From bcffbc88d43bd75f82801c62818980a95c41c81a Mon Sep 17 00:00:00 2001
From: rumblefrog <contact@zhenyangli.me>
Date: Thu, 5 Sep 2019 16:31:45 -0400
Subject: [PATCH] enhancement(bot): replace mention when using simple messages
 | closes #25

---
 server/bot/pipeline.go |  3 ++-
 server/bot/util.go     | 56 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/server/bot/pipeline.go b/server/bot/pipeline.go
index b38e9230..3f67891f 100644
--- a/server/bot/pipeline.go
+++ b/server/bot/pipeline.go
@@ -24,7 +24,8 @@ func Listen() {
 						if !config.Config.Bot.SimpleMessage {
 							RelayBot.ChannelMessageSendEmbed(channel.ID, message.Embed())
 						} else {
-							RelayBot.ChannelMessageSend(channel.ID, message.Plain())
+							content := TransformMentions(RelayBot, channel.ID, message.Plain())
+							RelayBot.ChannelMessageSend(channel.ID, content)
 						}
 					}
 				}
diff --git a/server/bot/util.go b/server/bot/util.go
index 4937e83e..34e8704c 100644
--- a/server/bot/util.go
+++ b/server/bot/util.go
@@ -1,14 +1,19 @@
 package bot
 
 import (
+	"fmt"
 	"regexp"
+	"strings"
 
 	"github.com/Necroforger/dgrouter/exrouter"
 	"github.com/bwmarrin/discordgo"
 )
 
 var (
+	ChannelRegex         = regexp.MustCompile("(?:<#)?([0-9]+)>?")
 	ChannelRegexExplicit = regexp.MustCompile("^(?:<#)?([0-9]+)>?$")
+	UserRegex            = regexp.MustCompile("(?:<@!?)?([0-9]+)>?")
+	RoleRegex            = regexp.MustCompile("(?:<@&)?([0-9]+)>?")
 )
 
 func GuildMemberPermissions(member *discordgo.Member, guild *discordgo.Guild) (apermissions int) {
@@ -63,3 +68,54 @@ func ParseChannel(arg string) (string, bool) {
 
 	return "", false
 }
+
+func TransformMentions(session *discordgo.Session, cid string, body string) string {
+	if ChannelRegex.Match([]byte(body)) {
+		matches := ChannelRegex.FindAllStringSubmatch(body, -1)
+
+		n := len(matches)
+
+		for i := 0; i < n; i++ {
+			channel, err := session.Channel(matches[i][1])
+
+			if err == nil {
+				body = strings.Replace(body, matches[i][0], fmt.Sprintf("#%s", channel.Name), -1)
+			}
+		}
+	}
+
+	// Role match has to be before user, otherwise UserRegex will partial match role
+	if RoleRegex.Match([]byte(body)) {
+		channel, err := session.Channel(cid)
+
+		if err == nil {
+			matches := RoleRegex.FindAllStringSubmatch(body, -1)
+
+			n := len(matches)
+
+			for i := 0; i < n; i++ {
+				role, err := session.State.Role(channel.GuildID, matches[i][1])
+
+				if err == nil {
+					body = strings.Replace(body, matches[i][0], fmt.Sprintf("@%s", role.Name), -1)
+				}
+			}
+		}
+	}
+
+	if UserRegex.Match([]byte(body)) {
+		matches := UserRegex.FindAllStringSubmatch(body, -1)
+
+		n := len(matches)
+
+		for i := 0; i < n; i++ {
+			user, err := session.User(matches[i][1])
+
+			if err == nil {
+				body = strings.Replace(body, matches[i][0], fmt.Sprintf("@%s", user.Username), -1)
+			}
+		}
+	}
+
+	return body
+}