//! Defines the Gotham `Router` and supporting types.

pub mod builder;
pub use builder::{build_router, build_simple_router};

pub mod response;
pub mod route;
pub mod tree;

mod non_match;
pub use self::non_match::RouteNonMatch;

use std::pin::Pin;
use std::sync::Arc;

use futures_util::future::{self, FutureExt, TryFutureExt};
use hyper::header::ALLOW;
use hyper::{Body, Response, StatusCode};
use log::{error, trace};

use crate::handler::{Handler, HandlerFuture, IntoResponse, NewHandler};
use crate::helpers::http::request::path::RequestPathSegments;
use crate::helpers::http::response::create_empty_response;
use crate::router::response::ResponseFinalizer;
use crate::router::route::{Delegation, Route};
use crate::router::tree::segment::SegmentMapping;
use crate::router::tree::Tree;
use crate::state::{request_id, State};

struct RouterData {
    tree: Tree,
    response_finalizer: ResponseFinalizer,
}

impl RouterData {
    fn new(tree: Tree, response_finalizer: ResponseFinalizer) -> RouterData {
        RouterData {
            tree,
            response_finalizer,
        }
    }
}

/// Responsible for dispatching HTTP requests to defined routes, and responding with appropriate
/// error codes when a valid `Route` is unable to be determined or the dispatch cannot be
/// performed.
///
/// A `Router` is constructed through the [`gotham::router::builder`](builder/index.html#functions)
/// API, and used with the `gotham::start` function when booting a Gotham web application.
///
/// The `Router` is capable of delegating requests to secondary `Router` instances, which allows
/// the support of "modular applications". A modular application contains multiple applications
/// within a single binary that have clear boundaries established via Rust module separation.
/// Please see the documentation for `DrawRoutes::delegate` within `gotham::router::builder` in
/// order to delegate to other `Router` instances.
#[derive(Clone)]
pub struct Router {
    data: Arc<RouterData>,
}

impl NewHandler for Router {
    type Instance = Router;

    // Creates a new Router instance to route new HTTP requests
    fn new_handler(&self) -> anyhow::Result<Self::Instance> {
        trace!(" cloning instance");
        Ok(self.clone())
    }
}

impl Handler for Router {
    /// Handles the `Request` by determining the correct `Route` from the internal `Tree`, storing
    /// any path related variables in `State` and dispatching to the associated `Handler`.
    fn handle(self, mut state: State) -> Pin<Box<HandlerFuture>> {
        trace!("[{}] starting", request_id(&state));

        let future = match state.try_take::<RequestPathSegments>() {
            Some(rps) => {
                if let Some((node, params, processed)) = self.data.tree.traverse(rps.segments()) {
                    match node.select_route(&state) {
                        Ok(route) => match route.delegation() {
                            Delegation::External => {
                                trace!("[{}] delegating to secondary router", request_id(&state));

                                state.put(rps.subsegments(processed));
                                route.dispatch(state)
                            }
                            Delegation::Internal => {
                                trace!("[{}] dispatching to route", request_id(&state));
                                self.dispatch(state, params, route)
                            }
                        },
                        Err(non_match) => {
                            let (status, allow) = non_match.deconstruct();

                            trace!("[{}] responding with error status", request_id(&state));
                            let mut res = create_empty_response(&state, status);
                            if let StatusCode::METHOD_NOT_ALLOWED = status {
                                for allowed in allow {
                                    res.headers_mut().append(
                                        ALLOW,
                                        allowed.as_str().to_string().parse().unwrap(),
                                    );
                                }
                            }
                            future::ok((state, res)).boxed()
                        }
                    }
                } else {
                    trace!("[{}] did not find routable node", request_id(&state));
                    let res = create_empty_response(&state, StatusCode::NOT_FOUND);
                    future::ok((state, res)).boxed()
                }
            }
            None => {
                trace!("[{}] invalid request path segments", request_id(&state));
                let res = create_empty_response(&state, StatusCode::INTERNAL_SERVER_ERROR);
                future::ok((state, res)).boxed()
            }
        };

        self.finalize_response(future)
    }
}

impl Router {
    /// Manually assembles a `Router` instance from a provided `Tree`.
    fn new(tree: Tree, response_finalizer: ResponseFinalizer) -> Router {
        let router_data = RouterData::new(tree, response_finalizer);
        Router {
            data: Arc::new(router_data),
        }
    }

    fn dispatch<'a>(
        &self,
        mut state: State,
        params: SegmentMapping<'a>,
        route: &Box<dyn Route<ResBody = Body> + Send + Sync>,
    ) -> Pin<Box<HandlerFuture>> {
        match route.extract_request_path(&mut state, params) {
            Ok(()) => {
                trace!("[{}] extracted request path", request_id(&state));
                match route.extract_query_string(&mut state) {
                    Ok(()) => {
                        trace!("[{}] extracted query string", request_id(&state));
                        trace!("[{}] dispatching", request_id(&state));
                        route.dispatch(state)
                    }
                    Err(_) => {
                        error!("[{}] the server cannot or will not process the request due to a client error within the query string",
                               request_id(&state));

