Added the playlist generator

shanty-data/src/musicbrainz.rs

@@ -21,14 +21,21 @@ pub struct MusicBrainzFetcher {
 
 impl MusicBrainzFetcher {
     pub fn new() -> DataResult<Self> {
+        Self::with_limiter(RateLimiter::new(RATE_LIMIT))
+    }
+
+    /// Create a fetcher that shares a rate limiter with other MB clients.
+    pub fn with_limiter(limiter: RateLimiter) -> DataResult<Self> {
         let client = reqwest::Client::builder()
             .user_agent(USER_AGENT)
             .timeout(Duration::from_secs(30))
             .build()?;
-        Ok(Self {
-            client,
-            limiter: RateLimiter::new(RATE_LIMIT),
-        })
+        Ok(Self { client, limiter })
+    }
+
+    /// Get a clone of the rate limiter for sharing with other MB clients.
+    pub fn limiter(&self) -> RateLimiter {
+        self.limiter.clone()
     }
 
     async fn get_json<T: serde::de::DeserializeOwned>(&self, url: &str) -> DataResult<T> {
@@ -84,6 +91,24 @@ impl MusicBrainzFetcher {
             urls,
         })
     }
+
+    /// Resolve a release-group MBID to a release MBID (first release in the group).
+    pub async fn resolve_release_from_group(&self, release_group_mbid: &str) -> DataResult<String> {
+        let url = format!("{BASE_URL}/release?release-group={release_group_mbid}&fmt=json&limit=1");
+        let resp: serde_json::Value = self.get_json(&url).await?;
+
+        resp.get("releases")
+            .and_then(|r| r.as_array())
+            .and_then(|arr| arr.first())
+            .and_then(|r| r.get("id"))
+            .and_then(|id| id.as_str())
+            .map(String::from)
+            .ok_or_else(|| {
+                DataError::Other(format!(
+                    "no releases for release-group {release_group_mbid}"
+                ))
+            })
+    }
 }
 
 impl MetadataFetcher for MusicBrainzFetcher {