import UIKit
import XCPlayground

XCPSetExecutionShouldContinueIndefinitely()

typealias JSON = AnyObject
typealias JSONDictionary = [String: JSON]
typealias JSONArray = [JSON]

let url = "http://api.openweathermap.org/data/2.5/weather?q=London,uk"
let request = NSURLRequest(URL: NSURL.URLWithString(url))

final class Box<A> {
    let value: A
    init(_ value: A) {
        self.value = value
    }
}

struct Weather {
    let id: Int
    let name: String
    
    static func create(id: Int)(name: String) -> Weather {
        return Weather(id: id, name: name)
    }
}

enum Result<A> {
    case Error(NSError)
    case Value(Box<A>)
}

func JSONString(object: JSON?) -> String? {
    return object as? String
}

func JSONInt(object: JSON?) -> Int? {
    return object as? Int
}

func JSONObject(object: JSON?) -> JSONDictionary? {
    return object as? JSONDictionary
}

infix operator >>> {associativity left precedence 150}
func >>><A, B>(a: A?, f: A->B?) -> B? {
    if let x = a {
        return f(x)
    } else {
        return .None
    }
}

func getData(request: NSURLRequest, callback: (Result<Weather>) -> ()) {
    let task = NSURLSession.sharedSession().dataTaskWithRequest(request) {
        data, urlResponse, error in
        if let err = error {
            callback(Result.Error(err))
            return
        }
        
        var jsonErrorOptional: NSError?
        let jsonOptional: JSON! = NSJSONSerialization.JSONObjectWithData(data, options: NSJSONReadingOptions(0), error: &jsonErrorOptional)
        
//        println(jsonOptional)
        
        if let err = jsonErrorOptional {
            callback(Result.Error(err))
            return
        }
        
        if let json = jsonOptional >>> JSONObject {
            if let id = json["id"] >>> JSONInt {
                if let name = json["name"] >>> JSONString {
                    let weather = Weather(id: id, name: name)
                    callback(Result.Value(Box(weather)))
                    return
                }
            }
        }
        
    }
    task.resume()
}

getData(request) {
    result in
    switch result {
    case let .Error(error):
        println(error)
    case let .Value(boxedUser):
        let weather = boxedUser.value
        println(weather.id)
        println(weather.name)
    }
}