live 0.3.1

A modular configuration framework with live reloading and atomic, format-agnostic updates.
Documentation 
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/* src/signal/worker.rs */

use std::collections::HashMap;
use std::path::{Path, PathBuf};
use std::time::{Duration, Instant};

use tokio::sync::broadcast;
use tokio::sync::mpsc;

use super::target::CompiledTarget;
use super::{Config, Event, EventKind};

struct DebounceState {
	last_seen: Instant,
	kind: EventKind,
}

pub(crate) async fn process_events(
	mut raw_rx: mpsc::Receiver<notify::Result<notify::Event>>,
	user_tx: broadcast::Sender<Event>,
	target: CompiledTarget,
	config: Config,
	root_path: PathBuf,
) {
	let mut pending: HashMap<PathBuf, DebounceState> = HashMap::new();

	let tick_rate = if config.debounce < Duration::from_millis(50) {
		config.debounce
	} else {
		config.debounce / 5
	};

	let mut interval = tokio::time::interval(tick_rate);

	loop {
		tokio::select! {
				maybe_event = raw_rx.recv() => {
						match maybe_event {
								Some(Ok(event)) => {
										handle_raw_event(event, &mut pending, &target, &config, &root_path);
								}
								Some(Err(e)) => tracing::error!("Notify error: {:?}", e),
								None => break,
						}
				}
				_ = interval.tick() => {
						flush_pending(&mut pending, &user_tx, &config).await;
				}
		}
	}
}

fn handle_raw_event(
	event: notify::Event,
	pending: &mut HashMap<PathBuf, DebounceState>,
	target: &CompiledTarget,
	config: &Config,
	root_path: &Path,
) {
	use notify::EventKind as NK;
	let kind = match event.kind {
		NK::Create(_) => EventKind::Create,
		NK::Modify(_) => EventKind::Modify,
		NK::Remove(_) => EventKind::Remove,
		_ => return,
	};

	for path in event.paths {
		if !target.matches(&path, config, root_path) {
			continue;
		}

		pending
			.entry(path.clone())
			.and_modify(|state| {
				let now = Instant::now();
				state.last_seen = now;

				let prev_kind = state.kind;

				if !config.coalesce {
					state.kind = kind;
					return;
				}

				match (prev_kind, kind) {
					(EventKind::Create, EventKind::Modify) => { /* Keep Create */ }
					(EventKind::Create, EventKind::Remove) => {
						state.kind = EventKind::Remove;
					}
					(EventKind::Modify, EventKind::Remove) => {
						state.kind = EventKind::Remove;
					}
					(EventKind::Remove, EventKind::Modify) => {
						// Ignore noise
					}
					_ => {
						state.kind = kind;
					}
				}
			})
			.or_insert(DebounceState {
				last_seen: Instant::now(),
				kind,
			});
	}
}

async fn flush_pending(
	pending: &mut HashMap<PathBuf, DebounceState>,
	tx: &broadcast::Sender<Event>,
	config: &Config,
) {
	let now = Instant::now();
	let mut to_remove = Vec::new();

	for (path, state) in pending.iter() {
		if now.duration_since(state.last_seen) >= config.debounce {
			let kind = state.kind;
			let allowed = match &config.listen_events {
				None => true,
				Some(list) => list.contains(&kind),
			};

			if allowed {
				let event = Event {
					paths: vec![path.clone()],
					kind,
				};
				let _ = tx.send(event);
			}
			to_remove.push(path.clone());
		}
	}

	for path in to_remove {
		pending.remove(&path);
	}
}