@fairfox/zws/dist/index.js

Zero-width steganography utilities for invisibly embedding data in text using Unicode zero-width characters

// src/index.ts
var START_MARKER = "​‌";
var ZERO_BIT = "​";
var ONE_BIT = "‌";
var LENGTH_BITS = 16;
var MAX_DATA_LENGTH = 100;
var MAX_ENCODED_LENGTH = MAX_DATA_LENGTH * 16;
function hasEmbeddedData(text) {
  return text.includes(START_MARKER);
}
function embed(text, data, options = {}) {
  if (hasEmbeddedData(text)) {
    throw new Error("Cannot embed: text already contains embedded data");
  }
  const payload = encodeData(data);
  const lengthPrefix = bitsForLength(data.length);
  const marker = START_MARKER + lengthPrefix + payload;
  if (options.position === "after-first-sentence") {
    const sentenceEnd = text.search(/[.!?]\s/);
    if (sentenceEnd !== -1) {
      const insertPos = sentenceEnd + 1;
      return text.substring(0, insertPos) + marker + text.substring(insertPos);
    }
  }
  return text + marker;
}
function extract(text) {
  if (!hasEmbeddedData(text))
    return "";
  const ranges = findEmbeds(text);
  if (ranges.length === 0)
    return "";
  const r = ranges[0];
  return decodeData(text.substring(r.payloadStart, r.payloadStart + r.payloadLength));
}
function extractAll(text) {
  if (!hasEmbeddedData(text))
    return [];
  return findEmbeds(text).map((r) => decodeData(text.substring(r.payloadStart, r.payloadStart + r.payloadLength)));
}
function getCleanText(text) {
  if (!hasEmbeddedData(text))
    return text;
  const ranges = findEmbeds(text);
  if (ranges.length === 0)
    return text;
  let out = "";
  let cursor = 0;
  for (const r of ranges) {
    out += text.substring(cursor, r.start);
    cursor = r.end;
  }
  out += text.substring(cursor);
  return out;
}
function encodeData(data) {
  if (data.length > MAX_DATA_LENGTH) {
    throw new Error(`Data too long: ${data.length} characters. Maximum allowed: ${MAX_DATA_LENGTH} characters.`);
  }
  for (let i = 0;i < data.length; i++) {
    const codePoint = data.codePointAt(i) || 0;
    if (codePoint > 65535) {
      throw new Error(`Invalid character in data: "${data[i]}" (U+${codePoint.toString(16).toUpperCase()}). Data must lie within the Basic Multilingual Plane.`);
    }
  }
  const binary = Array.from(data).map((char) => char.charCodeAt(0).toString(2).padStart(16, "0")).join("");
  return binary.split("").map((bit) => bit === "0" ? ZERO_BIT : ONE_BIT).join("");
}
function decodeData(encodedBinary) {
  if (encodedBinary.length > MAX_ENCODED_LENGTH) {
    throw new Error(`Encoded data too long: ${encodedBinary.length} characters. Maximum allowed: ${MAX_ENCODED_LENGTH} characters.`);
  }
  const cleanBinary = encodedBinary.split("").filter((char) => char === ZERO_BIT || char === ONE_BIT).map((char) => char === ZERO_BIT ? "0" : "1").join("");
  const chars = [];
  for (let i = 0;i < cleanBinary.length; i += 16) {
    const charBinary = cleanBinary.substring(i, i + 16);
    if (charBinary.length === 16) {
      const codePoint = Number.parseInt(charBinary, 2);
      chars.push(String.fromCharCode(codePoint));
    }
  }
  return chars.join("");
}
function bitsForLength(n) {
  return n.toString(2).padStart(LENGTH_BITS, "0").split("").map((bit) => bit === "0" ? ZERO_BIT : ONE_BIT).join("");
}
function findEmbeds(text) {
  const ranges = [];
  let i = 0;
  while (i <= text.length - START_MARKER.length) {
    const startIdx = text.indexOf(START_MARKER, i);
    if (startIdx === -1)
      break;
    const lengthStart = startIdx + START_MARKER.length;
    const payloadStart = lengthStart + LENGTH_BITS;
    if (payloadStart > text.length) {
      i = startIdx + 1;
      continue;
    }
    let lengthBinary = "";
    let valid = true;
    for (let k = 0;k < LENGTH_BITS; k++) {
      const c = text[lengthStart + k];
      if (c === ZERO_BIT)
        lengthBinary += "0";
      else if (c === ONE_BIT)
        lengthBinary += "1";
      else {
        valid = false;
        break;
      }
    }
    if (!valid) {
      i = startIdx + 1;
      continue;
    }
    const dataLength = Number.parseInt(lengthBinary, 2);
    if (dataLength > MAX_DATA_LENGTH) {
      i = startIdx + 1;
      continue;
    }
    const payloadLength = dataLength * 16;
    const end = payloadStart + payloadLength;
    if (end > text.length) {
      i = startIdx + 1;
      continue;
    }
    let payloadValid = true;
    for (let k = 0;k < payloadLength; k++) {
      const c = text[payloadStart + k];
      if (c !== ZERO_BIT && c !== ONE_BIT) {
        payloadValid = false;
        break;
      }
    }
    if (!payloadValid) {
      i = startIdx + 1;
      continue;
    }
    ranges.push({ start: startIdx, end, payloadStart, payloadLength });
    i = end;
  }
  return ranges;
}
var zws = {
  START_MARKER,
  ZERO_BIT,
  ONE_BIT,
  MAX_DATA_LENGTH,
  MAX_ENCODED_LENGTH,
  hasEmbeddedData,
  embed,
  extract,
  extractAll,
  getCleanText,
  encodeData,
  decodeData
};
var src_default = zws;
export {
  src_default as default
};