// todo: how does router work in multi-window contexts?
// does each window have its own router? probably, lol

use crate::cfg::RouterCfg;
use dioxus_core::ScopeId;
use futures_channel::mpsc::UnboundedSender;
use std::any::Any;
use std::{
    cell::{Cell, RefCell},
    collections::{HashMap, HashSet},
    rc::Rc,
    sync::Arc,
};
use url::Url;

/// An abstraction over the platform's history API.
///
/// The history is denoted using web-like semantics, with forward slashes delmitiing
/// routes and question marks denoting optional parameters.
///
/// This RouterService is exposed so you can modify the history directly. It
/// does not provide a high-level ergonomic API for your components. Instead,
/// you should consider using the components and hooks instead.
/// - [`Route`](struct.Route.html)
/// - [`Link`](struct.Link.html)
/// - [`UseRoute`](struct.UseRoute.html)
/// - [`Router`](struct.Router.html)
///
///
/// # Example
///
/// ```rust, ignore
/// let router = Router::new();
/// router.push_route("/home/custom");
/// cx.provide_context(router);
/// ```
///
/// # Platform Specific
///
/// - On the web, this is a [`BrowserHistory`](https://docs.rs/gloo/0.3.0/gloo/history/struct.BrowserHistory.html).
/// - On desktop, mobile, and SSR, this is just a Vec of Strings. Currently on
///   desktop, there is no way to tap into forward/back for the app unless explicitly set.
pub struct RouterCore {
    pub(crate) route_found: Cell<Option<ScopeId>>,

    pub(crate) stack: RefCell<Vec<Arc<ParsedRoute>>>,

    pub(crate) tx: UnboundedSender<RouteEvent>,

    pub(crate) slots: Rc<RefCell<HashMap<ScopeId, String>>>,

    pub(crate) onchange_listeners: Rc<RefCell<HashSet<ScopeId>>>,

    pub(crate) history: Box<dyn RouterProvider>,

    pub(crate) cfg: RouterCfg,
}

/// A shared type for the RouterCore.
pub type RouterService = Arc<RouterCore>;

/// A route is a combination of window title, saved state, and a URL.
#[derive(Debug, Clone)]
pub struct ParsedRoute {
    /// The URL of the route.
    pub url: Url,

    /// The title of the route.
    pub title: Option<String>,

    /// The serialized state of the route.
    pub serialized_state: Option<String>,
}

#[derive(Debug)]
pub(crate) enum RouteEvent {
    Push {
        route: String,
        title: Option<String>,
        serialized_state: Option<String>,
    },
    Replace {
        route: String,
        title: Option<String>,
        serialized_state: Option<String>,
    },
    Pop,
}

impl RouterCore {
    pub(crate) fn new(tx: UnboundedSender<RouteEvent>, cfg: RouterCfg) -> Arc<Self> {
        #[cfg(feature = "web")]
        let history = Box::new(web::new(tx.clone()));

        #[cfg(not(feature = "web"))]
        let history = Box::new(hash::new());

        let route = Arc::new(history.init_location());

        Arc::new(Self {
            cfg,
            tx,
            route_found: Cell::new(None),
            stack: RefCell::new(vec![route]),
            slots: Default::default(),
            onchange_listeners: Default::default(),
            history,
        })
    }

    /// Push a new route to the history.
    ///
    /// This will trigger a route change event.
    ///
    /// This does not modify the current route
    pub fn push_route(&self, route: &str, title: Option<String>, serialized_state: Option<String>) {
        let _ = self.tx.unbounded_send(RouteEvent::Push {
            route: route.to_string(),
            title,
            serialized_state,
        });
    }

    /// Pop the current route from the history.
    pub fn pop_route(&self) {
        let _ = self.tx.unbounded_send(RouteEvent::Pop);
    }

    /// Instead of pushing a new route, replaces the current route.
    pub fn replace_route(
        &self,
        route: &str,
        title: Option<String>,
        serialized_state: Option<String>,
    ) {
        let _ = self.tx.unbounded_send(RouteEvent::Replace {
            route: route.to_string(),
            title,
            serialized_state,
        });
    }

    /// Get the current location of the Router
    pub fn current_location(&self) -> Arc<ParsedRoute> {
        self.stack.borrow().last().unwrap().clone()
    }

    /// Get the current native location of the Router
    pub fn native_location<T: 'static>(&self) -> Option<Box<T>> {
        self.history.native_location().downcast::<T>().ok()
    }

    /// Registers a scope to regenerate on route change.
    ///
    /// This is useful if you've built some abstraction on top of the router service.
    pub fn subscribe_onchange(&self, id: ScopeId) {
        self.onchange_listeners.borrow_mut().insert(id);
    }

