//! Requires the "client", "standard_framework", and "voice" features be enabled
//! in your Cargo.toml, like so:
//!
//! ```toml
//! [dependencies.serenity]
//! git = "https://github.com/serenity-rs/serenity.git"
//! features = ["client", "standard_framework", "voice"]
//! ```
use std::env;

use serenity::{
    async_trait,
    client::{Client, Context, EventHandler},
    framework::{
        standard::{
            macros::{command, group},
            Args,
            CommandResult,
        },
        StandardFramework,
    },
    model::{channel::Message, gateway::Ready, id::ChannelId},
    prelude::{GatewayIntents, Mentionable},
    Result as SerenityResult,
};

use songbird::{
    driver::DecodeMode,
    model::payload::{ClientDisconnect, Speaking},
    Config,
    CoreEvent,
    Event,
    EventContext,
    EventHandler as VoiceEventHandler,
    SerenityInit,
};

struct Handler;

#[async_trait]
impl EventHandler for Handler {
    async fn ready(&self, _: Context, ready: Ready) {
        println!("{} is connected!", ready.user.name);
    }
}

struct Receiver;

impl Receiver {
    pub fn new() -> Self {
        // You can manage state here, such as a buffer of audio packet bytes so
        // you can later store them in intervals.
        Self {}
    }
}

#[async_trait]
impl VoiceEventHandler for Receiver {
    #[allow(unused_variables)]
    async fn act(&self, ctx: &EventContext<'_>) -> Option<Event> {
        use EventContext as Ctx;
        match ctx {
            Ctx::SpeakingStateUpdate(Speaking {
                speaking,
                ssrc,
                user_id,
                ..
            }) => {
                // Discord voice calls use RTP, where every sender uses a randomly allocated
                // *Synchronisation Source* (SSRC) to allow receivers to tell which audio
                // stream a received packet belongs to. As this number is not derived from
                // the sender's user_id, only Discord Voice Gateway messages like this one
                // inform us about which random SSRC a user has been allocated. Future voice
                // packets will contain *only* the SSRC.
                //
                // You can implement logic here so that you can differentiate users'
                // SSRCs and map the SSRC to the User ID and maintain this state.
                // Using this map, you can map the `ssrc` in `voice_packet`
                // to the user ID and handle their audio packets separately.
                println!(
                    "Speaking state update: user {:?} has SSRC {:?}, using {:?}",
                    user_id, ssrc, speaking,
                );
            },
            Ctx::SpeakingUpdate(data) => {
                // You can implement logic here which reacts to a user starting
                // or stopping speaking, and to map their SSRC to User ID.
                println!(
                    "Source {} has {} speaking.",
                    data.ssrc,
                    if data.speaking { "started" } else { "stopped" },
                );
            },
            Ctx::VoicePacket(data) => {
                // An event which fires for every received audio packet,
                // containing the decoded data.
                if let Some(audio) = data.audio {
                    println!(
                        "Audio packet's first 5 samples: {:?}",
                        audio.get(..5.min(audio.len()))
                    );
                    println!(
                        "Audio packet sequence {:05} has {:04} bytes (decompressed from {}), SSRC {}",
                        data.packet.sequence.0,
                        audio.len() * std::mem::size_of::<i16>(),
                        data.packet.payload.len(),
                        data.packet.ssrc,
                    );
                } else {
                    println!("RTP packet, but no audio. Driver may not be configured to decode.");
                }
            },
            Ctx::RtcpPacket(data) => {
                // An event which fires for every received rtcp packet,
                // containing the call statistics and reporting information.
                println!("RTCP packet received: {:?}", data.packet);
            },
            Ctx::ClientDisconnect(ClientDisconnect { user_id, .. }) => {
                // You can implement your own logic here to handle a user who has left the
                // voice channel e.g., finalise processing of statistics etc.
                // You will typically need to map the User ID to their SSRC; observed when
                // first speaking.

