NetworkKit

NetworkKit is a networking library written in Swift. It offers the following:

• Idiomatic Swift types for representing HTTP requests and related data types.
• A type-safe Retrofit inspired DSL for declaring HTTP interfaces.
• Utilities to manipulate standard certificate formats used in secure telecommunication (ASN.1, PKCS 7, X509)
• Common implementations for custom framing protocols.
• Extensions for the NetworkExtension framework.

Declarative HTTP Interfaces

NetworkKit allows for powerful declarative composition of various kinds of HTTP interfaces.

A NetworkKit HTTP interface is fundamentally composed of the following:

• A base URL.
• A list of endpoints.
• A generic Endpoint class (inheriting from BaseHTTPEndpoint) responsible for configuring a generic HTTP request containing shared parameters (such as API keys etc.).

Specific API endpoints by initializing the generic Endpoint class declared in the interface, and annotating them with NetworkKit provided decorators (i.e. property wrappers). The following decorators are supported:

• @Host(...)
• @Path(...)
• @AbsolutePath(...)
• @DELETE
• @GET
• @PATCH
• @POST
• @PUT
• @Query(...)
• @Header(...)
• @Body(...)

These decorators can be composed together to declare the configuration for an API endpoint.

Declaring a REST interface for GIPHY with NetworkKit

Here is a sample NetworkKit interface for the GIPHY API:

public struct GIPHY_API: RESTAPISpecification {
    public var apiKey: String
    public var host = URL(string: "https://api.giphy.com")!
    
    public init(apiKey: String) {
        self.apiKey = apiKey
    }
    
    public var baseURL: URL {
        host.appendingPathComponent("/v1")
    }
    
    public var id: some Hashable {
        apiKey
    }
    
    @Path("gifs/search")
    @GET
    @Query({ context in
        return [
            "api_key": context.root.apiKey,
            "q": context.input.q,
            "limit": context.input.limit?.description
        ]
    })
    var search = Endpoint<RequestBodies.Search, ResponseBodies.Search, Void> ()
}

extension GIPHY_API {
    public final class Endpoint<Input, Output, Options>: BaseHTTPEndpoint<GIPHY_API, Input, Output, Options> {
        override public func buildRequestBase(
            from input: Input,
            context: BuildRequestContext
        ) throws -> Request {
            let request = try super.buildRequestBase(from: input, context: context)
                .header(.accept(.json))
                .header(.contentType(.json))
            
            return request
        }
        
        override public func decodeOutputBase(
            from response: Request.Response,
            context: DecodeOutputContext
        ) throws -> Output {
            try response.validate()
            
            return try response.decode(Output.self, using: JSONDecoder(keyDecodingStrategy: .convertFromSnakeCase))
        }
    }
}

extension GIPHY_API {
    public enum RequestBodies {
        public struct Search: Codable, Hashable {
            public var q: String
            public var limit: Int32?
            public var offset: Int?
            public var lang = "en"
        }
    }
    
    public enum ResponseBodies {
        public struct Search: Codable, Hashable {
            public struct Pagination: Codable, Hashable {
                public let offset: Int32
                public let totalCount: Int32
                public let count: Int32
            }
            
            public struct Meta: Codable, Hashable {
                public let msg: String
                public let status: HTTPResponseStatusCode
                public let responseId: String
            }
            
            public let data: [GIPHY_API.Schema.GIFObject]
            public let pagination: Pagination
            public let meta: Meta
        }
    }
}

extension GIPHY_API {
    public enum Schema {
        public struct GIFObject: Codable, Hashable {
            public struct Images: Codable, Hashable {
                public struct Downsized: Codable, Hashable {
                    public let url: URL
                    public let width: String
                    public let height: String
                    public let size: String
                }
                
                public let downsized: Downsized
            }
            
            public let type: String
            public let id: String
            public let slug: String
            public let url: URL
            public let bitlyUrl: URL?
            public let embedUrl: URL?
            public let username: String?
            public let source: String
            public let rating: String?
            // ...
            public let images: Images
            public let title: String
        }
    }
}