MCE

mce.swift

//
//  main.swift
//  MCE
//
//  Created by Chris Eidhof on 05/02/15.
//  Copyright (c) 2015 Chris Eidhof. All rights reserved.
//

import Foundation

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


enum Result<T> {
    case Error(NSError)
    case Success(Box<T>)
}

let myURL = NSURL(string: "http://localhost:8000/users/objcio")

func getData(url: NSURL) -> Result<NSData> {
    var error: NSError? = nil
    let optionalData = NSData(contentsOfURL: url, options: NSDataReadingOptions.allZeros, error: &error)
    if let data = optionalData {
        return .Success(Box(data))
    } else {
        return .Error(error!)
    }
}

typealias JSONDict = [String:AnyObject]

func parseJSON(data: NSData) -> Result<JSONDict> {
    var error: NSError? = nil
    if let obj = NSJSONSerialization.JSONObjectWithData(data, options: .allZeros, error: &error) as? JSONDict {
        return .Success(Box(obj))
    } else {
        return .Error(error!)
    }
}


func parsePublicRepos(dict: JSONDict) -> Result<Int> {
    if let number = dict["public_repos"] as? Int {
        return .Success(Box(number))
    } else {
        let err = NSError(domain: "objc.io", code: 42, userInfo: [:])
        return .Error(err)
    }
}

infix operator >>> { associativity left }

func >>><A,B>(value: Result<A>, f: A -> Result<B>) -> Result<B> {
    switch value {
    case .Error(let e):
        return .Error(e)
    case .Success(let boxed):
        return f(boxed.unbox)
    }
}

func getReposFromURL(url: NSURL) -> Result<Int> {
    return getData(url) >>> parseJSON >>> parsePublicRepos
}

switch getReposFromURL(myURL!) {
case .Error(let e):
    println(e.localizedDescription)
case .Success(let n):
    println("SUCCESS! \(n.unbox)")
}