package scheduler

import (
	"encoding/json"
	"errors"
	"io/ioutil"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"runtime"
	"strings"
	"time"

	"imuslab.com/arozos/mod/agi"
	"imuslab.com/arozos/mod/user"
)

/*
	ArozOS System Scheduler
	author: tobychui

	This module provide scheduling executable feature for ArozOS
	Some feature was migrated from the v1.113 aecron module
*/

type Job struct {
	Name              string //The name of this job
	Creator           string //The creator of this job. When execute, this user permission will be used
	Description       string //Job description, can be empty
	Admin             bool   //If the creator has admin permission during the creation of this job. If this doesn't match with the runtime instance, this job wille be skipped
	ExecutionInterval int64  //Execuation interval in seconds
	BaseTime          int64  //Exeuction basetime. The next interval is calculated using (current time - base time ) % execution interval
	JobType           string //Job type, accept {file/function}. If not set default to file
	FshID             string
	ScriptFile        string                 //The script file being called. Can be an agi script (.agi / .js) or shell script (.bat or .sh)
	ScriptFunc        func() (string, error) `json:"-"` //The target function to execute
}

type Scheduler struct {
	jobs        []*Job
	cronfile    string
	userHandler *user.UserHandler
	gateway     *agi.Gateway
	ticker      chan bool
}

var (
	logFolder string = "./system/aecron/"
)

func NewScheduler(userHandler *user.UserHandler, gateway *agi.Gateway, cronfile string) (*Scheduler, error) {
	if !fileExists(cronfile) {
		//Cronfile not exists. Create it
		emptyJobList := []*Job{}
		ls, _ := json.Marshal(emptyJobList)
		err := ioutil.WriteFile(cronfile, ls, 0755)
		if err != nil {
			return nil, err
		}
	}

	//Load previous jobs from file
	jobs, err := loadJobsFromFile(cronfile)
	if err != nil {
		return nil, err
	}

	//Create the ArOZ Emulated Crontask
	thisScheduler := Scheduler{
		jobs:        jobs,
		userHandler: userHandler,
		gateway:     gateway,
		cronfile:    cronfile,
	}

	//Create log folder
	os.MkdirAll(logFolder, 0755)

	//Start the cronjob at 1 minute ticker interval
	go func() {
		//Delay start: Wait until seconds = 0
		for time.Now().Unix()%60 > 0 {
			time.Sleep(500 * time.Millisecond)
		}
		stopChannel := thisScheduler.createTicker(1 * time.Minute)
		thisScheduler.ticker = stopChannel
		log.Println("ArozOS System Scheduler Started")
	}()

	//Return the crontask
	return &thisScheduler, nil
}

//Load a list of jobs from file
func loadJobsFromFile(cronfile string) ([]*Job, error) {
	//Try to read the cronfile
	filecontent, err := ioutil.ReadFile(cronfile)
	if err != nil {
		return []*Job{}, err
	}

	//Phrase the cronfile
	prevousJobs := []Job{}
	err = json.Unmarshal(filecontent, &prevousJobs)
	if err != nil {
		return []*Job{}, err
	}

	//Convert the json objets to pointer for easy changing by other process
	jobsPointers := []*Job{}
	for _, thisJob := range prevousJobs {
		thisJob.JobType = "file"
		var newJobPointer Job = thisJob
		jobsPointers = append(jobsPointers, &newJobPointer)
	}

	return jobsPointers, nil
}

func (a *Scheduler) createTicker(duration time.Duration) chan bool {
	ticker := time.NewTicker(duration)
	stop := make(chan bool, 1)

	go func() {
		defer log.Println("Scheduler Stopped")
		for {
			select {
			case <-ticker.C:
				//Run jobs
				for _, thisJob := range a.jobs {
					if (time.Now().Unix()-thisJob.BaseTime)%thisJob.ExecutionInterval == 0 {
						//Execute this job
						if thisJob.JobType == "function" {
							//Execute the script function
							returnvalue, err := thisJob.ScriptFunc()
							if err != nil {
								//Execution error. Kill this scheule
								log.Println(`*Scheduler* Error occured when running task ` + thisJob.Name + ": " + err.Error())
								a.RemoveJobFromScheduleList(thisJob.Name)
								cronlog("[ERROR]: " + err.Error())
							}

							//Execution suceed. Log the return value
							if len(returnvalue) > 0 {
								cronlog(returnvalue)
							}

