package scheduler

import "context"

// Scheduler 三层编排器——串联 TaskGenerator → ConstraintFilter → PolicyEngine。
// 骨架阶段：只定义接口和编排流程，不直接修改 processor 包。
// 后续阶段：processor 包的 JobRuntime 将通过此 Scheduler 替代直接调用 Dispatcher。
type Scheduler struct {
	generator TaskGenerator
	filter    ConstraintFilter
	policy    PolicyEngine
}

func NewScheduler(g TaskGenerator, f ConstraintFilter, p PolicyEngine) *Scheduler {
	return &Scheduler{
		generator: g,
		filter:    f,
		policy:    p,
	}
}

// ScheduleAll 对多个 Job 执行三层调度，合并结果后排序。
// 用于全局调度场景（如收到 MachineTaskComplete 信号后重新评估所有 Job）。
func (s *Scheduler) ScheduleAll(ctx context.Context, jobs []JobView, state SystemState) []CandidateTask {
	var allCandidates []CandidateTask
	for _, job := range jobs {
		candidates := s.generator.Generate(job)
		allCandidates = append(allCandidates, candidates...)
	}

	if len(allCandidates) == 0 {
		return nil
	}

	feasible := s.filter.Filter(ctx, allCandidates, state)

	if len(feasible) == 0 {
		return nil
	}

	return s.policy.Rank(feasible, state)
}

// DefaultScheduler 创建默认配置的 Scheduler。
// 使用 RecipeTaskGenerator + 所有内置约束 + 默认优先级策略。
func DefaultScheduler() *Scheduler {
	generator := NewRecipeTaskGenerator()
	filter := NewCompositeFilter(
		NewMachineDisabledConstraint(),
		NewMachineBusyConstraint(),
		NewMachineEmptyConstraint(),
		NewTempSlotFullConstraint(),
		NewOrderPausedConstraint(),
		NewOrderPausingConstraint(),
		NewOrderCancellingConstraint(),
		NewJobSuspendedConstraint(),
		NewExchangePairConstraint(),
		NewReplenishConstraint(),
		NewWasteReadyConstraint(),
	)
	policy := NewPriorityPolicy(
		UnloadFirstRule,
		SamplingFirstRule,
		LaterStageUnloadFirstRule,
		IdleMachineLoadFirstRule,
		LaterStageLoadFirstRule,
		ExchangeFirstRule,
		BasePriorityRule,
		JobIDSmallerFirstRule,
		SameMachineRule,
	)

	return NewScheduler(generator, filter, policy)
}