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

/**
 * Several commands as one undo step. If one throws, the ones already done are rolled back before
 * re-throwing, so the project is never left half-changed.
 */
export class CompoundCommand implements Command {
  constructor(
    readonly label: string,
    private readonly commands: readonly Command[],
  ) {}

  execute(project: Project): void {
    const done: Command[] = [];
    try {
      for (const command of this.commands) {
        command.execute(project);
        done.push(command);
      }
    } catch (error) {
      for (const command of done.reverse()) command.undo(project);
      throw error;
    }
  }

  undo(project: Project): void {
    for (let i = this.commands.length - 1; i >= 0; i--) this.commands[i]!.undo(project);
  }
}

/** A lone command stays itself, so the undo step keeps its own label. */
export function oneStep(label: string, commands: readonly Command[]): Command {
  return commands.length === 1 ? commands[0]! : new CompoundCommand(label, commands);
}