handle 0.2.5

Example

use handle::Handle;
use async_trait::async_trait;
use futures::executor::block_on;
use std::{future::Future, pin::Pin, sync::Arc};

type Result = anyhow::Result<()>;
type Middleware = dyn for<'a> Handle<'a, Context, Result>;
type BoxFuture<'a, T = Result> = Pin<Box<dyn Future<Output = T> + Send + 'a>>;

struct Context {
    index: usize,
    middleware: Vec<Arc<Middleware>>,
}

impl Context {
    async fn next(&mut self) -> Result {
        if let Some(m) = self.middleware.pop() {
            m.call(Pin::new(self)).await
        } else {
            Ok(())
        }
    }
}

async fn a(mut cx: Pin<&mut Context>) -> Result {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn a --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 0);
    cx.index += 1;
    assert_eq!(cx.index, 1);

    let fut = cx.next().await;

    assert_eq!(cx.index, 1);
    cx.index -= 1;
    assert_eq!(cx.index, 0);

    println!("exec Fn a --{}<< {:>2}", repeat, cx.index);

    fut
}

fn b<'a>(mut cx: Pin<&'a mut Context>) -> BoxFuture<'a, Result> {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn b --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 1);
    cx.index += 1;
    assert_eq!(cx.index, 2);

    Box::pin(async move {
        let fut = cx.next().await;

        assert_eq!(cx.index, 2);
        cx.index -= 1;
        assert_eq!(cx.index, 1);

        println!("exec Fn b --{}<< {:>2}", repeat, cx.index);

        fut
    })
}

fn c(mut cx: Pin<&mut Context>) -> BoxFuture<'_, Result> {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn c --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 2);
    cx.index += 1;
    assert_eq!(cx.index, 3);

    Box::pin(async move {
        let fut = cx.next().await;

        assert_eq!(cx.index, 3);
        cx.index -= 1;
        assert_eq!(cx.index, 2);

        println!("exec Fn c --{}<< {:>2}", repeat, cx.index);

        fut
    })
}

fn d<'a>(mut cx: Pin<&'a mut Context>) -> impl Future<Output = Result> + 'a {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn d --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 3);
    cx.index += 1;
    assert_eq!(cx.index, 4);

    async move {
        let fut = cx.next().await;

        assert_eq!(cx.index, 4);
        cx.index -= 1;
        assert_eq!(cx.index, 3);

        println!("exec Fn d --{}<< {:>2}", repeat, cx.index);

        fut
    }
}

fn e(mut cx: Pin<&mut Context>) -> impl Future<Output = Result> + '_ {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn e --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 4);
    cx.index += 1;
    assert_eq!(cx.index, 5);

    async move {
        let fut = cx.next().await;

        assert_eq!(cx.index, 5);
        cx.index -= 1;
        assert_eq!(cx.index, 4);

        println!("exec Fn e --{}<< {:>2}", repeat, cx.index);

        fut
    }
}

async fn f(mut cx: Pin<&mut Context>) -> Result {
    let size = cx.middleware.len();
    let repeat = "-".repeat(2 * size);

    println!("exec Fn f --{}>> {:>2}", repeat, cx.index);

    assert_eq!(cx.index, 5);
    cx.index += 1;
    assert_eq!(cx.index, 6);

    let fut = cx.next().await;

    assert_eq!(cx.index, 6);
    cx.index -= 1;
    assert_eq!(cx.index, 5);

    println!("exec Fn f --{}<< {:>2}", repeat, cx.index);

    fut
}

#[derive(Clone)]
struct A {
    index: usize,
}

#[async_trait]
impl<'a> Handle<'a, Context, Result> for A {
    async fn call(&'a self, mut cx: Pin<&'a mut Context>) -> Result {
        let size = cx.middleware.len();
        let repeat = "-".repeat(2 * size);

        println!("exec St A --{}>> {:>2}", repeat, cx.index);

        assert_eq!(cx.index, 6);
        cx.index += self.index; // + 1
        assert_eq!(cx.index, 7);

        let fut = cx.next().await;

        assert_eq!(cx.index, 7);
        cx.index -= self.index; // - 1
        assert_eq!(cx.index, 6);

        println!("exec St A --{}<< {:>2}", repeat, cx.index);

