/**
  Closure describes declension rule for numerals depending on needs of application or language

  **Example:**

    { timeComponents -> (String, Bool) in
        if <condition> { return (<time_component_name>, <needs_display_numerical_value>) }
        else { return (<time_component_name>, <needs_display_numerical_value>) }
    }


  - parameters:

    - Double: integer part represents the number of complete time components in the considered time interval

  - returns:
    `(String, Bool)`, where `String` value is name of time component the required declination, `Bool` value sets need to display numerical value of time component in specified string format of time interval
*/
public typealias NKTimeComponentDeclensionRule = (Double) -> (String, Bool)?

public struct NKTextTimeIntervalConfiguration {
  /**
    Return string value if the compared dates are equal
    default: "" (empty string)
  */
  public var zeroTimeIntervalPlaceholder: String


  /*
    Output formats is similar to dateFormat of DateFormatter class: the corresponding key value is set to the corresponding value
    As example if set `pastFormat = "\(NKTextTimeIntervalConfiguration.numberValueKey) \(NKTextTimeIntervalConfiguration.timeComponentValueKey) ago"` in result will be something like "12 seconds ago"

  */

  /**
    Key for specifying location of numerical value of time component in string representation of time interval
  */
  public static let numberValueKey = "<VALUE>"

  /**
    Key for specifying location of numerical value of time component in string representation of time interval
  */
  public static let timeComponentValueKey = "<TIME_COMPONENT>"

  /**
    Time intreval output format as string for positive value
    If `date1.compare(date2) == .OrderedDescending` => `date1.timeIntervalSince(date2) > 0`
    default: "\(NKTextTimeIntervalConfiguration.numberValueKey)"
  */
  public var pastFormat: String

  /**
    Time intreval output format as string for negative value
    If `date1.compare(date2) == .OrderedAscending` => `date1.timeIntervalSince(date2) < 0`
    default: "\(NKTextTimeIntervalConfiguration.numberValueKey)"
  */
  public var futureFormat: String


  /*
    Declension Rules for each time component
  */
  ///Declension Rule for seconds
  public var seconds:   NKTimeComponentDeclensionRule?
  ///Declension Rule for minutes
  public var minutes:   NKTimeComponentDeclensionRule?
  ///Declension Rule for hours
  public var hours:     NKTimeComponentDeclensionRule?
  ///Declension Rule for days
  public var days:      NKTimeComponentDeclensionRule?
  ///Declension Rule for weeks
  public var weeks:     NKTimeComponentDeclensionRule?
  ///Declension Rule for months
  public var months:    NKTimeComponentDeclensionRule?
  ///Declension Rule for years
  public var years:     NKTimeComponentDeclensionRule?
  ///Declension Rule for centuries
  public var centuries: NKTimeComponentDeclensionRule?

  /**
    Base Init method
  */
  public init() 

  /**
    Method calculating count of maximum available time component in input time interval and returns it's string representation based on Declension Rules
    Count of maximum available time components calculates in in extension of the class TimeInterval wich implements NKTimeIntervalDateComponents protocol
    If `interval` equal zero method returns `zeroTimeIntervalPlaceholder`
    If some declension rule isn't setted method use previous rule
    If there is no declension rules from maximum available time component to minimum (seconds) method returns nil
    - parameters:
      - interval: Seconds beetween two dates
      - returns: Optional String
  */
  public func stringRepresentation(for interval: TimeInterval) -> String? 

  /**
    Method creats time interval string representation based on input rule and time component count
    If `value` is equal zero returns `zeroTimeIntervalPlaceholder`
    If `value > 0` will be used `pastFormat`, else - `futureFormat`
    If `rule` is equal zero returns `nil`
    - parameters:
      - rule: Declension rule
      - value: Time component count (Double used if it needs to make representation for floating point value)
    - returns: Optional String
  */
  public func formatedString(for rule: NKTimeComponentDeclensionRule?, with value: Double) -> String? 
}
  
  
//MARK: - NKTextTimeIntervalConfiguration default configurations
/**
  This extension contains static methods that generate configurations based on rules for declining the numerals of some languages
*/
public extension NKTextTimeIntervalConfiguration {
  
  /**
    Public static method generate default configuration based on rules for declining the numerals of English
  */
  public static func defaultEnglish() -> NKTextTimeIntervalConfiguration
  
  /**
    Public static method generate default configuration based on rules for declining the numerals of Russian
  */
  public static func defaultRussian() -> NKTextTimeIntervalConfiguration 
  
  /**
    Public static method generate default configuration based on rules for declining the numerals of Ukrainian
  */
  public static func defaultUkrainian() -> NKTextTimeIntervalConfiguration 
}

protocol NKTimeIntervalDateComponents {
  var seconds:    Double { get }
  var minutes:    Double { get }
  var hours:      Double { get }
  var days:       Double { get }
  var weeks:      Double { get }
  var months:     Double { get }
  var years:      Double { get }
  var centuries:  Double { get }
}

extension TimeInterval: NKTimeIntervalDateComponents { }

/**
  Protocol declares methods for obtaining a time interval between two dates in a string representation using NKTextTimeIntervalConfiguration
*/
public protocol NKTimeIntervalTextTransformable {
  /**
    Protocol declares methods for obtaining a time interval between two dates in a string representation using NKTextTimeIntervalConfiguration
  */
  static func timeIntervalFromNow(to date: Date, with config: NKTextTimeIntervalConfiguration) -> String?

  func timeInterval(to date: Date, with config: NKTextTimeIntervalConfiguration) -> String?

}

/**
  Implementation of NKTimeIntervalTextTransformable protocol in extension of the class Date
*/
extension Date: NKTimeIntervalTextTransformable {}