunks.push(bytes.slice(i, i + chunkSize));
  }
  return chunks;
}

function buildFrameBuffers(bytes, forcedEncoding) {
  const encoding = forcedEncoding || guessTextEncodingFromBuffer(bytes);
  if (encoding !== 'utf16le') {
    throw new Error(`当前模拟器只支持 utf16le 帧拆分（检测到 encoding=${encoding}）。如需发送 utf8，请先提供二进制或改造 framing。`);
  }

  const { frames, remainderBuffer } = extractFramesFromUtf16leBuffer(bytes);
  if (frames.length === 0) {
    throw new Error('未从输入中提取到任何 ORU_R31/ORF_R04 完整帧');
  }

  const frameBuffers = frames.map(f => iconv.encode(f, 'utf16le'));
  return { frameBuffers, remainderBuffer };
}

async function sleep(ms) {
  return new Promise(r => setTimeout(r, ms));
}

async function main() {
  const args = parseArgs(process.argv);
  if (args.help) { usage(); return; }

  let bytes;
  try {
    bytes = loadBytes(args);
  } catch (e) {
    // eslint-disable-next-line no-console
    console.error(`加载输入失败: ${e && e.message ? e.message : String(e)}`);
    usage();
    process.exitCode = 1;
    return;
  }

  let frameBuffers = null;
  let remainderBuffer = null;
  if (args.mode === 'frames') {
    try {
      const built = buildFrameBuffers(bytes, args.encoding);
      frameBuffers = built.frameBuffers;
      remainderBuffer = built.remainderBuffer;
    } catch (e) {
      // eslint-disable-next-line no-console
      console.error(`拆帧失败: ${e && e.message ? e.message : String(e)}`);
      process.exitCode = 1;
      return;
    }
  }

  const server = net.createServer();
  server.on('connection', (socket) => {
    // eslint-disable-next-line no-console
    console.log(`client connected: ${socket.remoteAddress}:${socket.remotePort}`);
    socket.setNoDelay(true);

    (async () => {
      try {
        if (args.mode === 'bytes') {
          const chunks = splitBytes(bytes, args.chunk || 0);
          // eslint-disable-next-line no-console
          console.log(`send mode=bytes: total=${bytes.length} bytes, writes=${chunks.length} (chunk=${args.chunk || 0})`);

          for (let i = 0; i < chunks.length; i++) {
            socket.write(chunks[i]);
            if (args.debug) {
              // eslint-disable-next-line no-console
              console.log(`write #${i + 1}: ${chunks[i].length} bytes`);
            }
            const wait = args.interval + (args.jitter ? Math.floor(Math.random() * (args.jitter + 1)) : 0);
            if (wait > 0) await sleep(wait);
          }

          if (args.once) {
            socket.end();
            server.close();
          }
          return;
        }

        // frames
        // eslint-disable-next-line no-console
        console.log(`send mode=frames: frames=${frameBuffers.length}, interval=${args.interval}ms`);
        if (remainderBuffer && remainderBuffer.length) {
          // eslint-disable-next-line no-console
          console.warn(`WARN: input has trailing ${remainderBuffer.length} bytes without a complete frame (capture may be truncated)`);
        }

        let round = 0;
        while (!socket.destroyed) {
          round++;
          for (let i = 0; i < frameBuffers.length; i++) {
            socket.write(frameBuffers[i]);
            if (args.debug) {
              // eslint-disable-next-line no-console
              console.log(`round=${round} frame #${i + 1}: ${frameBuffers[i].length} bytes`);
            }
            const wait = args.interval + (args.jitter ? Math.floor(Math.random() * (args.jitter + 1)) : 0);
            if (wait > 0) await sleep(wait);
          }

          if (args.once) {
            socket.end();
            server.close();
            return;
          }
        }
      } catch (e) {
        // eslint-disable-next-line no-console
        console.error(`发送失败: ${e && e.message ? e.message : String(e)}`);
        try { socket.destroy(); } catch (_) {}
      }
    })();

    socket.on('close', () => {
      // eslint-disable-next-line no-console
      console.log('client closed');
    });

    socket.on('error', (err) => {
      // eslint-disable-next-line no-console
      console.log(`socket error: ${err.message}`);
    });
  });

  server.on('error', (err) => {
    // eslint-disable-next-line no-console
    console.error(`server error: ${err.message}`);
    process.exitCode = 1;
  });

  server.listen(args.port, args.host, () => {
    // eslint-disable-next-line no-console
    console.log(`sim server listening: ${args.host}:${args.port}`);
    // eslint-disable-next-line no-console
    console.log(`client connect example: node .\\index.js --host ${args.host} --port ${args.port}`);

    const src = args.fromBinFile ? `bin:${args.fromBinFile}` : (args.fromHexFile ? `hex:${args.fromHexFile}` : 'demo');
    // eslint-disable-next-line no-console
    console.log(`source=${src}; mode=${args.mode}; interval=${args.interval}ms; chunk=${args.chunk || 0}`);
  });
}

main();