'use strict';

/**
 * 对线程级 gitea-mcp stdio 配置做最小 MCP initialize 预检。
 *
 * 预检只负责判断“命令能否启动并完成协议握手”，不调用 Gitea 工具，也不把
 * stderr、Token 或响应正文写入日志。真正的 Agent 工作仍由 Codex App 按线程
 * 配置启动另一份 gitea-mcp 进程完成。
 */

const { spawn: defaultSpawn } = require('child_process');
const readline = require('readline');

const DEFAULT_TIMEOUT_MS = 8000;
const MAX_TIMEOUT_MS = 30000;
const MCP_PROTOCOL_VERSION = '2024-11-05';

function safeText(value, max = 512) {
  return String(value ?? '').trim().slice(0, max);
}

function probeError(code, message, details = {}) {
  return Object.assign(new Error(message), { code, ...details });
}

function normalizeTimeout(value) {
  const numeric = Number(value);
  if (!Number.isFinite(numeric)) return DEFAULT_TIMEOUT_MS;
  return Math.min(MAX_TIMEOUT_MS, Math.max(250, Math.floor(numeric)));
}

function initializeRequest() {
  return {
    jsonrpc: '2.0',
    id: 1,
    method: 'initialize',
    params: {
      protocolVersion: MCP_PROTOCOL_VERSION,
      capabilities: {},
      clientInfo: { name: 'cc-web-gitea-preflight', version: '1.0.0' },
    },
  };
}

function isInitializeResponse(message) {
  return message
    && message.jsonrpc === '2.0'
    && (message.id === 1 || message.id === '1')
    && (Object.prototype.hasOwnProperty.call(message, 'result')
      || Object.prototype.hasOwnProperty.call(message, 'error'));
}

function sendJsonLine(stdin, value) {
  stdin.write(`${JSON.stringify(value)}\n`);
}

/**
 * @param {object} options
 * @param {string} options.command MCP 命令或绝对路径
 * @param {string[]} [options.args] 命令参数
 * @param {object} [options.env] 线程级环境变量
 * @param {string} [options.cwd] 子进程工作目录
 * @param {number} [options.timeoutMs] 握手超时，默认 8 秒
 * @param {Function} [options.spawnImpl] 测试替身，签名同 child_process.spawn
 * @returns {Promise<{ok:true,protocolVersion:string}>}
 */
function probeGiteaMcp(options = {}) {
  const command = safeText(options.command, 2048);
  if (!command) return Promise.reject(probeError('gitea_mcp_command_empty', 'Gitea MCP 命令为空。'));
  const args = Array.isArray(options.args) ? options.args.map((item) => String(item)) : [];
  const timeoutMs = normalizeTimeout(options.timeoutMs);
  const spawnImpl = typeof options.spawnImpl === 'function' ? options.spawnImpl : defaultSpawn;
  const env = { ...process.env, ...(options.env && typeof options.env === 'object' ? options.env : {}) };
  const cwd = safeText(options.cwd, 4096) || process.cwd();

  return new Promise((resolve, reject) => {
    let child;
    let settled = false;
    let timer = null;
    let sawInvalidLine = false;

    const finish = (error, result) => {
      if (settled) return;
      settled = true;
      if (timer) clearTimeout(timer);
      try {
        if (child?.stdin && !child.stdin.destroyed) child.stdin.end();
      } catch {}
      try {
        if (child && !child.killed) child.kill('SIGTERM');
      } catch {}
      if (error) reject(error);
      else resolve(result);
    };

    try {
      child = spawnImpl(command, args, {
        cwd,
        env,
        stdio: ['pipe', 'pipe', 'pipe'],
        windowsHide: true,
      });
    } catch (error) {
      finish(probeError('gitea_mcp_spawn_failed', 'Gitea MCP 进程无法启动。', { cause: error }));
      return;
    }

    const handleLine = (line) => {
      const text = String(line || '').trim();
      if (!text) return;
      let message;
      try {
        message = JSON.parse(text);
      } catch {
        // stdio 协议要求 JSONL；兼容少数实现的启动提示，最终仍以超时/退出分类。
        sawInvalidLine = true;
        return;
      }
      if (!isInitializeResponse(message)) return;
      if (message.error) {
        finish(probeError('gitea_mcp_handshake_failed', 'Gitea MCP initialize 握手失败。', {
          rpcCode: message.error.code ?? null,
        }));
        return;
      }
      const result = message.result && typeof message.result === 'object' ? message.result : {};
      try {
        // MCP 客户端在收到 initialize 响应后必须发送 initialized 通知。
        sendJsonLine(child.stdin, { jsonrpc: '2.0', method: 'notifications/initialized', params: {} });
      } catch (error) {
        finish(probeError('gitea_mcp_handshake_failed', 'Gitea MCP initialized 通知发送失败。', { cause: error }));
        return;
      }
      finish(null, {
        ok: true,
        protocolVersion: safeText(result.protocolVersion, 64) || MCP_PROTOCOL_VERSION,
      });
    };

    if (child?.stdout) {
      const lineReader = readline.createInterface({ input: child.stdout });
      lineReader.on('line', handleLine);
      child.once?.('close', () => lineReader.close());
    }
    child?.once?.('error', (error) => {
      finish(probeError('gitea_mcp_spawn_failed', 'Gitea MCP 进程启动失败。', { cause: error }));
    });
    child?.once?.('exit', (code, signal) => {
      if (settled) return;
      finish(probeError('gitea_mcp_start_failed', 'Gitea MCP 进程在握手前退出。', {
        exitCode: code ?? null,
        signal: signal || null,
        invalidOutput: sawInvalidLine,
      }));
    });

    timer = setTimeout(() => {
      finish(probeError('gitea_mcp_handshake_timeout', `Gitea MCP initialize 握手超时（${timeoutMs}ms）。`));
    }, timeoutMs);

    try {
      sendJsonLine(child.stdin, initializeRequest());
    } catch (error) {
      finish(probeError('gitea_mcp_handshake_failed', 'Gitea MCP initialize 请求发送失败。', { cause: error }));
    }
  });
}

module.exports = {
  DEFAULT_TIMEOUT_MS,
  MAX_TIMEOUT_MS,
  MCP_PROTOCOL_VERSION,
  probeGiteaMcp,
};