Resolve TypeScript .ts files as text previews

Sources/Panels/FilePreviewPanel.swift

@@ -709,6 +709,10 @@ enum FilePreviewKindResolver {
 
     private static func initialResolution(for url: URL) -> Resolution {
         let ext = url.pathExtension.lowercased()
+        if needsSniffBeforeTextOrMedia(url: url) {
+            return .needsSniff
+        }
+
         if let type = UTType(filenameExtension: ext),
            let mediaMode = mediaMode(for: type) {
             return .resolved(mediaMode)
@@ -731,6 +735,19 @@ enum FilePreviewKindResolver {
             return .resolved(.quickLook)
         }
 
+        if needsSniffBeforeTextOrMedia(url: url) {
+            if sniffLooksLikeText(url: url) {
+                return .resolved(.text)
+            }
+            if looksLikeMPEGTransportStream(url: url) {
+                return .resolved(.media)
+            }
+            if let mediaMode = contentTypes(for: url).lazy.compactMap({ mediaMode(for: $0) }).first {
+                return .resolved(mediaMode)
+            }
+            return .needsSniff
+        }
+
         for type in contentTypes(for: url) {
             if let mediaMode = mediaMode(for: type) {
                 return .resolved(mediaMode)
@@ -793,28 +810,72 @@ enum FilePreviewKindResolver {
         return false
     }
 
+    private static func needsSniffBeforeTextOrMedia(url: URL) -> Bool {
+        let filename = url.lastPathComponent.lowercased()
+        let ext = url.pathExtension.lowercased()
+        if ext == "ts" {
+            return true
+        }
+        guard textFilenames.contains(filename) || textExtensions.contains(ext),
+              let type = UTType(filenameExtension: ext) else {
+            return false
+        }
+
+        return mediaMode(for: type) != nil
+            && !type.conforms(to: .text)
+            && !type.conforms(to: .sourceCode)
+    }
+
     private static func looksLikeBinaryPropertyList(url: URL) -> Bool {
         guard let handle = try? FileHandle(forReadingFrom: url) else { return false }
         defer { try? handle.close() }
         let data = (try? handle.read(upToCount: 8)) ?? Data()
         return String(data: data, encoding: .ascii) == "bplist00"
     }
 
+    private static func looksLikeMPEGTransportStream(url: URL) -> Bool {
+        guard url.pathExtension.lowercased() == "ts",
+              let handle = try? FileHandle(forReadingFrom: url) else { return false }
+        defer { try? handle.close() }
+
+        let data = (try? handle.read(upToCount: 4096)) ?? Data()
+        guard data.count >= 376 else { return false }
+
+        let syncCandidates = [
+            (packetSize: 188, syncOffset: 0),
+            (packetSize: 192, syncOffset: 0),
+            (packetSize: 192, syncOffset: 4),
+            (packetSize: 204, syncOffset: 0)
+        ]
+
+        for candidate in syncCandidates where data.count > candidate.syncOffset {
+            var offset = candidate.syncOffset
+            var syncCount = 0
+            while offset < data.count {
+                guard data[offset] == 0x47 else { break }
+                syncCount += 1
+                offset += candidate.packetSize
+            }
+            if syncCount >= 2 {
+                return true
+            }
+        }
+
+        return false
+    }
+
     private static func sniffLooksLikeText(url: URL) -> Bool {
         guard let handle = try? FileHandle(forReadingFrom: url) else { return false }
         defer { try? handle.close() }
         let data = (try? handle.read(upToCount: 4096)) ?? Data()
         guard !data.isEmpty else { return true }
-        if String(data: data, encoding: .utf8) != nil {
-            return true
-        }
         if hasUTF16ByteOrderMark(data), String(data: data, encoding: .utf16) != nil {
             return true
         }
         if data.contains(0) {
             return false
         }
-        return false
+        return String(data: data, encoding: .utf8) != nil
     }
 
     private static func hasUTF16ByteOrderMark(_ data: Data) -> Bool {

cmuxTests/FilePreviewReviewFeedbackTests.swift

@@ -68,6 +68,118 @@ final class FilePreviewReviewFeedbackTests: XCTestCase {
         XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .text)
     }
 
+    func testExtensionlessANSITextResolvesAsTextAfterSniffing() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+        defer { try? FileManager.default.removeItem(at: url) }
+        try "\u{001B}[31mred\u{001B}[0m\n".write(to: url, atomically: true, encoding: .utf8)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .text)
+    }
+
+    func testTypeScriptFileResolvesAsTextInsteadOfTransportStreamMedia() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        try """
+        export const answer: number = 42;
+        console.log(answer);
+        """.write(to: url, atomically: true, encoding: .utf8)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .text)
+    }
+
+    func testUTF8BOMTypeScriptFileResolvesAsText() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        var data = Data([0xEF, 0xBB, 0xBF])
+        data.append(Data("export const answer: number = 42;\n".utf8))
+        try data.write(to: url, options: .atomic)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .text)
+    }
+
+    func testTypeScriptFileWithNULBytesDoesNotResolveAsText() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        var data = Data("export const answer = 42;".utf8)
+        data.append(contentsOf: [0x00, 0x00])
+        try data.write(to: url, options: .atomic)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertNotEqual(FilePreviewKindResolver.mode(for: url), .text)
+    }
+
+    func testTypeScriptTextWinsOverTransportStreamSyncBytePattern() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        let source = "G"
+            + String(repeating: "a", count: 187)
+            + "G"
+            + String(repeating: "b", count: 187)
+            + "\nexport const answer: number = 42;\n"
+        try source.write(to: url, atomically: true, encoding: .utf8)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .text)
+    }
+
+    func testBinaryTransportStreamFileKeepsMediaPreview() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        var data = Data(repeating: 0, count: 188 * 2)
+        data[0] = 0x47
+        data[1] = 0x40
+        data[2] = 0x00
+        data[3] = 0x10
+        data[188] = 0x47
+        data[189] = 0x41
+        data[190] = 0x00
+        data[191] = 0x10
+        try data.write(to: url, options: .atomic)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .media)
+    }
+
+    func testM2TSTransportStreamFileKeepsMediaPreview() throws {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(UUID().uuidString)
+            .appendingPathExtension("ts")
+        defer { try? FileManager.default.removeItem(at: url) }
+
+        var data = Data(repeating: 0, count: 192 * 2)
+        data[4] = 0x47
+        data[5] = 0x40
+        data[6] = 0x00
+        data[7] = 0x10
+        data[196] = 0x47
+        data[197] = 0x41
+        data[198] = 0x00
+        data[199] = 0x10
+        try data.write(to: url, options: .atomic)
+
+        XCTAssertEqual(FilePreviewKindResolver.initialMode(for: url), .quickLook)
+        XCTAssertEqual(FilePreviewKindResolver.mode(for: url), .media)
+    }
+
     func testQuickLookSessionCloseDoesNotDeactivateMountedRepresentableView() throws {
         let url = try temporaryBinaryFile()
         defer { try? FileManager.default.removeItem(at: url) }