zeph_core/
config_watcher.rs

1// SPDX-FileCopyrightText: 2026 Andrei G <bug-ops>
2// SPDX-License-Identifier: MIT OR Apache-2.0
3
4use std::path::Path;
5use std::time::Duration;
6
7use notify_debouncer_mini::{DebouncedEventKind, new_debouncer};
8use tokio::sync::mpsc;
9
10#[derive(Clone)]
11pub enum ConfigEvent {
12    Changed,
13}
14
15pub struct ConfigWatcher {
16    _handle: tokio::task::JoinHandle<()>,
17}
18
19impl ConfigWatcher {
20    /// Start watching a config file for changes.
21    ///
22    /// Watches the parent directory and filters for the target filename.
23    /// Sends `ConfigEvent::Changed` on any modification (debounced 500ms).
24    ///
25    /// # Errors
26    ///
27    /// Returns an error if the filesystem watcher cannot be initialized
28    /// or the config file path has no parent directory.
29    pub fn start(path: &Path, tx: mpsc::Sender<ConfigEvent>) -> anyhow::Result<Self> {
30        let dir = path
31            .parent()
32            .ok_or_else(|| anyhow::anyhow!("config path has no parent directory"))?
33            .to_path_buf();
34        let filename = path
35            .file_name()
36            .ok_or_else(|| anyhow::anyhow!("config path has no filename"))?
37            .to_os_string();
38
39        let (notify_tx, mut notify_rx) = mpsc::channel(16);
40
41        let mut debouncer = new_debouncer(
42            Duration::from_millis(500),
43            move |events: Result<Vec<notify_debouncer_mini::DebouncedEvent>, notify::Error>| {
44                let events = match events {
45                    Ok(events) => events,
46                    Err(e) => {
47                        tracing::warn!("config watcher error: {e}");
48                        return;
49                    }
50                };
51
52                let has_change = events.iter().any(|e| {
53                    e.kind == DebouncedEventKind::Any
54                        && e.path.file_name().is_some_and(|n| n == filename)
55                });
56
57                if has_change {
58                    let _ = notify_tx.blocking_send(());
59                }
60            },
61        )?;
62
63        debouncer
64            .watcher()
65            .watch(&dir, notify::RecursiveMode::NonRecursive)?;
66
67        let handle = tokio::spawn(async move {
68            let _debouncer = debouncer;
69            while notify_rx.recv().await.is_some() {
70                if tx.send(ConfigEvent::Changed).await.is_err() {
71                    break;
72                }
73            }
74        });
75
76        Ok(Self { _handle: handle })
77    }
78}
79
80#[cfg(test)]
81mod tests {
82    use super::*;
83
84    #[tokio::test]
85    async fn start_with_valid_config_file() {
86        let dir = tempfile::tempdir().unwrap();
87        let config_path = dir.path().join("config.toml");
88        std::fs::write(&config_path, "key = 1").unwrap();
89        let (tx, _rx) = mpsc::channel(16);
90        let watcher = ConfigWatcher::start(&config_path, tx);
91        assert!(watcher.is_ok());
92    }
93
94    #[tokio::test]
95    async fn start_with_nonexistent_parent_fails() {
96        let (tx, _rx) = mpsc::channel(16);
97        let result = ConfigWatcher::start(Path::new("/nonexistent/dir/config.toml"), tx);
98        assert!(result.is_err());
99    }
100
101    #[tokio::test]
102    async fn detects_config_file_change() {
103        let dir = tempfile::tempdir().unwrap();
104        let config_path = dir.path().join("config.toml");
105        std::fs::write(&config_path, "initial = true").unwrap();
106
107        let (tx, mut rx) = mpsc::channel(16);
108        let _watcher = ConfigWatcher::start(&config_path, tx).unwrap();
109
110        tokio::time::sleep(Duration::from_millis(100)).await;
111        std::fs::write(&config_path, "updated = true").unwrap();
112
113        let result = tokio::time::timeout(Duration::from_secs(3), rx.recv()).await;
114        assert!(
115            result.is_ok(),
116            "expected ConfigEvent::Changed within timeout"
117        );
118    }
119
120    #[tokio::test]
121    async fn ignores_other_files_in_directory() {
122        let dir = tempfile::tempdir().unwrap();
123        let config_path = dir.path().join("config.toml");
124        std::fs::write(&config_path, "key = 1").unwrap();
125
126        let (tx, mut rx) = mpsc::channel(16);
127        let _watcher = ConfigWatcher::start(&config_path, tx).unwrap();
128
129        // Drain any late FSEvents from the initial config write before creating other file
130        tokio::time::sleep(Duration::from_millis(800)).await;
131        while rx.try_recv().is_ok() {}
132
133        let other_path = dir.path().join("other.txt");
134        std::fs::write(&other_path, "content").unwrap();
135
136        let result = tokio::time::timeout(Duration::from_millis(1500), rx.recv()).await;
137        assert!(
138            result.is_err(),
139            "should not receive event for non-config file"
140        );
141    }
142}
zeph_core/config_watcher.rs

zeph_core/
config_watcher.rs
