'use strict';

const fs = require('fs');
const path = require('path');
const os = require('os');

/**
 * Resolve the OpsxDB Go MCP binary path.
 * Order: OPSXDB_MCP_BIN → PATH → common install locations.
 * Skips this package's Node launcher and any #! script shims (npm/npx bin
 * is also named opsxdb-mcp and must not be mistaken for the Go server).
 * @returns {string|null}
 */
function resolveBinary() {
  const envBin = process.env.OPSXDB_MCP_BIN;
  if (envBin) {
    const resolved = path.resolve(envBin);
    if (isGoMcpBinary(resolved)) return resolved;
  }

  const onPath = findOnPath('opsxdb-mcp');
  if (onPath) return onPath;

  const home = os.homedir();
  const candidates = [
    path.join(home, 'devops', 'opsxdb', 'bin', 'opsxdb-mcp'),
    path.join(home, '.opsxdb', 'bin', 'opsxdb-mcp'),
    path.join(home, '.local', 'bin', 'opsxdb-mcp'),
    '/usr/local/bin/opsxdb-mcp',
    '/opt/homebrew/bin/opsxdb-mcp',
  ];
  for (const c of candidates) {
    if (isGoMcpBinary(c)) return c;
  }
  return null;
}

function findOnPath(name) {
  const pathEnv = process.env.PATH || '';
  for (const dir of pathEnv.split(path.delimiter)) {
    if (!dir) continue;
    const p = path.join(dir, name);
    if (isGoMcpBinary(p)) return p;
    if (process.platform === 'win32') {
      const pe = p + '.exe';
      if (isGoMcpBinary(pe)) return pe;
    }
  }
  return null;
}

function selfCliPath() {
  return path.resolve(__dirname, '..', 'bin', 'cli.js');
}

function isSameFile(a, b) {
  try {
    return fs.realpathSync(a) === fs.realpathSync(b);
  } catch {
    return false;
  }
}

/**
 * True only for a real Go/native opsxdb-mcp binary (ELF / Mach-O / PE),
 * not npm bin shims or this package's Node cli.js.
 */
function isGoMcpBinary(filePath) {
  try {
    if (!filePath) return false;
    const st = fs.statSync(filePath);
    if (!st.isFile()) return false;
    if (isSameFile(filePath, selfCliPath())) return false;
    if (!isLikelyNativeBinary(filePath)) return false;
    fs.accessSync(filePath, fs.constants.X_OK);
    return true;
  } catch {
    return false;
  }
}

function isLikelyNativeBinary(filePath) {
  let fd;
  try {
    fd = fs.openSync(filePath, 'r');
    const buf = Buffer.alloc(8);
    const n = fs.readSync(fd, buf, 0, 8, 0);
    if (n < 2) return false;
    // Reject scripts (npm shims, node shebang)
    if (buf[0] === 0x23 && buf[1] === 0x21) return false; // #!
    // ELF
    if (n >= 4 && buf[0] === 0x7f && buf[1] === 0x45 && buf[2] === 0x4c && buf[3] === 0x46) {
      return true;
    }
    // PE
    if (buf[0] === 0x4d && buf[1] === 0x5a) return true;
    if (n < 4) return false;
    const be = buf.readUInt32BE(0);
    const le = buf.readUInt32LE(0);
    // Mach-O 64 / 32 (both endians) + fat
    const macho = new Set([
      0xfeedfacf, 0xcffaedfe, 0xfeedface, 0xcefaedfe,
      0xcafebabe, 0xbebafeca, 0xcafebabf, 0xbfbafeca,
    ]);
    if (macho.has(be) || macho.has(le)) return true;
    return false;
  } catch {
    return false;
  } finally {
    if (fd !== undefined) {
      try {
        fs.closeSync(fd);
      } catch {
        /* ignore */
      }
    }
  }
}

function missingBinaryMessage() {
  return `opsxdb-mcp: Go binary not found.

This npm package (@rlwj-lab/opsxdb-mcp) is a Node launcher for the OpsxDB
MCP server (stdio). The real server is a Go binary named opsxdb-mcp.

Build it from the opsxdb repo:

  cd server && go build -o ../bin/opsxdb-mcp ./cmd/opsxdb-mcp

Then either:
  - put that binary on your PATH (ahead of any npm shim), or
  - export OPSXDB_MCP_BIN=/absolute/path/to/opsxdb-mcp

Cursor / Claude Desktop example:

  {
    "mcpServers": {
      "opsxdb": {
        "command": "npx",
        "args": ["-y", "@rlwj-lab/opsxdb-mcp"],
        "env": {
          "OPSXDB_MCP_BIN": "/absolute/path/to/opsxdb-mcp"
        }
      }
    }
  }

Config files (same as native binary):
  ~/.opsxdb/mcp.json
  ~/.opsxdb/connections.json
`;
}

module.exports = {
  resolveBinary,
  missingBinaryMessage,
  isGoMcpBinary,
};