[GH-24] Implement channel welcome messages (#31)

* Implement channel welcome messages

* DRY up the command.go code by moving commands to separate functions

* Review fixes #1

* Change keys prefix ordering

* Switch back to sending ephemeral posts

* Send an opportunistic ephemeral post and a DM

Co-authored-by: Pawel Rozlach <[email protected]>

Author: vespian

README.md

@@ -61,7 +61,7 @@ where
 - **TeamName**: The team for which the Welcome Bot sends a message for. Must be the team handle used in the URL, in lowercase. For example, in the following URL the **TeamName** value is `my-team`: https://example.com/my-team/channels/my-channel
 - **DelayInSeconds**: The number of seconds after joining a team that the user receives a welcome message.
 - **Message**: The message posted to the user.
-- (Optional) **AttachmentMessage**: Message text in attachment containing user action buttons. 
+- (Optional) **AttachmentMessage**: Message text in attachment containing user action buttons.
 - (Optional) **Actions**: Use this to add new team members to channels automatically or based on which action button they pressed.
     - **ActionType**: One of `button` or `automatic`. When `button`: enables uses to select which types of channels they want to join. When `automatic`: the user is automatically added to the specified channels.
     - **ActionDisplayName**: Sets the display name for the user action buttons.
@@ -73,6 +73,9 @@ The preview of the configured messages can be done via bot commands:
 * `/welcomebot help` - show a short usage information
 * `/welcomebot list` - lists the teams for which greetings were defined
 * `/welcomebot preview [team-name]` - sends ephemeral messages to the user calling the command, with the preview of the welcome message[s] for the given team name and the user that requested the preview
+* `/welcomebot set_channel_welcome` - sets the given text as current's channel welcome message
+* `/welcomebot get_channel_welcome` - gets the current's channel welcome message
+* `/welcomebot delete_channel_welcome` - deletes the current's channel welcome message
 
 ## Example
 

server/command.go

@@ -10,24 +10,28 @@ import (
 )
 
 const COMMAND_HELP = `* |/welcomebot preview [team-name] [user-name]| - preview the welcome message for the given team name. The current user's username will be used to render the template.
-* |/welcomebot list| - list the teams for which welcome messages were defined`
+* |/welcomebot list| - list the teams for which welcome messages were defined
+* |/welcomebot set_channel_welcome [welcome-message]| - set the welcome message for the given channel. Direct channels are not supported.
+* |/welcomebot get_channel_welcome| - print the welcome message set for the given channel (if any)
+* |/welcomebot delete_channel_welcome| - delete the welcome message for the given channel (if any)
+`
 
 func getCommand() *model.Command {
 	return &model.Command{
 		Trigger:          "welcomebot",
 		DisplayName:      "welcomebot",
 		Description:      "Welcome Bot helps add new team members to channels.",
 		AutoComplete:     true,
-		AutoCompleteDesc: "Available commands: preview, help",
+		AutoCompleteDesc: "Available commands: preview, help, list, set_channel_welcome, get_channel_welcome, delete_channel_welcome",
 		AutoCompleteHint: "[command]",
 	}
 }
 
-func (p *Plugin) postCommandResponse(args *model.CommandArgs, text string) {
+func (p *Plugin) postCommandResponse(args *model.CommandArgs, text string, textArgs ...interface{}) {
 	post := &model.Post{
 		UserId:    p.botUserID,
 		ChannelId: args.ChannelId,
-		Message:   text,
+		Message:   fmt.Sprintf(text, textArgs...),
 	}
 	_ = p.API.SendEphemeralPost(args.UserId, post)
 }
@@ -43,7 +47,144 @@ func (p *Plugin) hasSysadminRole(userId string) (bool, error) {
 	return true, nil
 }
 
