Clean up code and strengthening (slack) (#519)

Changes include:
- Refactor of strings into package-wide constants.
- Predeclaration of regexps to be instantiated at package load time.
- Checking of unchecked errors.
- Structural changes:
  - Adding verifications to type-casting code.
  - Remove unnecessary 'len(X) > 0' checks before iterating over X.
  - Remove unnecessary 'else' clause after 'if' with 'return'.
  - Unexporting of public fields of Bridge struct.
- Formatting:
  - One-field-per-line struct definitions.

bridge/slack/slack.go

@@ -2,6 +2,7 @@ package bslack
 
 import (
 	"errors"
+	"fmt"
 	"strings"
 	"sync"
 
@@ -18,22 +19,52 @@ type Bslack struct {
 	mh           *matterhook.Client
 	sc           *slack.Client
 	rtm          *slack.RTM
-	Users        []slack.User
-	Usergroups   []slack.UserGroup
+	users        []slack.User
 	si           *slack.Info
 	channels     []slack.Channel
 	cache        *lru.Cache
-	UseChannelID bool
+	useChannelID bool
 	uuid         string
 	*bridge.Config
 	sync.RWMutex
 }
 
-const messageDeleted = "message_deleted"
+const (
+	sChannelJoin     = "channel_join"
+	sChannelLeave    = "channel_leave"
+	sMessageDeleted  = "message_deleted"
+	sSlackAttachment = "slack_attachment"
+	sPinnedItem      = "pinned_item"
+	sUnpinnedItem    = "unpinned_item"
+	sChannelTopic    = "channel_topic"
+	sChannelPurpose  = "channel_purpose"
+	sFileComment     = "file_comment"
+	sMeMessage       = "me_message"
+	sUserTyping      = "user_typing"
+	sLatencyReport   = "latency_report"
+	sSystemUser      = "system"
+
+	tokenConfig           = "Token"
+	incomingWebhookConfig = "WebhookBindAddress"
+	outgoingWebhookConfig = "WebhookURL"
+	skipTLSConfig         = "SkipTLSVerify"
+	useNickPrefixConfig   = "PrefixMessagesWithNick"
+	editDisableConfig     = "EditDisable"
+	editSuffixConfig      = "EditSuffix"
+	iconURLConfig         = "iconurl"
+	noSendJoinConfig      = "nosendjoinpart"
+)
 
 func New(cfg *bridge.Config) bridge.Bridger {
-	b := &Bslack{Config: cfg, uuid: xid.New().String()}
-	b.cache, _ = lru.New(5000)
+	newCache, err := lru.New(5000)
+	if err != nil {
+		cfg.Log.Fatalf("Could not create LRU cache for Slack bridge: %v", err)
+	}
+	b := &Bslack{
+		Config: cfg,
+		uuid:   xid.New().String(),
+		cache:  newCache,
+	}
 	return b
 }
 
