Function applyToText

src/static/js/Changeset.ts:404–440

(cs: string, str: string)

 * @returns {string}
 */
export const applyToText = (cs: string, str: string): string => {
  const unpacked = unpack(cs);
  assert(str.length === unpacked.oldLen, `mismatched apply: ${str.length} / ${unpacked.oldLen}`);
  const bankIter = new StringIterator(unpacked.charBank);
  const strIter = new StringIterator(str);
  const assem = new StringAssembler();
  for (const op of deserializeOps(unpacked.ops)) {
    switch (op.opcode) {
      case '+':
        // op is + and op.lines 0: no newlines must be in op.chars
        // op is + and op.lines >0: op.chars must include op.lines newlines
        if (op.lines !== bankIter.peek(op.chars).split('\n').length - 1) {
          throw new Error(`newline count is wrong in op +; cs:${cs} and text:${str}`);
        }
        assem.append(bankIter.take(op.chars));
        break;
      case '-':
        // op is - and op.lines 0: no newlines must be in the deleted string
        // op is - and op.lines >0: op.lines newlines must be in the deleted string
        if (op.lines !== strIter.peek(op.chars).split('\n').length - 1) {
          throw new Error(`newline count is wrong in op -; cs:${cs} and text:${str}`);
        }
        strIter.skip(op.chars);
        break;
      case '=':
        // op is = and op.lines 0: no newlines must be in the copied string
        // op is = and op.lines >0: op.lines newlines must be in the copied string
        if (op.lines !== strIter.peek(op.chars).split('\n').length - 1) {
          throw new Error(`newline count is wrong in op =; cs:${cs} and text:${str}`);
        }
        assem.append(strIter.take(op.chars));
        break;
    }
  }
  assem.append(strIter.take(strIter.remaining()));
  return assem.toString();
};

/**
 * Applies a changeset on an array of lines.