-func (p *Plugin) ExecuteCommand(c *plugin.Context, args *model.CommandArgs) (*model.CommandResponse, *model.AppError) {
+func (p *Plugin) validateCommand(action string, parameters []string) string {
+	switch action {
+	case "preview":
+		if len(parameters) != 1 {
+			return "Please specify a team, for which preview should be made."
+		}
+	case "list":
+		if len(parameters) > 0 {
+			return "List command does not accept any extra parameters"
+		}
+	case "set_channel_welcome":
+		if len(parameters) == 0 {
+			return "`set_channel_welcome` command requires the message to be provided"
+		}
+	case "get_channel_welcome":
+		if len(parameters) > 0 {
+			return "`get_channel_welcome` command does not accept any extra parameters"
+		}
+	case "delete_channel_welcome":
+		if len(parameters) > 0 {
+			return "`delete_channel_welcome` command does not accept any extra parameters"
+		}
+	}
+
+	return ""
+}
+
+func (p *Plugin) executeCommandPreview(teamName string, args *model.CommandArgs) {
+	found := false
+	for _, message := range p.getWelcomeMessages() {
+		if message.TeamName == teamName {
+			if err := p.previewWelcomeMessage(teamName, args, *message); err != nil {
+				p.postCommandResponse(args, "error occured while processing greeting for team `%s`: `%s`", teamName, err)
+				return
+			}
+
+			found = true
+		}
+	}
+
+	if !found {
+		p.postCommandResponse(args, "team `%s` has not been found", teamName)
+	}
+
+	return
+}
+
+func (p *Plugin) executeCommandList(args *model.CommandArgs) {
+	wecomeMessages := p.getWelcomeMessages()
+
+	if len(wecomeMessages) == 0 {
+		p.postCommandResponse(args, "There are no welcome messages defined")
+		return
+	}
+
+	// Deduplicate entries
+	teams := make(map[string]struct{})
+	for _, message := range wecomeMessages {
+		teams[message.TeamName] = struct{}{}
+	}
+
+	var str strings.Builder
+	str.WriteString("Teams for which welcome messages are defined:")
+	for team := range teams {
+		str.WriteString(fmt.Sprintf("\n * %s", team))
+	}
+	p.postCommandResponse(args, str.String())
+	return
+}
+
+func (p *Plugin) executeCommandSetWelcome(args *model.CommandArgs) {
+	channelInfo, appErr := p.API.GetChannel(args.ChannelId)
+	if appErr != nil {
+		p.postCommandResponse(args, "error occured while checking the type of the chanelId `%s`: `%s`", args.ChannelId, appErr)
+		return
+	}
+
+	if channelInfo.Type == model.CHANNEL_PRIVATE {
+		p.postCommandResponse(args, "welcome messages are not supported for direct channels")
+		return
+	}
+
+	// strings.Fields will consume ALL whitespace, so plain re-joining of the
+	// parameters slice will not produce the same message
+	message := strings.SplitN(args.Command, "set_channel_welcome", 2)[1]
+	message = strings.TrimSpace(message)
+
+	key := fmt.Sprintf("%s%s", WELCOMEBOT_CHANNEL_WELCOME_KEY, args.ChannelId)
+	if appErr := p.API.KVSet(key, []byte(message)); appErr != nil {
+		p.postCommandResponse(args, "error occured while storing the welcome message for the chanel: `%s`", appErr)
+		return
+	}
+
+	p.postCommandResponse(args, "stored the welcome message:\n%s", message)
+	return
+}
+
+func (p *Plugin) executeCommandGetWelcome(args *model.CommandArgs) {
+	key := fmt.Sprintf("%s%s", WELCOMEBOT_CHANNEL_WELCOME_KEY, args.ChannelId)
+	data, appErr := p.API.KVGet(key)
+	if appErr != nil {
+		p.postCommandResponse(args, "error occured while retrieving the welcome message for the chanel: `%s`", appErr)
+		return
+	}
+
+	if data == nil {
+		p.postCommandResponse(args, "welcome message has not been set yet")
+		return
+	}
+
+	p.postCommandResponse(args, "Welcome message is:\n%s", string(data))
+	return
+}
+
+func (p *Plugin) executeCommandDeleteWelcome(args *model.CommandArgs) {
+	key := fmt.Sprintf("%s%s", WELCOMEBOT_CHANNEL_WELCOME_KEY, args.ChannelId)
+	data, appErr := p.API.KVGet(key)
+
+	if appErr != nil {
+		p.postCommandResponse(args, "error occured while retrieving the welcome message for the chanel: `%s`", appErr)
+		return
+	}
+
+	if data == nil {
+		p.postCommandResponse(args, "welcome message has not been set yet")
+		return
+	}
+
+	if appErr := p.API.KVDelete(key); appErr != nil {
+		p.postCommandResponse(args, "error occured while deleting the welcome message for the chanel: `%s`", appErr)
+		return
+	}
+
+	p.postCommandResponse(args, "welcome message has been deleted")
+	return
+}
+
+func (p *Plugin) ExecuteCommand(_ *plugin.Context, args *model.CommandArgs) (*model.CommandResponse, *model.AppError) {
 	split := strings.Fields(args.Command)
 	command := split[0]
 	parameters := []string{}
@@ -59,9 +200,14 @@ func (p *Plugin) ExecuteCommand(c *plugin.Context, args *model.CommandArgs) (*mo
 		return &model.CommandResponse{}, nil
 	}
 