@@ -44,50 +75,54 @@ func (b *Bslack) Command(cmd string) string {
 func (b *Bslack) Connect() error {
 	b.RLock()
 	defer b.RUnlock()
-	if b.GetString("WebhookBindAddress") != "" {
-		if b.GetString("WebhookURL") != "" {
+	if b.GetString(incomingWebhookConfig) != "" {
+		if b.GetString(outgoingWebhookConfig) != "" {
 			b.Log.Info("Connecting using webhookurl (sending) and webhookbindaddress (receiving)")
-			b.mh = matterhook.New(b.GetString("WebhookURL"),
-				matterhook.Config{InsecureSkipVerify: b.GetBool("SkipTLSVerify"),
-					BindAddress: b.GetString("WebhookBindAddress")})
-		} else if b.GetString("Token") != "" {
+			b.mh = matterhook.New(b.GetString(outgoingWebhookConfig), matterhook.Config{
+				InsecureSkipVerify: b.GetBool(skipTLSConfig),
+				BindAddress:        b.GetString(incomingWebhookConfig),
+			})
+		} else if b.GetString(tokenConfig) != "" {
 			b.Log.Info("Connecting using token (sending)")
-			b.sc = slack.New(b.GetString("Token"))
+			b.sc = slack.New(b.GetString(tokenConfig))
 			b.rtm = b.sc.NewRTM()
 			go b.rtm.ManageConnection()
 			b.Log.Info("Connecting using webhookbindaddress (receiving)")
-			b.mh = matterhook.New(b.GetString("WebhookURL"),
-				matterhook.Config{InsecureSkipVerify: b.GetBool("SkipTLSVerify"),
-					BindAddress: b.GetString("WebhookBindAddress")})
+			b.mh = matterhook.New(b.GetString(outgoingWebhookConfig), matterhook.Config{
+				InsecureSkipVerify: b.GetBool(skipTLSConfig),
+				BindAddress:        b.GetString(incomingWebhookConfig),
+			})
 		} else {
 			b.Log.Info("Connecting using webhookbindaddress (receiving)")
-			b.mh = matterhook.New(b.GetString("WebhookURL"),
-				matterhook.Config{InsecureSkipVerify: b.GetBool("SkipTLSVerify"),
-					BindAddress: b.GetString("WebhookBindAddress")})
+			b.mh = matterhook.New(b.GetString(outgoingWebhookConfig), matterhook.Config{
+				InsecureSkipVerify: b.GetBool(skipTLSConfig),
+				BindAddress:        b.GetString(incomingWebhookConfig),
+			})
 		}
 		go b.handleSlack()
 		return nil
 	}
-	if b.GetString("WebhookURL") != "" {
+	if b.GetString(outgoingWebhookConfig) != "" {
 		b.Log.Info("Connecting using webhookurl (sending)")
-		b.mh = matterhook.New(b.GetString("WebhookURL"),
-			matterhook.Config{InsecureSkipVerify: b.GetBool("SkipTLSVerify"),
-				DisableServer: true})
-		if b.GetString("Token") != "" {
+		b.mh = matterhook.New(b.GetString(outgoingWebhookConfig), matterhook.Config{
+			InsecureSkipVerify: b.GetBool(skipTLSConfig),
+			DisableServer:      true,
+		})
+		if b.GetString(tokenConfig) != "" {
 			b.Log.Info("Connecting using token (receiving)")
-			b.sc = slack.New(b.GetString("Token"))
+			b.sc = slack.New(b.GetString(tokenConfig))
 			b.rtm = b.sc.NewRTM()
 			go b.rtm.ManageConnection()
 			go b.handleSlack()
 		}
-	} else if b.GetString("Token") != "" {
+	} else if b.GetString(tokenConfig) != "" {
 		b.Log.Info("Connecting using token (sending and receiving)")
-		b.sc = slack.New(b.GetString("Token"))
+		b.sc = slack.New(b.GetString(tokenConfig))
 		b.rtm = b.sc.NewRTM()
 		go b.rtm.ManageConnection()
 		go b.handleSlack()
 	}
-	if b.GetString("WebhookBindAddress") == "" && b.GetString("WebhookURL") == "" && b.GetString("Token") == "" {
+	if b.GetString(incomingWebhookConfig) == "" && b.GetString(outgoingWebhookConfig) == "" && b.GetString(tokenConfig) == "" {
 		return errors.New("no connection method found. See that you have WebhookBindAddress, WebhookURL or Token configured")
 	}
 	return nil
@@ -101,7 +136,7 @@ func (b *Bslack) JoinChannel(channel config.ChannelInfo) error {
 	// use ID:channelid and resolve it to the actual name
 	idcheck := strings.Split(channel.Name, "ID:")
 	if len(idcheck) > 1 {
-		b.UseChannelID = true
+		b.useChannelID = true
 		ch, err := b.sc.GetChannelInfo(idcheck[1])
 		if err != nil {
 			return err
@@ -114,7 +149,7 @@ func (b *Bslack) JoinChannel(channel config.ChannelInfo) error {
 
 	// we can only join channels using the API
 	if b.sc != nil {
-		if strings.HasPrefix(b.GetString("Token"), "xoxb") {
+		if strings.HasPrefix(b.GetString(tokenConfig), "xoxb") {
 			// TODO check if bot has already joined channel
 			return nil
 		}
@@ -141,11 +176,14 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 	}
 
 	// Use webhook to send the message
-	if b.GetString("WebhookURL") != "" {
+	if b.GetString(outgoingWebhookConfig) != "" {
 		return b.sendWebhook(msg)
 	}
 
-	channelID := b.getChannelID(msg.Channel)
+	channelInfo, err := b.getChannel(msg.Channel)
+	if err != nil {
+		return "", fmt.Errorf("could not send message: %v", err)
+	}
 