                println!("Client disconnected: user {:?}", user_id);
            },
            _ => {
                // We won't be registering this struct for any more event classes.
                unimplemented!()
            },
        }

        None
    }
}

#[group]
#[commands(join, leave, ping)]
struct General;

#[tokio::main]
async fn main() {
    tracing_subscriber::fmt::init();

    // Configure the client with your Discord bot token in the environment.
    let token = env::var("DISCORD_TOKEN").expect("Expected a token in the environment");

    let framework = StandardFramework::new()
        .group(&GENERAL_GROUP);
    framework.configure(|c| c.prefix("~"));

    let intents = GatewayIntents::non_privileged() | GatewayIntents::MESSAGE_CONTENT;

    // Here, we need to configure Songbird to decode all incoming voice packets.
    // If you want, you can do this on a per-call basis---here, we need it to
    // read the audio data that other people are sending us!
    let songbird_config = Config::default().decode_mode(DecodeMode::Decode);

    let mut client = Client::builder(&token, intents)
        .event_handler(Handler)
        .framework(framework)
        .register_songbird_from_config(songbird_config)
        .await
        .expect("Err creating client");

    let _ = client
        .start()
        .await
        .map_err(|why| println!("Client ended: {:?}", why));
}

#[command]
#[only_in(guilds)]
async fn join(ctx: &Context, msg: &Message, mut args: Args) -> CommandResult {
    let connect_to = match args.single::<std::num::NonZeroU64>() {
        Ok(id) => ChannelId(id),
        Err(_) => {
            check_msg(
                msg.reply(ctx, "Requires a valid voice channel ID be given")
                    .await,
            );

            return Ok(());
        },
    };

    let guild_id = msg.guild_id.unwrap();

    let manager = songbird::get(ctx)
        .await
        .expect("Songbird Voice client placed in at initialisation.")
        .clone();

    let (handler_lock, conn_result) = manager.join(guild_id, connect_to).await;

    if let Ok(_) = conn_result {
        // NOTE: this skips listening for the actual connection result.
        let mut handler = handler_lock.lock().await;

        handler.add_global_event(CoreEvent::SpeakingStateUpdate.into(), Receiver::new());

        handler.add_global_event(CoreEvent::SpeakingUpdate.into(), Receiver::new());

        handler.add_global_event(CoreEvent::VoicePacket.into(), Receiver::new());

        handler.add_global_event(CoreEvent::RtcpPacket.into(), Receiver::new());

        handler.add_global_event(CoreEvent::ClientDisconnect.into(), Receiver::new());

        check_msg(
            msg.channel_id
                .say(&ctx.http, &format!("Joined {}", connect_to.mention()))
                .await,
        );
    } else {
        check_msg(
            msg.channel_id
                .say(&ctx.http, "Error joining the channel")
                .await,
        );
    }

    Ok(())
}

#[command]
#[only_in(guilds)]
async fn leave(ctx: &Context, msg: &Message) -> CommandResult {
    let guild_id = msg.guild_id.unwrap();

    let manager = songbird::get(ctx)
        .await
        .expect("Songbird Voice client placed in at initialisation.")
        .clone();
    let has_handler = manager.get(guild_id).is_some();

    if has_handler {
        if let Err(e) = manager.remove(guild_id).await {
            check_msg(
                msg.channel_id
                    .say(&ctx.http, format!("Failed: {:?}", e))
                    .await,
            );
        }

        check_msg(msg.channel_id.say(&ctx.http, "Left voice channel").await);
    } else {
        check_msg(msg.reply(ctx, "Not in a voice channel").await);
    }

    Ok(())
}

#[command]
async fn ping(ctx: &Context, msg: &Message) -> CommandResult {
    check_msg(msg.channel_id.say(&ctx.http, "Pong!").await);

    Ok(())
}

/// Checks that a message successfully sent; if not, then logs why to stdout.
fn check_msg(result: SerenityResult<Message>) {
    if let Err(why) = result {
        println!("Error sending message: {:?}", why);
    }
}