Example
use handle::Handle;
use futures::executor::block_on;
use std::{future::Future, pin::Pin, sync::Arc};
use anyhow::Error;
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(cx: &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>(cx: &'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(cx: &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>(cx: &'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(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(cx: &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,
}
impl<'a> Handle<'a, Context, Result> for A {
fn call(
&'a self,
cx: &'a mut Context
) -> Pin<Box<dyn Future<Output = Result> + Send + 'a>> {
Box::pin(async move {
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; assert_eq!(cx.index, 7);
let fut = cx.next().await;
assert_eq!(cx.index, 7);
cx.index -= self.index; assert_eq!(cx.index, 6);
println!("exec St A --{}<< {:>2}", repeat, cx.index);
fut
})
}
}
struct B {
index: usize,
}
impl<'a> Handle<'a, Context, Result> for B {
fn call(
&'a self,
cx: &'a mut Context
) -> Pin<Box<dyn Future<Output = Result> + Send + 'a>> {
Box::pin(async move {
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; assert_eq!(cx.index, 9);
let fut = cx.next().await;
assert_eq!(cx.index, 9);
cx.index -= self.index; assert_eq!(cx.index, 7);
println!("exec St B --{}<< {:>2}", repeat, cx.index);
fut
})
}
}
struct C {
index: usize,
}
impl<'a> Handle<'a, Context, Result> for C {
fn call(
&'a self,
cx: &'a mut Context
) -> Pin<Box<dyn Future<Output = Result> + Send + 'a>> {
Box::pin(async move {
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; assert_eq!(cx.index, 12);
let fut = cx.next().await;
assert_eq!(cx.index, 12);
cx.index -= self.index; assert_eq!(cx.index, 9);
println!("exec St C --{}<< {:>2}", repeat, cx.index);
fut
})
}
}
fn main() {
assert!(block_on(async move {
let mut cx = Context {
index: 0,
middleware: Vec::new(),
};
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![];
v.push(Arc::new(|cx: &mut Context| {
assert_eq!(cx.index, 12);
println!("We handled it!");
async move {
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.middleware = v.clone();
println!("mw 0: {}", v.len());
let result = cx.next().await;
assert_eq!(result?, ());
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 }));
async fn handler(cx: &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_eq!(result?, ());
Ok::<_, Error>()
}).is_ok());
}
License
