// Copyright Project Harbor Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package period

import (
	"context"
	"fmt"
	"math/rand"
	"time"

	"github.com/gocraft/work"
	"github.com/goharbor/harbor/src/jobservice/common/rds"
	"github.com/goharbor/harbor/src/jobservice/common/utils"
	"github.com/goharbor/harbor/src/jobservice/job"
	"github.com/goharbor/harbor/src/jobservice/lcm"
	"github.com/goharbor/harbor/src/jobservice/logger"
	"github.com/gomodule/redigo/redis"
	"github.com/robfig/cron"
)

const (
	enqueuerSleep   = 2 * time.Minute
	enqueuerHorizon = 4 * time.Minute

	// PeriodicExecutionMark marks the scheduled job to a periodic execution
	PeriodicExecutionMark = "_job_kind_periodic_"
)

type enqueuer struct {
	namespace string
	context   context.Context
	pool      *redis.Pool
	ctl       lcm.Controller
	// Diff with other nodes
	nodeID string
	// Track the error of enqueuing
	lastEnqueueErr error
}

func newEnqueuer(ctx context.Context, namespace string, pool *redis.Pool, ctl lcm.Controller) *enqueuer {
	nodeID := ctx.Value(utils.NodeID)
	if nodeID == nil {
		// Must be failed
		panic("missing node ID in the system context of periodic enqueuer")
	}

	return &enqueuer{
		context:   ctx,
		namespace: namespace,
		pool:      pool,
		ctl:       ctl,
		nodeID:    nodeID.(string),
	}
}

// Blocking call
func (e *enqueuer) start() {
	go e.loop()
	logger.Info("Scheduler: periodic enqueuer is started")
}

func (e *enqueuer) loop() {
	defer func() {
		logger.Info("Scheduler: periodic enqueuer is stopped")
	}()

	// Do enqueue immediately when starting
	isHit := e.checkAndEnqueue()

	// Begin reaping periodically
	timer := time.NewTimer(e.nextTurn(isHit, e.lastEnqueueErr != nil))
	defer timer.Stop()

	for {
		select {
		case <-e.context.Done():
			return // exit
		case <-timer.C:
			// Check and enqueue.
			// Set next turn with lower priority to balance workload with long
			// round time if it hits.
			isHit = e.checkAndEnqueue()
			timer.Reset(e.nextTurn(isHit, e.lastEnqueueErr != nil))
		}
	}
}

// checkAndEnqueue checks if it should do enqueue and
// does enqueue when condition hit.
func (e *enqueuer) checkAndEnqueue() (isHit bool) {
	if isHit = e.shouldEnqueue(); isHit {
		e.enqueue()
	}

	return
}

// nextTurn returns the next check time slot by applying
// priorities to balance the workloads across multiple nodes
func (e *enqueuer) nextTurn(isHit bool, enqErr bool) time.Duration {
	base := enqueuerSleep

	if isHit {
		// Down the hit priority by adding more waiting time
		base = base + time.Duration(3)*time.Second
		if enqErr {
			// Downgrade the priority if the node has occurred error when enqueuing
			base = base + time.Duration(5)*time.Second
		}
	} else {
		// Upgrade the priority of hitting in the next turn
		base = base - time.Duration(3)*time.Second
	}

	// Add random waiting time [0,8)
	base = base + time.Duration(rand.Intn(5))*time.Second

	return base
}

func (e *enqueuer) enqueue() {
	conn := e.pool.Get()
	defer func() {
		_ = conn.Close()
	}()

	// Reset error track
	e.lastEnqueueErr = nil

	// Load policies and schedule next jobs for them
	pls, err := Load(e.namespace, conn)
	if err != nil {
		// Log error
		logger.Errorf("%s:%s", err, "enqueue error: enqueuer")
		return
	}

	for _, p := range pls {
		e.scheduleNextJobs(p, conn)
	}
}

// scheduleNextJobs schedules job for next time slots based on the policy
func (e *enqueuer) scheduleNextJobs(p *Policy, conn redis.Conn) {
	// Follow UTC time spec
	nowTime := time.Unix(time.Now().UTC().Unix(), 0).UTC()
	horizon := nowTime.Add(enqueuerHorizon)

	schedule, err := cron.Parse(p.CronSpec)
	if err != nil {
		// The cron spec should be already checked at upper layers.
		// Just in cases, if error occurred, ignore it
		e.lastEnqueueErr = err
		logger.Errorf("Invalid corn spec in periodic policy %s %s: %s", p.JobName, p.ID, err)
	} else {
		for t := schedule.Next(nowTime); t.Before(horizon); t = schedule.Next(t) {
			epoch := t.Unix()

			// Clone parameters
			// Add extra argument for job running too.
			// Notes: Only for system using
			wJobParams := cloneParameters(p.JobParameters, epoch)

			// Create an execution (job) based on the periodic job template (policy)
			j := &work.Job{
				Name: p.JobName,
				ID:   p.ID, // Use the ID of policy to avoid scheduling duplicated periodic job executions.

