Trying to ditch multipart-kit

Sources/RemoveBg/RemoveBgClient.swift

@@ -57,24 +57,25 @@ public class RemoveBgClient {
         return try await fetch(body: body)
     }
 
-    func createRequestBody(options: ApiOptions, configuration: (inout ApiOptions) -> Void) throws -> Data {
-        let encoder = FormDataEncoder()
+    func createRequestBody(options: ApiOptions, configuration: (inout ApiOptions) -> Void) throws -> MultipartFormData {
+        var multipart = MultipartFormData(boundary: boundary)
+
         var options = options
         options.imageUrl = nil
         options.imageFileB64 = nil
         options.imageFile = nil
         configuration(&options)
-
-        let body = try encoder.encode(options, boundary: boundary)
-        return body.data(using: .utf8) ?? .init()
+
+        if let data = options.imageFile {
+            multipart.addField(named: "image_file", filename: "image", data: data)
+        }
+
+        return multipart
     }
 
 
-    func fetch(body: Data) async throws -> ApiResult {
-        var httpRequest = URLRequest(url: RemoveBgClient.endpoint)
-        httpRequest.httpBody = body
-        httpRequest.httpMethod = "POST"
-        httpRequest.setValue("multipart/form-data; boundary=\(boundary)", forHTTPHeaderField: "Content-Type")
+    func fetch(body: MultipartFormData) async throws -> ApiResult {
+        let httpRequest = URLRequest(url: RemoveBgClient.endpoint, formData: body)
 
         let (data, response) = try await urlSession.data(for: httpRequest)
         if let httpResponse = response as? HTTPURLResponse {
@@ -122,3 +123,67 @@ extension ApiResult.Meta {
         foregroundHeight = parseHeader("X-Foreground-Height", Int.init)
     }
 }
+
+
+public struct MultipartFormData {
+    fileprivate let boundary: String
+    private var formData = Data()
+
+    init(boundary: String) {
+        self.boundary = boundary
+    }
+
+    fileprivate var httpBody: Data {
+        var data = formData
+        data.append("--\(boundary)--")
+        return data
+    }
+
+    public mutating func addField(named name: String, value: String) {
+        formData.addField("--\(boundary)")
+        formData.addField("Content-Disposition: form-data; name=\"\(name)\"")
+        formData.addField()
+        formData.addField(value)
+    }
+
+    public mutating func addField(named name: String, filename: String, data: Data) {
+        formData.addField("--\(boundary)")
+        formData.addField("Content-Disposition: form-data; name=\"\(name)\"; filename=\"\(filename)\"")
+        formData.addField()
+        formData.addField(data)
+    }
+}
+
+public extension URLRequest {
+    init(url: URL, formData: MultipartFormData) {
+        self.init(url: url)
+        httpMethod = "POST"
+        setValue("multipart/form-data; boundary=\(formData.boundary)", forHTTPHeaderField: "Content-Type")
+        setValue("*/*", forHTTPHeaderField: "Accept")
+        httpBody = formData.httpBody
+    }
+}
+
+fileprivate extension Data {
+    mutating func append(_ string: String) {
+        append(Data(string.utf8))
+    }
+
+    mutating func addField() {
+        append(.httpFieldDelimiter)
+    }
+
+    mutating func addField(_ string: String) {
+        append(string)
+        append(.httpFieldDelimiter)
+    }
+
+    mutating func addField(_ data: Data) {
+        append(data)
+        append(.httpFieldDelimiter)
+    }
+}
+
+fileprivate extension String {
+    static let httpFieldDelimiter = "\r\n"
+}

Tests/RemoveBgTests/RemoveBgTests.swift

@@ -9,6 +9,8 @@ final class RemoveBgParametersTests: XCTestCase {
         let sessionConfiguration = URLSessionConfiguration.ephemeral
         sessionConfiguration.protocolClasses = [MockURLProtocol.self]
         client = RemoveBgClient(urlSessionConfiguration: sessionConfiguration, apiKey: apiKey)
+
+        addMockResponse(response: .init(url: RemoveBgClient.endpoint, statusCode: 200, httpVersion: nil, headerFields: nil)!, data: "IMAGE".data(using: .utf8))
         super.setUp()
     }