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) })
     }

Sources/App/StreamQueue.swift

@@ -0,0 +1,69 @@
+import Foundation
+import Darwin
+
+struct StreamQueue: Sendable {
+    struct Entry: Sendable {
+        let url: URL
+        let identity: String
+        let progressFile: URL
+        let label: String
+    }
+    let entries: [Entry]
+
+    private struct Document: Decodable {
+        struct Item: Decodable { let url: String; let progress_file: String }
+        let version: Int
+        let items: [Item]
+    }
+    private struct InvalidQueue: LocalizedError {
+        var errorDescription: String? { "Invalid stream queue: expected version 1, 1–4096 unique supported videos and new absolute report files in private owned directories." }
+    }
+
+    static func load(from file: URL) throws -> StreamQueue {
+        do {
+            guard file.isFileURL, file.path.hasPrefix("/") else { throw InvalidQueue() }
+            let descriptor = Darwin.open(file.path, O_RDONLY | O_NONBLOCK | O_NOFOLLOW | O_CLOEXEC)
+            guard descriptor >= 0 else { throw InvalidQueue() }
+            let handle = FileHandle(fileDescriptor: descriptor, closeOnDealloc: true)
+            defer { try? handle.close() }
+            var info = stat()
+            guard fstat(descriptor, &info) == 0, (info.st_mode & S_IFMT) == S_IFREG else { throw InvalidQueue() }
+            let data = try handle.read(upToCount: 8 * 1024 * 1024 + 1) ?? Data()
+            guard data.count <= 8 * 1024 * 1024 else { throw InvalidQueue() }
+            let document = try JSONDecoder().decode(Document.self, from: data)
+            guard document.version == 1, (1...4096).contains(document.items.count) else { throw InvalidQueue() }
+            var identities = Set<String>()
+            var reports = Set<String>()
+            let entries = try document.items.map { item -> Entry in
+                let stream = try StreamURL.parse(item.url)
+                let url: URL
+                let identity: String
+                let label: String
+                switch stream {
+                case .youtube(let canonical):
+                    url = canonical
+                    identity = canonical.absoluteString
+                    label = "YouTube · " + (URLComponents(url: canonical, resolvingAgainstBaseURL: false)?.queryItems?.first?.value ?? "Video")
+                case .miruro(let mediaID, let episode):
+                    url = URL(string: item.url)!
+                    identity = "miruro:\(mediaID):\(episode)"
+                    label = "\(url.lastPathComponent.replacingOccurrences(of: "-", with: " ")) · Episode \(episode)"
+                }
+                guard identities.insert(identity).inserted,
+                      item.progress_file.hasPrefix("/"), !item.progress_file.contains("\0") else { throw InvalidQueue() }
+                let report = URL(fileURLWithPath: item.progress_file).standardizedFileURL
+                let parent = report.deletingLastPathComponent()
+                var directoryInfo = stat()
+                guard lstat(parent.path, &directoryInfo) == 0,
+                      (directoryInfo.st_mode & S_IFMT) == S_IFDIR,
+                      directoryInfo.st_uid == geteuid(), (directoryInfo.st_mode & 0o777) == 0o700,
+                      parent.resolvingSymlinksInPath().path == parent.path,
+                      reports.insert(report.path).inserted else { throw InvalidQueue() }
+                var existing = stat()
+                guard lstat(report.path, &existing) != 0, errno == ENOENT else { throw InvalidQueue() }
+                return Entry(url: url, identity: identity, progressFile: report, label: label)
+            }
+            return StreamQueue(entries: entries)
+        } catch { throw InvalidQueue() }
+    }
+}