strudel-docker/packages/repl-react/CodeMirror.jsx

import React from 'react';
import { Controlled as CodeMirror2 } from 'react-codemirror2';
import 'codemirror/mode/javascript/javascript.js';
import 'codemirror/mode/pegjs/pegjs.js';
// import 'codemirror/theme/material.css';
import 'codemirror/lib/codemirror.css';
import 'codemirror/theme/material.css';

export default function CodeMirror({ value, onChange, onCursor, options, editorDidMount }) {
  options = options || {
    mode: 'javascript',
    theme: 'material',
    lineNumbers: true,
    styleSelectedText: true,
    cursorBlinkRate: 500,
  };
  return (
    <CodeMirror2
      value={value}
      options={options}
      onBeforeChange={onChange}
      editorDidMount={editorDidMount}
      onCursor={(editor, data) => onCursor?.(editor, data)}
    />
  );
}

export const markEvent = (editor) => (time, event) => {
  const locs = event.context.locations;
  if (!locs || !editor) {
    return;
  }
  const col = event.context?.color || '#FFCA28';
  // mark active event
  const marks = locs.map(({ start, end }) =>
    editor.getDoc().markText(
      { line: start.line - 1, ch: start.column },
      { line: end.line - 1, ch: end.column },
      //{ css: 'background-color: #FFCA28; color: black' } // background-color is now used by parent marking
      { css: 'outline: 1px solid ' + col + '; box-sizing:border-box' },
      //{ css: `background-color: ${col};border-radius:5px` },
    ),
  );
  //Tone.Transport.schedule(() => { // problem: this can be cleared by scheduler...
  setTimeout(() => {
    marks.forEach((mark) => mark.clear());
    // }, '+' + event.duration * 0.5);
  }, event.duration /* * 0.9 */ * 1000);
};

let parenMark;
export const markParens = (editor, data) => {
  const v = editor.getDoc().getValue();
  const marked = getCurrentParenArea(v, data);
  parenMark?.clear();
  parenMark = editor.getDoc().markText(...marked, { css: 'background-color: #00007720' }); //
};

// returns { line, ch } from absolute character offset
export function offsetToPosition(offset, code) {
  const lines = code.split('\n');
  let line = 0;
  let ch = 0;
  for (let i = 0; i < offset; i++) {
    if (ch === lines[line].length) {
      line++;
      ch = 0;
    } else {
      ch++;
    }
  }
  return { line, ch };
}

// returns absolute character offset from { line, ch }
export function positionToOffset(position, code) {
  const lines = code.split('\n');
  let offset = 0;
  for (let i = 0; i < position.line; i++) {
    offset += lines[i].length + 1;
  }
  offset += position.ch;
  return offset;
}

// given code and caret position, the functions returns the indices of the parens we are in
export function getCurrentParenArea(code, caretPosition) {
  const caret = positionToOffset(caretPosition, code);
  let open, i, begin, end;
  // walk left
  i = caret;
  open = 0;
  while (i > 0) {
    if (code[i - 1] === '(') {
      open--;
    } else if (code[i - 1] === ')') {
      open++;
    }
    if (open === -1) {
      break;
    }
    i--;
  }
  begin = i;
  // walk right
  i = caret;
  open = 0;
  while (i < code.length) {
    if (code[i] === '(') {
      open--;
    } else if (code[i] === ')') {
      open++;
    }
    if (open === 1) {
      break;
    }
    i++;
  }
  end = i;
  return [begin, end].map((o) => offsetToPosition(o, code));
}