 	// Delete message
 	if msg.Event == config.EVENT_MSG_DELETE {
@@ -155,7 +193,7 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 		}
 		// we get a "slack <ID>", split it
 		ts := strings.Fields(msg.ID)
-		_, _, err := b.sc.DeleteMessage(channelID, ts[1])
+		_, _, err = b.sc.DeleteMessage(channelInfo.ID, ts[1])
 		if err != nil {
 			return msg.ID, err
 		}
@@ -163,14 +201,14 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 	}
 
 	// Prepend nick if configured
-	if b.GetBool("PrefixMessagesWithNick") {
+	if b.GetBool(useNickPrefixConfig) {
 		msg.Text = msg.Username + msg.Text
 	}
 
 	// Edit message if we have an ID
 	if msg.ID != "" {
 		ts := strings.Fields(msg.ID)
-		_, _, _, err := b.sc.UpdateMessage(channelID, ts[1], msg.Text)
+		_, _, _, err = b.sc.UpdateMessage(channelInfo.ID, ts[1], msg.Text)
 		if err != nil {
 			return msg.ID, err
 		}
@@ -179,12 +217,12 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 
 	// create slack new post parameters
 	np := slack.NewPostMessageParameters()
-	if b.GetBool("PrefixMessagesWithNick") {
+	if b.GetBool(useNickPrefixConfig) {
 		np.AsUser = true
 	}
 	np.Username = msg.Username
 	np.LinkNames = 1 // replace mentions
-	np.IconURL = config.GetIconURL(&msg, b.GetString("iconurl"))
+	np.IconURL = config.GetIconURL(&msg, b.GetString(iconURLConfig))
 	if msg.Avatar != "" {
 		np.IconURL = msg.Avatar
 	}
@@ -193,8 +231,8 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 	// add file attachments
 	np.Attachments = append(np.Attachments, b.createAttach(msg.Extra)...)
 	// add slack attachments (from another slack bridge)
-	if len(msg.Extra["slack_attachment"]) > 0 {
-		for _, attach := range msg.Extra["slack_attachment"] {
+	if msg.Extra != nil {
+		for _, attach := range msg.Extra[sSlackAttachment] {
 			np.Attachments = append(np.Attachments, attach.([]slack.Attachment)...)
 		}
 	}
@@ -202,16 +240,17 @@ func (b *Bslack) Send(msg config.Message) (string, error) {
 	// Upload a file if it exists
 	if msg.Extra != nil {
 		for _, rmsg := range helper.HandleExtra(&msg, b.General) {
-			b.sc.PostMessage(channelID, rmsg.Username+rmsg.Text, np)
-		}
-		// check if we have files to upload (from slack, telegram or mattermost)
-		if len(msg.Extra["file"]) > 0 {
-			b.handleUploadFile(&msg, channelID)
+			_, _, err = b.sc.PostMessage(channelInfo.ID, rmsg.Username+rmsg.Text, np)
+			if err != nil {
+				b.Log.Error(err)
+			}
 		}
+		// Upload files if necessary (from Slack, Telegram or Mattermost).
+		b.handleUploadFile(&msg, channelInfo.ID)
 	}
 
 	// Post normal message
-	_, id, err := b.sc.PostMessage(channelID, msg.Text, np)
+	_, id, err := b.sc.PostMessage(channelInfo.ID, msg.Text, np)
 	if err != nil {
 		return "", err
 	}
@@ -223,26 +262,36 @@ func (b *Bslack) Reload(cfg *bridge.Config) (string, error) {
 }
 
