func (e *Walter) runService() bool {
	// load .walter-update
	log.Infof("Loading update file... \"%s\"", e.Engine.Resources.RepoService.GetUpdateFilePath())
	update, err := services.LoadLastUpdate(e.Engine.Resources.RepoService.GetUpdateFilePath())
	log.Infof("Succeeded loading update file")

	log.Info("Updating status...")
	update.Status = "inprogress"
	result := services.SaveLastUpdate(e.Engine.Resources.RepoService.GetUpdateFilePath(), update)
	if result == false {
		log.Error("Failed to save status update")
		return false
	}
	log.Info("Succeeded updating status")

	// get latest commit and pull requests
	log.Info("downloading commits and pull requests...")
	commits, err := e.Engine.Resources.RepoService.GetCommits(update)
	if err != nil {
		log.Errorf("Failed getting commits: %s", err)
		return false
	}

	log.Info("Succeeded getting commits")
	log.Info("Size of commits: " + strconv.Itoa(commits.Len()))
	hasFailedProcess := false
	for commit := commits.Front(); commit != nil; commit = commit.Next() {
		commitType := reflect.TypeOf(commit.Value)
		if commitType.Name() == "RepositoryCommit" {
			log.Info("Found new repository commit")
			trunkCommit := commit.Value.(github.RepositoryCommit)
			if result := e.processTrunkCommit(trunkCommit); result == false {
				hasFailedProcess = true
			}
		} else if commitType.Name() == "PullRequest" {
			log.Info("Found new pull request commit")
			pullreq := commit.Value.(github.PullRequest)
			if result := e.processPullRequest(pullreq); result == false {
				hasFailedProcess = true
			}
		} else {
			log.Errorf("Nothing commit type: %s", commitType)
			hasFailedProcess = true
		}
	}

	// save .walter-update
	log.Info("Saving update file...")
	update.Status = "finished"
	update.Time = time.Now()
	result = services.SaveLastUpdate(e.Engine.Resources.RepoService.GetUpdateFilePath(), update)
	if result == false {
		log.Error("Failed to save update")
		return false
	}
	return !hasFailedProcess
}

//Post posts a message to slack
func (slack *Slack) Post(message string, c ...string) bool {
	if slack.Channel[0] != '#' {
		log.Infof("Add # to channel name: %s", slack.Channel)
		slack.Channel = "#" + slack.Channel
	}

	var color string
	if len(c) > 0 {
		color = c[0]
	}

	if strings.Contains(message, "[RESULT] Failed") {
		color = "danger"
	} else if strings.Contains(message, "[RESULT] Skipped") {
		color = "warning"
	} else if strings.Contains(message, "[RESULT] Succeeded") {
		color = "good"
	}

	attachment := map[string]string{
		"text":  message,
		"color": color,
	}

	attachments := []map[string]string{attachment}

	params, _ := json.Marshal(struct {
		FakeSlack
		Attachments []map[string]string `json:"attachments"`
	}{
		FakeSlack:   FakeSlack(*slack),
		Attachments: attachments,
	})

	resp, err := http.PostForm(
		slack.IncomingURL,
		url.Values{"payload": {string(params)}},
	)
	if err != nil {
		log.Errorf("Failed post message to Slack...: %s", message)
		return false
	}
	defer resp.Body.Close()

	if body, err := ioutil.ReadAll(resp.Body); err == nil {
		log.Infof("Slack post result...: %s", body)
		return true
	}
	log.Errorf("Failed to read result from Slack...")
	return false
}

func (e *Walter) processPullRequest(pullrequest github.PullRequest) bool {
	// checkout pullrequest
	num := *pullrequest.Number
	_, err := exec.Command("git", "fetch", "origin", "refs/pull/"+strconv.Itoa(num)+"/head:pr_"+strconv.Itoa(num)).Output()

	defer exec.Command("git", "checkout", "master", "-f").Output() // TODO: make trunk branch configurable
	defer log.Info("returning master branch...")

	if err != nil {
		log.Errorf("Failed to fetch pull request: %s", err)
		return false
	}

	_, err = exec.Command("git", "checkout", "pr_"+strconv.Itoa(num)).Output()
	if err != nil {
		log.Errorf("Failed to checkout pullrequest branch (\"%s\") : %s", "pr_"+strconv.Itoa(num), err)
		log.Error("Skip execution...")
		return false
	}

	// run pipeline
	log.Info("Running pipeline...")
	w, err := New(e.Opts)
	if err != nil {
		log.Errorf("Failed to create Walter object...: %s", err)
		log.Error("Skip execution...")
		return false
	}

	result := w.Engine.RunOnce()

	// register the result to hosting service
	if result.IsSucceeded() {
		log.Info("succeeded.")
		e.Engine.Resources.RepoService.RegisterResult(
			services.Result{
				State:   "success",
				Message: "Succeeded running pipeline...",
				SHA:     *pullrequest.Head.SHA})
		return true
	}
	log.Error("Error reported...")
	e.Engine.Resources.RepoService.RegisterResult(
		services.Result{
			State:   "failure",
			Message: "Failed running pipleline ...",
			SHA:     *pullrequest.Head.SHA})
	return false

