mod dice;
mod parsing;

use anyhow::bail;
use dotenv::dotenv;
use rand::{Rng, SeedableRng};
use serenity::all::{Command, CommandInteraction, CommandOptionType, CreateCommandOption, CreateComponent, FullEvent, Interaction, InteractionContext, MessageFlags, ResolvedOption, ResolvedValue};
use serenity::builder::{
    CreateCommand, CreateContainer, CreateContainerComponent, CreateInteractionResponse,
    CreateInteractionResponseFollowup, CreateInteractionResponseMessage, CreateTextDisplay,
};
use serenity::{async_trait, prelude::*};
use std::sync::Arc;
use tracing::{debug, info, warn};

#[tokio::main]
async fn main() -> anyhow::Result<()> {
    dotenv().ok();
    tracing_subscriber::fmt::init();

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

    // Build our client.
    let mut client = Client::builder(token, GatewayIntents::empty())
        .event_handler(Arc::new(Handler))
        .await
        .expect("Error creating client");

    client.start().await?;
    Ok(())
}

struct Handler;

#[async_trait]
impl EventHandler for Handler {
    async fn dispatch(&self, ctx: &Context, event: &FullEvent) {
        // clippy can't decide between if it wants it collapsed, or if it wants you to use if let
        // because it's a single pattern.
        #[expect(clippy::collapsible_match)]
        match event {
            FullEvent::InteractionCreate { interaction, .. } => {
                if let Interaction::Command(command) = interaction {
                    debug!("Received command interaction: {command:#?}");

                    let content = match command.data.name.as_str() {
                        "roll" => {
                            roll(ctx, command)
                                .await
                                .unwrap_or_else(|e| warn!("error! {}", e));
                            None
                        }
                        _ => Some("not implemented :(".to_string()),
                    };

                    if let Some(content) = content {
                        let data = CreateInteractionResponseMessage::new().content(content);
                        let builder = CreateInteractionResponse::Message(data);
                        if let Err(why) = command.create_response(&ctx.http, builder).await {
                            warn!("Cannot respond to slash command: {why}");
                        }
                    }
                }
            }
            FullEvent::Ready { data_about_bot, .. } => {
                let global_command = Command::create_global_command(
                    &ctx.http,
                    CreateCommand::new("roll")
                        .description("Roll some dice!")
                        .add_option(CreateCommandOption::new(
                            CommandOptionType::String,
                            "formula",
                            "The dice formula, something like 2d20kh1+3",
                        ).required(true))
                        .add_option(CreateCommandOption::new(
                            CommandOptionType::Integer,
                            "repeat",
                            "Repeat the rolled formula this many times. Useful if you're controlling too many units!",
                        ))
                        .add_option(CreateCommandOption::new(
                            CommandOptionType::String,
                            "description",
                            "What is that roll for? Add some context!",
                        ))
                        .add_option(CreateCommandOption::new(
                            CommandOptionType::Boolean,
                            "private",
                            "Keep the roll private and hidden, only for yourself.",
                        ))
                        .add_option(CreateCommandOption::new(
                            CommandOptionType::String,
                            "seed",
                            "Roll with a fixed seed. This bot uses xoshiro256++.",
                        ))
                        .add_context(InteractionContext::Guild)
                        .add_context(InteractionContext::BotDm)
                        .add_context(InteractionContext::PrivateChannel),
                )
                .await;

                debug!("I created the following global slash command: {global_command:#?}");

                info!("{} is connected!", data_about_bot.user.name);
            }
            _ => {}
        }
    }
}

pub async fn roll(ctx: &Context, command: &CommandInteraction) -> anyhow::Result<()> {
    let options = command.data.options();
    let Some(ResolvedOption {
        value: ResolvedValue::String(formula),
        ..
    }) = options.iter().find(|option| option.name == "formula")
    else {
        bail!("Formula was not provided.")
    };
    let repeat = options
        .iter()
        .find(|option| option.name == "repeat")
        .and_then(|option| {
            if let ResolvedValue::Integer(repeat) = option.value {
                Some(repeat)
            } else {
                None
            }
        })
        .unwrap_or(1)
        .min(20);
    let private = options
        .iter()
        .find(|option| option.name == "private")
        .and_then(|option| {
            if let ResolvedValue::Boolean(private) = option.value {
                Some(private)
            } else {
                None
            }
        })
        .unwrap_or(false);
    let description = options
        .iter()
        .find(|option| option.name == "description")
        .and_then(|option| {
            if let ResolvedValue::String(description) = option.value {
                Some(description)
            } else {
                None
            }
        });
    let fixed_seed = options
        .iter()
        .find(|option| option.name == "seed")
        .and_then(|option| {
            if let ResolvedValue::String(fixed_seed) = option.value {
                Some(fixed_seed)
            } else {
                None
            }
        })
        .and_then(|s| s.parse::<u64>().ok());

    let result = parsing::parse(&formula);
    let expression = match result {
        Ok(expression) => expression,
        Err(error) => {
            command
                .create_response(
                    &ctx.http,
                    CreateInteractionResponse::Message(
                        CreateInteractionResponseMessage::default()
                            .content(format!("Dice formula could not be parsed.\n{}", error))
                            .ephemeral(true),
                    ),
                )
                .await?;
            return Ok(());
        }
    };
    if private {
        command.defer_ephemeral(&ctx.http).await?;
    } else {
        command.defer(&ctx.http).await?;
    }

    let seed = fixed_seed.unwrap_or_else(|| rand::rng().next_u64());
    let mut rng = rand_xoshiro::Xoshiro256PlusPlus::seed_from_u64(seed);

    let average = match expression.average(&mut rng) {
        Ok(res) => res,
        Err(err) => {
            command
                .create_followup(
                    &ctx.http,
                    CreateInteractionResponseFollowup::new().content(format!("{}", err)),
                )
                .await?;
            return Err(err);
        }
    };
    let ev = (average * 10.0).round() / 10.0;

    let mut text_components = Vec::with_capacity((repeat + 2) as usize);
    if let Some(description) = description {
        text_components.push(CreateContainerComponent::TextDisplay(
            CreateTextDisplay::new(format!(">>> {description}\n")),
        ));
    }
    for _ in 0..repeat {
        let result = match expression.collect_evaluation(&mut rng) {
            Ok(res) => res,
            Err(err) => {
                command
                    .create_followup(
                        &ctx.http,
                        CreateInteractionResponseFollowup::new().content(format!("{}", err)),
                    )
                    .await?;
                return Err(err);
            }
        };
        text_components.push(CreateContainerComponent::TextDisplay(
            CreateTextDisplay::new(format!("{}\n", result)),
        ));
    }
    if fixed_seed.is_some() {
        text_components.push(CreateContainerComponent::TextDisplay(
            CreateTextDisplay::new("***⚠️  This is not a fair roll. The result was generated based on a fixed seed and is thus fully reproducible.***".to_string()),
        ));
    }
    text_components.push(CreateContainerComponent::TextDisplay(
        CreateTextDisplay::new(format!("-# Expected value: {ev}  |  Seed: {seed}")),
    ));

    command
        .create_followup(
            &ctx.http,
            CreateInteractionResponseFollowup::new()
                .components(vec![CreateComponent::Container(CreateContainer::new(
                    text_components,
                ))])
                .ephemeral(private)
                .flags(MessageFlags::IS_COMPONENTS_V2 | MessageFlags::SUPPRESS_NOTIFICATIONS),
        )
        .await?;
    Ok(())
}