From 1b523a924d52c323a65e5e9bd56e9982f7cea4eb Mon Sep 17 00:00:00 2001
From: Codex <codex@openai.com>
Date: Sun, 13 Sep 2026 13:19:33 +0200
Subject: [PATCH] Model vocalist section assignments

---
 .../Domain/SongProject.swift                  | 43 ++++++++++++++++++
 .../SongProjectModelTests.swift               | 44 +++++++++++++++++++
 docs/TASKS.md                                 |  2 +-
 3 files changed, 88 insertions(+), 1 deletion(-)

diff --git a/Sources/MusicAssistantCore/Domain/SongProject.swift b/Sources/MusicAssistantCore/Domain/SongProject.swift
index aab5e60..c6435a5 100644
--- a/Sources/MusicAssistantCore/Domain/SongProject.swift
+++ b/Sources/MusicAssistantCore/Domain/SongProject.swift
@@ -169,6 +169,44 @@ public extension SongProject {
         }
     }
 
+    var vocalistIDs: Set<String> {
+        Set(vocalists.map(\.id))
+    }
+
+    func vocalist(for vocalistID: String) -> Vocalist? {
+        vocalists.first { $0.id == vocalistID }
+    }
+
+    func vocalistsAssigned(toSectionID sectionID: String) -> [Vocalist] {
+        vocalists.filter { $0.assignedSections.contains(sectionID) }
+    }
+
+    mutating func upsertVocalist(_ vocalist: Vocalist) {
+        var normalizedVocalist = vocalist
+        normalizedVocalist.assignedSections = Self.uniqueOrderedIDs(vocalist.assignedSections)
+
+        if let index = vocalists.firstIndex(where: { $0.id == vocalist.id }) {
+            vocalists[index] = normalizedVocalist
+        } else {
+            vocalists.append(normalizedVocalist)
+        }
+    }
+
+    mutating func removeVocalist(id vocalistID: String) {
+        vocalists.removeAll { $0.id == vocalistID }
+    }
+
+    mutating func assignSection(_ sectionID: String, toVocalistID vocalistID: String) {
+        guard let index = vocalists.firstIndex(where: { $0.id == vocalistID }) else { return }
+        guard !vocalists[index].assignedSections.contains(sectionID) else { return }
+        vocalists[index].assignedSections.append(sectionID)
+    }
+
+    mutating func unassignSection(_ sectionID: String, fromVocalistID vocalistID: String) {
+        guard let index = vocalists.firstIndex(where: { $0.id == vocalistID }) else { return }
+        vocalists[index].assignedSections.removeAll { $0 == sectionID }
+    }
+
     mutating func appendSection(_ section: SongSection) {
         var orderedSection = section
         orderedSection.order = nextSectionOrder
@@ -200,6 +238,11 @@ public extension SongProject {
             return orderedSection
         }
     }
+
+    private static func uniqueOrderedIDs(_ ids: [String]) -> [String] {
+        var seenIDs = Set<String>()
+        return ids.filter { seenIDs.insert($0).inserted }
+    }
 }
 
 public enum ConversationMode: String, Codable, Equatable, Sendable {
diff --git a/Tests/MusicAssistantCoreTests/SongProjectModelTests.swift b/Tests/MusicAssistantCoreTests/SongProjectModelTests.swift
index 896e4a5..e86d8e1 100644
--- a/Tests/MusicAssistantCoreTests/SongProjectModelTests.swift
+++ b/Tests/MusicAssistantCoreTests/SongProjectModelTests.swift
@@ -191,4 +191,48 @@ final class SongProjectModelTests: XCTestCase {
         XCTAssertEqual(project.selectedInstrumentIDs, ["violin"])
         XCTAssertEqual(project.instrumentTrack(for: "oud")?.placements, [introPlacement])
     }
+
+    func testMultipleVocalistsCanBeAssignedToSections() {
+        var project = SongProject(
+            id: "project-6",
+            title: "Vocal Arrangement",
+            idea: "Lead and harmony share selected sections"
+        )
+        let lead = Vocalist(
+            id: "lead",
+            label: "Lead",
+            voiceType: "tenor",
+            genderSelection: "male",
+            performanceStyle: "sung",
+            assignedSections: ["verse", "verse"]
+        )
+        let harmony = Vocalist(
+            id: "harmony",
+            label: "Harmony",
+            voiceType: "alto",
+            genderSelection: "female",
+            performanceStyle: "harmony"
+        )
+
+        project.upsertVocalist(lead)
+        project.upsertVocalist(harmony)
+        project.assignSection("chorus", toVocalistID: "lead")
+        project.assignSection("chorus", toVocalistID: "lead")
+        project.assignSection("chorus", toVocalistID: "harmony")
+        project.assignSection("bridge", toVocalistID: "harmony")
+
+        XCTAssertEqual(project.vocalistIDs, ["lead", "harmony"])
+        XCTAssertEqual(project.vocalist(for: "lead")?.assignedSections, ["verse", "chorus"])
+        XCTAssertEqual(project.vocalist(for: "harmony")?.assignedSections, ["chorus", "bridge"])
+        XCTAssertEqual(project.vocalistsAssigned(toSectionID: "chorus").map(\.id), ["lead", "harmony"])
+
+        project.unassignSection("chorus", fromVocalistID: "lead")
+
+        XCTAssertEqual(project.vocalist(for: "lead")?.assignedSections, ["verse"])
+        XCTAssertEqual(project.vocalistsAssigned(toSectionID: "chorus").map(\.id), ["harmony"])
+
+        project.removeVocalist(id: "harmony")
+
+        XCTAssertNil(project.vocalist(for: "harmony"))
+    }
 }
diff --git a/docs/TASKS.md b/docs/TASKS.md
index d921947..6cd85bf 100644
--- a/docs/TASKS.md
+++ b/docs/TASKS.md
@@ -24,7 +24,7 @@ requirement is missing and blocks implementation, record it in
 -   [x] Model genres/styles as multi-select.
 -   [x] Model song sections with order and optional timestamps.
 -   [x] Model instruments, variants, roles and placements.
--   [ ] Model multiple vocalists and section assignments.
+-   [x] Model multiple vocalists and section assignments.
 -   [ ] Model language/dialect and Arabic pronunciation settings.
 -   [ ] Model BPM, key, scale and maqam with Manual/Auto state.
 -   [ ] Model emotional arc and production directions.