use std::{convert::Infallible, fs, net::SocketAddr};

use config::Config;
use http_body_util::{BodyExt, Full};
use hyper::{
    body::{self, Body, Bytes},
    server::conn::http1,
    service::service_fn,
    Method, Request, Response, StatusCode,
};
use hyper_util::rt::TokioIo;
use miniflux_requests::MinifluxEvent;
use ring::hmac;
use serenity::{all::GatewayIntents, Client};
use thiserror::Error;
use tokio::net::TcpListener;

use crate::discord::DiscordHolder;

mod config;
mod discord;
mod miniflux_requests;

//FIXME!
const CONFIG_PATH: &'static str = "./config.json";

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
    let config: Config = serde_json::from_slice(&fs::read(CONFIG_PATH).unwrap()).unwrap();

    stderrlog::new()
        .module(module_path!())
        .verbosity(config.log_level)
        .timestamp(stderrlog::Timestamp::Second)
        .init()
        .unwrap();

    let mut client = Client::builder(&config.discord_token, GatewayIntents::empty())
        .await
        .expect("Error creating Discord client");

    let addr = SocketAddr::from((config.host, config.port));
    let listener = TcpListener::bind(addr).await?;

    log::info!("Binded to {}:{}", config.host, config.port);

    let cache = client.cache.clone();
    let http = client.http.clone();

    let holder = DiscordHolder { cache, http, config };

    let client_handle = tokio::task::spawn(async move {
        log::info!("Discord client started, should show up online now!");
        client.start().await.expect("Failed starting Discord client!");
    });

    let loop_handle = tokio::task::spawn(async move {
        log::info!("Listening to TCP/HTTP connections now..");
        loop {
            let Ok((stream, addr)) = listener.accept().await else {
                log::warn!("Failed to accept TCP stream");
                continue;
            };
            log::debug!("=> {}", addr);

            let io = TokioIo::new(stream);

            let holder = holder.clone();

            // Spawn a tokio task to serve multiple connections concurrently
            tokio::task::spawn(async move {
                let service = service_fn(|req: Request<body::Incoming>| {
                    let holder = holder.clone();
                    async move {
                        Ok::<_, Infallible>(
                            process_webhook(req, &holder).await.unwrap_or_else(|e| e.into()),
                        )
                    }
                });
                let result = http1::Builder::new().serve_connection(io, service).await;
                if let Err(err) = result {
                    log::warn!("Error serving connection {}: {:?}", addr, err);
                }
            });
        }
    });

    let (res1, res2) = tokio::join!(client_handle, loop_handle);
    res1.expect("Failed unwrapping client handle result!");
    res2.expect("Failed unwrapping loop handle result!");

    Ok(())
}

async fn process_webhook(
    req: Request<body::Incoming>,
    holder: &DiscordHolder,
) -> Result<Response<Full<Bytes>>, CustomError> {
    let method = req.method();
    if method != Method::POST {
        Err(CustomError::InvalidMethod(method.clone()))?;
    }

    let userid: u64 =
        req.uri().path().split("/").nth(1).ok_or(CustomError::IdPathNotFound)?.parse()?;

    if !holder.config.whitelisted_user_ids.contains(&userid) {
        Err(CustomError::NotWhitelistedUser(userid))?;
    }

    let headers = req.headers();

    let signature_bytes =
        headers.get("x-miniflux-signature").ok_or(CustomError::SignatureMissing)?.as_bytes();
    let signature = data_encoding::HEXLOWER.decode(signature_bytes)?;
    let event_type =
        headers.get("x-miniflux-event-type").ok_or(CustomError::EventTypeMissing)?.clone();

    let upper = req.body().size_hint().upper().unwrap_or(u64::MAX);
    if upper > holder.config.payload_max_size {
        Err(CustomError::PayloadTooLarge(upper))?;
    }

    let whole_body = req.collect().await?.to_bytes();
    let bytes = whole_body.iter().cloned().collect::<Vec<u8>>();

    let key = hmac::Key::new(hmac::HMAC_SHA256, &holder.config.miniflux_webhook_secret.as_bytes());

    let () =
        hmac::verify(&key, &bytes, &signature).map_err(|_| CustomError::HmacValidationError)?;

    let event: MinifluxEvent = serde_json::from_slice(&bytes)?;
    match event {
        MinifluxEvent::New(_) => assert!(event_type == "new_entries"),
        MinifluxEvent::Save(_) => assert!(event_type == "save_entry"),
    }

    log::info!("received {} from miniflux!", event_type.to_str().unwrap_or_default());

    let res = holder.send(userid, event).await;
    if let Err(err) = res {
        log::error!("Error while trying to send discord message {}", err);
    }

    Ok(Response::new(Full::new(vec![].into())))
}

#[derive(Error, Debug)]
pub enum CustomError {
    #[error("id path not found")]
    IdPathNotFound,
    #[error("invalid method: {0}")]
    InvalidMethod(Method),
    #[error("parse int error: {0}")]
    ParseIntError(#[from] std::num::ParseIntError),
    #[error("{0} not allowed!")]
    NotWhitelistedUser(u64),
    #[error("signature missing")]
    SignatureMissing,
    #[error("event_type missing")]
    EventTypeMissing,
    #[error("signature decoding error: {0}")]
    DecodeError(#[from] data_encoding::DecodeError),
    #[error("payload too large ({0})")]
    PayloadTooLarge(u64),
    #[error("Hyper Error: {0}")]
    HyperError(#[from] hyper::Error),
    #[error("HMAC signature validation failed")]
    HmacValidationError,
    #[error("JSON deserialization failed: {0}")]
    JsonError(#[from] serde_json::Error),
}

impl Into<Response<Full<Bytes>>> for CustomError {
    fn into(self) -> Response<Full<Bytes>> {
        match &self {
            CustomError::JsonError(_) => log::error!("{}", self),
            CustomError::HmacValidationError => log::warn!("{}", self),
            CustomError::HyperError(_) => log::warn!("{}", self),
            CustomError::PayloadTooLarge(_) => log::warn!("{}", self),
            CustomError::SignatureMissing => log::warn!("{}", self),
            CustomError::EventTypeMissing => log::warn!("{}", self),
            _ => log::debug!("{}", self),
        }

        let mut resp = Response::new(Full::from(Bytes::from(self.to_string())));
        let status_code = match self {
            CustomError::IdPathNotFound => StatusCode::NOT_FOUND,
            CustomError::InvalidMethod(_) => StatusCode::METHOD_NOT_ALLOWED,
            CustomError::ParseIntError(_) => StatusCode::BAD_REQUEST,
            CustomError::NotWhitelistedUser(_) => StatusCode::FORBIDDEN,
            CustomError::SignatureMissing => StatusCode::BAD_REQUEST,
            CustomError::EventTypeMissing => StatusCode::BAD_REQUEST,
            CustomError::DecodeError(_) => StatusCode::BAD_REQUEST,
            CustomError::PayloadTooLarge(_) => StatusCode::PAYLOAD_TOO_LARGE,
            CustomError::HyperError(_) => StatusCode::INTERNAL_SERVER_ERROR,
            CustomError::HmacValidationError => StatusCode::FORBIDDEN,
            CustomError::JsonError(_) => StatusCode::BAD_REQUEST,
        };

        *resp.status_mut() = status_code;
        resp
    }
}