/*
   Copyright (c) 2016 VMware, Inc. All Rights Reserved.
   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 job

import (
	"fmt"
	"sync"

	"github.com/vmware/harbor/dao"
	"github.com/vmware/harbor/job/config"
	"github.com/vmware/harbor/job/replication"
	"github.com/vmware/harbor/job/utils"
	"github.com/vmware/harbor/models"
	uti "github.com/vmware/harbor/utils"
	"github.com/vmware/harbor/utils/log"
)

// RepJobParm wraps the parm of a job
type RepJobParm struct {
	LocalRegURL    string
	TargetURL      string
	TargetUsername string
	TargetPassword string
	Repository     string
	Tags           []string
	Enabled        int
	Operation      string
	Insecure       bool
}

// SM is the state machine to handle job, it handles one job at a time.
type SM struct {
	JobID         int64
	CurrentState  string
	PreviousState string
	//The states that don't have to exist in transition map, such as "Error", "Canceled"
	ForcedStates map[string]struct{}
	Transitions  map[string]map[string]struct{}
	Handlers     map[string]StateHandler
	desiredState string
	Logger       *log.Logger
	Parms        *RepJobParm
	lock         *sync.Mutex
}

// EnterState transit the statemachine from the current state to the state in parameter.
// It returns the next state the statemachine should tranit to.
func (sm *SM) EnterState(s string) (string, error) {
	log.Debugf("Job id: %d, transiting from State: %s, to State: %s", sm.JobID, sm.CurrentState, s)
	targets, ok := sm.Transitions[sm.CurrentState]
	_, exist := targets[s]
	_, isForced := sm.ForcedStates[s]
	if !exist && !isForced {
		return "", fmt.Errorf("Job id: %d, transition from %s to %s does not exist!", sm.JobID, sm.CurrentState, s)
	}
	exitHandler, ok := sm.Handlers[sm.CurrentState]
	if ok {
		if err := exitHandler.Exit(); err != nil {
			return "", err
		}
	} else {
		log.Debugf("Job id: %d, no handler found for state:%s, skip", sm.JobID, sm.CurrentState)
	}
	enterHandler, ok := sm.Handlers[s]
	var next = models.JobContinue
	var err error
	if ok {
		if next, err = enterHandler.Enter(); err != nil {
			return "", err
		}
	} else {
		log.Debugf("Job id: %d, no handler found for state:%s, skip", sm.JobID, s)
	}
	sm.PreviousState = sm.CurrentState
	sm.CurrentState = s
	log.Debugf("Job id: %d, transition succeeded, current state: %s", sm.JobID, s)
	return next, nil
}

// Start kicks off the statemachine to transit from current state to s, and moves on
// It will search the transit map if the next state is "_continue", and
// will enter error state if there's more than one possible path when next state is "_continue"
func (sm *SM) Start(s string) {
	n, err := sm.EnterState(s)
	log.Debugf("Job id: %d, next state from handler: %s", sm.JobID, n)
	for len(n) > 0 && err == nil {
		if d := sm.getDesiredState(); len(d) > 0 {
			log.Debugf("Job id: %d. Desired state: %s, will ignore the next state from handler", sm.JobID, d)
			n = d
			sm.setDesiredState("")
			continue
		}
		if n == models.JobContinue && len(sm.Transitions[sm.CurrentState]) == 1 {
			for n = range sm.Transitions[sm.CurrentState] {
				break
			}
			log.Debugf("Job id: %d, Continue to state: %s", sm.JobID, n)
			continue
		}
		if n == models.JobContinue && len(sm.Transitions[sm.CurrentState]) != 1 {
			log.Errorf("Job id: %d, next state is continue but there are %d possible next states in transition table", sm.JobID, len(sm.Transitions[sm.CurrentState]))
			err = fmt.Errorf("Unable to continue")
			break
		}
		n, err = sm.EnterState(n)
		log.Debugf("Job id: %d, next state from handler: %s", sm.JobID, n)
	}
	if err != nil {
		log.Warningf("Job id: %d, the statemachin will enter error state due to error: %v", sm.JobID, err)
		sm.EnterState(models.JobError)
	}
}

// AddTransition add a transition to the transition table of state machine, the handler is the handler of target state "to"
func (sm *SM) AddTransition(from string, to string, h StateHandler) {
	_, ok := sm.Transitions[from]
	if !ok {
		sm.Transitions[from] = make(map[string]struct{})
	}
	sm.Transitions[from][to] = struct{}{}
	sm.Handlers[to] = h
}

// RemoveTransition removes a transition from transition table of the state machine
func (sm *SM) RemoveTransition(from string, to string) {
	_, ok := sm.Transitions[from]
	if !ok {
		return
	}
	delete(sm.Transitions[from], to)
}

// Stop will set the desired state as "stopped" such that when next tranisition happen the state machine will stop handling the current job
// and the worker can release itself to the workerpool.
func (sm *SM) Stop(id int64) {
	log.Debugf("Trying to stop the job: %d", id)
	sm.lock.Lock()
	defer sm.lock.Unlock()
	//need to check if the sm switched to other job
	if id == sm.JobID {
		sm.desiredState = models.JobStopped
		log.Debugf("Desired state of job %d is set to stopped", id)
	} else {
		log.Debugf("State machine has switched to job %d, so the action to stop job %d will be ignored", sm.JobID, id)
	}
}

func (sm *SM) getDesiredState() string {
	sm.lock.Lock()
	defer sm.lock.Unlock()
	return sm.desiredState
}

func (sm *SM) setDesiredState(s string) {
	sm.lock.Lock()
	defer sm.lock.Unlock()
	sm.desiredState = s
}

