Method push

packages/core/src/runtime/inputEditor.ts:510–554

(
    before: InputEditorSnapshot,
    after: InputEditorSnapshot,
    timestamp: number,
    groupable = false,
  )

  private readonly redo: InputUndoEntry[] = [];

  push(
    before: InputEditorSnapshot,
    after: InputEditorSnapshot,
    timestamp: number,
    groupable = false,
  ): void {
    if (
      before.value === after.value &&
      before.cursor === after.cursor &&
      before.selectionStart === after.selectionStart &&
      before.selectionEnd === after.selectionEnd
    ) {
      return;
    }

    const t = Number.isFinite(timestamp) ? Math.trunc(timestamp) : 0;
    const last = this.undo[this.undo.length - 1];
    if (
      groupable &&
      last &&
      last.groupable &&
      t - last.timestamp <= INPUT_UNDO_GROUP_WINDOW_MS &&
      t >= last.timestamp
    ) {
      this.undo[this.undo.length - 1] = Object.freeze({
        before: last.before,
        after,
        timestamp: t,
        groupable: true,
      });
      this.redo.length = 0;
      return;
    }

    this.undo.push(
      Object.freeze({
        before,
        after,
        timestamp: t,
        groupable,
      }),
    );
    if (this.undo.length > INPUT_UNDO_STACK_CAP) this.undo.shift();
    this.redo.length = 0;
  }

  undoSnapshot(): InputEditorSnapshot | null {
    const entry = this.undo.pop();