From eba8822825e11548fcbfa66e3ce192fc0d579341 Mon Sep 17 00:00:00 2001
From: Jacob <jacob@katniss.top>
Date: Sat, 12 Apr 2025 12:50:24 -0400
Subject: [PATCH] feat: implement a Discord bot using the Gateway API that
 listens for and responds to commands

---
 discord-bot/src/main.rs | 169 +++++++++++++++++++++++++++++++++++++++-
 1 file changed, 167 insertions(+), 2 deletions(-)

diff --git a/discord-bot/src/main.rs b/discord-bot/src/main.rs
index e7a11a9..b5a016a 100644
--- a/discord-bot/src/main.rs
+++ b/discord-bot/src/main.rs
@@ -1,3 +1,168 @@
-fn main() {
-    println!("Hello, world!");
+use clap::Parser;
+use secrecy::{ExposeSecret, SecretString};
+use snafu::{ResultExt, Snafu};
+use std::{error::Error, time::Duration};
+use tracing_subscriber::fmt::format::FmtSpan;
+use twilight_cache_inmemory::{DefaultInMemoryCache, ResourceType};
+use twilight_gateway::{Event, EventTypeFlags, Intents, Shard, ShardId, StreamExt};
+use twilight_model::{
+    application::{command::CommandType, interaction::InteractionData},
+    gateway::payload::incoming::InteractionCreate,
+    http::interaction::{InteractionResponse, InteractionResponseType},
+};
+use twilight_util::builder::command::CommandBuilder;
+
+#[derive(Debug, Parser)]
+struct Args {
+    #[arg(long, env)]
+    discord_token: SecretString,
+}
+
+#[derive(Debug, Snafu)]
+enum AppError {
+    #[snafu(whatever, display("{message}"))]
+    Whatever {
+        message: String,
+        #[snafu(source(from(Box<dyn Error>, Some)))]
+        source: Option<Box<dyn Error>>,
+    },
+}
+
+#[tokio::main]
+#[snafu::report]
+async fn main() -> Result<(), AppError> {
+    let Args { discord_token } = Args::parse();
+
+    tracing_subscriber::fmt()
+        .pretty()
+        .with_span_events(FmtSpan::ACTIVE)
+        .init();
+
+    let shard_id = ShardId::ONE;
+    let intents = Intents::empty();
+    let mut shard = Shard::new(shard_id, discord_token.expose_secret().into(), intents);
+
+    let cache = DefaultInMemoryCache::builder()
+        .resource_types(ResourceType::empty())
+        .build();
+
+    tracing::info!("info");
+
+    let client = twilight_http::Client::new(discord_token.expose_secret().into());
+
+    let current_application = client
+        .current_user_application()
+        .await
+        .whatever_context("couldn't get current Discord application")?;
+
+    let current_application = current_application
+        .model()
+        .await
+        .whatever_context("couldn't get current Discord application")?;
+
+    let application_id = current_application.id;
+
+    let interaction_client = client.interaction(application_id);
+
+    let create_lobby = CommandBuilder::new(
+        "create",
+        "Create a lobby in this channel",
+        CommandType::ChatInput,
+    )
+    .validate()
+    .whatever_context("command wasn't correct")?
+    .build();
+    let commands = vec![create_lobby];
+
+    let returned_commands = interaction_client
+        .set_global_commands(&commands)
+        .await
+        .whatever_context("failed to set interaction commands")?
+        .models()
+        .await
+        .whatever_context("failed to deserialize set commands")?;
+    tracing::info!(?returned_commands);
+
+    while let Some(event_res) = shard.next_event(EventTypeFlags::INTERACTION_CREATE).await {
+        let event = match event_res {
+            Ok(event) => event,
+            Err(receive_message_error) => {
+                tracing::error!(?receive_message_error);
+                continue;
+            }
+        };
+
+        tracing::info!(?event);
+        cache.update(&event);
+
+        match event {
+            Event::GatewayClose(close_frame) => {
+                tracing::error!(?close_frame);
+                break;
+            }
+
+            Event::InteractionCreate(interaction_create) => {
+                let InteractionCreate(interaction) = *interaction_create;
+                tracing::info!(?interaction);
+
+                match interaction.data {
+                    None => {
+                        tracing::warn!("missing expected interaction data");
+                        continue;
+                    }
+                    Some(InteractionData::ApplicationCommand(command_data)) => {
+                        let command_data = *command_data;
+
+                        match command_data.name.as_str() {
+                            "create" => {
+                                tracing::info!("hurray for creating a lobby! TODO");
+
+                                let initial_response = InteractionResponse {
+                                    kind: InteractionResponseType::DeferredChannelMessageWithSource,
+                                    data: None,
+                                };
+                                if let Err(error) = interaction_client
+                                    .create_response(
+                                        interaction.id,
+                                        &interaction.token,
+                                        &initial_response,
+                                    )
+                                    .await
+                                {
+                                    tracing::error!(?error);
+                                }
+
+                                tokio::time::sleep(Duration::from_secs(5)).await;
+
+                                match interaction_client
+                                    .update_response(&interaction.token)
+                                    .content(Some("hello world!"))
+                                    .await
+                                {
+                                    Ok(message) => match message.model().await {
+                                        Ok(message) => {
+                                            tracing::info!(?message);
+                                        }
+                                        Err(error) => {
+                                            tracing::error!(?error);
+                                        }
+                                    },
+                                    Err(error) => {
+                                        tracing::error!(?error);
+                                    }
+                                }
+                            }
+                            command_name => {
+                                tracing::warn!(?command_name, "did not expect command");
+                            }
+                        }
+                    }
+                    _ => {}
+                }
+            }
+            _ => {}
+        }
+    }
+
+    Ok(())
 }