Support getting the color of a user. (#299)

state.go

@@ -14,6 +14,7 @@ package discordgo
 
 import (
 	"errors"
+	"sort"
 	"sync"
 )
 
@@ -749,3 +750,44 @@ func (s *State) UserChannelPermissions(userID, channelID string) (apermissions i
 
 	return memberPermissions(guild, channel, member), nil
 }
+
+// UserColor returns the color of a user in a channel.
+// While colors are defined at a Guild level, determining for a channel is more useful in message handlers.
+// 0 is returned in cases of error, which is the color of @everyone.
+// userID    : The ID of the user to calculate the color for.
+// channelID   : The ID of the channel to calculate the color for.
+func (s *State) UserColor(userID, channelID string) int {
+	if s == nil {
+		return 0
+	}
+
+	channel, err := s.Channel(channelID)
+	if err != nil {
+		return 0
+	}
+
+	guild, err := s.Guild(channel.GuildID)
+	if err != nil {
+		return 0
+	}
+
+	member, err := s.Member(guild.ID, userID)
+	if err != nil {
+		return 0
+	}
+
+	roles := Roles(guild.Roles)
+	sort.Sort(roles)
+
+	for _, role := range roles {
+		for _, roleID := range member.Roles {
+			if role.ID == roleID {
+				if role.Color != 0 {
+					return role.Color
+				}
+			}
+		}
+	}
+
+	return 0
+}

structs.go

@@ -252,6 +252,20 @@ type Role struct {
 	Permissions int    `json:"permissions"`
 }
 
+type Roles []*Role
+
+func (r Roles) Len() int {
+	return len(r)
+}
+
+func (r Roles) Less(i, j int) bool {
+	return r[i].Position > r[j].Position
+}
+
+func (r Roles) Swap(i, j int) {
+	r[i], r[j] = r[j], r[i]
+}
+
 // A VoiceState stores the voice states of Guilds
 type VoiceState struct {
 	UserID    string `json:"user_id"`