Command.swift

import Foundation
import HTTP
import Vapor

public protocol SideEffect {
    func perform() throws
}

public protocol Command: ResponseRepresentable {
    
    init(request: Request, droplet: Droplet) throws
    
    var status: Status { get }
    
    func validate() throws
    
    var sideEffects: [SideEffect] { get }
    
    func execute() throws -> JSON
}

extension Command {
    
    public var sideEffects: [SideEffect] {
        return []
    }
    
    public func validate() throws {
        
    }
    
    public func makeResponse() throws -> Response {
        let response = Response(status: self.status)
        try validate()
        response.json = try execute()
        try sideEffects.forEach({ try $0.perform() })
        return response
    }
}