#![deny(clippy::unwrap_used)]

use std::{
    collections::{BinaryHeap, HashMap},
    env,
    ops::Deref,
    sync::Arc,
};

use axum::{
    error_handling::HandleErrorLayer,
    extract::{Multipart, Path, Query, State},
    http::{header::CONTENT_TYPE, HeaderMap, HeaderValue, StatusCode, Uri},
    response::{
        sse::{Event, KeepAlive},
        Html, IntoResponse, Redirect, Sse,
    },
    routing::get,
    BoxError, Form, Router,
};
use axum_htmx::{HxRedirect, HxRequest};
use axum_oidc::{
    error::MiddlewareError, EmptyAdditionalClaims, OidcAuthLayer, OidcClaims, OidcLoginLayer,
};
use futures_util::Stream;
use game::{Game, GameId, GameParticipantsCollector, PlayerId, RunningGamesCollector};
use garbage_collector::{start_gc, GarbageCollectorItem};
use prometheus_client::{metrics::counter::Counter, registry::Registry};
use question::{single_choice::SingleChoiceQuestion, Question};
use sailfish::TemplateOnce;
use serde::{Deserialize, Serialize};
use stream::{PlayerBroadcastStream, ViewerBroadcastStream};
use tokio::{sync::RwLock, task::spawn_blocking};
use tower::ServiceBuilder;
use tower_http::services::ServeDir;
use tower_sessions::{cookie::SameSite, MemoryStore, SessionManagerLayer};

use crate::error::Error;

type HandlerResult<T> = Result<T, Error>;

mod error;
mod game;
mod garbage_collector;
mod stream;

mod question;

#[derive(Clone)]
pub struct AppState {
    games: Arc<RwLock<HashMap<GameId, Game>>>,
    game_expiry: Arc<RwLock<BinaryHeap<GarbageCollectorItem>>>,
    application_base: &'static str,
    prometheus_registry: Arc<Registry>,
    metrics: Arc<AppMetrics>,
}

#[derive(Clone, Default)]
pub struct AppMetrics {
    arc_games_total: Counter,
}

#[tokio::main]
pub async fn main() {
    dotenvy::dotenv().ok();
    env_logger::init();

    let application_base = env::var("APPLICATION_BASE").expect("APPLICATION_BASE env var");
    let issuer = env::var("ISSUER").expect("ISSUER env var");
    let client_id = env::var("CLIENT_ID").expect("CLIENT_ID env var");
    let client_secret = env::var("CLIENT_SECRET").ok();
    let scopes = env::var("SCOPES")
        .expect("SCOPES env var")
        .split(' ')
        .map(|x| x.to_owned())
        .collect::<Vec<_>>();

    let session_store = MemoryStore::default();
    let session_service = ServiceBuilder::new()
        .layer(HandleErrorLayer::new(|_: BoxError| async {
            StatusCode::BAD_REQUEST
        }))
        .layer(SessionManagerLayer::new(session_store).with_same_site(SameSite::Lax));

    let oidc_login_service = ServiceBuilder::new()
        .layer(HandleErrorLayer::new(|e: MiddlewareError| async {
            e.into_response()
        }))
        .layer(OidcLoginLayer::<EmptyAdditionalClaims>::new());

    let oidc_auth_service = ServiceBuilder::new()
        .layer(HandleErrorLayer::new(|e: MiddlewareError| async {
            e.into_response()
        }))
        .layer(
            OidcAuthLayer::<EmptyAdditionalClaims>::discover_client(
                Uri::from_maybe_shared(application_base.clone()).expect("valid APPLICATION_BASE"),
                issuer.to_string(),
                client_id.to_string(),
                client_secret.to_owned(),
                scopes.clone(),
            )
            .await
            .expect("OIDC Client"),
        );

    let game_expiry: Arc<RwLock<BinaryHeap<GarbageCollectorItem>>> =
        Arc::new(RwLock::new(BinaryHeap::new()));
    let games = Arc::new(RwLock::new(HashMap::new()));

    let app_metrics = Arc::new(AppMetrics::default());
    let mut registry = Registry::default();

    registry.register(
        "ars_games_total",
        "number of games created",
        app_metrics.arc_games_total.clone(),
    );

    registry.register_collector(Box::new(RunningGamesCollector::new(games.clone())));
    registry.register_collector(Box::new(GameParticipantsCollector::new(games.clone())));

