const fsp = require("node:fs/promises");
const path = require("node:path");
const { Buffer } = require("node:buffer");

/**
 * Efficiently determine if a file is binary without reading the whole file.
 * - Fast path by extension for common binaries
 * - Otherwise read a small prefix and check for NUL bytes
 * @param {string} filePath
 * @returns {Promise<boolean>}
 */
async function isBinaryFile(filePath) {
  try {
    const stats = await fsp.stat(filePath);
    if (stats.isDirectory()) {
      throw new Error("EISDIR: illegal operation on a directory");
    }

    const binaryExtensions = new Set([
      ".jpg", ".jpeg", ".png", ".gif", ".bmp", ".ico", ".svg",
      ".pdf", ".doc", ".docx", ".xls", ".xlsx", ".ppt", ".pptx",
      ".zip", ".tar", ".gz", ".rar", ".7z",
      ".exe", ".dll", ".so", ".dylib",
      ".mp3", ".mp4", ".avi", ".mov", ".wav",
      ".ttf", ".otf", ".woff", ".woff2",
      ".bin", ".dat", ".db", ".sqlite",
    ]);

    const ext = path.extname(filePath).toLowerCase();
    if (binaryExtensions.has(ext)) return true;
    if (stats.size === 0) return false;

    const sampleSize = Math.min(4096, stats.size);
    const fd = await fsp.open(filePath, "r");
    try {
      const buffer = Buffer.allocUnsafe(sampleSize);
      const { bytesRead } = await fd.read(buffer, 0, sampleSize, 0);
      const slice = bytesRead === sampleSize ? buffer : buffer.subarray(0, bytesRead);
      return slice.includes(0);
    } finally {
      await fd.close();
    }
  } catch (error) {
    console.warn(
      `Warning: Could not determine if file is binary: ${filePath} - ${error.message}`,
    );
    return false;
  }
}

module.exports = {
  isBinaryFile,
};