				// This is technically wrong, but this lets the bytes be identical for the same periodic job instance.
				// If we don't do this, we'd need to use a different approach -- probably giving each periodic job its own
				// history of the past 100 periodic jobs, and only scheduling a job if it's not in the history.
				EnqueuedAt: epoch,
				// Pass parameters to scheduled job here
				Args: wJobParams,
			}

			rawJSON, err := utils.SerializeJob(j)
			if err != nil {
				e.lastEnqueueErr = err
				// Actually this error should not happen if the object struct is well defined
				logger.Errorf("Serialize job object for periodic job %s error: %s", p.ID, err)
				break
			}

			// Persistent execution first.
			// Please pay attention that the job has not been really scheduled yet.
			// If job data is failed to persistent, then job schedule should be abandoned.
			execution := e.createExecution(p, epoch)
			eTracker, err := e.ctl.New(execution)
			if err != nil {
				e.lastEnqueueErr = err
				logger.Errorf("Save stats data of job execution '%s' error: %s", execution.Info.JobID, err)
				break
			}

			// Put job to the scheduled job queue
			_, err = conn.Do("ZADD", rds.RedisKeyScheduled(e.namespace), epoch, rawJSON)
			if err != nil {
				e.lastEnqueueErr = err
				logger.Errorf("Put the execution of the periodic job '%s' to the scheduled job queue error: %s", p.ID, err)

				// Mark job status to be error
				// If this happened, the job stats is definitely becoming dirty data at job service side.
				// For the consumer side, the retrying of web hook may fix the problem.
				if err := eTracker.Fail(); err != nil {
					e.lastEnqueueErr = err
					logger.Errorf("Mark execution '%s' to failure status error: %s", execution.Info.JobID, err)
				}

				break // Probably redis connection is broken
			}

			logger.Debugf("Scheduled execution for periodic job %s:%s at %d", j.Name, p.ID, epoch)
		}
	}
}

// createExecution creates execution object
func (e *enqueuer) createExecution(p *Policy, runAt int64) *job.Stats {
	eID := fmt.Sprintf("%s@%d", p.ID, runAt)

	return &job.Stats{
		Info: &job.StatsInfo{
			JobID:         eID,
			JobName:       p.JobName,
			WebHookURL:    p.WebHookURL,
			CronSpec:      p.CronSpec,
			UpstreamJobID: p.ID,
			RunAt:         runAt,
			Status:        job.ScheduledStatus.String(),
			JobKind:       job.KindScheduled, // For periodic job execution, it should be set to 'scheduled'
			EnqueueTime:   time.Now().Unix(),
			RefLink:       fmt.Sprintf("/api/v1/jobs/%s", eID),
			Parameters:    p.JobParameters,
		},
	}
}

func (e *enqueuer) shouldEnqueue() bool {
	conn := e.pool.Get()
	defer func() {
		_ = conn.Close()
	}()

	// Acquired a lock before doing checking
	// If failed, directly returns false.
	lockKey := rds.KeyPeriodicLock(e.namespace)
	if err := rds.AcquireLock(conn, lockKey, e.nodeID, 30); err != nil {
		logger.Errorf("acquire lock for periodic enqueuing error: %s", err)
		return false
	}
	// Acquired lock
	// For lock releasing
	defer func() {
		if err := rds.ReleaseLock(conn, lockKey, e.nodeID); err != nil {
			logger.Errorf("release lock for periodic enqueuing error: %s", err)
		}
	}()

	shouldEnq := false
	lastEnqueue, err := redis.Int64(conn.Do("GET", rds.RedisKeyLastPeriodicEnqueue(e.namespace)))
	if err != nil {
		if err.Error() != redis.ErrNil.Error() {
			// Logged error
			logger.Errorf("get timestamp of last enqueue error: %s", err)
		}

		// Should enqueue
		shouldEnq = true
	} else {
		// Check further condition
		shouldEnq = lastEnqueue < (time.Now().Unix() - int64(enqueuerSleep/time.Minute)*60)
	}

	if shouldEnq {
		// Set last periodic enqueue timestamp
		if _, err := conn.Do("SET", rds.RedisKeyLastPeriodicEnqueue(e.namespace), time.Now().Unix()); err != nil {
			logger.Errorf("set last periodic enqueue timestamp error: %s", err)
		}

		// Anyway the action should be enforced
		// The negative effect of this failure is just more re-enqueues by other nodes
		return true
	}

	return false
}

func cloneParameters(params job.Parameters, epoch int64) job.Parameters {
	p := make(job.Parameters)

	// Clone parameters to a new param map
	for k, v := range params {
		p[k] = v
	}

	p[PeriodicExecutionMark] = fmt.Sprintf("%d", epoch)

	return p
}
