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/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import stripAnsi from 'strip-ansi';
import { stripVTControlCharacters } from 'util';
/**
* Calculates the maximum width of a multi-line ASCII art string.
* @param asciiArt The ASCII art string.
* @returns The length of the longest line in the ASCII art.
*/
export const getAsciiArtWidth = (asciiArt: string): number => {
if (!asciiArt) {
return 0;
}
const lines = asciiArt.split('\n');
return Math.max(...lines.map((line) => line.length));
};
/*
* -------------------------------------------------------------------------
* Unicode‑aware helpers (work at the code‑point level rather than UTF‑16
* code units so that surrogate‑pair emoji count as one "column".)
* ---------------------------------------------------------------------- */
export function toCodePoints(str: string): string[] {
// [...str] or Array.from both iterate by UTF‑32 code point, handling
// surrogate pairs correctly.
return Array.from(str);
}
export function cpLen(str: string): number {
return toCodePoints(str).length;
}
export function cpSlice(str: string, start: number, end?: number): string {
// Slice by code‑point indices and re‑join.
const arr = toCodePoints(str).slice(start, end);
return arr.join('');
}
/**
* Strip characters that can break terminal rendering.
*
* Uses Node.js built-in stripVTControlCharacters to handle VT sequences,
* then filters remaining control characters that can disrupt display.
*
* Characters stripped:
* - ANSI escape sequences (via strip-ansi)
* - VT control sequences (via Node.js util.stripVTControlCharacters)
* - C0 control chars (0x00-0x1F) except CR/LF which are handled elsewhere
* - C1 control chars (0x80-0x9F) that can cause display issues
*
* Characters preserved:
* - All printable Unicode including emojis
* - DEL (0x7F) - handled functionally by applyOperations, not a display issue
* - CR/LF (0x0D/0x0A) - needed for line breaks
*/
export function stripUnsafeCharacters(str: string): string {
const strippedAnsi = stripAnsi(str);
const strippedVT = stripVTControlCharacters(strippedAnsi);
return toCodePoints(strippedVT)
.filter((char) => {
const code = char.codePointAt(0);
if (code === undefined) return false;
// Preserve CR/LF for line handling
if (code === 0x0a || code === 0x0d) return true;
// Remove C0 control chars (except CR/LF) that can break display
// Examples: BELL(0x07) makes noise, BS(0x08) moves cursor, VT(0x0B), FF(0x0C)
if (code >= 0x00 && code <= 0x1f) return false;
// Remove C1 control chars (0x80-0x9f) - legacy 8-bit control codes
if (code >= 0x80 && code <= 0x9f) return false;
// Preserve DEL (0x7f) - it's handled functionally by applyOperations as backspace
// and doesn't cause rendering issues when displayed
// Preserve all other characters including Unicode/emojis
return true;
})
.join('');
}
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