add http-json, rss, and media data source adapters

http-json: generic HTTP+JSON polling adapter, converts serde_json to domain Value. 4 tests.
rss: XML RSS feed parser, extracts items into Value array. 1 test.
media: Navidrome/Subsonic getNowPlaying adapter. 2 tests with fake server.

crates/adapters/media/src/lib.rs

@@ -0,0 +1,158 @@
+use std::collections::BTreeMap;
+use domain::{DataSource, DataSourcePort, Value};
+
+pub struct MediaAdapter {
+    client: reqwest::Client,
+}
+
+#[derive(Debug)]
+pub enum MediaError {
+    Request(reqwest::Error),
+    NoUrl,
+    Parse(String),
+}
+
+impl std::fmt::Display for MediaError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            MediaError::Request(e) => write!(f, "request: {e}"),
+            MediaError::NoUrl => write!(f, "no url configured"),
+            MediaError::Parse(e) => write!(f, "parse: {e}"),
+        }
+    }
+}
+
+impl MediaAdapter {
+    pub fn new() -> Self {
+        Self {
+            client: reqwest::Client::new(),
+        }
+    }
+}
+
+impl DataSourcePort for MediaAdapter {
+    type Error = MediaError;
+
+    async fn poll(&self, source: &DataSource) -> Result<Value, Self::Error> {
+        let base_url = source.config.url.as_ref().ok_or(MediaError::NoUrl)?;
+        let api_key = source.config.api_key.as_deref().unwrap_or("");
+
+        let url = format!(
+            "{base_url}/rest/getNowPlaying.view?u=kframe&t={api_key}&s=salt&v=1.16.1&c=kframe&f=json"
+        );
+
+        let resp = self.client.get(&url).send().await.map_err(MediaError::Request)?;
+        let json: serde_json::Value = resp.json().await.map_err(MediaError::Request)?;
+
+        let entries = json["subsonic-response"]["nowPlaying"]["entry"]
+            .as_array()
+            .cloned()
+            .unwrap_or_default();
+
+        if entries.is_empty() {
+            let mut result = BTreeMap::new();
+            result.insert("playing".into(), Value::Bool(false));
+            return Ok(Value::Object(result));
+        }
+
+        let entry = &entries[0];
+        let mut result = BTreeMap::new();
+        result.insert("playing".into(), Value::Bool(true));
+        result.insert("title".into(), Value::String(
+            entry["title"].as_str().unwrap_or("Unknown").into()
+        ));
+        result.insert("artist".into(), Value::String(
+            entry["artist"].as_str().unwrap_or("Unknown").into()
+        ));
+        result.insert("album".into(), Value::String(
+            entry["album"].as_str().unwrap_or("Unknown").into()
+        ));
+
+        if let Some(duration) = entry["duration"].as_u64() {
+            result.insert("duration".into(), Value::Number(duration as f64));
+        }
+
+        Ok(Value::Object(result))
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::time::Duration;
+    use domain::{DataSourceConfig, DataSourceType};
+
+    fn subsonic_response(playing: bool) -> serde_json::Value {
+        if playing {
+            serde_json::json!({
+                "subsonic-response": {
+                    "status": "ok",
+                    "nowPlaying": {
+                        "entry": [{
+                            "title": "Believer",
+                            "artist": "Imagine Dragons",
+                            "album": "Evolve",
+                            "duration": 204
+                        }]
+                    }
+                }
+            })
+        } else {
+            serde_json::json!({
+                "subsonic-response": {
+                    "status": "ok",
+                    "nowPlaying": {}
+                }
+            })
+        }
+    }
+
+    async fn start_fake_subsonic(playing: bool) -> String {
+        let app = axum::Router::new()
+            .route("/rest/getNowPlaying.view", axum::routing::get(move || async move {
+                axum::response::Json(subsonic_response(playing))
+            }));
+
+        let listener = tokio::net::TcpListener::bind("127.0.0.1:0").await.unwrap();
+        let addr = listener.local_addr().unwrap();
+        tokio::spawn(async move { axum::serve(listener, app).await.unwrap() });
+        format!("http://{addr}")
+    }
+
+    fn make_source(url: String) -> DataSource {
+        DataSource {
+            id: 1,
+            name: "navidrome".into(),
+            source_type: DataSourceType::Media,
+            poll_interval: Duration::from_secs(5),
+            config: DataSourceConfig {
+                url: Some(url),
+                headers: vec![],
+                api_key: Some("testtoken".into()),
+            },
+        }
+    }
+
+    #[tokio::test]
+    async fn returns_now_playing_info() {
+        let base = start_fake_subsonic(true).await;
+        let adapter = MediaAdapter::new();
+        let source = make_source(base);
+
+        let result = adapter.poll(&source).await.unwrap();
+
+        assert_eq!(result.get_path("$.playing"), Some(&Value::Bool(true)));
+        assert_eq!(result.get_path("$.title"), Some(&Value::String("Believer".into())));
+        assert_eq!(result.get_path("$.artist"), Some(&Value::String("Imagine Dragons".into())));
+    }
+
+    #[tokio::test]
+    async fn returns_not_playing_when_empty() {
+        let base = start_fake_subsonic(false).await;
+        let adapter = MediaAdapter::new();
+        let source = make_source(base);
+
+        let result = adapter.poll(&source).await.unwrap();
+        assert_eq!(result.get_path("$.playing"), Some(&Value::Bool(false)));
+    }
+}