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use std::{rc::Rc, task::Context, task::Poll};

use ntex::router::{IntoPattern, RouterBuilder};
use ntex::service::boxed::{self, BoxService, BoxServiceFactory};
use ntex::service::{IntoServiceFactory, Service, ServiceCtx, ServiceFactory};

use super::{publish::Publish, Session};

type Handler<S, E> = BoxServiceFactory<Session<S>, Publish, (), E, E>;
type HandlerService<E> = BoxService<Publish, (), E>;

/// Router - structure that follows the builder pattern
/// for building publish packet router instances for mqtt server.
pub struct Router<S, Err> {
    router: RouterBuilder<usize>,
    handlers: Vec<Handler<S, Err>>,
    default: Handler<S, Err>,
}

impl<S, Err> Router<S, Err>
where
    S: 'static,
    Err: 'static,
{
    /// Create mqtt application router.
    ///
    /// Default service to be used if no matching resource could be found.
    pub fn new<F, U>(default_service: F) -> Self
    where
        F: IntoServiceFactory<U, Publish, Session<S>>,
        U: ServiceFactory<Publish, Session<S>, Response = (), Error = Err, InitError = Err>
            + 'static,
    {
        Router {
            router: ntex::router::Router::build(),
            handlers: Vec::new(),
            default: boxed::factory(default_service.into_factory()),
        }
    }

    /// Configure mqtt resource for a specific topic.
    pub fn resource<T, F, U>(mut self, address: T, service: F) -> Self
    where
        T: IntoPattern,
        F: IntoServiceFactory<U, Publish, Session<S>>,
        U: ServiceFactory<Publish, Session<S>, Response = (), Error = Err> + 'static,
        Err: From<U::InitError>,
    {
        self.router.path(address, self.handlers.len());
        self.handlers.push(boxed::factory(service.into_factory().map_init_err(Err::from)));
        self
    }
}

impl<S, Err> IntoServiceFactory<RouterFactory<S, Err>, Publish, Session<S>> for Router<S, Err>
where
    S: 'static,
    Err: 'static,
{
    fn into_factory(self) -> RouterFactory<S, Err> {
        RouterFactory {
            router: Rc::new(self.router.finish()),
            handlers: self.handlers,
            default: self.default,
        }
    }
}

pub struct RouterFactory<S, Err> {
    router: Rc<ntex::router::Router<usize>>,
    handlers: Vec<Handler<S, Err>>,
    default: Handler<S, Err>,
}

impl<S, Err> ServiceFactory<Publish, Session<S>> for RouterFactory<S, Err>
where
    S: 'static,
    Err: 'static,
{
    type Response = ();
    type Error = Err;
    type InitError = Err;
    type Service = RouterService<Err>;

    async fn create(&self, session: Session<S>) -> Result<Self::Service, Self::Error> {
        let fut: Vec<_> = self.handlers.iter().map(|h| h.create(session.clone())).collect();

        let mut handlers = Vec::new();
        for handler in fut {
            handlers.push(handler.await?);
        }

        Ok(RouterService {
            handlers,
            router: self.router.clone(),
            default: self.default.create(session).await?,
        })
    }
}

pub struct RouterService<Err> {
    router: Rc<ntex::router::Router<usize>>,
    handlers: Vec<HandlerService<Err>>,
    default: HandlerService<Err>,
}

impl<Err> Service<Publish> for RouterService<Err> {
    type Response = ();
    type Error = Err;

    fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        let mut not_ready = false;
        for hnd in &self.handlers {
            if hnd.poll_ready(cx)?.is_pending() {
                not_ready = true;
            }
        }

        if self.default.poll_ready(cx)?.is_pending() {
            not_ready = true;
        }

        if not_ready {
            Poll::Pending
        } else {
            Poll::Ready(Ok(()))
        }
    }

    async fn call(
        &self,
        mut req: Publish,
        ctx: ServiceCtx<'_, Self>,
    ) -> Result<Self::Response, Self::Error> {
        if let Some((idx, _info)) = self.router.recognize(req.topic_mut()) {
            ctx.call(&self.handlers[*idx], req).await
        } else {
            ctx.call(&self.default, req).await
        }
    }
}