feat(vectors): add vector builder with MB and Qobuz sources

- Add weights.rs with configurable RelationshipWeights
- Add builder.rs with ArtistVectorBuilder for constructing vectors
- Integrate MusicBrainz relationships (members, groups, collaborators)
- Integrate Qobuz similar artists API
- Add ensure_vector() with TTL for lazy building
- Add resolve_qobuz_to_mbid() for ID resolution via name search
- 21 tests passing (sparse_vector, store, weights, builder)

src-tauri/src/artist_vectors/builder.rs

@@ -0,0 +1,374 @@
+//! Vector builder - constructs artist vectors from MusicBrainz and Qobuz data
+//!
+//! This module integrates with MusicBrainz for relationship data and Qobuz
+//! for similarity data to build sparse vectors for each artist.
+
+use std::sync::Arc;
+use tokio::sync::Mutex;
+
+use crate::api::QobuzClient;
+use crate::musicbrainz::models::{
+    ArtistFullResponse, ArtistRelationships, Period, RelatedArtist,
+};
+use crate::musicbrainz::{MusicBrainzCache, MusicBrainzClient};
+
+use super::sparse_vector::SparseVector;
+use super::store::ArtistVectorStore;
+use super::weights::RelationshipWeights;
+
+/// Builder for constructing artist vectors from multiple data sources
+pub struct ArtistVectorBuilder {
+    /// Vector store for persistence
+    store: Arc<Mutex<ArtistVectorStore>>,
+    /// MusicBrainz client for relationship data
+    mb_client: Arc<MusicBrainzClient>,
+    /// MusicBrainz cache
+    mb_cache: Arc<Mutex<MusicBrainzCache>>,
+    /// Qobuz client for similar artists
+    qobuz_client: Arc<Mutex<QobuzClient>>,
+    /// Configurable weights
+    weights: RelationshipWeights,
+}
+
+/// Result of building a vector
+#[derive(Debug, Clone)]
+pub struct BuildResult {
+    /// The built vector
+    pub vector: SparseVector,
+    /// Number of MusicBrainz relationships found
+    pub mb_relations_count: usize,
+    /// Number of Qobuz similar artists found
+    pub qobuz_similar_count: usize,
+    /// Sources that contributed to the vector
+    pub sources: Vec<String>,
+}
+
+impl ArtistVectorBuilder {
+    /// Create a new builder with the given dependencies
+    pub fn new(
+        store: Arc<Mutex<ArtistVectorStore>>,
+        mb_client: Arc<MusicBrainzClient>,
+        mb_cache: Arc<Mutex<MusicBrainzCache>>,
+        qobuz_client: Arc<Mutex<QobuzClient>>,
+        weights: RelationshipWeights,
+    ) -> Self {
+        Self {
+            store,
+            mb_client,
+            mb_cache,
+            qobuz_client,
+            weights,
+        }
+    }
+
+    /// Build a vector for an artist, fetching data from all sources
+    ///
+    /// This method:
+    /// 1. Fetches MusicBrainz relationships (members, groups, collaborators)
+    /// 2. Fetches Qobuz similar artists (if Qobuz ID available)
+    /// 3. Combines all data into a weighted sparse vector
+    /// 4. Persists the vector to the store
+    pub async fn build_vector(
+        &self,
+        artist_mbid: &str,
+        artist_name: Option<&str>,
+        qobuz_artist_id: Option<u64>,
+    ) -> Result<BuildResult, String> {
+        let mut vector = SparseVector::new();
+        let mut sources = Vec::new();
+        let mut mb_relations_count = 0;
+        let mut qobuz_similar_count = 0;
+
+        // 1. Get or create index for this artist
+        {
+            let mut store = self.store.lock().await;
+            store.get_or_create_idx(artist_mbid, artist_name)?;
+        }
+
+        // 2. Fetch MusicBrainz relationships
+        match self.build_from_musicbrainz(artist_mbid).await {
+            Ok((mb_vec, count)) => {
+                vector = vector.add(&mb_vec);
+                mb_relations_count = count;
+                if count > 0 {
+                    sources.push("musicbrainz".to_string());
+                }
+            }
+            Err(e) => {
+                log::warn!("Failed to fetch MusicBrainz relations for {}: {}", artist_mbid, e);
+            }
+        }
+
+        // 3. Fetch Qobuz similar artists (if we have the ID)
+        if let Some(qobuz_id) = qobuz_artist_id {
+            match self.build_from_qobuz(qobuz_id).await {
+                Ok((qobuz_vec, count)) => {
+                    vector = vector.add(&qobuz_vec);
+                    qobuz_similar_count = count;
+                    if count > 0 {
+                        sources.push("qobuz".to_string());
+                    }
+                }
