#![feature(once_cell)]

mod config;

use serenity::framework::StandardFramework;
use serenity::model::id::ChannelId;
use serenity::Client;
use std::lazy::SyncLazy;
use std::sync::{Arc, Mutex};

fn configure(conf: &mut serenity::framework::standard::Configuration) {
    conf.prefix(config::GLOBAL_COMMAND_PREFIX)
        .with_whitespace((true, true, true))
        .case_insensitivity(true);
}

struct Handler;

#[derive(Debug, Clone)]
pub enum BotError {
    MissingGuild,
}

impl std::fmt::Display for BotError {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
        match self {
            Self::MissingGuild => write!(f, "this command is only usable in a guild"),
        }
    }
}

impl std::error::Error for BotError {}

#[derive(Debug, Clone, Default)]
pub struct ChannelCache {
    pub meta: Option<ChannelId>,
    pub lobby: Option<ChannelId>,
}

static CHANNEL_CACHE: SyncLazy<Arc<Mutex<ChannelCache>>> =
    SyncLazy::new(|| Arc::new(Mutex::new(Default::default())));

mod commands {
    use super::{ChannelCache, CHANNEL_CACHE};
    use crate::config;
    use serenity::client::Context;
    use serenity::framework::standard::{macros::*, CommandError, CommandResult};
    use serenity::model::{
        channel::{Channel, ChannelType, GuildChannel, Message},
        guild::Guild,
        id::ChannelId,
    };

    #[group]
    #[description("Commands for this bot")]
    #[commands(help, create)]
    struct Group;

    #[derive(Debug, Clone)]
    struct ChannelDescriptor<'n, 'd> {
        name: &'n str,
        description: &'d str,
        kind: ChannelType,
        parent: Option<ChannelId>,
    }

    async fn get_guild(ctx: &Context, msg: &Message) -> Result<Guild, CommandError> {
        msg.guild(&ctx.cache)
            .await
            .ok_or_else(|| Box::new(super::BotError::MissingGuild).into())
    }

    async fn create_channel_no_cache<'n, 'd>(
        ctx: &Context,
        guild: &Guild,
        desc: ChannelDescriptor<'n, 'd>,
    ) -> Result<GuildChannel, CommandError> {
        Ok(guild
            .create_channel(ctx, |c| {
                let c = c.name(desc.name).topic(desc.description).kind(desc.kind);
                if let Some(parent) = desc.parent {
                    c.category(parent)
                } else {
                    c
                }
            })
            .await?)
    }

    async fn get_guild_channel_by_optional_id(
        ctx: &Context,
        id: Option<ChannelId>,
    ) -> Option<GuildChannel> {
        match id {
            Some(id) => ctx.cache.guild_channel(id).await,
            None => None,
        }
    }

    async fn get_channel_by_optional_id(
        ctx: &Context,
        kind: ChannelType,
        id: Option<ChannelId>,
    ) -> Option<Channel> {
        match (kind, id) {
            (ChannelType::Category, Some(id)) => ctx
                .cache
                .categories()
                .await
                .get(&id)
                .cloned()
                .map(Channel::Category),
            (_, opt_id) => get_guild_channel_by_optional_id(ctx, opt_id)
                .await
                .map(Channel::Guild),
        }
    }

    async fn create_channel<'n, 'd>(
        ctx: &Context,
        guild: &Guild,
        desc: ChannelDescriptor<'n, 'd>,
    ) -> Result<Channel, CommandError> {
        let optional_channel = match desc.kind {
            ChannelType::Category => {
                println!("{:?}", ctx.cache.categories().await);
                ctx.cache.categories().await.values().find_map(|channel| {
                    if channel.name() == desc.name {
                        Some(Channel::Category(channel.clone()))
                    } else {
                        None
                    }
                })
            }
            _ => get_guild_channel_by_optional_id(
                ctx,
                guild.channel_id_from_name(&ctx.cache, desc.name).await,
            )
            .await
            .map(Channel::Guild),
        };
        match optional_channel {
            Some(channel) => Ok(channel),
            None => {
                let channel = create_channel_no_cache(ctx, guild, desc)
                    .await
                    .map(Channel::Guild);
                channel
            }
        }
    }

    async fn get_channel_or_create<'n, 'd, F: Fn(&mut ChannelCache) -> &mut Option<ChannelId>>(
        ctx: &Context,
        guild: &Guild,
        desc: ChannelDescriptor<'n, 'd>,
        f: F,
    ) -> Result<Channel, CommandError> {
        let lock = || CHANNEL_CACHE.lock().unwrap();
        Ok({
            let optional_id = *f(&mut *lock());
            match get_channel_by_optional_id(ctx, desc.kind, optional_id).await {
                Some(channel) => channel,
                None => {
                    let channel = create_channel(ctx, &guild, desc).await?;
                    *f(&mut *lock()) = Some(channel.id());
                    channel
                }
            }
        })
    }

    async fn get_meta_channel_or_create(
        ctx: &Context,
        guild: &Guild,
    ) -> Result<Channel, CommandError> {
        let desc = ChannelDescriptor {
            name: config::META_CHANNEL_NAME,
            description: config::META_CHANNEL_DESCRIPTION,
            kind: ChannelType::Category,
            parent: None,
        };
        get_channel_or_create(ctx, guild, desc, |cache| &mut cache.meta).await
    }

    async fn get_lobby_channel_or_create(
        ctx: &Context,
        guild: &Guild,
        meta_channel_id: ChannelId,
    ) -> Result<Channel, CommandError> {
        let desc = ChannelDescriptor {
            name: config::LOBBY_CHANNEL_NAME,
            description: config::LOBBY_CHANNEL_DESCRIPTION,
            kind: ChannelType::Voice,
            parent: Some(meta_channel_id),
        };
        get_channel_or_create(ctx, guild, desc, |cache| &mut cache.lobby).await
    }

    #[command]
    #[aliases("hepl", "?", "h")]
    async fn help(ctx: &Context, msg: &Message) -> CommandResult {
        msg.reply(ctx, crate::config::HELP_TEXT).await?;
        Ok(())
    }

    #[command]
    #[aliases("craete", "+", "c", "init")]
    async fn create(ctx: &Context, msg: &Message) -> CommandResult {
        let guild = get_guild(ctx, msg).await?;
        let meta_channel = get_meta_channel_or_create(ctx, &guild).await?;

        let lobby_channel = get_lobby_channel_or_create(ctx, &guild, meta_channel.id()).await?;

        Ok(())
    }

    #[command]
    #[aliases("strat", "s", "r", "run", "rnu")]
    async fn start(ctx: &Context, msg: &Message) -> CommandResult {
        let guild = get_guild(ctx, msg).await?;

        Ok(())
    }
}

impl serenity::client::EventHandler for Handler {}

#[tokio::main]
async fn main() {
    println!("crate framework");

    let framework = StandardFramework::new()
        .configure(|c| {
            configure(c);
            c
        })
        .group(&commands::GROUP_GROUP);

    let token = std::env::var(config::TOKEN_ENV).expect("missing token");
    println!("crate a new client with token: \"{}\"", token);
    let mut client = Client::new(token)
        .framework(framework)
        .event_handler(Handler)
        .await
        .expect("Error creating client");

    println!("starting the client");
    client.start().await.expect("client error");
}