#!/usr/bin/env perl
#
# You are given a start date and offset counter. Optionally you also get bank
# holiday date list.
# 
# Given a number (of days) and a start date, return the number (of days)
# adjusted to take into account non-banking days. In other words: convert a
# banking day offset to a calendar day offset.
# 
# Non-banking days are:
# 
# a) Weekends
# b) Bank holidays
# 
# Example 1
# 
# Input: $start_date = '2018-06-28', $offset = 3, $bank_holidays = ['2018-07-03']
# Output: '2018-07-04'
# 
# Thursday bumped to Wednesday (3 day offset, with Monday a bank holiday)
# 
# Example 2
# 
# Input: $start_date = '2018-06-28', $offset = 3
# Output: '2018-07-03'
# 

use strict;
use warnings;
use Test2::V0 -no_srand => 1;
use Data::Dumper;
use Date::Calc qw/Add_Delta_Days Day_of_Week/;

my $cases = [
	[ '2018-06-28', 3, ['2018-07-03']],
	[ '2018-06-28', 3],
];

sub banking_day_offset
{
	my $date     = $_[0]->[0];
	my $offset   = $_[0]->[1];
	my $holidays = $_[0]->[2];

	my %holidays = map { $_, 1 } @$holidays;

	my @date = split(/-/, $date);

	while ($offset > 0) {
		@date = Add_Delta_Days(@date, 1);
		my $dow = Day_of_Week(@date);
		--$offset unless $dow == 6 or $dow == 7 or defined $holidays{sprintf("%04d-%02d-%02d", @date)};
	}
	return sprintf("%04d-%02d-%02d", @date);
}

is(banking_day_offset($cases->[0]), '2018-07-04', 'Example 1');
is(banking_day_offset($cases->[1]), '2018-07-03', 'Example 2');
done_testing();

exit 0;