cache stremio subtitles before vlc attach

Dreamio/StreamResolver.swift

@@ -35,9 +35,14 @@ enum StreamResolverError: LocalizedError {
 
 final class SubtitleResolver: SubtitleResolving {
     private let session: URLSession
+    private let cacheDirectory: URL
 
-    init(session: URLSession = .shared) {
+    init(
+        session: URLSession = .shared,
+        cacheDirectory: URL = FileManager.default.temporaryDirectory.appendingPathComponent("DreamioSubtitles", isDirectory: true)
+    ) {
         self.session = session
+        self.cacheDirectory = cacheDirectory
     }
 
     func resolve(_ candidate: SubtitleCandidate) async -> SubtitleCandidate? {
@@ -69,6 +74,10 @@ final class SubtitleResolver: SubtitleResolving {
                 return SubtitleCandidate(url: finalURL, label: candidate.label, language: candidate.language)
             }
 
+            if let cachedCandidate = cacheSubtitleDataIfNeeded(data, original: candidate) {
+                return cachedCandidate
+            }
+
             return Self.bestPlayableCandidate(
                 from: data,
                 responseURL: response.url,
@@ -87,6 +96,31 @@ final class SubtitleResolver: SubtitleResolving {
         }
     }
 
+    private func cacheSubtitleDataIfNeeded(_ data: Data, original: SubtitleCandidate) -> SubtitleCandidate? {
+        guard let subtitleType = Self.subtitleType(in: data) else {
+            return nil
+        }
+
+        do {
+            try FileManager.default.createDirectory(
+                at: cacheDirectory,
+                withIntermediateDirectories: true
+            )
+            let filename = "\(UUID().uuidString).\(subtitleType.fileExtension)"
+            let fileURL = cacheDirectory.appendingPathComponent(filename)
+            try data.write(to: fileURL, options: .atomic)
+#if DEBUG
+            print("[DreamioSubtitles] cached subtitle url=\(URLRedactor.redactedURLString(original.url.absoluteString)) file=\(fileURL.lastPathComponent)")
+#endif
+            return SubtitleCandidate(url: fileURL, label: original.label, language: original.language)
+        } catch {
+#if DEBUG
+            print("[DreamioSubtitles] cache failure=\(error.localizedDescription) url=\(URLRedactor.redactedURLString(original.url.absoluteString))")
+#endif
+            return nil
+        }
+    }
+
     static func bestPlayableCandidate(
         from data: Data,
         responseURL: URL?,
@@ -131,7 +165,6 @@ final class SubtitleResolver: SubtitleResolving {
         let lowercased = url.absoluteString.lowercased()
         return ["srt", "vtt", "ass", "ssa", "sub"].contains(url.pathExtension.lowercased())
             || [".srt?", ".vtt?", ".ass?", ".ssa?", ".sub?", ".srt&", ".vtt&", ".ass&", ".ssa&", ".sub&"].contains(where: lowercased.contains)
-            || isStremioSubtitleDownloadURL(url)
     }
 
     private static func shouldResolve(_ url: URL) -> Bool {
@@ -154,6 +187,50 @@ final class SubtitleResolver: SubtitleResolving {
             || path.range(of: #"(^|/)download(/|$)"#, options: .regularExpression) != nil
     }
 
+    private enum SubtitlePayloadType {
+        case srt
+        case vtt
+        case ass
+
+        var fileExtension: String {
+            switch self {
+            case .srt:
+                return "srt"
+            case .vtt:
+                return "vtt"
+            case .ass:
+                return "ass"
+            }
+        }
+    }
+
+    private static func subtitleType(in data: Data) -> SubtitlePayloadType? {
+        guard !data.isEmpty,
+              let text = String(data: data.prefix(4096), encoding: .utf8)?
+                .trimmingCharacters(in: .whitespacesAndNewlines),
+              !text.isEmpty
+        else {
+            return nil
+        }
+
+        let lowercased = text.lowercased()
+        if lowercased.hasPrefix("webvtt") {
+            return .vtt
+        }
+        if lowercased.hasPrefix("[script info]")
+            || lowercased.contains("\n[events]")
+            || lowercased.contains("\r\n[events]") {
+            return .ass
+        }
+        if lowercased.range(
+            of: #"(?m)^\d+\s*[\r\n]+(?:\d{1,2}:)?\d{2}:\d{2}[,.]\d{3}\s*-->\s*(?:\d{1,2}:)?\d{2}:\d{2}[,.]\d{3}"#,
+            options: .regularExpression
+        ) != nil {
+            return .srt
+        }
+        return nil
+    }
+
     private static func logRejected(_ candidate: SubtitleCandidate, responseURL: URL?, data: Data) -> SubtitleCandidate? {
 #if DEBUG
         let responseDescription = responseURL.map { URLRedactor.redactedURLString($0.absoluteString) } ?? "none"

