introduce & use JobPool

Signed-off-by: kernelkind <kernelkind@gmail.com>

crates/notedeck/src/app.rs

@@ -1,6 +1,7 @@
 use crate::persist::{AppSizeHandler, ZoomHandler};
 use crate::wallet::GlobalWallet;
 use crate::zaps::Zaps;
+use crate::JobPool;
 use crate::{
     frame_history::FrameHistory, AccountStorage, Accounts, AppContext, Args, DataPath,
     DataPathType, Directory, Images, NoteAction, NoteCache, RelayDebugView, ThemeHandler,
@@ -43,6 +44,7 @@ pub struct Notedeck {
     clipboard: Clipboard,
     zaps: Zaps,
     frame_history: FrameHistory,
+    job_pool: JobPool,
 }
 
 /// Our chrome, which is basically nothing
@@ -219,6 +221,7 @@ impl Notedeck {
 
         let global_wallet = GlobalWallet::new(&path);
         let zaps = Zaps::default();
+        let job_pool = JobPool::default();
 
         Self {
             ndb,
@@ -238,6 +241,7 @@ impl Notedeck {
             frame_history: FrameHistory::default(),
             clipboard: Clipboard::new(None),
             zaps,
+            job_pool,
         }
     }
 
@@ -261,6 +265,7 @@ impl Notedeck {
             clipboard: &mut self.clipboard,
             zaps: &mut self.zaps,
             frame_history: &mut self.frame_history,
+            job_pool: &mut self.job_pool,
         }
     }
 

crates/notedeck/src/context.rs

@@ -1,6 +1,6 @@
 use crate::{
     frame_history::FrameHistory, wallet::GlobalWallet, zaps::Zaps, Accounts, Args, DataPath,
-    Images, NoteCache, ThemeHandler, UnknownIds,
+    Images, JobPool, NoteCache, ThemeHandler, UnknownIds,
 };
 use egui_winit::clipboard::Clipboard;
 
@@ -23,4 +23,5 @@ pub struct AppContext<'a> {
     pub clipboard: &'a mut Clipboard,
     pub zaps: &'a mut Zaps,
     pub frame_history: &'a mut FrameHistory,
+    pub job_pool: &'a mut JobPool,
 }

crates/notedeck/src/job_pool.rs

@@ -0,0 +1,99 @@
+use std::{
+    future::Future,
+    sync::{
+        mpsc::{self, Sender},
+        Arc, Mutex,
+    },
+};
+use tokio::sync::oneshot;
+
+type Job = Box<dyn FnOnce() + Send + 'static>;
+
+pub struct JobPool {
+    tx: Sender<Job>,
+}
+
+impl Default for JobPool {
+    fn default() -> Self {
+        JobPool::new(2)
+    }
+}
+
+impl JobPool {
+    pub fn new(num_threads: usize) -> Self {
+        let (tx, rx) = mpsc::channel::<Job>();
+
+        let arc_rx = Arc::new(Mutex::new(rx));
+        for _ in 0..num_threads {
+            let arc_rx_clone = arc_rx.clone();
+            std::thread::spawn(move || loop {
+                let job = {
+                    let Ok(unlocked) = arc_rx_clone.lock() else {
+                        continue;
+                    };
+                    let Ok(job) = unlocked.recv() else {
+                        continue;
+                    };
+
+                    job
+                };
+
+                job();
+            });
+        }
+
+        Self { tx }
+    }
+
+    pub fn schedule<F, T>(&self, job: F) -> impl Future<Output = T>
+    where
+        F: FnOnce() -> T + Send + 'static,
+        T: Send + 'static,
+    {
+        let (tx_result, rx_result) = oneshot::channel::<T>();
+
+        let job = Box::new(move || {
+            let output = job();
+            let _ = tx_result.send(output);
+        });
+
+        self.tx
+            .send(job)
+            .expect("receiver should not be deallocated");
+
+        async move {
+            rx_result.await.unwrap_or_else(|_| {
+                panic!("Worker thread or channel dropped before returning the result.")
+            })
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::job_pool::JobPool;
+
+    fn test_fn(a: u32, b: u32) -> u32 {
+        a + b
+    }
+
+    #[tokio::test]
+    async fn test() {
+        let pool = JobPool::default();
+
+        // Now each job can return different T
+        let future_str = pool.schedule(|| -> String { "hello from string job".into() });
+
+        let a = 5;
+        let b = 6;
+        let future_int = pool.schedule(move || -> u32 { test_fn(a, b) });
+
+        println!("(Meanwhile we can do more async work) ...");
+
+        let s = future_str.await;
+        let i = future_int.await;
+
+        println!("Got string: {:?}", s);
+        println!("Got integer: {}", i);
+    }
+}

crates/notedeck/src/lib.rs

@@ -9,6 +9,7 @@ pub mod filter;
 pub mod fonts;
 mod frame_history;
 mod imgcache;
+mod job_pool;
 mod muted;
 pub mod name;
 pub mod note;
@@ -43,6 +44,7 @@ pub use imgcache::{
     Animation, GifState, GifStateMap, ImageFrame, Images, MediaCache, MediaCacheType,
     MediaCacheValue, TextureFrame, TexturedImage,
 };
+pub use job_pool::JobPool;
 pub use muted::{MuteFun, Muted};
 pub use name::NostrName;
 pub use note::{