feature: adds discord integration to GoMud (#245)

This PR adds a very simple discord integration to GoMud.

To use the integration:
1. Setup a discord webhook: https://support.discord.com/hc/en-us/articles/228383668-Intro-to-Webhooks
2. Set the environment variable "DISCORD_WEBHOOK_URL" prior to running GoMud. (`DISCORD_WEBHOOK_URL=https://www.mywebhook.com ./gomud` on linux).

All feedback is encouraged and welcome, learning Golang slowly.

.gitignore

@@ -3,3 +3,4 @@ private-notes.txt
 _datafiles/**/users/*
 **/config-overrides.yaml
 **/.roundcount
+vendor/

internal/integrations/discord/client.go

@@ -0,0 +1,116 @@
+// Package discord
+//
+// This package provides programatic access to discord messages integrated with GoMud.
+//
+// References:
+// https://leovoel.github.io/embed-visualizer/
+// https://birdie0.github.io/discord-webhooks-guide/discord_webhook.html
+package discord
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+
+	"github.com/volte6/gomud/internal/events"
+)
+
+var (
+	WebhookUrl string
+	initialized bool
+)
+
+// Initializes and sets the webhook so we can send messages to discord
+// and registers listeners to listen for events
+func Init(webhookUrl string) {
+	if initialized {
+		return
+	}
+
+	WebhookUrl = webhookUrl
+	registerListeners()
+	initialized = true	
+}
+
+func registerListeners() {
+	events.RegisterListener(events.PlayerSpawn{}, HandlePlayerSpawn)
+	events.RegisterListener(events.PlayerDespawn{}, HandlePlayerDespawn)
+}
+
+// Sends an embed message to discord which includes a colored bar to the left
+// hexColor should be specified as a string in this format "#000000"
+func SendRichMessage(message string, hexColor string) error {
+	if !initialized {
+		return errors.New("Discord client was not initialized.")
+	}
+
+	if strings.HasPrefix(hexColor, "#") {
+		hexColor = hexColor[1:]
+	}
+
+	color, err := strconv.ParseInt(hexColor, 16, 32)
+	if err != nil {
+		message := fmt.Sprintf("Invalid color specified, expected format #000000")
+		return errors.New(message)
+	}
+
+	payload := richMessage{
+		Embeds: []embed{
+			{
+				Description: message,
+				Color: int32(color),
+			},
+		},
+	}		
+
+	marshalled, err := json.Marshal(payload)
+	if err != nil {
+		message := fmt.Sprintf("Couldn't marshal discord message")
+		return errors.New(message)
+	}
+
+	return send(marshalled)
+}
+
+// Sends a simple message to discord
+func SendMessage(message string) error {
+	if !initialized {
+		return errors.New("Discord client was not initialized.")
+	}
+
+	payload := simpleMessage{
+		Content: message,
+	}
+
+	marshalled, err := json.Marshal(payload)
+	if err != nil {
+		message := fmt.Sprintf("Couldn't marshal discord message")
+		return errors.New(message)
+	}
+
+	return send(marshalled)
+}
+
+func send(marshalled []byte) error {
+	request, err := http.NewRequest("POST", WebhookUrl, bytes.NewReader(marshalled))
+	request.Header.Set("Content-Type", "application/json; charset=UTF-8")
+
+	client := &http.Client{}
+	response, err := client.Do(request)
+	if err != nil {
+		message := fmt.Sprintf("Couldn't send POST request to discord.")
+		return errors.New(message)
+	}
+
+	// Expect 204 No Content reply
+	if response.StatusCode != 204 {
+		message := fmt.Sprintf("Expected discord to send status code 204, got %v.", response.StatusCode)
+		return errors.New(message)
+	}
+
+	return nil
+}

internal/integrations/discord/listeners.go

@@ -0,0 +1,50 @@
+package discord
+
+import (
+	"fmt"
+
+	"github.com/volte6/gomud/internal/events"
+	"github.com/volte6/gomud/internal/users"
+)
+
+// Player enters the world event
+func HandlePlayerSpawn(e events.Event) bool {
+	evt, typeOk := e.(events.PlayerSpawn)
+	if !typeOk {
+		return false
+	}
+
+	user := users.GetByUserId(evt.UserId)
+	if user == nil {
+		return false
+	}
+
+	message := fmt.Sprintf(":white_check_mark: **%v** connected", user.Character.Name)
+	err := SendMessage(message)
+	if err != nil {
+		return false
+	}
+
+	return true
+}
+
+// Player leaves the world event
+func HandlePlayerDespawn(e events.Event) bool {
+	evt, typeOk := e.(events.PlayerDespawn)
+	if !typeOk {
+		return false
+	}
+
+	user := users.GetByUserId(evt.UserId)
+	if user == nil {
+		return false
+	}
+
+	message := fmt.Sprintf(":x: **%v** disconnected", user.Character.Name)
+	err := SendMessage(message)
+	if err != nil {
+		return false
+	}
+
+	return true
+}

internal/integrations/discord/types.go

@@ -0,0 +1,20 @@
+package discord
+
+// Reference: https://birdie0.github.io/discord-webhooks-guide/discord_webhook.html
+
+// Discord message payload for non-rich content
+// This object has many more fields, see reference
+type simpleMessage struct {
+	Content string `json:"content"`
+}
+
+// Discord message payload for rich content
+type richMessage struct {
+	Embeds []embed `json:"embeds"`
+}
+
+// These objects have many more fields, see reference
+type embed struct {
+	Description string `json:"description"`
+	Color       int32    `json:"color"`
+}

main.go

@@ -25,6 +25,7 @@ import (
 	"github.com/volte6/gomud/internal/gametime"
 	"github.com/volte6/gomud/internal/hooks"
 	"github.com/volte6/gomud/internal/inputhandlers"
+	"github.com/volte6/gomud/internal/integrations/discord"
 	"github.com/volte6/gomud/internal/items"
 	"github.com/volte6/gomud/internal/keywords"
 	"github.com/volte6/gomud/internal/leaderboard"
@@ -119,6 +120,14 @@ func main() {
 		os.Exit(1)
 	}
 
+	// Discord integration
+	if webhookUrl := os.Getenv("DISCORD_WEBHOOK_URL"); webhookUrl != "" {
+		discord.Init(webhookUrl)
+		mudlog.Info("Discord", "info", "integration is enabled")
+	} else {
+		mudlog.Warn("Discord", "info", "integration is disabled")
+	}
+
 	hooks.RegisterListeners()
 
 	// Load all the data files up front.