package proxy

import (
	"container/list"
	"context"
	"log"
	"sync"
)

type baseTaskQueue struct {
	unissuedTasks *list.List
	activeTasks   map[Timestamp]*task
	utLock        sync.Mutex
	atLock        sync.Mutex
}

type ddTaskQueue struct {
	baseTaskQueue
	lock sync.Mutex
}

type dmTaskQueue struct {
	baseTaskQueue
}

type dqTaskQueue struct {
	baseTaskQueue
}

func (queue *baseTaskQueue) Empty() bool {
	queue.utLock.Lock()
	defer queue.utLock.Unlock()
	queue.atLock.Lock()
	defer queue.atLock.Unlock()
	return queue.unissuedTasks.Len() <= 0 && len(queue.activeTasks) <= 0
}

func (queue *baseTaskQueue) AddUnissuedTask(t *task) {
	queue.utLock.Lock()
	defer queue.utLock.Unlock()
	queue.unissuedTasks.PushBack(t)
}

func (queue *baseTaskQueue) FrontUnissuedTask() *task {
	queue.utLock.Lock()
	defer queue.utLock.Unlock()
	if queue.unissuedTasks.Len() <= 0 {
		log.Fatal("sorry, but the unissued task list is empty!")
		return nil
	}
	return queue.unissuedTasks.Front().Value.(*task)
}

func (queue *baseTaskQueue) PopUnissuedTask() *task {
	queue.utLock.Lock()
	defer queue.utLock.Unlock()
	if queue.unissuedTasks.Len() <= 0 {
		log.Fatal("sorry, but the unissued task list is empty!")
		return nil
	}
	ft := queue.unissuedTasks.Front()
	return queue.unissuedTasks.Remove(ft).(*task)
}

func (queue *baseTaskQueue) AddActiveTask(t *task) {
	queue.atLock.Lock()
	defer queue.atLock.Lock()
	ts := (*t).EndTs()
	_, ok := queue.activeTasks[ts]
	if ok {
		log.Fatalf("task with timestamp %v already in active task list!", ts)
	}
	queue.activeTasks[ts] = t
}

func (queue *baseTaskQueue) PopActiveTask(ts Timestamp) *task {
	queue.atLock.Lock()
	defer queue.atLock.Lock()
	t, ok := queue.activeTasks[ts]
	if ok {
		delete(queue.activeTasks, ts)
		return t
	}
	log.Fatalf("sorry, but the timestamp %d was not found in the active task list!", ts)
	return nil
}

func (queue *baseTaskQueue) TaskDoneTest(ts Timestamp) bool {
	queue.utLock.Lock()
	defer queue.utLock.Unlock()
	for e := queue.unissuedTasks.Front(); e != nil; e = e.Next() {
		if (*(e.Value.(*task))).EndTs() >= ts {
			return false
		}
	}

	queue.atLock.Lock()
	defer queue.atLock.Unlock()
	for ats := range queue.activeTasks {
		if ats >= ts {
			return false
		}
	}

	return true
}

func (queue *ddTaskQueue) Enqueue(t *task) error {
	queue.lock.Lock()
	defer queue.lock.Unlock()
	// TODO: set Ts, ReqId, ProxyId
	queue.AddUnissuedTask(t)
	return nil
}

func (queue *dmTaskQueue) Enqueue(t *task) error {
	// TODO: set Ts, ReqId, ProxyId
	queue.AddUnissuedTask(t)
	return nil
}

func (queue *dqTaskQueue) Enqueue(t *task) error {
	// TODO: set Ts, ReqId, ProxyId
	queue.AddUnissuedTask(t)
	return nil
}

type TaskScheduler struct {
	DdQueue *ddTaskQueue
	DmQueue *dmTaskQueue
	DqQueue *dqTaskQueue

	// tsAllocator, ReqIdAllocator
	wg     sync.WaitGroup
	ctx    context.Context
	cancel context.CancelFunc
}

func (sched *TaskScheduler) scheduleDdTask() *task {
	return sched.DdQueue.PopUnissuedTask()
}

func (sched *TaskScheduler) scheduleDmTask() *task {
	return sched.DmQueue.PopUnissuedTask()
}

func (sched *TaskScheduler) scheduleDqTask() *task {
	return sched.DqQueue.PopUnissuedTask()
}

func (sched *TaskScheduler) definitionLoop() {
	defer sched.wg.Done()
	defer sched.cancel()
}

func (sched *TaskScheduler) manipulationLoop() {
	defer sched.wg.Done()
	defer sched.cancel()

	for {
		if sched.DmQueue.Empty() {
			continue
		}

		sched.DmQueue.atLock.Lock()
		t := sched.scheduleDmTask()

		if err := (*t).PreExecute(); err != nil {
			return
		}

		go func() {
			err := (*t).Execute()
			if err != nil {
				log.Printf("execute manipulation task failed, error = %v", err)
			}
			(*t).Notify(err)
		}()

		sched.DmQueue.AddActiveTask(t)
		sched.DmQueue.atLock.Unlock()

		go func() {
			(*t).WaitToFinish()
			(*t).PostExecute()

			// remove from active list
			sched.DmQueue.PopActiveTask((*t).EndTs())
		}()
	}
}

func (sched *TaskScheduler) queryLoop() {
	defer sched.wg.Done()
	defer sched.cancel()
}

func (sched *TaskScheduler) Start(ctx context.Context) error {
	sched.ctx, sched.cancel = context.WithCancel(ctx)
	sched.wg.Add(3)

	go sched.definitionLoop()
	go sched.manipulationLoop()
	go sched.queryLoop()

	return nil
}

func (sched *TaskScheduler) Close() {
	sched.cancel()
	sched.wg.Wait()
}

func (sched *TaskScheduler) TaskDoneTest(ts Timestamp) bool {
	ddTaskDone := sched.DdQueue.TaskDoneTest(ts)
	dmTaskDone := sched.DmQueue.TaskDoneTest(ts)
	dqTaskDone := sched.DqQueue.TaskDoneTest(ts)
	return ddTaskDone && dmTaskDone && dqTaskDone
}