libr-ios/librx/NSURL-Extensions.swift

//
//  NSURL-Extensions.swift
//  librx
//
//  Created by Yunlong Zheng on 11/23/15.
//  Copyright © 2015 librx. All rights reserved.
//

import Foundation

extension NSURL
{
    
    class func validateUrl(urlString: String?, completion:(success: Bool, urlString: String? , error: NSString) -> Void)
    {
        // Description: This function will validate the format of a URL, re-format if necessary, then attempt to make a header request to verify the URL actually exists and responds.
        // Return Value: This function has no return value but uses a closure to send the response to the caller.
        
        var formattedUrlString : String?
        
        // Ignore Nils & Empty Strings
        if (urlString == nil || urlString == "")
        {
            completion(success: false, urlString: nil, error: "Url String was empty")
            return
        }
        
        // Ignore prefixes (including partials)
        let prefixes = ["http://www.", "https://www.", "www."]
        for prefix in prefixes
        {
            if ((prefix.rangeOfString(urlString!, options: NSStringCompareOptions.CaseInsensitiveSearch, range: nil, locale: nil)) != nil){
                completion(success: false, urlString: nil, error: "Url String was prefix only")
                return
            }
        }
        
        // Ignore URLs with spaces (NOTE - You should use the below method in the caller to remove spaces before attempting to validate a URL)
        // Example:
        // textField.text = textField.text.stringByReplacingOccurrencesOfString(" ", withString: "", options: nil, range: nil)
        let range = urlString!.rangeOfCharacterFromSet(NSCharacterSet.whitespaceCharacterSet())
        if let _ = range {
            completion(success: false, urlString: nil, error: "Url String cannot contain whitespaces")
            return
        }
        
        // Check that URL already contains required 'http://' or 'https://', prepend if it does not
        formattedUrlString = urlString
        if (!formattedUrlString!.hasPrefix("http://") && !formattedUrlString!.hasPrefix("https://"))
        {
            formattedUrlString = "http://"+urlString!
        }
        
        completion(success: true, urlString: urlString, error: "")
        return
        
    }
}