feat: receive ordered stream playback queues

Sources/App/PlaybackQueue.swift

@@ -4,11 +4,14 @@ struct PlaybackQueue {
     struct Item: Identifiable {
         let id = UUID()
         let url: URL
+        var label: String? = nil
+        var displayName: String { label ?? url.lastPathComponent }
     }
 
     private(set) var items: [Item] = []
     private(set) var currentID: UUID?
-    var currentURL: URL? { items.first { $0.id == currentID }?.url }
+    var currentItem: Item? { items.first { $0.id == currentID } }
+    var currentURL: URL? { currentItem?.url }
     private var currentIndex: Int? { items.firstIndex { $0.id == currentID } }
     var canPrevious: Bool { currentIndex.map { $0 > 0 } ?? false }
     var canNext: Bool { currentIndex.map { $0 + 1 < items.count } ?? false }
@@ -18,6 +21,17 @@ struct PlaybackQueue {
         currentID = items.first?.id
     }
 
+    // Unlike file batches, stream entries already have an intentional playback order.
+    mutating func replaceStreams(_ entries: [(url: URL, label: String)]) {
+        items = entries.map { Item(url: $0.url, label: $0.label) }
+        currentID = items.first?.id
+    }
+
+    mutating func updateCurrentLabel(_ label: String) {
+        guard let index = currentIndex else { return }
+        items[index].label = label
+    }
+
     mutating func append(_ urls: [URL]) {
         items.append(contentsOf: sortedFiles(urls).map { Item(url: $0) })
     }