feat(snippets): implement keyboard event handling

This commit sets up the codebase for the Snippets feature. Specifically, it implements an InputManager trait, which listens for, well, inputs. In the future, we will be using this to keep track of the user's keypresses, triggering the text expansion when the trigger word is entered.

src-tauri/src/snippets/input_manager.rs

@@ -0,0 +1,98 @@
+use anyhow::Result;
+use rdev::Key;
+use std::thread;
+
+#[derive(Debug)]
+pub enum InputEvent {
+    KeyPress(Key),
+}
+
+pub trait InputManager {
+    fn start_listening(&self, callback: Box<dyn Fn(InputEvent) + Send>) -> Result<()>;
+    fn inject_text(&self, text: &str) -> Result<()>;
+}
+
+pub struct RdevInputManager;
+
+impl RdevInputManager {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl InputManager for RdevInputManager {
+    fn start_listening(&self, callback: Box<dyn Fn(InputEvent) + Send>) -> Result<()> {
+        thread::spawn(move || {
+            let cb = move |event: rdev::Event| {
+                if let rdev::EventType::KeyPress(key) = event.event_type {
+                    callback(InputEvent::KeyPress(key));
+                }
+            };
+            if let Err(error) = rdev::listen(cb) {
+                eprintln!("rdev error: {:?}", error)
+            }
+        });
+        Ok(())
+    }
+
+    fn inject_text(&self, _text: &str) -> Result<()> {
+        unimplemented!()
+    }
+}
+
+// this implementation for wayland, because wayland is a pain and rdev no worky
+#[cfg(target_os = "linux")]
+pub struct EvdevInputManager;
+
+#[cfg(target_os = "linux")]
+impl EvdevInputManager {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+#[cfg(target_os = "linux")]
+impl InputManager for EvdevInputManager {
+    fn start_listening(&self, callback: Box<dyn Fn(InputEvent) + Send>) -> Result<()> {
+        let devices = evdev::enumerate()
+            .map(|t| t.1)
+            .filter(|d| {
+                d.supported_keys()
+                    .map_or(false, |keys| keys.contains(evdev::KeyCode::KEY_ENTER))
+            })
+            .collect::<Vec<_>>();
+
+        if devices.is_empty() {
+            return Err(anyhow::anyhow!(
+                "No keyboard devices found. Check permissions for /dev/input/*."
+            ));
+        }
+
+        for mut device in devices {
+            let cb = callback.as_ref();
+            thread::spawn(move || {
+                loop {
+                    match device.fetch_events() {
+                        Ok(events) => {
+                            for ev in events {
+                                if ev.event_type() == evdev::EventType::KEY && ev.value() == 1 {
+                                    println!("[evdev] Raw key press: code={}", ev.code());
+                                }
+                            }
+                        }
+                        Err(e) => {
+                            eprintln!("Error fetching evdev events: {}", e);
+                            break;
+                        }
+                    }
+                }
+            });
+        }
+
+        Ok(())
+    }
+
+    fn inject_text(&self, _text: &str) -> Result<()> {
+        unimplemented!()
+    }
+}