SvelteKit-based WebUI (#14839)

tools/server/webui/src/lib/utils/text-files.ts

@@ -0,0 +1,83 @@
+/**
+ * Text file processing utilities
+ * Handles text file detection, reading, and validation
+ */
+
+import { FileExtensionText } from '$lib/enums/files';
+
+/**
+ * Check if a filename indicates a text file based on its extension
+ * @param filename - The filename to check
+ * @returns True if the filename has a recognized text file extension
+ */
+export function isTextFileByName(filename: string): boolean {
+	const textExtensions = Object.values(FileExtensionText);
+
+	return textExtensions.some((ext: FileExtensionText) => filename.toLowerCase().endsWith(ext));
+}
+
+/**
+ * Read a file's content as text
+ * @param file - The file to read
+ * @returns Promise resolving to the file's text content
+ */
+export async function readFileAsText(file: File): Promise<string> {
+	return new Promise((resolve, reject) => {
+		const reader = new FileReader();
+
+		reader.onload = (event) => {
+			if (event.target?.result !== null && event.target?.result !== undefined) {
+				resolve(event.target.result as string);
+			} else {
+				reject(new Error('Failed to read file'));
+			}
+		};
+
+		reader.onerror = () => reject(new Error('File reading error'));
+
+		reader.readAsText(file);
+	});
+}
+
+/**
+ * Heuristic check to determine if content is likely from a text file
+ * Detects binary files by counting suspicious characters and null bytes
+ * @param content - The file content to analyze
+ * @returns True if the content appears to be text-based
+ */
+export function isLikelyTextFile(content: string): boolean {
+	if (!content) return true;
+
+	const sample = content.substring(0, 1000);
+
+	let suspiciousCount = 0;
+	let nullCount = 0;
+
+	for (let i = 0; i < sample.length; i++) {
+		const charCode = sample.charCodeAt(i);
+
+		// Count null bytes
+		if (charCode === 0) {
+			nullCount++;
+			suspiciousCount++;
+
+			continue;
+		}
+
+		// Count suspicious control characters (excluding common ones like tab, newline, carriage return)
+		if (charCode < 32 && charCode !== 9 && charCode !== 10 && charCode !== 13) {
+			suspiciousCount++;
+		}
+
+		// Count replacement characters (indicates encoding issues)
+		if (charCode === 0xfffd) {
+			suspiciousCount++;
+		}
+	}
+
+	// Reject if too many null bytes or suspicious characters
+	if (nullCount > 2) return false;
+	if (suspiciousCount / sample.length > 0.1) return false;
+
+	return true;
+}