}

//RegisterResult registers the supplied result
func (githubClient *GitHubClient) RegisterResult(result Result) error {
	ts := oauth2.StaticTokenSource(
		&oauth2.Token{AccessToken: githubClient.Token},
	)
	tc := oauth2.NewClient(oauth2.NoContext, ts)
	client := github.NewClient(tc)

	if githubClient.BaseUrl != nil {
		client.BaseURL = githubClient.BaseUrl
	}

	log.Info("Submitting result")
	repositories := client.Repositories
	status, _, err := repositories.CreateStatus(
		githubClient.From,
		githubClient.Repo,
		result.SHA,
		&github.RepoStatus{
			State:       github.String(result.State),
			TargetURL:   github.String(result.Url),
			Description: github.String(result.Message),
			Context:     github.String("continuous-integraion/walter"),
		})
	log.Infof("Submit status: %s", status)
	if err != nil {
		log.Errorf("Failed to register result: %s", err)
	}
	return err
}

func (e *Walter) processTrunkCommit(commit github.RepositoryCommit) bool {
	log.Infof("Checkout master branch")
	_, err := exec.Command("git", "checkout", "master", "-f").Output()
	if err != nil {
		log.Errorf("Failed to checkout master branch: %s", err)
		return false
	}
	log.Infof("Downloading new commit from master")
	_, err = exec.Command("git", "pull", "origin", "master").Output()
	if err != nil {
		log.Errorf("Failed to download new commit from master: %s", err)
		return false
	}
	log.Infof("Running the latest commit in master")
	w, err := New(e.Opts)
	if err != nil {
		log.Errorf("Failed to create Walter object...: %s", err)
		log.Error("Skip execution...")
		return false
	}
	result := w.Engine.RunOnce()

	// register the result to hosting service
	if result.IsSucceeded() {
		log.Info("Succeeded.")
		e.Engine.Resources.RepoService.RegisterResult(
			services.Result{
				State:   "success",
				Message: "Succeeded running pipeline...",
				SHA:     *commit.SHA})
		return true
	}
	log.Error("Error reported...")
	e.Engine.Resources.RepoService.RegisterResult(
		services.Result{
			State:   "failure",
			Message: "Failed running pipleline ...",
			SHA:     *commit.SHA})
	return false

}

func (hc *HipChat2) newClient() *hipchat.Client {
	client := hipchat.NewClient(hc.Token)
	if hc.BaseURL == "" {
		return client
	}

	baseURL, err := url.Parse(hc.BaseURL)
	if err != nil {
		log.Errorf("Invalid Hipchat Base URL...: %s", err.Error())
		return nil
	}
	client.BaseURL = baseURL
	return client
}

//GetCommits get a list of all the commits for the current update
func (githubClient *GitHubClient) GetCommits(update Update) (*list.List, error) {
	log.Info("getting commits\n")
	commits := list.New()
	ts := oauth2.StaticTokenSource(
		&oauth2.Token{AccessToken: githubClient.Token},
	)
	tc := oauth2.NewClient(oauth2.NoContext, ts)
	client := github.NewClient(tc)

	// get a list of pull requests with Pull Request API
	pullreqs, _, err := client.PullRequests.List(
		githubClient.From, githubClient.Repo,
		&github.PullRequestListOptions{})
	if err != nil {
		log.Errorf("Failed to get pull requests")
		return list.New(), err
	}

	re, err := regexp.Compile(githubClient.TargetBranch)
	if err != nil {
		log.Error("Failed to compile branch pattern...")
		return list.New(), err
	}

	log.Infof("Size of pull reqests: %d", len(pullreqs))
	for _, pullreq := range pullreqs {
		log.Infof("Branch name is \"%s\"", *pullreq.Head.Ref)

		if githubClient.TargetBranch != "" {
			matched := re.Match([]byte(*pullreq.Head.Ref))
			if matched != true {
				log.Infof("Not add a branch, \"%s\" since this branch name is not match the filtering pattern", *pullreq.Head.Ref)
				continue
			}
		}

		if *pullreq.State == "open" && pullreq.UpdatedAt.After(update.Time) {
			log.Infof("Adding pullrequest %d", *pullreq.Number)
			commits.PushBack(pullreq)
		}
	}

	// get the latest commit with Commit API if the commit is newer than last update
	masterCommits, _, _ := client.Repositories.ListCommits(
		githubClient.From, githubClient.Repo, &github.CommitsListOptions{})
	if masterCommits[0].Commit.Author.Date.After(update.Time) {
		commits.PushBack(masterCommits[0])
	}
	return commits, nil
}

// Run registered commands.
func (commandStage *CommandStage) Run() bool {
	// Check OnlyIf
	if commandStage.runOnlyIf() == false {
		log.Warnf("[command] exec: skipped this stage \"%s\", since only_if condition failed", commandStage.BaseStage.StageName)
		return true
	}

	// Run command
	result := commandStage.runCommand()
	if result == false {
		log.Errorf("[command] exec: failed stage \"%s\"", commandStage.BaseStage.StageName)
	}
	return result
}

