Adding EnsureBot plugin helper. (#10542)

* Adding EnsureBot plugin helper.

* Removing unessisary GetBot call.

* Moving to own file and error handling cleanup.

* Removing patch functionaliy. Plugins should manage their own bot account updates for now.

* Adding tests and cleaning up errors.

* Modify to not shadow err.

* Moving helpers to seperate interface.

* Feedback fixes

plugin/helpers_bots.go

@@ -0,0 +1,66 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+package plugin
+
+import (
+	"time"
+
+	"github.com/mattermost/mattermost-server/model"
+	"github.com/pkg/errors"
+)
+
+func (p *HelpersImpl) EnsureBot(bot *model.Bot) (retBotId string, retErr error) {
+	// Must provide a bot with a username
+	if bot == nil || len(bot.Username) < 1 {
+		return "", errors.New("passed a bad bot, nil or no username")
+	}
+
+	// If we fail for any reason, this could be a race between creation of bot and
+	// retreval from anouther EnsureBot. Just try the basic retrieve existing again.
+	defer func() {
+		if retBotId == "" || retErr != nil {
+			time.Sleep(time.Second)
+			botIdBytes, err := p.API.KVGet(BOT_USER_KEY)
+			if err == nil && botIdBytes != nil {
+				retBotId = string(botIdBytes)
+				retErr = nil
+			}
+		}
+	}()
+
+	botIdBytes, kvGetErr := p.API.KVGet(BOT_USER_KEY)
+	if kvGetErr != nil {
+		return "", errors.Wrap(kvGetErr, "failed to get bot")
+	}
+
+	// If the bot has already been created, there is nothing to do.
+	if botIdBytes != nil {
+		botId := string(botIdBytes)
+		return botId, nil
+	}
+
+	// Check for an existing bot user with that username. If one exists, then use that.
+	if user, userGetErr := p.API.GetUserByUsername(bot.Username); userGetErr == nil && user != nil {
+		if user.IsBot {
+			if kvSetErr := p.API.KVSet(BOT_USER_KEY, []byte(user.Id)); kvSetErr != nil {
+				p.API.LogWarn("Failed to set claimed bot user id.", "userid", user.Id, "err", kvSetErr)
+			}
+			return user.Id, nil
+		} else {
+			return "", errors.New("unable to create bot because user exists with the same name")
+		}
+	}
+
+	// Create a new bot user for the plugin
+	createdBot, createBotErr := p.API.CreateBot(bot)
+	if createBotErr != nil {
+		return "", errors.Wrap(createBotErr, "failed to create bot")
+	}
+
+	if kvSetErr := p.API.KVSet(BOT_USER_KEY, []byte(createdBot.UserId)); kvSetErr != nil {
+		p.API.LogWarn("Failed to set created bot user id.", "userid", createdBot.UserId, "err", kvSetErr)
+	}
+
+	return createdBot.UserId, nil
+}