package alerting

import (
	"fmt"
	"time"

	"github.com/Unknwon/log"
	"github.com/grafana/grafana/pkg/services/alerting/alertstates"
)

type Scheduler struct {
	jobs          map[int64]*AlertJob
	runQueue      chan *AlertJob
	responseQueue chan *AlertResult
}

func NewScheduler() *Scheduler {
	return &Scheduler{
		jobs:          make(map[int64]*AlertJob, 0),
		runQueue:      make(chan *AlertJob, 1000),
		responseQueue: make(chan *AlertResult, 1000),
	}
}

func (scheduler *Scheduler) dispatch(reader RuleReader) {
	reschedule := time.NewTicker(time.Second * 10)
	secondTicker := time.NewTicker(time.Second)

	scheduler.updateJobs(reader.Fetch)

	for {
		select {
		case <-secondTicker.C:
			scheduler.queueJobs()
		case <-reschedule.C:
			scheduler.updateJobs(reader.Fetch)
		}
	}
}

func (scheduler *Scheduler) updateJobs(alertRuleFn func() []AlertRule) {
	log.Debug("Scheduler: UpdateJobs()")

	jobs := make(map[int64]*AlertJob, 0)
	rules := alertRuleFn()

	for i, rule := range rules {
		var job *AlertJob
		if scheduler.jobs[rule.Id] != nil {
			job = scheduler.jobs[rule.Id]
		} else {
			job = &AlertJob{
				Running:    false,
				RetryCount: 0,
			}
		}

		job.Rule = rule
		job.Offset = int64(i)

		jobs[rule.Id] = job
	}

	log.Debug("Scheduler: Selected %d jobs", len(jobs))
	scheduler.jobs = jobs
}

func (scheduler *Scheduler) queueJobs() {
	now := time.Now().Unix()
	for _, job := range scheduler.jobs {
		if now%job.Rule.Frequency == 0 && job.Running == false {
			log.Info("Scheduler: Putting job on to run queue: %s", job.Rule.Title)
			scheduler.runQueue <- job
		}
	}
}

func (scheduler *Scheduler) executor(executor Executor) {
	for job := range scheduler.runQueue {
		//log.Info("Executor: queue length %d", len(this.runQueue))
		log.Info("Executor: executing %s", job.Rule.Title)
		job.Running = true
		scheduler.measureAndExecute(executor, job)
	}
}

func (scheduler *Scheduler) handleResponses() {
	for response := range scheduler.responseQueue {
		log.Info("Response: alert(%d) status(%s) actual(%v) retry(%d)", response.Id, response.State, response.ActualValue, response.AlertJob.RetryCount)
		response.AlertJob.Running = false

		if response.IsResultIncomplete() {
			response.AlertJob.RetryCount++
			if response.AlertJob.RetryCount < maxRetries {
				scheduler.runQueue <- response.AlertJob
			} else {
				saveState(&AlertResult{
					Id:          response.Id,
					State:       alertstates.Critical,
					Description: fmt.Sprintf("Failed to run check after %d retires", maxRetries),
				})
			}
		} else {
			response.AlertJob.RetryCount = 0
			saveState(response)
		}
	}
}

func (scheduler *Scheduler) measureAndExecute(exec Executor, job *AlertJob) {
	now := time.Now()

	responseChan := make(chan *AlertResult, 1)
	go exec.Execute(job, responseChan)

	select {
	case <-time.After(time.Second * 5):
		scheduler.responseQueue <- &AlertResult{
			Id:       job.Rule.Id,
			State:    alertstates.Pending,
			Duration: float64(time.Since(now).Nanoseconds()) / float64(1000000),
			AlertJob: job,
		}
	case result := <-responseChan:
		result.Duration = float64(time.Since(now).Nanoseconds()) / float64(1000000)
		log.Info("Schedular: exeuction took %vms", result.Duration)
		scheduler.responseQueue <- result
	}
}