//SaveLastUpdate saves the supplied update to the filename
func SaveLastUpdate(fname string, update Update) bool {
	log.Infof("writing down new update: \"%s\"\n", string(fname))
	bytes, err := json.Marshal(update)
	if err != nil {
		log.Errorf("failed to convert update to string...: %s\n", err)
		return false
	}

	if exist := fileExists(fname); exist == true {
		log.Infof("file exist: \"%s\"", fname)
		if err := os.Remove(fname); err != nil {
			log.Errorf("failed to remove \"%s\" with error: \"%s\"", fname, err)
			return false
		}
		log.Infof("succeeded to remove: \"%s\"", fname)
	}

	if err := ioutil.WriteFile(fname, bytes, 0644); err != nil {
		log.Errorf("failed to write update to file...: \"%s\"\n", err)
		return false
	}
	log.Infof("succeeded to write update file: \"%s\"", fname)
	return true
}

//Validate validates if the command can be executed
func (resourceValidator *ResourceValidator) Validate() bool {
	// check if files exists
	for file := resourceValidator.files.Front(); file != nil; file = file.Next() {
		filePath := file.Value.(string)
		log.Debugf("checking file: %v", filePath)
		if _, err := os.Stat(filePath); err == nil {
			log.Debugf("file exists")
		} else {
			log.Errorf("file: %v does not exists", filePath)
			return false
		}
	}
	// check if command exists
	if len(resourceValidator.command) == 0 { // return true when no command is registrated
		return true
	}
	cmd := exec.Command("which", resourceValidator.command)
	err := cmd.Run()
	if err != nil {
		log.Errorf("command: %v does not exists", resourceValidator.command)
		return false
	}
	return true
}

// Post posts a hipchat message
// TODO: make hipchat api endpoint configurable for on-premises servers
func (hipChat *HipChat) Post(message string) bool {
	client := hipchat.Client{AuthToken: hipChat.Token}
	req := hipchat.MessageRequest{
		RoomId:        hipChat.RoomID,
		From:          hipChat.From,
		Message:       message,
		Color:         hipchat.ColorPurple,
		MessageFormat: hipchat.FormatText,
		Notify:        true,
	}
	if err := client.PostMessage(req); err != nil {
		log.Errorf("Failed post message...: %s", message)
		return false
	}
	return true
}

func validateWaitForCondition(wait *WaitFor) bool {
	// check duplicate targets
	if wait.Port != 0 && wait.File != "" {
		log.Error("[command] Port and File are not able to be specified at the same time.")
		return false
	} else if wait.Port != 0 && wait.Delay > 0.0 {
		log.Error("[command] Port and Delay are not able to be specified at the same time.")
		return false
	} else if wait.File != "" && wait.Delay > 0.0 {
		log.Error("[command] File and Delay are not able to be specified at the same time.")
		return false
	}

	// check illegal conditions
	if wait.Delay < 0 {
		log.Error("[command] Delay must be positive.")
		return false
	} else if wait.Port < 0 {
		log.Error("[command] Port must be positive.")
		return false
	} else if wait.Port > 0 && wait.Host == "" {
		log.Error("[command] Host must be specified when port number is specified.")
		return false
	}

	// check illegal states
	if wait.State != "present" && wait.State != "ready" && wait.State != "absent" && wait.State != "unready" {
		log.Errorf("[command] \"%s\" is an unsupported state", wait.State)
		return false
	}

	// misc checks
	if wait.Port > 0 && wait.State == "" {
		log.Error("[command] State must be specified for port.")
		return false
	} else if wait.File != "" && wait.State == "" {
		log.Error("[command] State must be specified for file.")
		return false
	}

	return true
}

// Post sends a new HipChat message using V2 of the API
func (hc *HipChat2) Post(message string, color ...string) bool {
	if hc.client == nil {
		hc.client = hc.newClient()
		if hc.client == nil {
			return false
		}
	}

	msg := &hipchat.NotificationRequest{
		Color:         "purple",
		Message:       message,
		Notify:        true,
		MessageFormat: "text",
	}

	if _, err := hc.client.Room.Notification(hc.RoomID, msg); err != nil {
		log.Errorf("Failed post message...: %s", msg.Message)
		return false
	}

	return true
}

//RegisterResult registers the supplied result
func (githubClient *GitHubClient) RegisterResult(result Result) error {
	t := &oauth.Transport{
		Token: &oauth.Token{AccessToken: githubClient.Token},
	}
	client := github.NewClient(t.Client())

	log.Info("Submitting result")
	repositories := client.Repositories
	status, _, err := repositories.CreateStatus(
		githubClient.From,
		githubClient.Repo,
		result.SHA,
		&github.RepoStatus{
			State:       github.String(result.State),
			TargetURL:   github.String(result.Url),
			Description: github.String(result.Message),
			Context:     github.String("continuous-integraion/walter"),
		})
	log.Infof("Submit status: %s", status)
	if err != nil {
		log.Errorf("Failed to register result: %s", err)
	}
	return err
}