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/**
* Text file processing utilities
* Handles text file detection, reading, and validation
*/
import {
DEFAULT_BINARY_DETECTION_OPTIONS,
type BinaryDetectionOptions
} from '$lib/constants/binary-detection';
import { FileExtensionText } from '$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
* @param options - Optional configuration for detection parameters
* @returns True if the content appears to be text-based
*/
export function isLikelyTextFile(
content: string,
options: Partial<BinaryDetectionOptions> = {}
): boolean {
if (!content) return true;
const config = { ...DEFAULT_BINARY_DETECTION_OPTIONS, ...options };
const sample = content.substring(0, config.prefixLength);
let nullCount = 0;
let suspiciousControlCount = 0;
for (let i = 0; i < sample.length; i++) {
const charCode = sample.charCodeAt(i);
// Count null bytes - these are strong indicators of binary files
if (charCode === 0) {
nullCount++;
continue;
}
// Count suspicious control characters
// Allow common whitespace characters: tab (9), newline (10), carriage return (13)
if (charCode < 32 && charCode !== 9 && charCode !== 10 && charCode !== 13) {
// Count most suspicious control characters
if (charCode < 8 || (charCode > 13 && charCode < 27)) {
suspiciousControlCount++;
}
}
// Count replacement characters (indicates encoding issues)
if (charCode === 0xfffd) {
suspiciousControlCount++;
}
}
// Reject if too many null bytes
if (nullCount > config.maxAbsoluteNullBytes) return false;
// Reject if too many suspicious characters
if (suspiciousControlCount / sample.length > config.suspiciousCharThresholdRatio) return false;
return true;
}
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