    start_gc(game_expiry.clone(), games.clone());

    let app_state = AppState {
        games,
        game_expiry,
        application_base: Box::leak(application_base.into()),
        prometheus_registry: Arc::new(registry),
        metrics: app_metrics,
    };

    let app = Router::new()
        .route("/", get(handle_index).post(handle_create))
        .route("/:id/view", get(handle_view).post(handle_view_next))
        .route("/:id/view/events", get(sse_view))
        .layer(oidc_login_service)
        .route("/:id", get(handle_player).post(handle_player_answer))
        .route("/:id/events", get(sse_player))
        .route("/metrics", get(metrics))
        .nest_service("/static", ServeDir::new("static"))
        .with_state(app_state)
        .layer(oidc_auth_service)
        .layer(session_service);

    axum::Server::bind(&"[::]:8080".parse().expect("valid listen address"))
        .serve(app.into_make_service())
        .await
        .expect("axum server");
}

pub async fn handle_index() -> HandlerResult<impl IntoResponse> {
    Ok(Html(IndexTemplate {}.render_once()?))
}

pub async fn handle_create(
    State(state): State<AppState>,
    OidcClaims(claims): OidcClaims<EmptyAdditionalClaims>,
    mut body: Multipart,
) -> HandlerResult<impl IntoResponse> {
    let mut quiz: Option<Quiz> = None;
    while let Some(field) = body.next_field().await? {
        if field.name() == Some("quizfile") {
            quiz = Some(toml::from_str::<Quiz>(&field.text().await?)?);
        }
    }

    let quiz = quiz.ok_or(Error::QuizFileNotFound)?;

    let game_id = GameId::random();

    let game = Game::new(game_id.clone(), claims.subject().to_string(), quiz);

    let mut games = state.games.write().await;

    games.insert(game_id.clone(), game);

    let url = format!("{}/{}/view", state.application_base, &game_id.deref());

    let mut game_expiry = state.game_expiry.write().await;
    game_expiry.push(GarbageCollectorItem::new_in(game_id, 24 * 3600));

    state.metrics.arc_games_total.inc();

    Ok((HxRedirect(Uri::from_maybe_shared(url.clone())?), "Ok"))
}

pub async fn handle_view(
    Path(id): Path<GameId>,
    State(state): State<AppState>,
    HxRequest(htmx): HxRequest,
    OidcClaims(claims): OidcClaims<EmptyAdditionalClaims>,
) -> HandlerResult<impl IntoResponse> {
    let games = state.games.read().await;
    let game = games.get(&id).ok_or(Error::NotFound)?;

    if game.owner != claims.subject().to_string() {
        return Err(Error::Forbidden);
    }

    Ok(Html(game.viewer_view(htmx, state.application_base).await?))
}

pub async fn handle_view_next(
    Path(id): Path<GameId>,
    State(state): State<AppState>,
    OidcClaims(claims): OidcClaims<EmptyAdditionalClaims>,
) -> HandlerResult<impl IntoResponse> {
    let mut games = state.games.write().await;
    let game = games.get_mut(&id).ok_or(Error::NotFound)?;

    if game.owner != claims.subject().to_string() {
        return Err(Error::Forbidden);
    }

    game.next().await;

    Ok("Ok".into_response())
}

pub async fn sse_view(
    Path(id): Path<GameId>,
    State(state): State<AppState>,
    OidcClaims(claims): OidcClaims<EmptyAdditionalClaims>,
) -> HandlerResult<Sse<impl Stream<Item = Result<Event, Error>>>> {
    let games = state.games.read().await;
    let game = games.get(&id).ok_or(Error::NotFound)?;

    if game.owner != claims.subject().to_string() {
        return Err(Error::Forbidden);
    }

    let rx1 = game.on_state_update.subscribe();
    let rx2 = game.on_submission.subscribe();

    let stream =
        ViewerBroadcastStream::new(rx1, rx2, state.games.clone(), id, state.application_base);

