feat: add echo example (#1530)

examples/echo/README.md

@@ -0,0 +1,40 @@
+<img align="right" alt="DiscordGo logo" src="/docs/img/discordgo.svg" width="200">
+
+## DiscordGo Echo Example
+
+This example demonstrates how to utilize DiscordGo to create a simple, 
+slash commands based bot, that will echo your messages. 
+
+**Join [Discord Gophers](https://discord.gg/0f1SbxBZjYoCtNPP)
+Discord chat channel for support.**
+
+### Build
+
+This assumes you already have a working Go environment setup and that
+DiscordGo is correctly installed on your system.
+
+From within the example folder, run the below command to compile the
+example.
+
+```sh
+go build
+```
+
+### Usage
+
+```
+Usage of echo:
+  -app string
+        Application ID
+  -guild string
+        Guild ID
+  -token string
+        Bot authentication token
+
+```
+
+Run the command below to start the bot.
+
+```sh
+./echo -guild YOUR_TESTING_GUILD -app YOUR_TESTING_APP -token YOUR_BOT_TOKEN
+```

examples/echo/main.go

@@ -0,0 +1,119 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"os/signal"
+	"strings"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+type optionMap = map[string]*discordgo.ApplicationCommandInteractionDataOption
+
+func parseOptions(options []*discordgo.ApplicationCommandInteractionDataOption) (om optionMap) {
+	om = make(optionMap)
+	for _, opt := range options {
+		om[opt.Name] = opt
+	}
+	return
+}
+
+func interactionAuthor(i *discordgo.Interaction) *discordgo.User {
+	if i.Member != nil {
+		return i.Member.User
+	}
+	return i.User
+}
+
+func handleEcho(s *discordgo.Session, i *discordgo.InteractionCreate, opts optionMap) {
+	builder := new(strings.Builder)
+	if v, ok := opts["author"]; ok && v.BoolValue() {
+		author := interactionAuthor(i.Interaction)
+		builder.WriteString("**" + author.String() + "** says: ")
+	}
+	builder.WriteString(opts["message"].StringValue())
+
+	err := s.InteractionRespond(i.Interaction, &discordgo.InteractionResponse{
+		Type: discordgo.InteractionResponseChannelMessageWithSource,
+		Data: &discordgo.InteractionResponseData{
+			Content: builder.String(),
+		},
+	})
+
+	if err != nil {
+		log.Panicf("could not respond to interaction: %s", err)
+	}
+}
+
+var commands = []*discordgo.ApplicationCommand{
+	{
+		Name:        "echo",
+		Description: "Say something through a bot",
+		Options: []*discordgo.ApplicationCommandOption{
+			{
+				Name:        "message",
+				Description: "Contents of the message",
+				Type:        discordgo.ApplicationCommandOptionString,
+				Required:    true,
+			},
+			{
+				Name:        "author",
+				Description: "Whether to prepend message's author",
+				Type:        discordgo.ApplicationCommandOptionBoolean,
+			},
+		},
+	},
+}
+
+var (
+	Token = flag.String("token", "", "Bot authentication token")
+	App   = flag.String("app", "", "Application ID")
+	Guild = flag.String("guild", "", "Guild ID")
+)
+
+func main() {
+	flag.Parse()
+	if *App == "" {
+		log.Fatal("application id is not set")
+	}
+
+	session, _ := discordgo.New("Bot " + *Token)
+
+	session.AddHandler(func(s *discordgo.Session, i *discordgo.InteractionCreate) {
+		if i.Type != discordgo.InteractionApplicationCommand {
+			return
+		}
+
+		data := i.ApplicationCommandData()
+		if data.Name != "echo" {
+			return
+		}
+
+		handleEcho(s, i, parseOptions(data.Options))
+	})
+
+	session.AddHandler(func(s *discordgo.Session, r *discordgo.Ready) {
+		log.Printf("Logged in as %s", r.User.String())
+	})
+
+	_, err := session.ApplicationCommandBulkOverwrite(*App, *Guild, commands)
+	if err != nil {
+		log.Fatalf("could not register commands: %s", err)
+	}
+
+	err = session.Open()
+	if err != nil {
+		log.Fatalf("could not open session: %s", err)
+	}
+
+	sigch := make(chan os.Signal, 1)
+	signal.Notify(sigch, os.Interrupt)
+	<-sigch
+
+	err = session.Close()
+	if err != nil {
+		log.Printf("could not close session gracefully: %s", err)
+	}
+}