Initial commit: Rust notification badge daemon for KDE Plasma 6

Monitors D-Bus for desktop notifications and emits Unity LauncherEntry
badge updates so KDE Plasma task manager shows notification counts.

- Streaming dbus-monitor parser with app matching and lifecycle tracking
- KWin window discovery for automatic desktop file detection
- Systemd user service, Makefile install/uninstall targets
- 38 tests (32 unit + 6 integration), 97% line coverage via cargo-llvm-cov
- CodeScene code health: 10/10 on all source files

1 files changed, 157 insertions, 0 deletions

diff --git a/src/discovery.rs b/src/discovery.rs
new file mode 100644
index 0000000..4418068
--- /dev/null
+++ b/src/discovery.rs
@@ -0,0 +1,157 @@
+use regex::Regex;
+use std::collections::HashMap;
+
+/// Query KWin for open windows and return a pattern map:
+/// pattern (lowercase) -> "application://<desktop_file>.desktop"
+///
+/// Two keys per app:
+/// - The last dot-segment (e.g. "firefox") -- matches native app_name
+/// - The full desktop file ID (e.g. "org.mozilla.firefox") -- matches Flatpak desktop-entry hints
+pub fn discover_apps() -> HashMap<String, String> {
+    discover_apps_with(
+        crate::dbus_glue::kwin_match,
+        crate::dbus_glue::kwin_window_info,
+    )
+}
+
+/// Testable version that accepts function pointers for the D-Bus calls.
+pub fn discover_apps_with<F, G>(match_fn: F, info_fn: G) -> HashMap<String, String>
+where
+    F: Fn() -> Option<String>,
+    G: Fn(&str) -> Option<String>,
+{
+    let output = match match_fn() {
+        Some(s) => s,
+        None => return HashMap::new(),
+    };
+
+    let uuid_re = Regex::new(r"\{([0-9a-f-]{36})\}").unwrap();
+    let desktop_re = Regex::new(r"'desktopFile':\s*<'([^']+)'>").unwrap();
+
+    let mut map = HashMap::new();
+
+    for caps in uuid_re.captures_iter(&output) {
+        let uid = &caps[1];
+        if let Some(entries) = extract_desktop_entries(uid, &info_fn, &desktop_re) {
+            map.extend(entries);
+        }
+    }
+
+    map
+}
+
+fn extract_desktop_entries<G>(
+    uid: &str,
+    info_fn: &G,
+    desktop_re: &Regex,
+) -> Option<Vec<(String, String)>>
+where
+    G: Fn(&str) -> Option<String>,
+{
+    let info_output = info_fn(uid)?;
+    let dcaps = desktop_re.captures(&info_output)?;
+    let desktop_file = &dcaps[1];
+    if desktop_file.is_empty() {
+        return None;
+    }
+    let key = desktop_file
+        .rsplit('.')
+        .next()
+        .unwrap_or(desktop_file)
+        .to_lowercase();
+    let desktop_id = format!("application://{desktop_file}.desktop");
+    Some(vec![
+        (key, desktop_id.clone()),
+        (desktop_file.to_lowercase(), desktop_id),
+    ])
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_discover_apps_parses_kwin_output() {
+        let match_output = r#"([('0_{aabbccdd-1234-5678-9abc-def012345678}', 'Some Window — Firefox', 'firefox', 100, 0.8, {'subtext': <'Activate running window on Desktop 1'>}), ('0_{11223344-5566-7788-99aa-bbccddeeff00}', 'Slack', 'com.slack.Slack', 100, 0.8, {'subtext': <'Activate running window on Desktop 1'>})],)"#;
+
+        let info_firefox =
+            r#"({'desktopFile': <'org.mozilla.firefox'>, 'caption': <'Some Window — Firefox'>},)"#;
+        let info_slack = r#"({'desktopFile': <'com.slack.Slack'>, 'caption': <'Slack'>},)"#;
+
+        let match_fn = || Some(match_output.to_string());
+        let info_fn = |uuid: &str| match uuid {
+            "aabbccdd-1234-5678-9abc-def012345678" => Some(info_firefox.to_string()),
+            "11223344-5566-7788-99aa-bbccddeeff00" => Some(info_slack.to_string()),
+            _ => None,
+        };
+
+        let map = discover_apps_with(match_fn, info_fn);
+
+        assert_eq!(
+            map.get("firefox"),
+            Some(&"application://org.mozilla.firefox.desktop".to_string())
+        );
+        assert_eq!(
+            map.get("org.mozilla.firefox"),
+            Some(&"application://org.mozilla.firefox.desktop".to_string())
+        );
+        assert_eq!(
+            map.get("slack"),
+            Some(&"application://com.slack.Slack.desktop".to_string())
+        );
+        assert_eq!(
+            map.get("com.slack.slack"),
+            Some(&"application://com.slack.Slack.desktop".to_string())
+        );
+    }
+
+    #[test]
+    fn test_discover_apps_empty_match() {
+        let map = discover_apps_with(|| None, |_| None);
+        assert!(map.is_empty());
+    }
+
+    #[test]
+    fn test_discover_apps_no_uuids() {
+        let map = discover_apps_with(|| Some("([],)".to_string()), |_| None);
+        assert!(map.is_empty());
+    }
+
+    #[test]
+    fn test_discover_apps_empty_desktop_file() {
+        let match_output =
+            r#"([('0_{aabbccdd-1234-5678-9abc-def012345678}', 'Window', 'icon', 100, 0.8, {})],)"#;
+        let info_output = r#"({'desktopFile': <''>, 'caption': <'Window'>},)"#;
+
+        let map = discover_apps_with(
+            || Some(match_output.to_string()),
+            |_| Some(info_output.to_string()),
+        );
+        assert!(map.is_empty());
+    }
+
+    #[test]
+    fn test_discover_apps_window_info_fails() {
+        let match_output =
+            r#"([('0_{aabbccdd-1234-5678-9abc-def012345678}', 'Window', 'icon', 100, 0.8, {})],)"#;
+
+        let map = discover_apps_with(|| Some(match_output.to_string()), |_| None);
+        assert!(map.is_empty());
+    }
+
+    #[test]
+    fn test_discover_apps_deduplicates_same_app() {
+        // Two windows from the same app
+        let match_output = r#"([('0_{aaaaaaaa-1234-5678-9abc-def012345678}', 'Tab 1 — Firefox', 'firefox', 100, 0.8, {}), ('0_{bbbbbbbb-1234-5678-9abc-def012345678}', 'Tab 2 — Firefox', 'firefox', 100, 0.8, {})],)"#;
+        let info_output = r#"({'desktopFile': <'org.mozilla.firefox'>, 'caption': <'Firefox'>},)"#;
+
+        let map = discover_apps_with(
+            || Some(match_output.to_string()),
+            |_| Some(info_output.to_string()),
+        );
+        // Should have exactly 2 entries (short name + full name), not duplicated
+        assert_eq!(map.len(), 2);
+        assert!(map.contains_key("firefox"));
+        assert!(map.contains_key("org.mozilla.firefox"));
+    }
+}