        fut
    }
}

struct B {
    index: usize,
}

#[async_trait]
impl<'a> Handle<'a, Context, Result> for B {
    async fn call(&'a self, mut cx: Pin<&'a mut Context>) -> Result {
        let size = cx.middleware.len();
        let repeat = "-".repeat(2 * size);

        println!("exec St B --{}>> {:>2}", repeat, cx.index);

        assert_eq!(cx.index, 7);
        cx.index += self.index; // + 2
        assert_eq!(cx.index, 9);

        let fut = cx.next().await;

        assert_eq!(cx.index, 9);
        cx.index -= self.index; // - 2
        assert_eq!(cx.index, 7);

        println!("exec St B --{}<< {:>2}", repeat, cx.index);

        fut
    }
}

struct C {
    index: usize,
}

#[async_trait]
impl<'a> Handle<'a, Context, Result> for C {
    async fn call(&'a self, mut cx: Pin<&'a mut Context>) -> Result {
        let size = cx.middleware.len();
        let repeat = "-".repeat(2 * size);

        println!("exec St C --{}>> {:>2}", repeat, cx.index);

        assert_eq!(cx.index, 9);
        cx.index += self.index; // + 3
        assert_eq!(cx.index, 12);

        let fut = cx.next().await;

        assert_eq!(cx.index, 12);
        cx.index -= self.index; // - 3
        assert_eq!(cx.index, 9);

        println!("exec St C --{}<< {:>2}", repeat, cx.index);

        fut
    }
}

fn main() {
    block_on(async move {
        let mut cx = Context {
            index: 0,
            middleware: Vec::new(),
        };

        let mut cx: Pin<&mut Context> = Pin::new(&mut cx);

        // let _ = a(cx.as_mut()).await;
        // let _ = b(cx.as_mut()).await;
        // let _ = c(cx.as_mut()).await;
        // let _ = d(cx.as_mut()).await;
        // let _ = e(cx.as_mut()).await;
        // let _ = f(cx.as_mut()).await;
        // let _ = (B {}).call(cx.as_mut()).await;
        // let _ = (A {}).call(cx.as_mut()).await;

        let mut v: Vec<Box<Middleware>> = vec![];
        v.push(Box::new(a));
        v.push(Box::new(b));
        v.push(Box::new(c));
        v.push(Box::new(d));
        v.push(Box::new(e));
        v.push(Box::new(f));

        let mut v: Vec<Arc<Middleware>> = vec![];

        // Handled it!
        // A Closure cant use `cx.next()` in async block.
        v.push(Arc::new(|cx: Pin<&mut Context>| {
            assert_eq!(cx.index, 12);

            println!("We handled it!");

            async move {
                // assert_eq!(cx.index, 12); // compiled panic!
                Ok(())
            }
        }));
        v.push(Arc::new(C { index: 3 }));
        v.push(Arc::new(B { index: 2 }));
        v.push(Arc::new(A { index: 1 }));
        v.push(Arc::new(f));
        v.push(Arc::new(e));
        v.push(Arc::new(d));
        v.push(Arc::new(c));
        v.push(Arc::new(b));
        v.push(Arc::new(a));

        cx.as_mut().middleware = v.clone();
        println!("mw 0: {}", v.len());

        let result = cx.next().await;
        assert!(result.is_ok());
        assert_eq!(result.unwrap(), ());

        v.clear();

        v.insert(0, Arc::new(a));
        v.insert(0, Arc::new(b));
        v.insert(0, Arc::new(c));
        v.insert(0, Arc::new(d));
        v.insert(0, Arc::new(e));
        v.insert(0, Arc::new(f));
        v.insert(0, Arc::new(A { index: 1 }));
        v.insert(0, Arc::new(B { index: 2 }));
        v.insert(0, Arc::new(C { index: 3 }));
        // Handled it!
        async fn handler(cx: Pin<&mut Context>) -> Result {
            assert_eq!(cx.index, 12);

            println!("We handled it!");

            Ok(())
        }
        v.insert(0, Arc::new(handler));

        println!("mw 1: {}", v.len());

        let result = cx.next().await;
        assert!(result.is_ok());
        assert_eq!(result.unwrap(), ());
    });
}

License