A tiny networking library

## LICENSE
Copyright 2015 Chris Eidhof

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

## tiny-networking.swift
// See the accompanying blog post: http://chris.eidhof.nl/posts/tiny-networking-in-swift.html


public enum Method: String { // Bluntly stolen from Alamofire
    case OPTIONS = "OPTIONS"
    case GET = "GET"
    case HEAD = "HEAD"
    case POST = "POST"
    case PUT = "PUT"
    case PATCH = "PATCH"
    case DELETE = "DELETE"
    case TRACE = "TRACE"
    case CONNECT = "CONNECT"
}

public struct Resource<A> {
    let path: String
    let method : Method
    let requestBody: NSData?
    let headers : [String:String]
    let parse: NSData -> A?
}

public enum Reason {
    case CouldNotParseJSON
    case NoData
    case NoSuccessStatusCode(statusCode: Int)
    case Other(NSError)
}

public func apiRequest<A>(modifyRequest: NSMutableURLRequest -> (), baseURL: NSURL, resource: Resource<A>, failure: (Reason, NSData?) -> (), completion: A -> ()) {
    let session = NSURLSession.sharedSession()
    let url = baseURL.URLByAppendingPathComponent(resource.path)
    let request = NSMutableURLRequest(URL: url)
    request.HTTPMethod = resource.method.rawValue
    request.HTTPBody = resource.requestBody
    modifyRequest(request)
    for (key,value) in resource.headers {
        request.setValue(value, forHTTPHeaderField: key)
    }
    let task = session.dataTaskWithRequest(request){ (data, response, error) -> Void in
        if let httpResponse = response as? NSHTTPURLResponse {
            if httpResponse.statusCode == 200 {
                if let responseData = data {
                    if let result = resource.parse(responseData) {
                        completion(result)
                    } else {
                        failure(Reason.CouldNotParseJSON, data)
                    }
                } else {
                    failure(Reason.NoData, data)
                }
            } else {
                failure(Reason.NoSuccessStatusCode(statusCode: httpResponse.statusCode), data)
            }
        } else {
            failure(Reason.Other(error), data)
        }
    }
    task.resume()
}

// Here are some convenience functions for dealing with JSON APIs

public typealias JSONDictionary = [String:AnyObject]

func decodeJSON(data: NSData) -> JSONDictionary? {
    return NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions.allZeros, error: nil) as? [String:AnyObject]
}

func encodeJSON(dict: JSONDictionary) -> NSData? {
    return dict.count > 0 ? NSJSONSerialization.dataWithJSONObject(dict, options: NSJSONWritingOptions.allZeros, error: nil) : nil
}

public func jsonResource<A>(path: String, method: Method, requestParameters: JSONDictionary, parse: JSONDictionary -> A?) -> Resource<A> {
    let f = { decodeJSON($0) >>= parse }
    let jsonBody = encodeJSON(requestParameters)
    let headers = ["Content-Type": "application/json"]
    return Resource(path: path, method: method, requestBody: jsonBody, headers: headers, parse: f)
}