import 'models.dart';
import 'scheduling_engine.dart';

/// Quick actions available from a flexible task card.
enum FlexibleTaskQuickAction {
  done,
  push,
  backlog,
  breakUp,
}

/// Explicit push destinations shown after choosing the push quick action.
enum PushDestination {
  nextAvailableSlot,
  tomorrowTopOfQueue,
  backlog,
}

/// Domain result for a flexible task quick action.
class FlexibleTaskActionResult {
  const FlexibleTaskActionResult({
    required this.action,
    required this.task,
    this.pushDestinations = const <PushDestination>[],
    this.startsChildTaskFlow = false,
  });

  final FlexibleTaskQuickAction action;
  final Task task;
  final List<PushDestination> pushDestinations;
  final bool startsChildTaskFlow;

  bool get changedTask => !startsChildTaskFlow && pushDestinations.isEmpty;
}

/// Applies low-friction quick actions for flexible task cards.
class FlexibleTaskActionService {
  const FlexibleTaskActionService({
    this.schedulingEngine = const SchedulingEngine(),
  });

  final SchedulingEngine schedulingEngine;

  FlexibleTaskActionResult apply({
    required Task task,
    required FlexibleTaskQuickAction action,
    DateTime? updatedAt,
  }) {
    if (!task.isFlexible) {
      throw ArgumentError.value(
          task.type, 'task.type', 'Task must be flexible.');
    }

    switch (action) {
      case FlexibleTaskQuickAction.done:
        return FlexibleTaskActionResult(
          action: action,
          task: task.copyWith(
            status: TaskStatus.completed,
            updatedAt: updatedAt ?? DateTime.now(),
          ),
        );
      case FlexibleTaskQuickAction.push:
        return FlexibleTaskActionResult(
          action: action,
          task: task,
          pushDestinations: const [
            PushDestination.nextAvailableSlot,
            PushDestination.tomorrowTopOfQueue,
            PushDestination.backlog,
          ],
        );
      case FlexibleTaskQuickAction.backlog:
        return FlexibleTaskActionResult(
          action: action,
          task: schedulingEngine.moveToBacklog(task, updatedAt: updatedAt),
        );
      case FlexibleTaskQuickAction.breakUp:
        return FlexibleTaskActionResult(
          action: action,
          task: task,
          startsChildTaskFlow: true,
        );
    }
  }
}