use base64::Engine;
use openssl::{hash::MessageDigest, pkey::PKey, sign::Signer};
use reqwest::header::USER_AGENT;
use sea_orm::{ColumnTrait, Condition, DatabaseConnection, DbErr, EntityTrait, Order, QueryFilter, QueryOrder, QuerySelect, SelectColumns};
use tokio::task::JoinHandle;

use crate::{VERSION, activitypub::{activity::ap_activity, object::ap_object}, activitystream::{object::activity::ActivityMut, Node}, model};

pub struct Dispatcher;

impl Dispatcher {
	pub fn spawn(db: DatabaseConnection, domain: String, poll_interval: u64) -> JoinHandle<Result<(), DbErr>> {
		tokio::spawn(async move {
			let mut nosleep = true;
			loop {
				if nosleep { nosleep = false } else {
					tokio::time::sleep(std::time::Duration::from_secs(poll_interval)).await;
				}
				let Some(delivery) = model::delivery::Entity::find()
					.filter(Condition::all().add(model::delivery::Column::NotBefore.lte(chrono::Utc::now())))
					.order_by(model::delivery::Column::NotBefore, Order::Asc)
					.one(&db)
					.await?
				else { continue };

				let del_row = model::delivery::ActiveModel {
					id: sea_orm::ActiveValue::Set(delivery.id),
					..Default::default()
				};
				let del = model::delivery::Entity::delete(del_row)
					.exec(&db)
					.await?;

				if del.rows_affected == 0 {
					// another worker claimed this delivery
					nosleep = true;
					continue; // go back to the top
				}
				if delivery.expired() {
					// try polling for another one
					nosleep = true;
					continue; // go back to top
				}

				tracing::info!("delivering {} to {}", delivery.activity, delivery.target);

				let payload = match model::activity::Entity::find_by_id(&delivery.activity)
					.find_also_related(model::object::Entity)
					.one(&db)
					.await? // TODO probably should not fail here and at least re-insert the delivery
				{
					Some((activity, Some(object))) => ap_activity(activity).set_object(Node::object(ap_object(object))),
					Some((activity, None)) => ap_activity(activity),
					None => {
						tracing::warn!("skipping dispatch for deleted object {}", delivery.activity);
						continue;
					},
				};

				let Some(key_pem) = model::user::Entity::find_by_id(&delivery.actor)
					.select_only()
					.select_column(model::user::Column::PrivateKey)
					.into_tuple::<String>()
					.one(&db)
					.await?
				else { 
					tracing::error!("can not dispatch activity for user without private key: {}", delivery.actor);
					continue;
				};

				let Ok(key) = PKey::private_key_from_pem(key_pem.as_bytes())
				else {
					tracing::error!("failed parsing private key for user {}", delivery.actor);
					continue;
				};

				let mut signer = Signer::new(MessageDigest::sha256(), &key).unwrap();

				let without_protocol = delivery.target.replace("https://", "").replace("http://", "");
				let host = without_protocol.replace('/', "");
				let request_target = without_protocol.replace(&host, "");
				let date = chrono::Utc::now().to_rfc2822();
				let signed_string = format!("(request-target): post {request_target}\nhost: {host}\ndate: {date}");
				signer.update(signed_string.as_bytes()).unwrap();
				let signature = base64::prelude::BASE64_URL_SAFE.encode(signer.sign_to_vec().unwrap());
				let signature_header = format!("keyId=\"{}\",algorithm=\"rsa-sha256\",headers=\"(request-target) host date\",signature=\"{signature}\"", delivery.actor);

				if let Err(e) = reqwest::Client::new()
					.post(&delivery.target)
					.json(&payload)
					.header("Host", host)
					.header("Date", date)
					.header("Signature", signature_header)
					.header(USER_AGENT, format!("upub+{VERSION} ({domain})")) // TODO put instance admin email
					.send()
					.await
				{
					tracing::warn!("failed delivery of {} to {} : {e}", delivery.activity, delivery.target);
					let new_delivery = model::delivery::ActiveModel {
						id: sea_orm::ActiveValue::NotSet,
						not_before: sea_orm::ActiveValue::Set(delivery.next_delivery()),
						actor: sea_orm::ActiveValue::Set(delivery.actor),
						target: sea_orm::ActiveValue::Set(delivery.target),
						activity: sea_orm::ActiveValue::Set(delivery.activity),
						created: sea_orm::ActiveValue::Set(delivery.created),
						attempt: sea_orm::ActiveValue::Set(delivery.attempt + 1),
					};
					model::delivery::Entity::insert(new_delivery)
						.exec(&db)
						.await?;
				}
			}
		})
	}
}