use axum::{Form, response::{IntoResponse, Response}, Extension};
use axum::http::StatusCode;

use self::queue::JobQueue;
pub mod queue;

#[derive(Clone, Debug, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
#[cfg_attr(feature = "sqlx", derive(sqlx::FromRow))]
pub struct Webmention {
    source: String,
    target: String,
}

async fn accept_webmention<Q: JobQueue<Webmention>>(
    Form(webmention): Form<Webmention>,
    Extension(queue): Extension<Q>
) -> Response {
    if let Err(err) = webmention.source.parse::<url::Url>() {
        return (StatusCode::BAD_REQUEST, err.to_string()).into_response()
    }
    if let Err(err) = webmention.target.parse::<url::Url>() {
        return (StatusCode::BAD_REQUEST, err.to_string()).into_response()
    }

    match queue.put(&webmention).await {
        Ok(id) => (StatusCode::ACCEPTED, [
            ("Location", format!("/.kittybox/webmention/{id}"))
        ]).into_response(),
        Err(err) => (StatusCode::INTERNAL_SERVER_ERROR, [
            ("Content-Type", "text/plain")
        ], err.to_string()).into_response()
    }
}

pub fn router<Q: JobQueue<Webmention>>(queue: Q) -> axum::Router {
    // Automatically spawn a background task to handle webmentions
    tokio::task::spawn(supervised_webmentions_task(queue.clone()));

    axum::Router::new()
        .route("/.kittybox/webmention",
            axum::routing::post(accept_webmention::<Q>)
        )
        .layer(Extension(queue))
}

async fn supervisor<E: std::error::Error + std::fmt::Debug + Send + 'static, A: futures_util::Future<Output = Result<std::convert::Infallible, E>> + Send + 'static, F: FnMut() -> A>(mut f: F) -> std::convert::Infallible {
    loop {
        match tokio::task::spawn(f()).await {
            Err(e) => tracing::error!("background task exited unexpectedly: {}", e),
            Ok(Err(e)) => tracing::error!("background task returned error: {}", e),
            Ok(Ok(_)) => unreachable!("task's Ok is Infallible")
        }
    }
}

async fn process_webmentions_from_queue<Q: JobQueue<Webmention>>(queue: Q) -> Result<std::convert::Infallible, Q::Error> {
    use futures_util::StreamExt;
    use self::queue::Job;

    let mut stream = queue.into_stream().await?;
    while let Some(item) = stream.next().await.transpose()? {
        let job = item.job();
        let (source, target) = (
            job.source.parse::<url::Url>().unwrap(),
            job.target.parse::<url::Url>().unwrap()
        );

        todo!()
    }
    unreachable!()
}

async fn supervised_webmentions_task<Q: JobQueue<Webmention>>(queue: Q) {
    supervisor::<Q::Error, _, _>(|| process_webmentions_from_queue(queue.clone())).await;
}