@atlaskit/editor-plugin-code-block-advanced/dist/es2019/nodeviews/codemirrorSync/updateCMSelection.js

CodeBlockAdvanced plugin for @atlaskit/editor-core

/**
 *
 * Compares the updated text with the current to determine the transaction to fire
 * in the CodeMirror editor.
 *
 * @param curText string - the current CodeMirror text
 * @param newText string - the new ProseMirror text
 * @returns The changes or undefined if no change
 */

const N_LINE_FEED = '\n'.charCodeAt(0);
const R_LINE_FEED = '\r'.charCodeAt(0);

/**
 * Example of CRLF differences:
 * newText: 'abc\r\ndef\r\nghi'
 * curText: 'abc\ndef\nghi'
 */
export const getCMSelectionChanges = (curText, newText) => {
  if (newText !== curText) {
    let curStart = 0,
      newStart = 0;
    let curEnd = curText.length,
      newEnd = newText.length;
    while (curStart < curEnd && (curText.charCodeAt(curStart) === newText.charCodeAt(newStart) || newText.charCodeAt(newStart) === R_LINE_FEED && curText.charCodeAt(curStart) === N_LINE_FEED)) {
      if (newText.charCodeAt(newStart) === R_LINE_FEED && curText.charCodeAt(curStart) === N_LINE_FEED && newText.charCodeAt(newStart + 1) === N_LINE_FEED) {
        newStart++;
      }
      curStart++;
      newStart++;
    }
    while (curEnd > curStart && newEnd > newStart && (curText.charCodeAt(curEnd - 1) === newText.charCodeAt(newEnd - 1) || newText.charCodeAt(newEnd - 1) === N_LINE_FEED && curText.charCodeAt(curEnd - 1) === N_LINE_FEED)) {
      if (newText.charCodeAt(newEnd - 1) === N_LINE_FEED && curText.charCodeAt(curEnd - 1) === N_LINE_FEED && newText.charCodeAt(newEnd - 2) === R_LINE_FEED) {
        newEnd--;
      }
      curEnd--;
      newEnd--;
    }
    return {
      from: curStart,
      to: curEnd,
      insert: newText.slice(newStart, newEnd)
    };
  }
};