Tests/StreamResolverTests.swift

@@ -16,6 +16,7 @@ struct StreamResolverTests {
         testStremioSubtitleDownloadURLParsing()
         testOpenSubtitlesV3DownloadResponseResolution()
         testOpenSubtitlesNestedDownloadResponseResolution()
+        await testSubtitleResolverCachesStremioDownloadBody()
         await testSubtitleResolverDownloadJSONReturningLink()
         await testSubtitleResolverRedirectToDirectSubtitle()
         await testSubtitleResolverRejectsNonSubtitleAPIResponse()
@@ -270,7 +271,7 @@ struct StreamResolverTests {
         assertEqual(candidates[0].url.absoluteString, "https://subs5.strem.io/en/download/subencoding-stremio-utf8/src-api/file/1952341941")
         assertEqual(candidates[0].label, "English")
         assertEqual(candidates[0].language, "eng")
-        assert(SubtitleResolver.isDirectSubtitleFile(candidates[0].url), "Expected Stremio subtitle downloads to be attachable without another resolver hop")
+        assert(!SubtitleResolver.isDirectSubtitleFile(candidates[0].url), "Expected Stremio subtitle downloads to be resolved before VLC attachment")
     }
 
     private static func testContentRangeParsing() {
@@ -437,7 +438,46 @@ struct StreamResolverTests {
         assertEqual(candidate?.language, "eng")
     }
 
+    private static func testSubtitleResolverCachesStremioDownloadBody() async {
+        let sourceURL = "https://subs5.strem.io/en/download/subencoding-stremio-utf8/src-api/file/1952341941"
+        let subtitleBody = """
+        1
+        00:00:01,000 --> 00:00:02,000
+        Hello from Stremio
+
+        """
+        MockURLProtocol.handler = nil
+        MockURLProtocol.handlers = [
+            sourceURL: (
+                200,
+                URL(string: sourceURL)!,
+                subtitleBody.data(using: .utf8)!
+            )
+        ]
+
+        let cacheDirectory = FileManager.default.temporaryDirectory
+            .appendingPathComponent("DreamioSubtitleResolverTests-\(UUID().uuidString)", isDirectory: true)
+        defer {
+            try? FileManager.default.removeItem(at: cacheDirectory)
+        }
+
+        let resolver = SubtitleResolver(session: mockSession(), cacheDirectory: cacheDirectory)
+        let candidate = await resolver.resolve(SubtitleCandidate(
+            url: URL(string: sourceURL)!,
+            label: "English",
+            language: "eng"
+        ))
+
+        assertEqual(candidate?.url.isFileURL, true)
+        assertEqual(candidate?.url.pathExtension, "srt")
+        assertEqual(candidate?.label, "English")
+        assertEqual(candidate?.language, "eng")
+        let cachedBody = try? String(contentsOf: candidate!.url, encoding: .utf8)
+        assertEqual(cachedBody, subtitleBody)
+    }
+
     private static func testSubtitleResolverDownloadJSONReturningLink() async {
+        MockURLProtocol.handler = nil
         MockURLProtocol.handlers = [
             "https://api.opensubtitles.com/api/v1/download/123": (
                 200,
@@ -458,6 +498,7 @@ struct StreamResolverTests {
     }
 
     private static func testSubtitleResolverRedirectToDirectSubtitle() async {
+        MockURLProtocol.handler = nil
         MockURLProtocol.handlers = [
             "https://api.opensubtitles.com/api/v1/download/redirect": (
                 200,
@@ -476,6 +517,7 @@ struct StreamResolverTests {
     }
 
     private static func testSubtitleResolverRejectsNonSubtitleAPIResponse() async {
+        MockURLProtocol.handler = nil
         MockURLProtocol.handlers = [
             "https://api.opensubtitles.com/api/v1/download/not-found": (
                 200,