                        let mut res = Response::new(Body::empty());
                        route.extend_response_on_query_string_error(&mut state, &mut res);
                        future::ok((state, res)).boxed()
                    }
                }
            }
            Err(_) => {
                error!(
                    "[{}] the server cannot or will not process the request due to a client error on the request path",
                    request_id(&state)
                );
                let mut res = Response::new(Body::empty());
                route.extend_response_on_path_error(&mut state, &mut res);
                future::ok((state, res)).boxed()
            }
        }
    }

    fn finalize_response(&self, result: Pin<Box<HandlerFuture>>) -> Pin<Box<HandlerFuture>> {
        let response_finalizer = self.data.response_finalizer.clone();
        result
            .or_else(|(state, err)| {
                trace!(
                    "[{}] converting error into http response \
                     during finalization: {:?}",
                    request_id(&state),
                    err
                );
                let response = err.into_response(&state);
                future::ok((state, response))
            })
            .and_then(move |(state, res)| {
                trace!("[{}] handler complete", request_id(&state));
                response_finalizer.finalize(state, res)
            })
            .boxed()
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use hyper::header::{HeaderMap, CONTENT_LENGTH, CONTENT_TYPE};
    use hyper::{Body, Method, Uri};
    use mime::TEXT_PLAIN;
    use std::str::FromStr;

    use crate::extractor::{NoopPathExtractor, NoopQueryStringExtractor};
    use crate::handler::HandlerError;
    use crate::pipeline::{finalize_pipeline_set, new_pipeline_set};
    use crate::router::response::ResponseFinalizerBuilder;
    use crate::router::route::dispatch::DispatcherImpl;
    use crate::router::route::matcher::{
        AndRouteMatcher, ContentTypeHeaderRouteMatcher, MethodOnlyRouteMatcher,
    };
    use crate::router::route::{Extractors, RouteImpl};
    use crate::router::tree::node::Node;
    use crate::router::tree::segment::SegmentType;
    use crate::router::tree::Tree;
    use crate::state::set_request_id;

    fn handler(state: State) -> (State, Response<Body>) {
        (state, Response::new(Body::empty()))
    }

    fn send_request(
        r: Router,
        method: Method,
        uri: &str,
    ) -> ::std::result::Result<(State, Response<Body>), (State, HandlerError)> {
        let uri = Uri::from_str(uri).unwrap();

        let mut headers = HeaderMap::new();
        if method == Method::POST {
            headers.insert(CONTENT_TYPE, "application/json".parse().unwrap());
            headers.insert(CONTENT_LENGTH, 0.into());
        }

        let mut state = State::new();
        state.put(RequestPathSegments::new(uri.path()));
        state.put(method);
        state.put(uri);
        state.put(headers);
        set_request_id(&mut state);

        futures_executor::block_on(r.handle(state))
    }

    #[test]
    fn internal_server_error_if_no_request_path_segments() {
        let tree = Tree::new();
        let router = Router::new(tree, ResponseFinalizerBuilder::new().finalize());

        let method = Method::GET;
        let uri = Uri::from_str("https://test.gotham.rs").unwrap();

        let mut state = State::new();
        state.put(method);
        state.put(uri);
        state.put(HeaderMap::new());
        set_request_id(&mut state);

        match futures_executor::block_on(router.handle(state)) {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::INTERNAL_SERVER_ERROR);
            }
            Err(_) => unreachable!("Router should have handled request"),
        };
    }

    #[test]
    fn not_found_error_if_request_path_is_not_found() {
        let tree = Tree::new();
        let router = Router::new(tree, ResponseFinalizerBuilder::new().finalize());

        match send_request(router, Method::GET, "https://test.gotham.rs") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::NOT_FOUND);
            }
            Err(_) => unreachable!("Router should have handled request"),
        };
    }

