NSData+MimeType Extension in Swift

NSData+MimeType.swift

//
//  NSData+MimeType.swift
//  Extension Playground
//
//  Created by Tobias Scholze on 27.11.15.
//  Copyright © 2015 Tobias Scholze. All rights reserved.
//

import Foundation

extension NSData
{
    enum MimeType
    {
        case Jpeg
        case Png
        case Gif
        case Mp4
        case Avi
        case Ogv
        case Webm
        case Pdf
        case Text
        case Stream
        
        /// Represents the ISO string value of the mime type.
        /// E.g.: "image/jpeg"
        var stringValue: String
        {
            switch self
            {
            case .Jpeg:
                return "image/jpeg"
                
            case .Png:
                return "image/png"
                
            case .Gif:
                return "image/gif"
                
            case .Mp4:
                return "video/mp4"
                
            case .Avi:
                return "video/avi"
                
            case .Ogv:
                return "video/ogg"
            
            case .Webm:
                return "video/webm"
                
            case .Pdf:
                return "application/pdf"
                
            case .Text:
                return "text/plain"
                
            case .Stream:
                return "application/octect-stream"
            }
        }
        
        /// Represents if the mime type is a pdf file
        var isPdf: Bool
        {
            return self == .Pdf
        }
        
        /// Represents if the mime type is an image file
        /// Valid image file mime types: jpg, png, gif
        var isImage: Bool
        {
            let imageTypes: [MimeType] = [.Jpeg, .Png, .Gif]
            
            return imageTypes.contains(self)
        }
        
        /// Represents if the mime type is an image file
        /// Valid image file mime types: mp4, avi, ogv, webm
        var isVideo: Bool
        {
            let videoTypes: [MimeType] = [.Mp4, .Avi, .Ogv, .Webm]
            
            return videoTypes.contains(self)
        }
    }
    
    /// Returns mime type according to the first character of file stream's content
    /// Based on: http://www.garykessler.net/library/file_sigs.html
    var mimeType: MimeType
    {
        var firstCharacter: UInt8 = 0
        self.getBytes(&firstCharacter, length: 1)

        switch firstCharacter
        {
        case 255:
            return .Jpeg
                
        case 137:
            return .Png
                
        case 71:
            return .Gif
            
        case 102:
            return .Mp4
            
        case 82:
            return .Avi
            
        case 79:
            return .Ogv
            
        case 26:
            return .Webm

        case 37:
            return .Pdf

        case 70:
            return .Text

        default:
            return .Stream
        }
    }
}