feat: modularize flattener tool into separate components with improved project root detection (#417)

tools/flattener/binary.js

@@ -0,0 +1,53 @@
+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,
+};