+	if response := p.validateCommand(action, parameters); response != "" {
+		p.postCommandResponse(args, response)
+		return &model.CommandResponse{}, nil
+	}
+
 	isSysadmin, err := p.hasSysadminRole(args.UserId)
 	if err != nil {
-		p.postCommandResponse(args, fmt.Sprintf("authorization failed: %v", err))
+		p.postCommandResponse(args, "authorization failed: %s", err)
 		return &model.CommandResponse{}, nil
 	}
 	if !isSysadmin {
@@ -71,55 +217,20 @@ func (p *Plugin) ExecuteCommand(c *plugin.Context, args *model.CommandArgs) (*mo
 
 	switch action {
 	case "preview":
-		if len(parameters) != 1 {
-			p.postCommandResponse(args, "Please specify a team, for which preview should be made.")
-			return &model.CommandResponse{}, nil
-		}
-
 		teamName := parameters[0]
-
-		found := false
-		for _, message := range p.getWelcomeMessages() {
-			if message.TeamName == teamName {
-				if err := p.previewWelcomeMessage(teamName, args, *message); err != nil {
-					errMsg := fmt.Sprintf("error occured while processing greeting for team `%s`: `%s`", teamName, err)
-					p.postCommandResponse(args, errMsg)
-					return &model.CommandResponse{}, nil
-				}
-
-				found = true
-			}
-		}
-
-		if !found {
-			p.postCommandResponse(args, fmt.Sprintf("team `%s` has not been found", teamName))
-		}
+		p.executeCommandPreview(teamName, args)
 		return &model.CommandResponse{}, nil
 	case "list":
-		if len(parameters) > 0 {
-			p.postCommandResponse(args, "List command does not accept any extra parameters")
-			return &model.CommandResponse{}, nil
-		}
-
-		wecomeMessages := p.getWelcomeMessages()
-
-		if len(wecomeMessages) == 0 {
-			p.postCommandResponse(args, "There are no welcome messages defined")
-			return &model.CommandResponse{}, nil
-		}
-
-		// Deduplicate entries
-		teams := make(map[string]struct{})
-		for _, message := range wecomeMessages {
-			teams[message.TeamName] = struct{}{}
-		}
-
-		var str strings.Builder
-		str.WriteString("Teams for which welcome messages are defined:")
-		for team := range teams {
-			str.WriteString(fmt.Sprintf("\n * %s", team))
-		}
-		p.postCommandResponse(args, str.String())
+		p.executeCommandList(args)
+		return &model.CommandResponse{}, nil
+	case "set_channel_welcome":
+		p.executeCommandSetWelcome(args)
+		return &model.CommandResponse{}, nil
+	case "get_channel_welcome":
+		p.executeCommandGetWelcome(args)
+		return &model.CommandResponse{}, nil
+	case "delete_channel_welcome":
+		p.executeCommandDeleteWelcome(args)
 		return &model.CommandResponse{}, nil
 	case "help":
 		fallthrough
@@ -129,7 +240,6 @@ func (p *Plugin) ExecuteCommand(c *plugin.Context, args *model.CommandArgs) (*mo
 		return &model.CommandResponse{}, nil
 	}
 
