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//! Actor-based endpoints, i.e. responders for all of the ActivityPub ids
//! created by this server.

use crate::activitypub::activity_broker::ActivityBrokeringError;
use crate::activitypub::{activity_broker, Date, Object, ObjectOrLink};
use crate::http_api::{activity_id, activity_json, actor_id, get_ap_object, note_id, CanonicalServerUrl};
use crate::remote::RemoteAccessor;
use crate::{activitypub, Database};
use actix_web::{post, web, HttpResponse, Scope};
use once_cell::sync::Lazy;
use regex::Regex;
use time::OffsetDateTime;

/// Creates a scope at "/u" containing all the actor endpoints - actors'
/// inboxes, outboxes, activities, notes.
///
/// POSTable endpoints:
/// - `/u/<user>`: [register]
/// - `/u/<user>/inbox.json`: [post_inbox]
/// - `/u/<user>/outbox.json`: [post_outbox]
///
/// GETable endpoints (ActivityPub object ids) are all routed to [get_ap_object]:
/// - `/u/<user>`
/// - `/u/<user>/inbox.json`
/// - `/u/<user>/outbox.json`
/// - `/u/<user>/activities/<snowflake id>`
/// - `/u/<user>/notes/<snowflake id>`
pub fn service() -> Scope {
    let accept_ap = activity_json::accept_guard;
    web::scope("/u")
        .service(post_inbox)
        .service(post_outbox)
        .service(register)
        .route("/{user}", web::get().guard(accept_ap).to(get_ap_object))
        .route("/{user}/inbox.json", web::get().guard(accept_ap).to(get_ap_object))
        .route("/{user}/outbox.json", web::get().guard(accept_ap).to(get_ap_object))
        .route("/{user}/activities/{id}", web::get().guard(accept_ap).to(get_ap_object))
        .route("/{user}/notes/{id}", web::get().guard(accept_ap).to(get_ap_object))
}

/// Creates a new [Actor] with the name in the url, and returns a 201 Created
/// with the newly created actor's id in the Location header.
///
/// [Actor]: https://www.w3.org/TR/activitypub/#actors
#[post("/{username}")]
async fn register(
    path: web::Path<String>,
    db: web::Data<&'static Database>,
    server_url: web::Data<CanonicalServerUrl>,
) -> HttpResponse {
    tracing::debug!("Registering new user \"{path}\"");

    static USERNAME_VALIDATOR: Lazy<Regex> = Lazy::new(|| Regex::new(r#"[A-Za-z0-9_]+"#).unwrap());
    let username = path.as_str();
    if !USERNAME_VALIDATOR.is_match(username) {
        return HttpResponse::BadRequest().body("Username should only contain A-Z, a-z, 0-9, and underscores.");
    }

    let id = actor_id(&server_url, username);
    let inbox = format!("{id}/inbox.json");
    let outbox = format!("{id}/outbox.json");

    let create_actor = || async {
        let make_collection = |id: String| Object {
            context: activitypub::activitystreams_context(),
            type_: activitypub::type_ordered_collection(),
            id: Some(id.into()),
            ..Default::default()
        };
        let inbox_collection = make_collection(inbox.clone());
        let outbox_collection = make_collection(outbox.clone());
        let actor = Object {
            context: activitypub::activitystreams_context(),
            type_: activitypub::type_person(),
            id: Some(id.as_str().into()),
            inbox: Some(inbox.into()),
            outbox: Some(outbox.into()),
            preferred_username: Some(username.into()),
            name: Some(username.into()),
            summary: Some("".into()),
            ..Default::default()
        };
        db.insert(&inbox_collection).await?;
        db.insert(&outbox_collection).await?;
        db.insert(&actor).await?;
        Ok::<(), sqlx::Error>(())
    };

    match create_actor().await {
        Ok(_) => HttpResponse::Created().insert_header(("Location", id)).finish(),
        Err(err) => {
            if let Ok(Some(existing_user)) = db.get_object(&id, None).await {
                HttpResponse::Created()
                    .insert_header(("Location", existing_user.id.unwrap().as_ref()))
                    .finish()
            } else {
                tracing::warn!("Failed to insert new actor to db: {err}");
                HttpResponse::ServiceUnavailable().finish()
            }
        }
    }
}