+                Err(e) => {
+                    log::warn!("Failed to fetch Qobuz similar for {}: {}", qobuz_id, e);
+                }
+            }
+        }
+
+        // 4. Persist the vector
+        {
+            let mut store = self.store.lock().await;
+
+            // Store MB relationships
+            if mb_relations_count > 0 {
+                // We need to rebuild just the MB part for proper source tagging
+                if let Ok((mb_vec, _)) = self.build_from_musicbrainz(artist_mbid).await {
+                    store.set_vector(artist_mbid, &mb_vec, "musicbrainz")?;
+                }
+            }
+
+            // Store Qobuz similarities
+            if qobuz_similar_count > 0 {
+                if let Some(qobuz_id) = qobuz_artist_id {
+                    if let Ok((qobuz_vec, _)) = self.build_from_qobuz(qobuz_id).await {
+                        store.set_vector(artist_mbid, &qobuz_vec, "qobuz")?;
+                    }
+                }
+            }
+        }
+
+        Ok(BuildResult {
+            vector,
+            mb_relations_count,
+            qobuz_similar_count,
+            sources,
+        })
+    }
+
+    /// Build vector component from MusicBrainz relationships
+    async fn build_from_musicbrainz(&self, artist_mbid: &str) -> Result<(SparseVector, usize), String> {
+        // Try cache first
+        let cached = {
+            let cache = self.mb_cache.lock().await;
+            cache.get_artist_relations(artist_mbid)?
+        };
+
+        let relations = if let Some(rel) = cached {
+            rel
+        } else {
+            // Fetch from API
+            let response = self.mb_client.get_artist_with_relations(artist_mbid).await?;
+
+            // Extract relationships from raw response
+            let extracted = extract_relationships(&response);
+
+            // Cache it
+            {
+                let cache = self.mb_cache.lock().await;
+                cache.set_artist_relations(artist_mbid, &extracted)?;
+            }
+
+            extracted
+        };
+
+        let mut vector = SparseVector::new();
+        let mut count = 0;
+
+        // Get store for index lookups
+        let mut store = self.store.lock().await;
+
+        // Process members (band → person)
+        for member in &relations.members {
+            let idx = store.get_or_create_idx(&member.mbid, Some(&member.name))?;
+            let weight = self.weights.member_of_band;
+            vector.set(idx, weight);
+            count += 1;
+        }
+
+        // Process past members (slightly lower weight)
+        for member in &relations.past_members {
+            let idx = store.get_or_create_idx(&member.mbid, Some(&member.name))?;
+            let weight = self.weights.member_of_band * 0.8; // Past members slightly less relevant
+            vector.set(idx, weight);
+            count += 1;
+        }
+
+        // Process groups (person → band)
+        for group in &relations.groups {
+            let idx = store.get_or_create_idx(&group.mbid, Some(&group.name))?;
+            let weight = self.weights.has_member;
+            vector.set(idx, weight);
+            count += 1;
+        }
+
+        // Process collaborators
+        for collab in &relations.collaborators {
+            let idx = store.get_or_create_idx(&collab.mbid, Some(&collab.name))?;
+            let weight = self.weights.collaboration;
+            vector.set(idx, weight);
+            count += 1;
+        }
+
+        Ok((vector, count))
+    }
+
+    /// Build vector component from Qobuz similar artists
+    async fn build_from_qobuz(&self, qobuz_artist_id: u64) -> Result<(SparseVector, usize), String> {
+        let similar = {
+            let client = self.qobuz_client.lock().await;
+            client
+                .get_similar_artists(qobuz_artist_id, 20, 0)
+                .await
+                .map_err(|e| format!("Qobuz API error: {}", e))?
+        };
+
+        let mut vector = SparseVector::new();
+        let mut count = 0;
+        let mut store = self.store.lock().await;
+
+        for artist in similar.items {
+            // We need to resolve Qobuz artist to MBID
+            // For now, use a synthetic MBID based on Qobuz ID (we'll improve this later)
+            let synthetic_mbid = format!("qobuz:{}", artist.id);
+
+            let idx = store.get_or_create_idx(&synthetic_mbid, Some(&artist.name))?;