-	p.postCommandResponse(args, fmt.Sprintf("Unknown action %v", action))
-
+	p.postCommandResponse(args, "Unknown action %v", action)
 	return &model.CommandResponse{}, nil
 }

server/hooks.go

@@ -0,0 +1,90 @@
+package main
+
+import (
+	"fmt"
+	"time"
+
+	"github.com/mattermost/mattermost-server/v5/mlog"
+	"github.com/mattermost/mattermost-server/v5/model"
+	"github.com/mattermost/mattermost-server/v5/plugin"
+)
+
+// UserHasJoinedTeam is invoked after the membership has been committed to the database. If
+// actor is not nil, the user was added to the team by the actor.
+func (p *Plugin) UserHasJoinedTeam(c *plugin.Context, teamMember *model.TeamMember, actor *model.User) {
+	data := p.constructMessageTemplate(teamMember.UserId, teamMember.TeamId)
+	if data == nil {
+		return
+	}
+
+	for _, message := range p.getWelcomeMessages() {
+		if message.TeamName == data.Team.Name {
+			go p.processWelcomeMessage(*data, *message)
+		}
+	}
+}
+
+// UserHasJoinedChannel is invoked after the membership has been committed to
+// the database. If actor is not nil, the user was invited to the channel by
+// the actor.
+func (p *Plugin) UserHasJoinedChannel(c *plugin.Context, channelMember *model.ChannelMember, _ *model.User) {
+	if channelInfo, appErr := p.API.GetChannel(channelMember.ChannelId); appErr != nil {
+		mlog.Error(
+			"error occured while checking the type of the chanel",
+			mlog.String("channelId", channelMember.ChannelId),
+			mlog.Err(appErr),
+		)
+		return
+	} else if channelInfo.Type == model.CHANNEL_PRIVATE {
+		return
+	}
+
+	key := fmt.Sprintf("%s%s", WELCOMEBOT_CHANNEL_WELCOME_KEY, channelMember.ChannelId)
+	data, appErr := p.API.KVGet(key)
+	if appErr != nil {
+		mlog.Error(
+			"error occured while retrieving the welcome message",
+			mlog.String("channelId", channelMember.ChannelId),
+			mlog.Err(appErr),
+		)
+		return
+	}
+
+	if data == nil {
+		// No welcome message for the given channel
+		return
+	}
+
+	dmChannel, err := p.API.GetDirectChannel(channelMember.UserId, p.botUserID)
+	if err != nil {
+		mlog.Error(
+			"error occured while creating direct channel to the user",
+			mlog.String("UserId", channelMember.UserId),
+			mlog.Err(err),
+		)
+		return
+	}
+
+	// We send a DM and an opportunistic ephemeral message to the channel. See
+	// the discussion at the link below for more details:
+	// https://github.com/mattermost/mattermost-plugin-welcomebot/pull/31#issuecomment-611691023
+	postDM := &model.Post{
+		UserId:    p.botUserID,
+		ChannelId: dmChannel.Id,
+		Message:   string(data),
+	}
+	if _, appErr := p.API.CreatePost(postDM); appErr != nil {
+		mlog.Error("failed to post welcome message to the channel",
+			mlog.String("channelId", dmChannel.Id),
+			mlog.Err(appErr),
+		)
+	}
+
+	postChannel := &model.Post{
+		UserId:    p.botUserID,
+		ChannelId: channelMember.ChannelId,
+		Message:   string(data),
+	}
+	time.Sleep(1 * time.Second)
+	_ = p.API.SendEphemeralPost(channelMember.UserId, postChannel)
+}

server/plugin.go

@@ -12,6 +12,8 @@ const (
 	botUsername    = "welcomebot"
 	botDisplayName = "Welcomebot"
 	botDescription = "A bot account created by the Welcomebot plugin."
+
+	WELCOMEBOT_CHANNEL_WELCOME_KEY = "chanmsg_"
 )
 
 // Plugin represents the welcome bot plugin