preserve opensubtitles caption labels

Dreamio/StreamCandidate.swift

@@ -40,6 +40,108 @@ struct SubtitleTrack: Equatable {
     let name: String
 }
 
+enum SubtitleDisplayName {
+    private static let genericLabels = [
+        "external subtitle",
+        "subtitle",
+        "unknown"
+    ]
+
+    private static let languageCodeAliases = [
+        "eng": "en",
+        "en": "en",
+        "spa": "es",
+        "es": "es",
+        "fre": "fr",
+        "fra": "fr",
+        "fr": "fr"
+    ]
+
+    static func displayName(for candidate: SubtitleCandidate) -> String {
+        if let label = meaningfulDisplayText(candidate.label) {
+            return label
+        }
+
+        if let languageName = languageName(for: candidate.language) {
+            return languageName
+        }
+
+        return fallbackName(from: candidate)
+    }
+
+    static func name(forVLCTrackName trackName: String, preservedName: String?) -> String {
+        guard isGenericLabel(trackName), let preservedName else {
+            return trackName
+        }
+        return preservedName
+    }
+
+    static func isGenericLabel(_ value: String) -> Bool {
+        let normalized = value.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !normalized.isEmpty else {
+            return true
+        }
+
+        let lowercased = normalized.lowercased()
+        if genericLabels.contains(lowercased) {
+            return true
+        }
+        if Int(normalized) != nil {
+            return true
+        }
+        if lowercased.range(of: #"^track\s*\d+$"#, options: .regularExpression) != nil {
+            return true
+        }
+        return false
+    }
+
+    private static func meaningfulDisplayText(_ value: String?) -> String? {
+        guard let value else {
+            return nil
+        }
+        let trimmed = value.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !isGenericLabel(trimmed) else {
+            return nil
+        }
+        guard trimmed.count <= 3 else {
+            return trimmed
+        }
+        return languageName(for: trimmed) ?? trimmed
+    }
+
+    private static func languageName(for value: String?) -> String? {
+        guard let value else {
+            return nil
+        }
+
+        let trimmed = value.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !trimmed.isEmpty, Int(trimmed) == nil else {
+            return nil
+        }
+
+        if trimmed.count > 3 {
+            return trimmed.capitalized
+        }
+
+        let lowercased = trimmed.lowercased()
+        let languageCode = languageCodeAliases[lowercased] ?? lowercased
+        guard let name = Locale.current.localizedString(forLanguageCode: languageCode) else {
+            return nil
+        }
+        return name.capitalized
+    }
+
+    private static func fallbackName(from candidate: SubtitleCandidate) -> String {
+        let trimmedLabel = candidate.label.trimmingCharacters(in: .whitespacesAndNewlines)
+        if !isGenericLabel(trimmedLabel) {
+            return trimmedLabel
+        }
+
+        let fileName = candidate.url.deletingPathExtension().lastPathComponent
+        return fileName.isEmpty ? "External Subtitle" : fileName
+    }
+}
+
 #if DEBUG
 enum SubtitleDebugFormatter {
     static func candidateSummary(_ candidates: [SubtitleCandidate]) -> String {

Dreamio/VLCNativePlaybackBackend.swift

@@ -28,6 +28,8 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
     private var autoSelectedSubtitleTrackID: Int32?
     private var externalSubtitleBaselineTrackIDs = Set<Int32>()
     private var hasPendingExternalSubtitleSelection = false
+    private var pendingExternalSubtitleDisplayNames: [String] = []
+    private var externalSubtitleDisplayNamesByTrackID: [Int32: String] = [:]
 
     override init() {
         super.init()
@@ -51,6 +53,8 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
         autoSelectedSubtitleTrackID = nil
         externalSubtitleBaselineTrackIDs.removeAll()
         hasPendingExternalSubtitleSelection = false
+        pendingExternalSubtitleDisplayNames.removeAll()
+        externalSubtitleDisplayNamesByTrackID.removeAll()
         let media = VLCMedia(url: request.playbackURL)
         let headerValue = request.headers
             .map { "\($0.key): \($0.value)" }
@@ -199,10 +203,15 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
 
     var subtitleTracks: [SubtitleTrack] {
 #if canImport(MobileVLCKit)
-        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
-        let indexes = mediaPlayer.videoSubTitlesIndexes as? [NSNumber] ?? []
-        return zip(indexes, names).map { index, name in
-            SubtitleTrack(id: index.int32Value, name: name)
+        reconcileExternalSubtitleDisplayNames()
+        return rawSubtitleTracks().map { track in
+            SubtitleTrack(
+                id: track.id,
+                name: SubtitleDisplayName.name(
+                    forVLCTrackName: track.name,
+                    preservedName: externalSubtitleDisplayNamesByTrackID[track.id]
+                )
+            )
         }
 #else
         []
@@ -229,7 +238,7 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
     private func attachSubtitles(_ candidates: [SubtitleCandidate]) -> Int {
         var attachedCount = 0
         var duplicateCount = 0
-        let baselineTrackIDs = Set(subtitleTracks.filter { $0.id >= 0 }.map(\.id))
+        let baselineTrackIDs = Set(rawSubtitleTracks().filter { $0.id >= 0 }.map(\.id))
         candidates.forEach { candidate in
             guard !attachedSubtitleURLs.contains(candidate.url) else {
                 duplicateCount += 1
@@ -238,6 +247,7 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
             attachedSubtitleURLs.insert(candidate.url)
             externalSubtitleBaselineTrackIDs.formUnion(baselineTrackIDs)
             hasPendingExternalSubtitleSelection = true
+            pendingExternalSubtitleDisplayNames.append(SubtitleDisplayName.displayName(for: candidate))
             mediaPlayer.addPlaybackSlave(candidate.url, type: .subtitle, enforce: false)
             attachedCount += 1
 #if DEBUG
@@ -268,6 +278,32 @@ final class VLCNativePlaybackBackend: NSObject, NativePlaybackBackend {
         return attachedCount
     }
 
+    private func rawSubtitleTracks() -> [SubtitleTrack] {
+        let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []
+        let indexes = mediaPlayer.videoSubTitlesIndexes as? [NSNumber] ?? []
+        return zip(indexes, names).map { index, name in
+            SubtitleTrack(id: index.int32Value, name: name)
+        }
+    }
+
+    private func reconcileExternalSubtitleDisplayNames() {
+        guard !pendingExternalSubtitleDisplayNames.isEmpty else {
+            return
+        }
+
+        rawSubtitleTracks()
+            .filter { $0.id >= 0 }
+            .filter { !externalSubtitleBaselineTrackIDs.contains($0.id) }
+            .filter { externalSubtitleDisplayNamesByTrackID[$0.id] == nil }
+            .sorted { $0.id < $1.id }
+            .forEach { track in
+                guard !pendingExternalSubtitleDisplayNames.isEmpty else {
+                    return
+                }
+                externalSubtitleDisplayNamesByTrackID[track.id] = pendingExternalSubtitleDisplayNames.removeFirst()
+            }
+    }
+
 #if DEBUG
     private func logSubtitleTracks(reason: String) {
         let names = mediaPlayer.videoSubTitlesNames as? [String] ?? []