    #[test]
    fn custom_error_if_leaf_found_but_matching_route_not_found() {
        let pipeline_set = finalize_pipeline_set(new_pipeline_set());
        let mut tree = Tree::new();

        let route = {
            let methods = vec![Method::POST];
            let matcher = AndRouteMatcher::new(
                MethodOnlyRouteMatcher::new(methods),
                ContentTypeHeaderRouteMatcher::new(vec![TEXT_PLAIN]),
            );
            let dispatcher = Box::new(DispatcherImpl::new(|| Ok(handler), (), pipeline_set));
            let extractors: Extractors<NoopPathExtractor, NoopQueryStringExtractor> =
                Extractors::new();
            let route = RouteImpl::new(matcher, dispatcher, extractors, Delegation::Internal);
            Box::new(route)
        };
        tree.add_route(route);
        let router = Router::new(tree, ResponseFinalizerBuilder::new().finalize());

        match send_request(router.clone(), Method::GET, "https://test.gotham.rs") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::METHOD_NOT_ALLOWED);
                assert_eq!(
                    res.headers()
                        .get_all(ALLOW)
                        .iter()
                        .map(|it| it.to_str().unwrap())
                        .collect::<Vec<&str>>(),
                    vec!["POST"]
                );
            }
            Err(_) => unreachable!("Router should have handled request"),
        };

        match send_request(router, Method::POST, "https://test.gotham.rs") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::UNSUPPORTED_MEDIA_TYPE);
                assert!(res.headers().get_all(ALLOW).iter().next().is_none());
            }
            Err(_) => unreachable!("Router should have handled request"),
        };
    }

    #[test]
    fn success_if_leaf_and_route_found() {
        let pipeline_set = finalize_pipeline_set(new_pipeline_set());
        let mut tree = Tree::new();

        let route = {
            let methods = vec![Method::GET];
            let matcher = MethodOnlyRouteMatcher::new(methods);
            let dispatcher = Box::new(DispatcherImpl::new(|| Ok(handler), (), pipeline_set));
            let extractors: Extractors<NoopPathExtractor, NoopQueryStringExtractor> =
                Extractors::new();
            let route = RouteImpl::new(matcher, dispatcher, extractors, Delegation::Internal);
            Box::new(route)
        };
        tree.add_route(route);
        let router = Router::new(tree, ResponseFinalizerBuilder::new().finalize());

        match send_request(router, Method::GET, "https://test.gotham.rs") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::OK);
            }
            Err(_) => unreachable!("Router should have handled request"),
        };
    }

    #[test]
    fn delegates_to_secondary_router() {
        let delegated_router = {
            let pipeline_set = finalize_pipeline_set(new_pipeline_set());
            let mut tree = Tree::new();

            let route = {
                let methods = vec![Method::GET];
                let matcher = MethodOnlyRouteMatcher::new(methods);
                let dispatcher = Box::new(DispatcherImpl::new(|| Ok(handler), (), pipeline_set));
                let extractors: Extractors<NoopPathExtractor, NoopQueryStringExtractor> =
                    Extractors::new();
                let route = RouteImpl::new(matcher, dispatcher, extractors, Delegation::Internal);
                Box::new(route)
            };
            tree.add_route(route);

            Router::new(tree, ResponseFinalizerBuilder::new().finalize())
        };

        let pipeline_set = finalize_pipeline_set(new_pipeline_set());
        let mut tree = Tree::new();
        let mut delegated_node = Node::new("var", SegmentType::Dynamic);

        let route = {
            let methods = vec![Method::GET];
            let matcher = MethodOnlyRouteMatcher::new(methods);
            let dispatcher = Box::new(DispatcherImpl::new(delegated_router, (), pipeline_set));
            let extractors: Extractors<NoopPathExtractor, NoopQueryStringExtractor> =
                Extractors::new();
            let route = RouteImpl::new(matcher, dispatcher, extractors, Delegation::External);
            Box::new(route)
        };

        delegated_node.add_route(route);
        tree.add_child(delegated_node);
        let router = Router::new(tree, ResponseFinalizerBuilder::new().finalize());

        // Ensure that top level tree has no route
        match send_request(router.clone(), Method::GET, "https://test.gotham.rs") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::NOT_FOUND);
            }
            Err(_) => unreachable!("Router should have handled request"),
        };

        // Ensure that top level tree of delegated router has route that responds correctly
        match send_request(router, Method::GET, "https://test.gotham.rs/api") {
            Ok((_state, res)) => {
                assert_eq!(res.status(), StatusCode::OK);
            }
            Err(_) => unreachable!("Router should have handled request"),
        };
    }

    #[test]
    fn executes_response_finalizer_when_present() {
        let tree = Tree::new();

        let mut response_finalizer_builder = ResponseFinalizerBuilder::new();
        let not_found_extender = |_s: &mut State, r: &mut Response<Body>| {
            r.headers_mut()
                .insert(CONTENT_LENGTH, "3".to_owned().parse().unwrap());
        };
        response_finalizer_builder.add(StatusCode::NOT_FOUND, Box::new(not_found_extender));
        let response_finalizer = response_finalizer_builder.finalize();
        let router = Router::new(tree, response_finalizer);

        match send_request(router, Method::GET, "https://test.gotham.rs/api") {
            Ok((_state, res)) => {
                assert_eq!(res.headers().get(CONTENT_LENGTH).unwrap(), "3");
            }
            Err(_) => unreachable!("Router should have correctly handled request"),
        };
    }
}