!7

cmodule TextAssist > DynPrintLogAndEnabled {
  int moduleID = 576; // editor ID, XXX
  S lastText;
  new L<Edit> lastEdits;

  srecord Edit(int lineNr, TextEdit edit) {}
  
  start {
    doEvery(1.0, r check);
  }
  
  void check enter {
    if (!enabled) ret;
    S text = cast dm_rcall getText(moduleID);
    pcall {
      compareTexts(lastText, text);
    }
    setField(lastText := text);
  }

  void compareTexts(S lastText, S text) {
    LS linesA = lines(lastText);
    LS linesB = lines(text);

    // need same number of lines
    if (l(linesA) != l(linesB)) ret with print("Line count changed, exiting");

    L<Int> indices = differingIndices(linesA, linesB);
    if (empty(indices)) ret;
    if (l(indices) != 1) ret with print("# changed lines: " + l(indices) + ", exiting");

    int i = first(indices);
    S oldLine = linesA.get(i), newLine = linesB.get(i);

    // Make a TextEdit to see what is changed in line
    TextEdit edit = createTextEdit(oldLine, newLine);
    if (edit == null) ret with print("Line not changed? Weird.");

    print("Line " + i + ": " + edit);

    addToListWithMaxSize(lastEdits, new Edit(i, edit), 2); // keep last 2 edits
    change();

    proposeEdit(text);
  }

  void proposeEdit(S currentText) {
    L<Edit> edits = takeLast(2, lastEdits);
    if (l(edits) < 2) ret;
    int lineNr = first(edits).lineNr;
    if (second(edits).lineNr != lineNr+1) ret;
    TextEdit edit1 = first(edits).edit, edit2 = second(edits).edit;
    //if (!eq(edit1.text, edit2.text)) ret with print("Differing text: " + edit1.text + "/" + edit2.text);
    if (!eq(edit1, edit2)) ret with print("Differing edits: " + edit1 + "/" + edit2);

    S lineToEdit = get(lines(text), lineNr+2);
    print("Line to edit: " + lineToEdit);
    if (lineToEdit == null) ret;
    Edit edit = new Edit(lineNr+2, edit1);
    print("Proposed edit: " + edit);
    print("Would yield: " + replayTextEdit(edit, lineToEdit));
  }
}