+            let weight = self.weights.qobuz_similar;
+            vector.set(idx, weight);
+            count += 1;
+        }
+
+        Ok((vector, count))
+    }
+
+    /// Ensure a vector exists and is fresh, building if necessary
+    ///
+    /// Returns true if vector was built/updated, false if existing vector was used
+    pub async fn ensure_vector(
+        &self,
+        artist_mbid: &str,
+        artist_name: Option<&str>,
+        qobuz_artist_id: Option<u64>,
+        max_age_days: i64,
+    ) -> Result<bool, String> {
+        let max_age_secs = max_age_days * 24 * 60 * 60;
+
+        // Check if we have a fresh vector
+        let has_fresh = {
+            let store = self.store.lock().await;
+            store.has_fresh_vector(artist_mbid, max_age_secs)
+        };
+
+        if has_fresh {
+            return Ok(false);
+        }
+
+        // Build new vector
+        self.build_vector(artist_mbid, artist_name, qobuz_artist_id).await?;
+
+        Ok(true)
+    }
+}
+
+/// Resolve a Qobuz artist ID to a MusicBrainz ID by searching
+///
+/// This is a best-effort match based on artist name
+pub async fn resolve_qobuz_to_mbid(
+    qobuz_client: &Arc<Mutex<QobuzClient>>,
+    mb_client: &Arc<MusicBrainzClient>,
+    _mb_cache: &Arc<Mutex<MusicBrainzCache>>,
+    qobuz_artist_id: u64,
+) -> Result<Option<String>, String> {
+    // Get artist name from Qobuz
+    let artist_name = {
+        let client = qobuz_client.lock().await;
+        let artist = client
+            .get_artist(qobuz_artist_id, false)
+            .await
+            .map_err(|e| format!("Failed to get Qobuz artist: {}", e))?;
+        artist.name
+    };
+
+    // Search MusicBrainz for this artist
+    let mb_result = mb_client.search_artist(&artist_name).await?;
+
+    // Return first high-confidence match (score >= 80)
+    if let Some(artist) = mb_result.artists.first() {
+        if let Some(score) = artist.score {
+            if score >= 80 {
+                return Ok(Some(artist.id.clone()));
+            }
+        }
+    }
+
+    Ok(None)
+}
+
+/// Extract ArtistRelationships from raw MusicBrainz response
+fn extract_relationships(artist: &ArtistFullResponse) -> ArtistRelationships {
+    let mut members = Vec::new();
+    let mut past_members = Vec::new();
+    let mut groups = Vec::new();
+    let mut collaborators = Vec::new();
+
+    if let Some(relations) = &artist.relations {
+        for relation in relations {
+            let Some(related_artist) = &relation.artist else {
+                continue;
+            };
+
+            let related = RelatedArtist {
+                mbid: related_artist.id.clone(),
+                name: related_artist.name.clone(),
+                role: relation.attributes.as_ref().and_then(|a| a.first().cloned()),
+                period: Some(Period {
+                    begin: relation.begin.clone(),
+                    end: relation.end.clone(),
+                }),
+                ended: relation.ended.unwrap_or(false),
+            };
+
+            match relation.relation_type.as_str() {
+                "member of band" => {
+                    if relation.direction.as_deref() == Some("backward") {
+                        // We're viewing a BAND, the related artist is a MEMBER
+                        if related.ended {
+                            past_members.push(related);
+                        } else {
+                            members.push(related);
+                        }
+                    } else {
+                        // We're viewing a PERSON, the related artist is a BAND/GROUP
+                        groups.push(related);
+                    }
+                }
+                "collaboration" => {
+                    collaborators.push(related);
+                }
+                _ => {}
+            }
+        }
+    }
+
+    ArtistRelationships {
+        members,
+        past_members,
+        groups,
+        collaborators,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    // Integration tests would require mocking the clients
+    // For now, we test the weight application logic
+
+    #[test]
+    fn test_weights_applied() {
+        let weights = RelationshipWeights::default();
+
+        assert!(weights.member_of_band > weights.collaboration);
+        assert!(weights.collaboration > weights.shared_tag);
+    }
+}

