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use std::sync::{
Arc,
atomic::{AtomicBool, AtomicUsize, Ordering},
};
use super::{CellValue, Watchable};
use crate::{
cell::{Cell, CellImmutable, CellMutable},
signal::Signal,
};
pub trait RetryExt<T>: Watchable<T> {
/// Retry on error up to max_attempts times.
///
/// When an error signal is received, resubscribes to the source.
/// After max_attempts errors, propagates the error.
///
/// # Example
///
/// ```
/// use hyphae::{Cell, Mutable, RetryExt, Watchable};
///
/// let source = Cell::new(0);
/// let retried = source.retry(3);
///
/// // Errors will be retried up to 3 times before propagating
/// // Values pass through normally
/// source.set(1);
/// ```
#[track_caller]
fn retry(&self, max_attempts: usize) -> Cell<T, CellImmutable>
where
T: CellValue,
Self: Clone + Send + Sync + 'static,
{
let derived = Cell::<T, CellMutable>::new(self.get());
let weak = derived.downgrade();
let attempts = Arc::new(AtomicUsize::new(0));
let first = Arc::new(AtomicBool::new(true));
let source = self.clone();
let guard = self.subscribe(move |signal| {
if let Some(d) = weak.upgrade() {
match signal {
Signal::Value(value) => {
if first.swap(false, Ordering::SeqCst) {
return;
}
// Reset attempts on successful value
attempts.store(0, Ordering::SeqCst);
d.notify(Signal::Value(value.clone()));
}
Signal::Complete => d.notify(Signal::Complete),
Signal::Error(e) => {
let attempt = attempts.fetch_add(1, Ordering::SeqCst) + 1;
if attempt >= max_attempts {
d.notify(Signal::Error(e.clone()));
} else {
// Resubscribe to source
let weak2 = d.downgrade();
let attempts2 = attempts.clone();
let max = max_attempts;
let guard2 = source.subscribe(move |sig| {
if let Some(d2) = weak2.upgrade() {
match sig {
Signal::Value(v) => {
attempts2.store(0, Ordering::SeqCst);
d2.notify(Signal::Value(v.clone()));
}
Signal::Complete => d2.notify(Signal::Complete),
Signal::Error(e2) => {
let a = attempts2.fetch_add(1, Ordering::SeqCst) + 1;
if a >= max {
d2.notify(Signal::Error(e2.clone()));
}
// Note: nested retries would need recursion
}
}
}
});
d.own(guard2);
}
}
}
}
});
derived.own(guard);
derived.lock()
}
/// Retry on error with a predicate to decide whether to retry.
///
/// # Example
///
/// ```
/// use hyphae::{Cell, Mutable, RetryExt, Watchable};
///
/// let source = Cell::new(0);
/// let retried = source.retry_when(|_err, attempt| {
/// // Only retry up to 5 times
/// attempt < 5
/// });
/// source.set(1);
/// ```
#[track_caller]
fn retry_when<F>(&self, predicate: F) -> Cell<T, CellImmutable>
where
T: CellValue,
F: Fn(&dyn std::any::Any, usize) -> bool + Send + Sync + 'static,
Self: Clone + Send + Sync + 'static,
{
let derived = Cell::<T, CellMutable>::new(self.get());
let weak = derived.downgrade();
let attempts = Arc::new(AtomicUsize::new(0));
let first = Arc::new(AtomicBool::new(true));
let predicate = Arc::new(predicate);
let source = self.clone();
let guard = self.subscribe(move |signal| {
if let Some(d) = weak.upgrade() {
match signal {
Signal::Value(value) => {
if first.swap(false, Ordering::SeqCst) {
return;
}
attempts.store(0, Ordering::SeqCst);
d.notify(Signal::Value(value.clone()));
}
Signal::Complete => d.notify(Signal::Complete),
Signal::Error(e) => {
let attempt = attempts.fetch_add(1, Ordering::SeqCst) + 1;
if predicate(&**e, attempt) {
// Resubscribe
let weak2 = d.downgrade();
let attempts2 = attempts.clone();
let pred2 = predicate.clone();
let guard2 = source.subscribe(move |sig| {
if let Some(d2) = weak2.upgrade() {
match sig {
Signal::Value(v) => {
attempts2.store(0, Ordering::SeqCst);
d2.notify(Signal::Value(v.clone()));
}
Signal::Complete => d2.notify(Signal::Complete),
Signal::Error(e2) => {
let a = attempts2.fetch_add(1, Ordering::SeqCst) + 1;
if !pred2(&**e2, a) {
d2.notify(Signal::Error(e2.clone()));
}
}
}
}
});
d.own(guard2);
} else {
d.notify(Signal::Error(e.clone()));
}
}
}
}
});
derived.own(guard);
derived.lock()
}
}
impl<T, W: Watchable<T>> RetryExt<T> for W {}
#[cfg(test)]
mod tests {
use std::sync::atomic::AtomicU32;
use super::*;
use crate::Mutable;
#[test]
fn test_retry_passes_values() {
let source = Cell::new(0);
let retried = source.retry(3);
let count = Arc::new(AtomicU32::new(0));
let c = count.clone();
let _guard = retried.subscribe(move |signal| {
if let Signal::Value(_) = signal {
c.fetch_add(1, Ordering::SeqCst);
}
});
assert_eq!(count.load(Ordering::SeqCst), 1); // Initial
source.set(1);
source.set(2);
assert_eq!(count.load(Ordering::SeqCst), 3);
}
#[test]
fn test_retry_retries_on_error() {
// Note: retry(1) means propagate after first error (no retries)
// retry(3) means allow 2 retries before propagating
let source = Cell::new(0);
let retried = source.retry(1); // Propagate immediately
let error_count = Arc::new(AtomicU32::new(0));
let ec = error_count.clone();
let _guard = retried.subscribe(move |signal| {
if let Signal::Error(_) = signal {
ec.fetch_add(1, Ordering::SeqCst);
}
});
// With retry(1), first error should propagate
source.fail(anyhow::anyhow!("error 1"));
assert_eq!(error_count.load(Ordering::SeqCst), 1);
}
#[test]
fn test_retry_resets_on_success() {
let source = Cell::new(0);
let retried = source.retry(2);
let error_count = Arc::new(AtomicU32::new(0));
let ec = error_count.clone();
let _guard = retried.subscribe(move |signal| {
if let Signal::Error(_) = signal {
ec.fetch_add(1, Ordering::SeqCst);
}
});
source.fail(anyhow::anyhow!("error 1"));
source.set(1); // Success resets counter
source.fail(anyhow::anyhow!("error 2"));
// Should not propagate yet
assert_eq!(error_count.load(Ordering::SeqCst), 0);
}
}