From 1e6f98595b66c8fbbc6e12994827ea44f12fcb7e Mon Sep 17 00:00:00 2001
From: "Christoph J. Scherr" <Christoph.Scherr@newtec.de>
Date: Mon, 19 Feb 2024 11:53:39 +0100
Subject: [PATCH] back to the future

---
 Cargo.lock                        |  8 ++++++++
 Cargo.toml                        |  3 +++
 members/future_stream/Cargo.toml  | 10 +++++++++
 members/future_stream/src/main.rs | 34 +++++++++++++++++++++++++++++++
 4 files changed, 55 insertions(+)
 create mode 100644 members/future_stream/Cargo.toml
 create mode 100644 members/future_stream/src/main.rs

diff --git a/Cargo.lock b/Cargo.lock
index feafeec..0ab4f0a 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -517,6 +517,14 @@ dependencies = [
  "windows-sys 0.52.0",
 ]
 
+[[package]]
+name = "future_stream"
+version = "0.1.0"
+dependencies = [
+ "futures",
+ "tokio",
+]
+
 [[package]]
 name = "futures"
 version = "0.3.30"
diff --git a/Cargo.toml b/Cargo.toml
index f682855..d596c26 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -13,6 +13,7 @@ members = [
   "members/tokryon",
   "members/tokio-send-sync",
   "members/matchmatchmatch",
+  "members/future_stream",
 ]
 default-members = [
   ".",
@@ -28,6 +29,7 @@ default-members = [
   "members/tokryon",
   "members/tokio-send-sync",
   "members/matchmatchmatch",
+  "members/future_stream",
 ]
 
 [workspace.dependencies]
@@ -42,6 +44,7 @@ tokio = { version = "1.35.1", features = [
   "time",
   "sync",
 ] }
+futures = { version = "0.3.30", features = ["executor"] }
 
 [package]
 name = "rs-basic"
diff --git a/members/future_stream/Cargo.toml b/members/future_stream/Cargo.toml
new file mode 100644
index 0000000..67f1383
--- /dev/null
+++ b/members/future_stream/Cargo.toml
@@ -0,0 +1,10 @@
+[package]
+name = "future_stream"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+tokio.workspace = true
+futures.workspace = true
diff --git a/members/future_stream/src/main.rs b/members/future_stream/src/main.rs
new file mode 100644
index 0000000..3d313a2
--- /dev/null
+++ b/members/future_stream/src/main.rs
@@ -0,0 +1,34 @@
+// see https://stackoverflow.com/questions/70774671/tokioselect-but-for-a-vec-of-futures
+use futures::{stream::FuturesUnordered, StreamExt};
+use std::time::Duration;
+use tokio::time::{sleep, Instant};
+
+async fn wait(millis: u64) -> u64 {
+    sleep(Duration::from_millis(millis)).await;
+    millis
+}
+
+#[tokio::main]
+async fn main() {
+    let mut futures = FuturesUnordered::new();
+    futures.push(wait(500));
+    futures.push(wait(300));
+    futures.push(wait(100));
+    futures.push(wait(200));
+
+    let start_time = Instant::now();
+
+    let mut num_added = 0;
+    while let Some(wait_time) = futures.next().await {
+        println!("Waited {}ms", wait_time);
+        if num_added < 3 {
+            num_added += 1;
+            futures.push(wait(200));
+        }
+    }
+
+    println!(
+        "Completed all work in {}ms",
+        start_time.elapsed().as_millis()
+    );
+}