// Init initialzie the state machine, it will be called once in the lifecycle of state machine.
func (sm *SM) Init() {
	sm.lock = &sync.Mutex{}
	sm.Handlers = make(map[string]StateHandler)
	sm.Transitions = make(map[string]map[string]struct{})
	sm.ForcedStates = map[string]struct{}{
		models.JobError:    struct{}{},
		models.JobStopped:  struct{}{},
		models.JobCanceled: struct{}{},
		models.JobRetrying: struct{}{},
	}
}

// Reset resets the state machine so it will start handling another job.
func (sm *SM) Reset(jid int64) error {
	//To ensure the new jobID is visible to the thread to stop the SM
	sm.lock.Lock()
	sm.JobID = jid
	sm.desiredState = ""
	sm.lock.Unlock()

	//init parms
	job, err := dao.GetRepJob(sm.JobID)
	if err != nil {
		return fmt.Errorf("Failed to get job, error: %v", err)
	}
	if job == nil {
		return fmt.Errorf("The job doesn't exist in DB, job id: %d", sm.JobID)
	}
	policy, err := dao.GetRepPolicy(job.PolicyID)
	if err != nil {
		return fmt.Errorf("Failed to get policy, error: %v", err)
	}
	if policy == nil {
		return fmt.Errorf("The policy doesn't exist in DB, policy id:%d", job.PolicyID)
	}
	sm.Parms = &RepJobParm{
		LocalRegURL: config.LocalRegURL(),
		Repository:  job.Repository,
		Tags:        job.TagList,
		Enabled:     policy.Enabled,
		Operation:   job.Operation,
		Insecure:    !config.VerifyRemoteCert(),
	}
	if policy.Enabled == 0 {
		//worker will cancel this job
		return nil
	}
	target, err := dao.GetRepTarget(policy.TargetID)
	if err != nil {
		return fmt.Errorf("Failed to get target, error: %v", err)
	}
	if target == nil {
		return fmt.Errorf("The target doesn't exist in DB, target id: %d", policy.TargetID)
	}
	sm.Parms.TargetURL = target.URL
	sm.Parms.TargetUsername = target.Username
	pwd := target.Password

	if len(pwd) != 0 {
		pwd, err = uti.ReversibleDecrypt(pwd)
		if err != nil {
			return fmt.Errorf("failed to decrypt password: %v", err)
		}
	}

	sm.Parms.TargetPassword = pwd

	//init states handlers
	sm.Logger = utils.NewLogger(sm.JobID)
	sm.Handlers = make(map[string]StateHandler)
	sm.Transitions = make(map[string]map[string]struct{})
	sm.CurrentState = models.JobPending

	sm.AddTransition(models.JobPending, models.JobRunning, StatusUpdater{sm.JobID, models.JobRunning})
	sm.AddTransition(models.JobRetrying, models.JobRunning, StatusUpdater{sm.JobID, models.JobRunning})
	sm.Handlers[models.JobError] = StatusUpdater{sm.JobID, models.JobError}
	sm.Handlers[models.JobStopped] = StatusUpdater{sm.JobID, models.JobStopped}
	sm.Handlers[models.JobRetrying] = Retry{sm.JobID}

	switch sm.Parms.Operation {
	case models.RepOpTransfer:
		err = addImgTransferTransition(sm)
	case models.RepOpDelete:
		err = addImgDeleteTransition(sm)
	default:
		err = fmt.Errorf("unsupported operation: %s", sm.Parms.Operation)
	}

	return err
}

//for testing onlly
func addTestTransition(sm *SM) error {
	sm.AddTransition(models.JobRunning, "pull-img", ImgPuller{img: sm.Parms.Repository, logger: sm.Logger})
	return nil
}

func addImgTransferTransition(sm *SM) error {
	base, err := replication.InitBaseHandler(sm.Parms.Repository, sm.Parms.LocalRegURL, config.UISecret(),
		sm.Parms.TargetURL, sm.Parms.TargetUsername, sm.Parms.TargetPassword,
		sm.Parms.Insecure, sm.Parms.Tags, sm.Logger)
	if err != nil {
		return err
	}
	sm.AddTransition(models.JobRunning, replication.StateCheck, &replication.Checker{BaseHandler: base})
	sm.AddTransition(replication.StateCheck, replication.StatePullManifest, &replication.ManifestPuller{BaseHandler: base})
	sm.AddTransition(replication.StatePullManifest, replication.StateTransferBlob, &replication.BlobTransfer{BaseHandler: base})
	sm.AddTransition(replication.StatePullManifest, models.JobFinished, &StatusUpdater{sm.JobID, models.JobFinished})
	sm.AddTransition(replication.StateTransferBlob, replication.StatePushManifest, &replication.ManifestPusher{BaseHandler: base})
	sm.AddTransition(replication.StatePushManifest, replication.StatePullManifest, &replication.ManifestPuller{BaseHandler: base})
	return nil
}

func addImgDeleteTransition(sm *SM) error {
	deleter, err := replication.NewDeleter(sm.Parms.Repository, sm.Parms.Tags, sm.Parms.TargetURL,
		sm.Parms.TargetUsername, sm.Parms.TargetPassword, sm.Parms.Insecure, sm.Logger)
	if err != nil {
		return err
	}

	sm.AddTransition(models.JobRunning, replication.StateDelete, deleter)
	sm.AddTransition(replication.StateDelete, models.JobFinished, &StatusUpdater{sm.JobID, models.JobFinished})

	return nil
}