Ace editor and ShareJS text adapter

share_text_attach_ace.js

function attachAce(editor, doc) {
  if (!doc.provides.text) {
    throw new Error("Cannot attach ace to non-text share document");
  }

  let suppress = false;
  editor.setValue(doc.getSnapshot() || "");
  check();

  const newline = editor.getDocument().getNewLineCharacter();
  const newlineLength = newline.length;

  const countChar = (lines) => {
    let cnt = 0;
    for (let i = 0, l = lines.length; i < l; i++) {
      cnt += lines[i].length;
    }
    return cnt + lines.length * newlineLength;
  };

  const indexToPosition = (index) => {
    let line = "";
    const len = editor.getLength();
    for (let i = 0; i < len; i++) {
      line = editor.getLine(i);
      index -= line.length + newlineLength;
      if (index < 0)
        return {
          row: i,
          column: index + line.length + newlineLength
        };
    }

    return {
      row: len - 1,
      column: line.length
    };
  };

  doc.on("op", (op, local) => {
    if (!local) {
      suppress = true;

      let retain = 0;
      for (let i = 0, l = op.length; i < l; i += 1) {
        const x = op[i];
        if (is.integer(x)) {
          retain += x;
        } else if (is.string(x)) {
          editor.insert(indexToPosition(retain), x);
          retain += x.length;
        } else {
          editor.remove({
            start: indexToPosition(retain),
            end: indexToPosition(retain + x.d)
          });
        }
      }

      suppress = false;
      check();
    }
  });

  const onLocalChange = (change) => {
    if (suppress) {
      return;
    }
    applyToShareJS(change);
    check();
  }

  editor.on("change", onLocalChange);

  editor.detachShareJsDoc = () => {
    doc.onRemove = null;
    doc.onInsert = null;
    editor.off("change", onLocalChange);
  }

  function applyToShareJS(data) {
    let startPos = 0;
    if (data.start.row - 1 >= 0) {
        startPos = countChar(editor.getLines(0, data.start.row - 1));
    }
    startPos += data.start.column;

    const len = data.lines.length;
    if (data.action === "insert" && len === 1) {
      doc.submitOp([startPos, data.lines[0]]);
    } else if (data.action === "insert" && len > 1) {
      let text = "";
      for (let i = 0; i < len; i++) {
        text += data.lines[i] + (i === len - 1 ? "" : newline);
      }
      doc.submitOp([startPos, text]);
    } else if (data.action === "remove" && len === 1) {
      doc.submitOp([startPos, {
        d: data.lines[0].length
      }]);
    } else if (data.action === "remove" && len > 1) {
      let cnt = 0;
      for (let i = 0; i < len; i++) {
        cnt += data.lines[i].length + (i === 0 ? 0 : newlineLength);
      }
      doc.submitOp([startPos, {
        d: cnt
      }]);
    } else {
      console.error(`Unknown action: ${data.action}`);
    }
  }

  function check() {
    setTimeout(function() {
      const editorText = editor.getValue();
      const shareText = doc.getSnapshot() || "";

      if (editorText !== shareText) {
        console.error("Editor and share text does not match!");

        let similar = "";
        for (let i = 0; i < Math.min(editorText.length, shareText.length); i += 1) {
          if (editorText[i] === shareText[i]) {
            similar += editorText[i];
          } else {
            console.error(`Similar: ${similar}`);
            console.error(`Diff: editor: ${editorText[i]}; share: ${shareText[i]}`);
            break;
          }
        }

        suppress = true;
        const range = editor.getSelection().getRange();

        editor.setValue(shareText);
        editor.getUndoManager().reset();
        editor.getSelection().setSelectionRange(range);

        suppress = false;
      }
    }, 0);
  }

  return doc;
}