// Reserved characters defined by RFC 3986

// Reference: https://www.ietf.org/rfc/rfc3986.txt

let generalDelimiters = ":#[]@"

let subDelimiters = "!$&'()*+,;="

let reservedCharacters = generalDelimiters + subDelimiters

let allowedCharacterSet = NSMutableCharacterSet()

allowedCharacterSet.formUnionWithCharacterSet(NSCharacterSet.URLQueryAllowedCharacterSet())

allowedCharacterSet.removeCharactersInString(reservedCharacters)

// Crashes due to internal bug in iOS 7 ~ iOS 8.2.

// References:

// - https://github.com/Alamofire/Alamofire/issues/206

// - https://github.com/AFNetworking/AFNetworking/issues/3028

// return string.stringByAddingPercentEncodingWithAllowedCharacters(allowedCharacterSet) ?? string

let batchSize = 50

var index = string.startIndex

var escaped = ""

while index != string.endIndex {

let startIndex = index

let endIndex = index.advancedBy(batchSize, limit: string.endIndex)

let range = Range(start: startIndex, end: endIndex)

let substring = string.substringWithRange(range)

escaped += substring.stringByAddingPercentEncodingWithAllowedCharacters(allowedCharacterSet) ?? substring

index = endIndex

}

return escaped

public enum Error: ErrorType {

case CannotGetStringFromData(NSData, NSStringEncoding)

case CannotGetDataFromString(String, NSStringEncoding)

case CannotCastObjectToDictionary(AnyObject)

case InvalidFormatString(String)

}

/// - Throws: URLEncodedSerialization.Error

public static func objectFromData(data: NSData, encoding: NSStringEncoding) throws -> [String: String] {

guard let string = String(data: data, encoding: encoding) else {

throw Error.CannotGetStringFromData(data, encoding)

}

var dictionary = [String: String]()

for pair in string.componentsSeparatedByString("&") {

let contents = pair.componentsSeparatedByString("=")

guard contents.count == 2 else {

throw Error.InvalidFormatString(string)

}

dictionary[contents[0]] = unescape(contents[1])

}

return dictionary

}

/// - Throws: URLEncodedSerialization.Error

public static func dataFromObject(object: AnyObject, encoding: NSStringEncoding) throws -> NSData {

guard let dictionary = object as? [String: AnyObject] else {

throw Error.CannotCastObjectToDictionary(object)

}

let string = stringFromDictionary(dictionary)

guard let data = string.dataUsingEncoding(encoding, allowLossyConversion: false) else {

throw Error.CannotGetDataFromString(string, encoding)

}

return data

}

public static func stringFromDictionary(dictionary: [String: AnyObject]) -> String {

let pairs = dictionary.map { key, value -> String in

if value is NSNull {

return "\(escape(key))"

}

let valueAsString = (value as? String) ?? "\(value)"

return "\(escape(key))=\(escape(valueAsString))"

}

return pairs.joinWithSeparator("&")

}