use axum::{
    extract::State,
    response::{
        sse::{self, Sse},
        IntoResponse, Response,
    },
    routing::get,
    Router,
};
use futures::stream::{Stream, StreamExt as _};

use super::{
    extract::LastEventId,
    types::{self, ResumePoint},
};
use crate::{app::App, error::Internal, login::extract::Identity};

#[cfg(test)]
mod test;

pub fn router() -> Router<App> {
    Router::new().route("/api/events", get(events))
}

async fn events(
    State(app): State<App>,
    identity: Identity,
    last_event_id: Option<LastEventId<ResumePoint>>,
) -> Result<Events<impl Stream<Item = types::ResumableEvent> + std::fmt::Debug>, Internal> {
    let resume_at = last_event_id
        .map(LastEventId::into_inner)
        .unwrap_or_default();

    let stream = app.events().subscribe(resume_at).await?;
    let stream = app.logins().limit_stream(identity.token, stream);

    Ok(Events(stream))
}

#[derive(Debug)]
struct Events<S>(S);

impl<S> IntoResponse for Events<S>
where
    S: Stream<Item = types::ResumableEvent> + Send + 'static,
{
    fn into_response(self) -> Response {
        let Self(stream) = self;
        let stream = stream.map(sse::Event::try_from);
        Sse::new(stream)
            .keep_alive(sse::KeepAlive::default())
            .into_response()
    }
}

impl TryFrom<types::ResumableEvent> for sse::Event {
    type Error = serde_json::Error;

    fn try_from(value: types::ResumableEvent) -> Result<Self, Self::Error> {
        let types::ResumableEvent(resume_at, data) = value;

        let id = serde_json::to_string(&resume_at)?;
        let data = serde_json::to_string_pretty(&data)?;

        let event = Self::default().id(id).data(data);

        Ok(event)
    }
}