/// Http responder for handling activity deliveries from remote servers
/// (ActivityPub server-to-server part).
///
/// Passes the activity on to [`activity_broker::receive`].
#[post("/{username}/inbox.json", guard = "activity_json::content_type_guard")]
async fn post_inbox<'a>(
    username: web::Path<String>,
    activity: web::Json<activitypub::Object<'a>>,
    db: web::Data<&'static Database>,
    server_url: web::Data<CanonicalServerUrl>,
    remote: web::Data<RemoteAccessor>,
) -> HttpResponse {
    let actor_id = actor_id(&server_url, &username);
    let inbox_id = format!("{actor_id}/inbox.json");
    tracing::debug!("Post to inbox {inbox_id} received");
    let Some(activity_id) = activity.0.id.clone() else {
        return HttpResponse::BadRequest().body("Activity is missing the id");
    };
    match activity_broker::receive(activity.0, &db, &remote, false).await {
        Ok(_) => match db.insert_to_collection(&inbox_id, &activity_id).await {
            Ok(_) => HttpResponse::Ok().finish(),
            Err(err) => {
                tracing::warn!("Failed to insert activity {activity_id} to inbox {inbox_id}: {err}");
                HttpResponse::ServiceUnavailable().finish()
            }
        },
        Err(ActivityBrokeringError::Database(err)) => {
            tracing::warn!("Failed to receive activity because of a database error: {err}");
            HttpResponse::ServiceUnavailable().finish()
        }
        Err(err) => HttpResponse::BadRequest().body(format!("{err}")),
    }
}

/// Http responder for handling activity deliveries from clients (ActivityPub
/// client-to-server part).
///
/// Passes the created activity on to [`activity_broker::receive`].
#[post("/{username}/outbox.json", guard = "activity_json::content_type_guard")]
async fn post_outbox<'a>(
    username: web::Path<String>,
    post: web::Json<activitypub::Object<'a>>,
    db: web::Data<&'static Database>,
    remote: web::Data<RemoteAccessor>,
    server_url: web::Data<CanonicalServerUrl>,
) -> HttpResponse {
    let mut note = post.0;
    if note.has_type("Note") {
        let actor_id = actor_id(&server_url, &username);
        let activity_id = activity_id(&actor_id);
        let note_id = note_id(&actor_id);
        note.id = Some((&note_id).into());
        let Ok(Some(actor)) = db.get_object(&actor_id, None).await else {
            return HttpResponse::NotFound().body("This outbox does not exist.");
        };
        let outbox = actor.outbox.as_ref().unwrap();
        tracing::debug!("Post to outbox {outbox} received");
        let ok_response = HttpResponse::Created()
            .insert_header(("Location", activity_id.as_str()))
            .finish();
        let activity = activitypub::Object {
            context: activitypub::activitystreams_context(),
            type_: activitypub::type_create(),
            id: Some((&activity_id).into()),
            actor: Some(activitypub::ObjectsOrLinks::link((&actor_id).into())),
            to: note.to.clone(),
            cc: note.cc.clone(),
            audience: note.audience.clone(),
            bto: note.bto.take(),
            bcc: note.bcc.take(),
            published: Some(Date(OffsetDateTime::now_utc())),
            object: Some(ObjectOrLink::Object(Box::new(note))),
            ..Default::default()
        };
        match activity_broker::receive(activity, db.as_ref(), remote.as_ref(), true).await {
            Ok(_) => match db.insert_to_collection(outbox, &activity_id).await {
                Ok(_) => ok_response,
                Err(err) => {
                    tracing::error!("Failed to insert Note to outbox: {err}");
                    HttpResponse::ServiceUnavailable().finish()
                }
            },
            Err(err @ ActivityBrokeringError::InboxActorDeref(_))
            | Err(err @ ActivityBrokeringError::UnrecognizedType)
            | Err(err @ ActivityBrokeringError::Deref(_))
            | Err(err @ ActivityBrokeringError::MissingInbox(_))
            | Err(err @ ActivityBrokeringError::MissingObject)
            | Err(err @ ActivityBrokeringError::MissingActor)
            | Err(err @ ActivityBrokeringError::NonActorAddress(_)) => {
                HttpResponse::BadRequest().body(format!("{err}"))
            }
            Err(err) => {
                tracing::error!("Failed to receive Note posted to outbox: {err}");
                HttpResponse::ServiceUnavailable().finish()
            }
        }
    } else {
        HttpResponse::BadRequest().body("Not a Note.")
    }
}