 func (b *Bslack) createAttach(extra map[string][]interface{}) []slack.Attachment {
-	var attachs []slack.Attachment
+	var attachements []slack.Attachment
 	for _, v := range extra["attachments"] {
 		entry := v.(map[string]interface{})
-		s := slack.Attachment{}
-		s.Fallback = entry["fallback"].(string)
-		s.Color = entry["color"].(string)
-		s.Pretext = entry["pretext"].(string)
-		s.AuthorName = entry["author_name"].(string)
-		s.AuthorLink = entry["author_link"].(string)
-		s.AuthorIcon = entry["author_icon"].(string)
-		s.Title = entry["title"].(string)
-		s.TitleLink = entry["title_link"].(string)
-		s.Text = entry["text"].(string)
-		s.ImageURL = entry["image_url"].(string)
-		s.ThumbURL = entry["thumb_url"].(string)
-		s.Footer = entry["footer"].(string)
-		s.FooterIcon = entry["footer_icon"].(string)
-		attachs = append(attachs, s)
+		s := slack.Attachment{
+			Fallback:   extractStringField(entry, "fallback"),
+			Color:      extractStringField(entry, "color"),
+			Pretext:    extractStringField(entry, "pretext"),
+			AuthorName: extractStringField(entry, "author_name"),
+			AuthorLink: extractStringField(entry, "author_link"),
+			AuthorIcon: extractStringField(entry, "author_icon"),
+			Title:      extractStringField(entry, "title"),
+			TitleLink:  extractStringField(entry, "title_link"),
+			Text:       extractStringField(entry, "text"),
+			ImageURL:   extractStringField(entry, "image_url"),
+			ThumbURL:   extractStringField(entry, "thumb_url"),
+			Footer:     extractStringField(entry, "footer"),
+			FooterIcon: extractStringField(entry, "footer_icon"),
+		}
+		attachements = append(attachements, s)
 	}
-	return attachs
+	return attachements
+}
+
+func extractStringField(data map[string]interface{}, field string) string {
+	if rawValue, found := data[field]; found {
+		if value, ok := rawValue.(string); ok {
+			return value
+		}
+	}
+	return ""
 }
 
 // sendWebhook uses the configured WebhookURL to send the message
@@ -252,39 +301,48 @@ func (b *Bslack) sendWebhook(msg config.Message) (string, error) {
 		return "", nil
 	}
 
-	if b.GetBool("PrefixMessagesWithNick") {
+	if b.GetBool(useNickPrefixConfig) {
 		msg.Text = msg.Username + msg.Text
 	}
 
 	if msg.Extra != nil {
 		// this sends a message only if we received a config.EVENT_FILE_FAILURE_SIZE
 		for _, rmsg := range helper.HandleExtra(&msg, b.General) {
-			iconURL := config.GetIconURL(&rmsg, b.GetString("iconurl"))
-			matterMessage := matterhook.OMessage{IconURL: iconURL, Channel: msg.Channel, UserName: rmsg.Username, Text: rmsg.Text}
-			b.mh.Send(matterMessage)
+			iconURL := config.GetIconURL(&rmsg, b.GetString(iconURLConfig))
+			matterMessage := matterhook.OMessage{
+				IconURL:  iconURL,
+				Channel:  msg.Channel,
+				UserName: rmsg.Username,
+				Text:     rmsg.Text,
+			}
+			if err := b.mh.Send(matterMessage); err != nil {
+				b.Log.Errorf("Failed to send message: %v", err)
+			}
 		}
 
 		// webhook doesn't support file uploads, so we add the url manually
-		if len(msg.Extra["file"]) > 0 {
-			for _, f := range msg.Extra["file"] {
-				fi := f.(config.FileInfo)
-				if fi.URL != "" {
-					msg.Text += " " + fi.URL
-				}
+		for _, f := range msg.Extra["file"] {
+			fi := f.(config.FileInfo)
+			if fi.URL != "" {
+				msg.Text += " " + fi.URL
 			}
 		}
 	}
 
 	// if we have native slack_attachments add them
 	var attachs []slack.Attachment
-	if len(msg.Extra["slack_attachment"]) > 0 {
-		for _, attach := range msg.Extra["slack_attachment"] {
-			attachs = append(attachs, attach.([]slack.Attachment)...)
-		}
+	for _, attach := range msg.Extra[sSlackAttachment] {
+		attachs = append(attachs, attach.([]slack.Attachment)...)
 	}
 
-	iconURL := config.GetIconURL(&msg, b.GetString("iconurl"))
-	matterMessage := matterhook.OMessage{IconURL: iconURL, Attachments: attachs, Channel: msg.Channel, UserName: msg.Username, Text: msg.Text}
+	iconURL := config.GetIconURL(&msg, b.GetString(iconURLConfig))
+	matterMessage := matterhook.OMessage{
+		IconURL:     iconURL,
+		Attachments: attachs,
+		Channel:     msg.Channel,
+		UserName:    msg.Username,
+		Text:        msg.Text,
+	}
 	if msg.Avatar != "" {
 		matterMessage.IconURL = msg.Avatar
 	}