Add slash command support

Fixes #101

service/slack.go

@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"html"
 	"log"
+	"net/url"
 	"regexp"
 	"sort"
 	"strconv"
@@ -337,6 +338,12 @@ func (s *SlackService) SendReply(channelID string, threadID string, message stri
 // SendCommand will send a specific command to slack. First we check
 // wether we are dealing with a command, and if it is one of the supported
 // ones.
+//
+// NOTE: slack slash commands that are sent to the slack api are undocumented,
+// and as such we need to update the message option that direct it to the
+// correct api endpoint.
+//
+// https://github.com/ErikKalkoken/slackApiDoc/blob/master/chat.command.md
 func (s *SlackService) SendCommand(channelID string, message string) (bool, error) {
 	// First check if it begins with slash and a command
 	r, err := regexp.Compile(`^/\w+`)
@@ -367,6 +374,31 @@ func (s *SlackService) SendCommand(channelID string, message string) (bool, erro
 			return false, err
 		}
 
+		return true, nil
+	default:
+		r := regexp.MustCompile(`(?P<cmd>^/\w+) (?P<text>.*)`)
+		subMatch := r.FindStringSubmatch(message)
+
+		if len(subMatch) < 3 {
+			return false, errors.New("slash command malformed")
+		}
+
+		cmd := subMatch[1]
+		text := subMatch[2]
+
+		msgOption := slack.UnsafeMsgOptionEndpoint(
+			fmt.Sprintf("%s%s", slack.APIURL, "chat.command"),
+			func(urlValues url.Values) {
+				urlValues.Add("command", cmd)
+				urlValues.Add("text", text)
+			},
+		)
+
+		_, _, err := s.Client.PostMessage(channelID, msgOption)
+		if err != nil {
+			return false, err
+		}
+
 		return true, nil
 	}