//  BadLuckDays.swift  Copyright (c) Kari Laitinen

//  http://www.naturalprogramming.com

//  2016-11-08 File created.   2016-11-08 Last modification.

//  This program demonstrates:
//    - use of standard types Date, Calendar, etc.

import Foundation


let calendar = Calendar.current

let date_of_today = Date()

let year_today = calendar.component( Calendar.Component.year,
                                     from: date_of_today )

let month_today = calendar.component( Calendar.Component.month,
                                      from: date_of_today )

var components_of_date_to_test = DateComponents()
components_of_date_to_test.year  = year_today
components_of_date_to_test.month = month_today
components_of_date_to_test.day   = 13

var date_to_test = calendar.date( from: components_of_date_to_test )!

let date_formatter = DateFormatter()

print( "\n The following are Fridays which also are "
    +  "\n the 13th days of a month:  \n" )

var number_of_friday13_dates_to_print = 10

while  number_of_friday13_dates_to_print > 0
{
   let day_of_week_of_date_to_test  =
                            calendar.component( Calendar.Component.weekday,
                                                from: date_to_test )

   if day_of_week_of_date_to_test == 6
   {
      let year_of_date_to_test = calendar.component( Calendar.Component.year,
                                                     from: date_to_test )
      let month_of_date_to_test = calendar.component( Calendar.Component.month,
                                                      from: date_to_test )

      print( String( format: "     %04d-%02d-13, %@",
             year_of_date_to_test, month_of_date_to_test,
             date_formatter.weekdaySymbols[ day_of_week_of_date_to_test - 1 ] ) )

      number_of_friday13_dates_to_print -= 1
   }

   // The following statement creates a new Date object that contains 
   // the 13th day of the following month.

   date_to_test = calendar.date( byAdding: Calendar.Component.month, value: 1,
                                 to: date_to_test )!
}

print( "\n" )