    /// Unregisters a scope to regenerate on route change.
    ///
    /// This is useful if you've built some abstraction on top of the router service.
    pub fn unsubscribe_onchange(&self, id: ScopeId) {
        self.onchange_listeners.borrow_mut().remove(&id);
    }

    pub(crate) fn register_total_route(&self, route: String, scope: ScopeId) {
        let clean = clean_route(route);
        self.slots.borrow_mut().insert(scope, clean);
    }

    pub(crate) fn should_render(&self, scope: ScopeId) -> bool {
        if let Some(root_id) = self.route_found.get() {
            return root_id == scope;
        }

        let roots = self.slots.borrow();

        if let Some(route) = roots.get(&scope) {
            if route_matches_path(
                &self.current_location().url,
                route,
                self.cfg.base_url.as_ref(),
            ) || route.is_empty()
            {
                self.route_found.set(Some(scope));
                true
            } else {
                false
            }
        } else {
            false
        }
    }
}

fn clean_route(route: String) -> String {
    if route.as_str() == "/" {
        return route;
    }
    route.trim_end_matches('/').to_string()
}

fn clean_path(path: &str) -> &str {
    if path == "/" {
        return path;
    }
    let sub = path.trim_end_matches('/');

    if sub.starts_with('/') {
        &path[1..]
    } else {
        sub
    }
}

fn route_matches_path(cur: &Url, attempt: &str, base_url: Option<&String>) -> bool {
    let cur_piece_iter = cur.path_segments().unwrap();

    let cur_pieces = match base_url {
        // baseurl is naive right now and doesn't support multiple nesting levels
        Some(_) => cur_piece_iter.skip(1).collect::<Vec<_>>(),
        None => cur_piece_iter.collect::<Vec<_>>(),
    };

    let attempt_pieces = clean_path(attempt).split('/').collect::<Vec<_>>();

    if attempt == "/" && cur_pieces.len() == 1 && cur_pieces[0].is_empty() {
        return true;
    }

    if attempt_pieces.len() != cur_pieces.len() {
        return false;
    }

    for (i, r) in attempt_pieces.iter().enumerate() {
        // If this is a parameter then it matches as long as there's
        // _any_thing in that spot in the path.
        if r.starts_with(':') {
            continue;
        }

        if cur_pieces[i] != *r {
            return false;
        }
    }

    true
}

pub(crate) trait RouterProvider {
    fn push(&self, route: &ParsedRoute);
    fn replace(&self, route: &ParsedRoute);
    fn native_location(&self) -> Box<dyn Any>;
    fn init_location(&self) -> ParsedRoute;
}

#[cfg(not(feature = "web"))]
mod hash {
    use super::*;

    pub fn new() -> HashRouter {
        HashRouter {}
    }

    /// a simple cross-platform hash-based router
    pub struct HashRouter {}

    impl RouterProvider for HashRouter {
        fn push(&self, _route: &ParsedRoute) {}

        fn native_location(&self) -> Box<dyn Any> {
            Box::new(())
        }

        fn init_location(&self) -> ParsedRoute {
            ParsedRoute {
                url: Url::parse("app:///").unwrap(),
                title: None,
                serialized_state: None,
            }
        }

        fn replace(&self, _route: &ParsedRoute) {}
    }
}

#[cfg(feature = "web")]
mod web {
    use super::RouterProvider;
    use crate::{ParsedRoute, RouteEvent};

    use futures_channel::mpsc::UnboundedSender;
    use gloo_events::EventListener;
    use std::any::Any;
    use web_sys::History;

    pub struct WebRouter {
        // keep it around so it drops when the router is dropped
        _listener: gloo_events::EventListener,

        window: web_sys::Window,
        history: History,
    }

    impl RouterProvider for WebRouter {
        fn push(&self, route: &ParsedRoute) {
            let ParsedRoute {
                url,
                title,
                serialized_state,
            } = route;

            let _ = self.history.push_state_with_url(
                &wasm_bindgen::JsValue::from_str(serialized_state.as_deref().unwrap_or("")),
                title.as_deref().unwrap_or(""),
                Some(url.as_str()),
            );
        }

        fn replace(&self, route: &ParsedRoute) {
            let ParsedRoute {
                url,
                title,
                serialized_state,
            } = route;

            let _ = self.history.replace_state_with_url(
                &wasm_bindgen::JsValue::from_str(serialized_state.as_deref().unwrap_or("")),
                title.as_deref().unwrap_or(""),
                Some(url.as_str()),
            );
        }

        fn native_location(&self) -> Box<dyn Any> {
            Box::new(self.window.location())
        }

        fn init_location(&self) -> ParsedRoute {
            ParsedRoute {
                url: url::Url::parse(&web_sys::window().unwrap().location().href().unwrap())
                    .unwrap(),
                title: web_sys::window()
                    .unwrap()
                    .document()
                    .unwrap()
                    .title()
                    .into(),
                serialized_state: None,
            }
        }
    }

    pub(crate) fn new(tx: UnboundedSender<RouteEvent>) -> WebRouter {
        WebRouter {
            history: web_sys::window().unwrap().history().unwrap(),
            window: web_sys::window().unwrap(),
            _listener: EventListener::new(&web_sys::window().unwrap(), "popstate", move |_| {
                let _ = tx.unbounded_send(RouteEvent::Pop);
            }),
        }
    }
}