import type { Project } from '../model/Project';

/**
 * An undoable edit of the project. Commands mutate the project in place and remember
 * whatever they need to revert. They validate first: `execute` throws a `CommandError` on
 * an invalid operation (e.g. placing a scene into a scene) before it changes anything.
 *
 * The same holds for `undo`: when its target is gone it throws a `CommandError` rather than
 * reverting half of the edit. The command then stays on the undo stack (see `CommandStack`)
 * and the editor shows the message. Validation belongs in `execute`/`undo`, never in the
 * constructor – commands are built outside the editor's error handling.
 */
export interface Command {
  readonly label: string;
  execute(project: Project): void;
  undo(project: Project): void;
}

/** A rejected edit with a message fit for the user; the editor shows it as a notice. */
export class CommandError extends Error {
  constructor(message: string) {
    super(message);
    this.name = 'CommandError';
  }
}