src-tauri/src/artist_vectors/mod.rs

@@ -43,8 +43,12 @@
 //!    ...]
 //! ```
 
+pub mod builder;
 pub mod sparse_vector;
 pub mod store;
+pub mod weights;
 
+pub use builder::{ArtistVectorBuilder, BuildResult};
 pub use sparse_vector::SparseVector;
 pub use store::{ArtistVectorStore, ArtistVectorStoreState, SimilarArtist, StoreStats, VectorEntry};
+pub use weights::RelationshipWeights;

src-tauri/src/artist_vectors/weights.rs

@@ -0,0 +1,200 @@
+//! Configurable weights for different relationship types
+//!
+//! These weights determine how strongly different types of relationships
+//! contribute to artist similarity vectors.
+
+use serde::{Deserialize, Serialize};
+
+/// Weights for different relationship types when building artist vectors
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct RelationshipWeights {
+    // === MusicBrainz artist-to-artist relationships ===
+
+    /// Weight for band membership (artist was/is member of group)
+    /// Strongest connection - same creative unit
+    pub member_of_band: f32,
+
+    /// Weight for collaboration (artists worked together)
+    pub collaboration: f32,
+
+    /// Weight for "is person" in a group (reverse of member_of_band)
+    pub has_member: f32,
+
+    /// Weight for founder relationship
+    pub founder: f32,
+
+    // === MusicBrainz recording/release relationships ===
+
+    /// Weight for performer credit on a recording
+    pub performer: f32,
+
+    /// Weight for composer credit
+    pub composer: f32,
+
+    /// Weight for producer credit
+    pub producer: f32,
+
+    /// Weight for conductor credit
+    pub conductor: f32,
+
+    /// Weight for engineer/mixer credit
+    pub engineer: f32,
+
+    // === Qobuz relationships ===
+
+    /// Weight for Qobuz similar artists
+    pub qobuz_similar: f32,
+
+    // === Tag-based relationships ===
+
+    /// Weight for shared MusicBrainz tags (genres)
+    pub shared_tag: f32,
+
+    // === Behavioral relationships ===
+
+    /// Weight for user listening affinity (artists played together)
+    pub user_affinity: f32,
+}
+
+impl Default for RelationshipWeights {
+    fn default() -> Self {
+        Self {
+            // Band relationships - strongest
+            member_of_band: 1.0,
+            has_member: 0.9,
+            founder: 0.85,
+            collaboration: 0.8,
+
+            // Credit relationships - medium
+            performer: 0.6,
+            composer: 0.55,
+            producer: 0.5,
+            conductor: 0.5,
+            engineer: 0.3,
+
+            // Qobuz similarity - good signal
+            qobuz_similar: 0.7,
+
+            // Tags - weak but useful
+            shared_tag: 0.3,
+
+            // User behavior - medium
+            user_affinity: 0.5,
+        }
+    }
+}
+
+impl RelationshipWeights {
+    /// Create weights optimized for discovering band-related artists
+    pub fn band_focused() -> Self {
+        Self {
+            member_of_band: 1.0,
+            has_member: 1.0,
+            founder: 0.9,
+            collaboration: 0.7,
+            performer: 0.4,
+            composer: 0.3,
+            producer: 0.2,
+            conductor: 0.3,
+            engineer: 0.1,
+            qobuz_similar: 0.5,
+            shared_tag: 0.2,
+            user_affinity: 0.3,
+        }
+    }
+
+    /// Create weights optimized for sound-alike discovery
+    pub fn similarity_focused() -> Self {
+        Self {
+            member_of_band: 0.6,
+            has_member: 0.5,
+            founder: 0.5,
+            collaboration: 0.7,
+            performer: 0.5,
+            composer: 0.4,
+            producer: 0.3,
+            conductor: 0.3,
+            engineer: 0.2,
