Multipart Form Data implementation on Swift

MultipartFormData.swift

//
//  MultipartFormData.swift
//  https://gist.github.com/KoCMoHaBTa/a4a422cd5daa1c040ca3ab6803202c70
//
//  Created by Milen Halachev on 20.07.18.
//  Copyright © 2018 Milen Halachev. All rights reserved.
//

import Foundation

public struct MultipartFormData {
    
    ///The boundary of the form data. Default to random UUID.
    public var boundary: String = "---------------------" + UUID().uuidString + "---------------------"
    
    ///The line ending of the form data. Default to `\r\n`
    public var lineEnding: String = "\r\n"
    
    ///The parts, used to build the form data.
    public var parts: [Part] = []
    
    ///Creates an instance of the receiver with a single part
    public init(parts: [Part]) {
        
        self.parts = parts
    }
    
    ///Creates an instance of the receiver with multiple parts
    public init(part: Part) {
        
        self.init(parts: [part])
    }
    
    ///Computes the combined data of all parts and returns the result.
    public var data: Data {
        
        //if there are no parts - return empty data
        guard self.parts.isEmpty == false else {
            
            return Data()
        }
        
        let boundary = "--\(self.boundary)".data(using: .utf8)!     //preppend -- to the boundary - MIME standart
        let lineEnding = self.lineEnding.data(using: .utf8)!
        
        var data = self.parts.reduce(into: Data(), { (data, part) in
            
            let contentDisposition = "Content-Disposition: form-data; name=\"\(part.name)\"; filename=\"\(part.fileName)\"".data(using: .utf8)!
            let contentType = "Content-Type: \(part.contentType)".data(using: .utf8)!
            
            data.append(boundary)
            data.append(lineEnding)
            data.append(contentDisposition)
            data.append(lineEnding)
            data.append(contentType)
            data.append(lineEnding)
            data.append(lineEnding)             //extra line
            data.append(part.data)
            data.append(lineEnding)
        })
        
        data.append(boundary)                   //append the last boundar
        data.append("--".data(using: .utf8)!)   //append -- to the last boundary - MIME standart
        
        return data
    }
}

extension MultipartFormData {
    
    public struct Part {
        
        ///The binary data of the part.
        public let data: Data
        
        ///The value of the `Content-Type` header of the part
        public let contentType: String
        
        ///The value of the `name` parameter in the `Content-Disposition` header section of the part.
        public let name: String
        
        ///The value of the `filename` parameter in the `Content-Disposition` header section of the part.
        public let fileName: String
        
        public init(data: Data, contentType: String, name: String, fileName: String) {
            
            self.data = data
            self.contentType = contentType
            self.name = name
            self.fileName = fileName
        }
        
        ///Creates an instance of the receiver with the provided data. The name is set to random UUID
        public init(data: Data, contentType: String, fileName: String) {

            self.init(data: data, contentType: contentType, name: .uuid, fileName: fileName)
        }

        ///Creates an instance of the receiver with the provided data. The name and fileName are set to random UUID
        public init(data: Data, contentType: String) {

            self.init(data: data, contentType: contentType, name: .uuid, fileName: .uuid)
        }
        
        ///Creates an instance of the receiver with the provided data. The content type is set to `application/octet-stream` and the name and fileName are set to random GUID
        public init(data: Data) {
            
            self.init(data: data, contentType: "application/octet-stream", name: .uuid, fileName: .uuid)
        }
    }
}

MultipartFormDataTests.swift

//
//  MultipartFormDataTests.swift
//  https://gist.github.com/KoCMoHaBTa/a4a422cd5daa1c040ca3ab6803202c70
//
//  Created by Milen Halachev on 20.07.18.
//  Copyright © 2018 Milen Halachev. All rights reserved.
//

import Foundation
import XCTest

class MultipartFormDataTests: XCTestCase {
    
    //when no parts are provided - produces empty data
    func testNoParts() {
        
        let multipart = MultipartFormData(parts: [])
        XCTAssertEqual(multipart.data, Data())
    }
    
    func testSinglePart() {
        
        let expectedResult =
        """
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a
        Content-Disposition: form-data; name="gg"; filename="gg.txt"
        Content-Type: text/plain

        123ABC
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a--
        """

        var multipart = MultipartFormData(part: MultipartFormData.Part(data: "123ABC".data(using: .utf8)!, contentType: "text/plain", name: "gg", fileName: "gg.txt"))
        multipart.boundary = "812dfde1-e9eb-447c-a4e7-e19d3a32290a"
        multipart.lineEnding = "\n"
        
        let data = multipart.data
        let string = String(data: data, encoding: .utf8)
        
        XCTAssertEqual(expectedResult, string)
    }
    
    func testMultipleParts() {
        
        let expectedResult =
        """
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a
        Content-Disposition: form-data; name="gg"; filename="gg.txt"
        Content-Type: text/plain

        123ABC
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a
        Content-Disposition: form-data; name="gson"; filename="omg.json"
        Content-Type: application/json

        {"value":123}
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a
        Content-Disposition: form-data; name="snimka"; filename="omg.png"
        Content-Type: image/png

        lkjaskjldakljfjkdah
        --812dfde1-e9eb-447c-a4e7-e19d3a32290a--
        """
        
        let parts = [
            
            MultipartFormData.Part(data: "123ABC".data(using: .utf8)!, contentType: "text/plain", name: "gg", fileName: "gg.txt"),
            MultipartFormData.Part(data: try! JSONSerialization.data(withJSONObject: ["value": 123], options: []), contentType: "application/json", name: "gson", fileName: "omg.json"),
            MultipartFormData.Part(data: "lkjaskjldakljfjkdah".data(using: .utf8)!, contentType: "image/png", name: "snimka", fileName: "omg.png")
        ]
        
        var multipart = MultipartFormData(parts: parts)
        multipart.boundary = "812dfde1-e9eb-447c-a4e7-e19d3a32290a"
        multipart.lineEnding = "\n"
        
        let data = multipart.data
        let string = String(data: data, encoding: .utf8)
        
        XCTAssertEqual(expectedResult, string)
    }
}