						} else {
							//This is requesting to execute a script file
							scriptFile := thisJob.ScriptFile
							if !fileExists(scriptFile) {
								//This job no longer exists in the file system. Remove it
								a.RemoveJobFromScheduleList(thisJob.Name)
							}
							clonedJobStructure := *thisJob
							ext := filepath.Ext(scriptFile)
							if ext == ".js" || ext == ".agi" {
								//Run using AGI interface in go routine
								go func(thisJob Job) {
									userinfo, err := a.userHandler.GetUserInfoFromUsername(thisJob.Creator)
									if err != nil {
										//This user not exists. Skip this script
										cronlog("[ERROR] User not exists: " + thisJob.Creator + ". Skipping scheduled job: " + thisJob.Name + ".")
										return
									}

									//Run the script with this user scope
									resp, err := a.gateway.ExecuteAGIScriptAsUser(thisJob.ScriptFile, userinfo, nil)
									if err != nil {
										cronlog("[ERROR] " + thisJob.Name + " " + err.Error())
									} else {
										cronlog(thisJob.Name + " " + resp)
									}
								}(clonedJobStructure)

							} else if ext == ".bat" || ext == ".sh" {
								//Run as shell script
								go func(thisJob Job) {
									scriptPath := thisJob.ScriptFile
									if runtime.GOOS == "windows" {
										scriptPath = strings.ReplaceAll(filepath.ToSlash(scriptPath), "/", "\\")
									}
									cmd := exec.Command(scriptPath)
									out, err := cmd.CombinedOutput()
									if err != nil {
										cronlog("[ERROR] " + thisJob.Name + " " + err.Error() + " => " + string(out))
									}
									cronlog(thisJob.Name + " " + string(out))
								}(clonedJobStructure)
							} else {
								//Unknown script file. Ignore this
								log.Println("This extension is not yet supported: ", ext)
							}
						}

					}
				}
			case <-stop:
				return
			}
		}
	}()

	return stop
}

func (a *Scheduler) Close() {
	if a.ticker != nil {
		//Stop the ticker
		a.ticker <- true
	}
}

//Add an job object to system scheduler
func (a *Scheduler) AddJobToScheduler(job *Job) error {
	if job.JobType == "" {
		if job.ScriptFunc == nil && job.ScriptFile == "" {
			return errors.New("Invalid job file or function")
		}

		if job.ScriptFunc != nil {
			job.JobType = "function"
		} else if job.ScriptFile != "" {
			job.JobType = "file"
		}

	}
	a.jobs = append(a.jobs, job)
	return nil
}

//Create a new scheduled function job in the scheduler
func (a *Scheduler) CreateNewScheduledFunctionJob(name string, desc string, executionInterval int64, targetFunction func() (string, error)) error {
	if name == "" || desc == "" {
		return errors.New("Name or description of a scheduled task cannot be empty")
	}

	if executionInterval < 60 {
		return errors.New("The minimum execution interval is 60 seconds.")
	}

	//Get the cloest minute
	baseTime := time.Now().Unix() - (time.Now().Unix() % 60)

	//Create a new scehduled job
	newJob := Job{
		Name:              name,
		Creator:           "system",
		Description:       desc,
		Admin:             true,
		ExecutionInterval: executionInterval,
		BaseTime:          baseTime,
		JobType:           "function",
		ScriptFunc:        targetFunction,
	}

	//Add the new job to scheduler
	a.AddJobToScheduler(&newJob)

	return nil
}

func (a *Scheduler) GetScheduledJobByName(name string) *Job {
	for _, thisJob := range a.jobs {
		if thisJob.Name == name {
			return thisJob
		}
	}

	return nil
}

func (a *Scheduler) RemoveJobFromScheduleList(taskName string) {
	newJobSlice := []*Job{}
	for _, j := range a.jobs {
		if j.Name != taskName {
			thisJob := j
			newJobSlice = append(newJobSlice, thisJob)
		}
	}
	a.jobs = newJobSlice
}

func (a *Scheduler) JobExists(name string) bool {
	targetJob := a.GetScheduledJobByName(name)
	if targetJob == nil {
		return false
	} else {
		return true
	}
}

//Write the output to log file. Default to ./system/aecron/{date}.log
func cronlog(message string) {
	currentTime := time.Now()
	timestamp := currentTime.Format("2006-01-02 15:04:05")
	message = timestamp + " " + message
	currentLogFile := filepath.ToSlash(filepath.Clean(logFolder)) + "/" + time.Now().Format("2006-02-01") + ".log"
	f, err := os.OpenFile(currentLogFile, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		//Unable to write to file. Log to STDOUT instead
		log.Println(message)
		return
	}
	if _, err := f.WriteString(message + "\n"); err != nil {
		log.Println(message)
		return
	}
	defer f.Close()

}