+            qobuz_similar: 1.0,  // Prioritize Qobuz similarity
+            shared_tag: 0.5,
+            user_affinity: 0.6,
+        }
+    }
+
+    /// Get weight for a MusicBrainz relationship type
+    pub fn weight_for_mb_relation(&self, relation_type: &str) -> f32 {
+        match relation_type.to_lowercase().as_str() {
+            // Band relationships
+            "member of band" | "member_of_band" => self.member_of_band,
+            "has member" | "has_member" => self.has_member,
+            "founder" | "founded" => self.founder,
+
+            // Collaboration
+            "collaboration" | "collaborated" | "collaborator" => self.collaboration,
+
+            // Performance credits
+            "performer" | "vocal" | "instrument" | "performing orchestra"
+            | "orchestra" | "chorus master" => self.performer,
+
+            // Composition
+            "composer" | "writer" | "lyricist" | "librettist" | "arranger" => self.composer,
+
+            // Production
+            "producer" | "executive producer" | "co-producer" => self.producer,
+            "conductor" => self.conductor,
+            "engineer" | "mix" | "mixer" | "mastering" | "recording" => self.engineer,
+
+            // Unknown - use small default weight
+            _ => 0.2,
+        }
+    }
+
+    /// Get weight for a source type string
+    pub fn weight_for_source(&self, source: &str) -> f32 {
+        match source {
+            "qobuz_similar" => self.qobuz_similar,
+            "shared_tag" => self.shared_tag,
+            "user_affinity" => self.user_affinity,
+            s if s.starts_with("mb:") => {
+                let rel_type = &s[3..];
+                self.weight_for_mb_relation(rel_type)
+            }
+            _ => 0.2,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_default_weights() {
+        let weights = RelationshipWeights::default();
+
+        assert_eq!(weights.member_of_band, 1.0);
+        assert!(weights.qobuz_similar > weights.shared_tag);
+        assert!(weights.collaboration > weights.engineer);
+    }
+
+    #[test]
+    fn test_mb_relation_weight() {
+        let weights = RelationshipWeights::default();
+
+        assert_eq!(weights.weight_for_mb_relation("member of band"), 1.0);
+        assert_eq!(weights.weight_for_mb_relation("collaboration"), 0.8);
+        assert_eq!(weights.weight_for_mb_relation("producer"), 0.5);
+
+        // Unknown type gets default
+        assert_eq!(weights.weight_for_mb_relation("unknown_type"), 0.2);
+    }
+
+    #[test]
+    fn test_source_weight() {
+        let weights = RelationshipWeights::default();
+
+        assert_eq!(weights.weight_for_source("qobuz_similar"), 0.7);
+        assert_eq!(weights.weight_for_source("mb:member of band"), 1.0);
+        assert_eq!(weights.weight_for_source("mb:collaboration"), 0.8);
+    }
+}

src-tauri/src/musicbrainz/mod.rs

@@ -22,9 +22,10 @@ pub mod smart_playlists;
 pub use cache::{CacheStats, MusicBrainzCache, MusicBrainzCacheState};
 pub use client::{MusicBrainzClient, MusicBrainzConfig};
 pub use models::{
-    AlbumAppearance, ArtistRelationships, ArtistType, MatchConfidence, Medium, MediumTrack,
-    MusicianAppearances, MusicianConfidence, Period, RelatedArtist, ReleaseFullResponse,
-    ReleaseSearchResponse, ResolvedArtist, ResolvedMusician, ResolvedRelease, ResolvedTrack, Tag,
+    AlbumAppearance, ArtistFullResponse, ArtistRelationships, ArtistType, MatchConfidence, Medium,
+    MediumTrack, MusicianAppearances, MusicianConfidence, Period, RelatedArtist, Relation,
+    ReleaseFullResponse, ReleaseSearchResponse, ResolvedArtist, ResolvedMusician, ResolvedRelease,
+    ResolvedTrack, Tag,
 };
 
 use std::sync::Arc;