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use dbuff::*;
use std::collections::HashMap;
use std::time::{Duration, Instant};
// --- Domain data: the shared state your app reads from ---
// We use TaskStatus<usize> so Resolved(i) tells us which mutation "won".
// In a real app this might be TaskStatus<SaveResult> or similar.
#[derive(Debug, Clone, Default)]
struct AppData {
task_statuses: HashMap<String, TaskStatus<usize>>,
}
#[tokio::main]
async fn main() {
// --- Tokio runtime handle: lets the pool spawn tasks on this runtime ---
let rt = tokio::runtime::Handle::current();
// --- SharedDomainData: dbuff's coalesced state wrapper ---
// Wraps AppData so reads/writes are batched at 500µs intervals
let (domain, wh) =
SharedDomainData::with_coalesce(AppData::default(), Duration::from_micros(500));
tokio::spawn(wh.run()); // starts the coalescing worker
// --- Clone for the callback closure (moved into TaskPool) ---
let domain_for_pool = domain.clone();
// --- TaskPool<String, usize> ---
// K = String → task identifier ("save" in this case)
// T = usize → which mutation index completed (0, 1, 2, 3, or 4)
//
// The key insight: we always spawn under the SAME key "save".
// Each new spawn auto-aborts the previous task, so only the last
// one gets to finish. This is the debounce pattern.
let pool: TaskPool<String, usize> = TaskPool::new(rt, move |key: &String, status| {
// ^^^ key is a reference to the K you passed to spawn()
// ^^^^^^ status is TaskStatus<T> = TaskStatus<usize>
let key = key.clone();
domain_for_pool.modify(move |d: &mut AppData| {
d.task_statuses.insert(key, status);
});
});
// --- Simulate 5 rapid user edits, 50ms apart ---
// Each "save" takes 200ms to complete. Since we fire every 50ms,
// each new spawn aborts the previous one before it can finish.
// Only the LAST spawn (mutation 4) has enough time to complete.
println!("=== Firing 5 rapid mutations ===");
let start = Instant::now();
for i in 0..5 {
pool.spawn("save".to_string(), move || {
let mutation_id = i;
async move {
tokio::time::sleep(Duration::from_millis(200)).await;
mutation_id // ← this becomes TaskStatus::Resolved(mutation_id)
}
});
println!(" mutation {i} fired at {}ms", start.elapsed().as_millis());
tokio::time::sleep(Duration::from_millis(50)).await;
}
// --- Wait for the last mutation to resolve ---
// Mutation 4 fires at ~200ms, finishes at ~400ms.
// Mutations 0-3 were all aborted before they could complete.
println!("\n=== Waiting for result ===");
loop {
let snap = domain.read();
match snap.task_statuses.get("save") {
Some(TaskStatus::Resolved(mutation_id)) => {
let elapsed = start.elapsed();
println!(" resolved: mutation {mutation_id} at {}ms", elapsed.as_millis());
assert_eq!(*mutation_id, 4, "only the last mutation should resolve");
break;
}
Some(TaskStatus::Pending) => {
// Still running — the last spawn hasn't finished yet
tokio::time::sleep(Duration::from_millis(10)).await;
}
other => {
panic!("unexpected status: {other:?}");
}
}
}
println!("\nAll examples passed!");
}