gistfile1.txt

func uploadChunks(videoURL: URL, sessionId: String, fileSize: Int64) async throws {
    var offset: Int64 = 0
    let chunkSize: Int64 = 512 * 1024

    while offset < fileSize {
        let handle = try FileHandle(forReadingFrom: videoURL)
        defer { try? handle.close() }
        try handle.seek(toOffset: UInt64(offset))
        let chunkData = try handle.read(upToCount: Int(min(chunkSize, fileSize - offset))) ?? Data()

        let chunkFile = FileManager.default.temporaryDirectory
            .appendingPathComponent("chunk-\(UUID().uuidString).bin")
        try chunkData.write(to: chunkFile)

        let request = makeChunkRequest(sessionId: sessionId, offset: offset, totalBytes: fileSize)
        let task = session.uploadTask(with: request, fromFile: chunkFile)
        task.resume()

        offset += Int64(chunkData.count)
    }
}