    Ok(Sse::new(stream).keep_alive(KeepAlive::default()))
}

#[derive(Deserialize)]
pub struct PlayerQuery {
    player: Option<String>,
}

pub async fn handle_player(
    Query(query): Query<PlayerQuery>,
    Path(id): Path<GameId>,
    State(state): State<AppState>,
    HxRequest(htmx): HxRequest,
) -> HandlerResult<impl IntoResponse> {
    let mut games = state.games.write().await;
    let game = games.get_mut(&id).ok_or(Error::NotFound)?;

    if let Some(player_id) = query.player.map(PlayerId::from) {
        Ok(Html(game.player_view(&player_id, htmx).await?).into_response())
    } else {
        let player_id = PlayerId::random();
        game.players.insert(player_id.clone());
        game.on_submission.send(());

        Ok(Redirect::temporary(&format!(
            "{}/{}?player={}",
            state.application_base,
            id.deref(),
            player_id.deref()
        ))
        .into_response())
    }
}

#[derive(Deserialize)]
pub struct SubmissionPayload {
    player_id: PlayerId,
    #[serde(flatten)]
    values: HashMap<String, String>,
}

pub async fn handle_player_answer(
    Path(id): Path<GameId>,
    State(state): State<AppState>,
    Form(form): Form<SubmissionPayload>,
) -> HandlerResult<impl IntoResponse> {
    let mut games = state.games.write().await;
    let game = games.get_mut(&id).ok_or(Error::NotFound)?;

    game.handle_answer(&form.player_id, &form.values).await?;

    Ok(Html(game.player_view(&form.player_id, true).await?))
}

#[derive(Deserialize)]
pub struct SsePlayerQuery {
    player: PlayerId,
}

pub async fn sse_player(
    Query(query): Query<SsePlayerQuery>,
    Path(id): Path<GameId>,
    State(state): State<AppState>,
) -> HandlerResult<Sse<impl Stream<Item = Result<Event, Error>>>> {
    let games = state.games.read().await;
    let game = games.get(&id).ok_or(Error::NotFound)?;
    let rx = game.on_state_update.subscribe();

    let stream = PlayerBroadcastStream::new(rx, state.games.clone(), id, query.player);

    Ok(Sse::new(stream).keep_alive(KeepAlive::default()))
}

async fn metrics(State(app_state): State<AppState>) -> HandlerResult<impl IntoResponse> {
    let registry = app_state.prometheus_registry.clone();
    let buffer = spawn_blocking::<_, Result<String, Error>>(move || {
        let mut buffer = String::new();
        prometheus_client::encoding::text::encode(&mut buffer, &registry)
            .map_err(Error::Prometheus)?;
        Ok(buffer)
    })
    .await??;

    let mut headers = HeaderMap::new();
    headers.insert(
        CONTENT_TYPE,
        HeaderValue::from_static("text/plain; version=0.0.4"),
    );

    Ok((headers, buffer))
}

#[derive(TemplateOnce)]
#[template(path = "index.stpl")]
struct IndexTemplate {}

#[derive(TemplateOnce)]
#[template(path = "play.stpl")]
struct PlayTemplate<'a> {
    htmx: bool,
    id: &'a str,
    player_id: &'a str,
    state: PlayerState,
}

pub enum PlayerState {
    NotStarted,
    Answering { inner_body: String },
    Waiting(u32),
    Result { inner_body: String },
    Completed(f32),
}

#[derive(TemplateOnce)]
#[template(path = "view.stpl")]
struct ViewTemplate<'a> {
    htmx: bool,
    id: &'a str,
    state: ViewerState,
}

pub enum ViewerState {
    NotStarted((u32, String, String)),
    Answering {
        inner_body: String,
    },
    Result {
        last_question: bool,
        inner_body: String,
    },
    Completed,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct Quiz {
    pub wait_for: u64,
    pub questions: Vec<QuizQuestion>,
}

#[derive(Debug, Serialize, Deserialize, Clone)]
#[serde(tag = "type")]
pub enum QuizQuestion {
    #[serde(rename = "single_choice")]
    SingleChoice(SingleChoice),
}

#[derive(Debug, Serialize, Deserialize, Clone)]
pub struct SingleChoice {
    name: Box<str>,
    answers: Box<[Box<str>]>,
    correct: u32,
}

impl From<QuizQuestion> for Box<dyn Question> {
    fn from(value: QuizQuestion) -> Self {
        match value {
            QuizQuestion::SingleChoice(x) => Box::new(SingleChoiceQuestion::new(x)) as _,
        }
    }
}