fix native external subtitle overlay fallback

Dreamio/ExternalSubtitleTrackParser.swift

@@ -0,0 +1,102 @@
+import Foundation
+
+struct ExternalSubtitleTrack {
+    let id: Int
+    let name: String
+    let cues: [ExternalSubtitleCue]
+
+    func cue(at playbackTime: TimeInterval) -> ExternalSubtitleCue? {
+        cues.first { playbackTime >= $0.start && playbackTime < $0.end }
+    }
+}
+
+struct ExternalSubtitleCue {
+    let start: TimeInterval
+    let end: TimeInterval
+    let text: String
+}
+
+enum ExternalSubtitleTrackParser {
+    static func track(from candidate: SubtitleCandidate, id: Int) -> ExternalSubtitleTrack? {
+        guard let text = try? String(contentsOf: candidate.url, encoding: .utf8) else {
+            return nil
+        }
+
+        let cues = parseCues(from: text)
+        guard !cues.isEmpty else {
+            return nil
+        }
+
+        return ExternalSubtitleTrack(
+            id: id,
+            name: SubtitleDisplayName.displayName(for: candidate),
+            cues: cues
+        )
+    }
+
+    static func parseCues(from text: String) -> [ExternalSubtitleCue] {
+        let normalized = text
+            .replacingOccurrences(of: "\r\n", with: "\n")
+            .replacingOccurrences(of: "\r", with: "\n")
+        let blocks = normalized.components(separatedBy: "\n\n")
+        return blocks.compactMap(parseCueBlock)
+    }
+
+    private static func parseCueBlock(_ block: String) -> ExternalSubtitleCue? {
+        let lines = block
+            .components(separatedBy: .newlines)
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            .filter { !$0.isEmpty && !$0.lowercased().hasPrefix("webvtt") }
+        guard !lines.isEmpty else {
+            return nil
+        }
+
+        guard let timingIndex = lines.firstIndex(where: { $0.contains("-->") }) else {
+            return nil
+        }
+        let timingParts = lines[timingIndex].components(separatedBy: "-->")
+        guard timingParts.count == 2,
+              let start = parseTimestamp(timingParts[0]),
+              let end = parseTimestamp(timingParts[1]),
+              end > start
+        else {
+            return nil
+        }
+
+        let cueText = lines
+            .dropFirst(timingIndex + 1)
+            .map(cleanCueText)
+            .filter { !$0.isEmpty }
+            .joined(separator: "\n")
+        guard !cueText.isEmpty else {
+            return nil
+        }
+
+        return ExternalSubtitleCue(start: start, end: end, text: cueText)
+    }
+
+    private static func parseTimestamp(_ value: String) -> TimeInterval? {
+        let timestamp = value
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+            .replacingOccurrences(of: ",", with: ".")
+            .components(separatedBy: .whitespaces)
+            .first ?? ""
+        let pieces = timestamp.split(separator: ":").map(String.init)
+        guard let secondsPiece = pieces.last,
+              let seconds = Double(secondsPiece)
+        else {
+            return nil
+        }
+
+        let minutes = pieces.count >= 2 ? Double(pieces[pieces.count - 2]) ?? 0 : 0
+        let hours = pieces.count >= 3 ? Double(pieces[pieces.count - 3]) ?? 0 : 0
+        return hours * 3600 + minutes * 60 + seconds
+    }
+
+    private static func cleanCueText(_ value: String) -> String {
+        value
+            .replacingOccurrences(of: #"<[^>]+>"#, with: "", options: .regularExpression)
+            .replacingOccurrences(of: #"\{\\[^}]+\}"#, with: "", options: .regularExpression)
+            .trimmingCharacters(in: .whitespacesAndNewlines)
+    }
+}