use crate::{
    AnyView, AnyWindowHandle, AppCell, AppContext, AsyncAppContext, BackgroundExecutor, Context,
    EventEmitter, ForegroundExecutor, Model, ModelContext, Result, Task, TestDispatcher,
    TestPlatform, WindowContext,
};
use anyhow::{anyhow, bail};
use futures::{Stream, StreamExt};
use std::{future::Future, rc::Rc, sync::Arc, time::Duration};

#[derive(Clone)]
pub struct TestAppContext {
    pub app: Rc<AppCell>,
    pub background_executor: BackgroundExecutor,
    pub foreground_executor: ForegroundExecutor,
}

impl Context for TestAppContext {
    type Result<T> = T;

    fn build_model<T: 'static>(
        &mut self,
        build_model: impl FnOnce(&mut ModelContext<'_, T>) -> T,
    ) -> Self::Result<Model<T>>
    where
        T: 'static,
    {
        let mut app = self.app.borrow_mut();
        app.build_model(build_model)
    }

    fn update_model<T: 'static, R>(
        &mut self,
        handle: &Model<T>,
        update: impl FnOnce(&mut T, &mut ModelContext<'_, T>) -> R,
    ) -> Self::Result<R> {
        let mut app = self.app.borrow_mut();
        app.update_model(handle, update)
    }

    fn update_window<T, F>(&mut self, window: AnyWindowHandle, f: F) -> Result<T>
    where
        F: FnOnce(AnyView, &mut WindowContext<'_>) -> T,
    {
        let mut lock = self.app.borrow_mut();
        lock.update_window(window, f)
    }
}

impl TestAppContext {
    pub fn new(dispatcher: TestDispatcher) -> Self {
        let dispatcher = Arc::new(dispatcher);
        let background_executor = BackgroundExecutor::new(dispatcher.clone());
        let foreground_executor = ForegroundExecutor::new(dispatcher);
        let platform = Rc::new(TestPlatform::new(
            background_executor.clone(),
            foreground_executor.clone(),
        ));
        let asset_source = Arc::new(());
        let http_client = util::http::FakeHttpClient::with_404_response();
        Self {
            app: AppContext::new(platform, asset_source, http_client),
            background_executor,
            foreground_executor,
        }
    }

    pub fn quit(&self) {
        self.app.borrow_mut().quit();
    }

    pub fn refresh(&mut self) -> Result<()> {
        let mut app = self.app.borrow_mut();
        app.refresh();
        Ok(())
    }

    pub fn executor(&self) -> &BackgroundExecutor {
        &self.background_executor
    }

    pub fn foreground_executor(&self) -> &ForegroundExecutor {
        &self.foreground_executor
    }

    pub fn update<R>(&self, f: impl FnOnce(&mut AppContext) -> R) -> R {
        let mut cx = self.app.borrow_mut();
        cx.update(f)
    }

    pub fn spawn<Fut, R>(&self, f: impl FnOnce(AsyncAppContext) -> Fut) -> Task<R>
    where
        Fut: Future<Output = R> + 'static,
        R: 'static,
    {
        self.foreground_executor.spawn(f(self.to_async()))
    }

    pub fn has_global<G: 'static>(&self) -> bool {
        let app = self.app.borrow();
        app.has_global::<G>()
    }

    pub fn read_global<G: 'static, R>(&self, read: impl FnOnce(&G, &AppContext) -> R) -> R {
        let app = self.app.borrow();
        read(app.global(), &app)
    }

    pub fn try_read_global<G: 'static, R>(
        &self,
        read: impl FnOnce(&G, &AppContext) -> R,
    ) -> Option<R> {
        let lock = self.app.borrow();
        Some(read(lock.try_global()?, &lock))
    }

    pub fn update_global<G: 'static, R>(
        &mut self,
        update: impl FnOnce(&mut G, &mut AppContext) -> R,
    ) -> R {
        let mut lock = self.app.borrow_mut();
        lock.update_global(update)
    }

    pub fn to_async(&self) -> AsyncAppContext {
        AsyncAppContext {
            app: Rc::downgrade(&self.app),
            background_executor: self.background_executor.clone(),
            foreground_executor: self.foreground_executor.clone(),
        }
    }

    pub fn notifications<T: 'static>(&mut self, entity: &Model<T>) -> impl Stream<Item = ()> {
        let (tx, rx) = futures::channel::mpsc::unbounded();

        entity.update(self, move |_, cx: &mut ModelContext<T>| {
            cx.observe(entity, {
                let tx = tx.clone();
                move |_, _, _| {
                    let _ = tx.unbounded_send(());
                }
            })
            .detach();

            cx.on_release(move |_, _| tx.close_channel()).detach();
        });

        rx
    }

    pub fn events<T: 'static + EventEmitter>(
        &mut self,
        entity: &Model<T>,
    ) -> futures::channel::mpsc::UnboundedReceiver<T::Event>
    where
        T::Event: 'static + Clone,
    {
        let (tx, rx) = futures::channel::mpsc::unbounded();
        entity
            .update(self, |_, cx: &mut ModelContext<T>| {
                cx.subscribe(entity, move |_model, _handle, event, _cx| {
                    let _ = tx.unbounded_send(event.clone());
                })
            })
            .detach();
        rx
    }

    pub async fn condition<T: 'static>(
        &mut self,
        model: &Model<T>,
        mut predicate: impl FnMut(&mut T, &mut ModelContext<T>) -> bool,
    ) {
        let timer = self.executor().timer(Duration::from_secs(3));
        let mut notifications = self.notifications(model);

        use futures::FutureExt as _;
        use smol::future::FutureExt as _;

        async {
            while notifications.next().await.is_some() {
                if model.update(self, &mut predicate) {
                    return Ok(());
                }
            }
            bail!("model dropped")
        }
        .race(timer.map(|_| Err(anyhow!("condition timed out"))))
        .await
        .unwrap();
    }
}

impl<T: Send + EventEmitter> Model<T> {
    pub fn next_event(&self, cx: &mut TestAppContext) -> T::Event
    where
        T::Event: Send + Clone,
    {
        let (tx, mut rx) = futures::channel::mpsc::unbounded();
        let _subscription = self.update(cx, |_, cx| {
            cx.subscribe(self, move |_, _, event, _| {
                tx.unbounded_send(event.clone()).ok();
            })
        });

        cx.executor().run_until_parked();
        rx.try_next()
            .expect("no event received")
            .expect("model was dropped")
    }
}