#!/usr/bin/perl -w

use strict;
use warnings;

use Time::Local;
use Test::More "no_plan";

test();

sub test
{

    ok ( identify_quarter("201101") eq "2011Q1");
    ok ( identify_quarter("201102") eq "2011Q1");
    ok ( identify_quarter("201103") eq "2011Q1");
    ok ( identify_quarter("201104") eq "2011Q2");
    ok ( identify_quarter("201105") eq "2011Q2");
    ok ( identify_quarter("201106") eq "2011Q2");
    ok ( identify_quarter("201107") eq "2011Q3");
    ok ( identify_quarter("201108") eq "2011Q3");
    ok ( identify_quarter("201109") eq "2011Q3");
    ok ( identify_quarter("201110") eq "2011Q4");
    ok ( identify_quarter("201111") eq "2011Q4");
    ok ( identify_quarter("201112") eq "2011Q4");
    ok ( identify_quarter("201201") eq "2012Q1");
    ok ( get_previous_quarter("2011Q4") eq "2011Q3");
    ok ( get_previous_quarter("2011Q3") eq "2011Q2");
    ok ( get_previous_quarter("2012Q1") eq "2011Q4");
    ok ( last_month_of_quarter(1) == 3);
    ok ( last_month_of_quarter(2) == 6);
    ok ( last_month_of_quarter(3) == 9);
    ok ( last_month_of_quarter(4) == 12);
    ok ( get_next_month("201101") eq "201102");
    ok ( get_next_month("201112") eq "201201");
    ok ( last_day_of_month("201101") == 31);
    ok ( last_day_of_month("201202") == 29);
    ok ( get_last_month_of_quarter("2011Q1") eq "201103");
    ok ( get_last_month_of_quarter("2011Q2") eq "201106");
    ok ( get_last_month_of_quarter("2011Q3") eq "201109");
    ok ( get_last_month_of_quarter("2011Q4") eq "201112");
    ok ( get_last_month_of_quarter("2012Q1") eq "201203");
    ok ( get_last_day_of_prev_quarter("20110101") eq "20101231");
    ok ( get_last_day_of_prev_quarter("20110203") eq "20101231");
    ok ( get_last_day_of_prev_quarter("20110310") eq "20101231");
    ok ( get_last_day_of_prev_quarter("20110331") eq "20101231");
    ok ( get_last_day_of_prev_quarter("20110415") eq "20110331");
    ok ( get_last_day_of_prev_quarter("20110516") eq "20110331");
    ok ( get_last_day_of_prev_quarter("20110629") eq "20110331");
    ok ( get_last_day_of_prev_quarter("20110731") eq "20110630");
    ok ( get_last_day_of_prev_quarter("20110805") eq "20110630");
    ok ( get_last_day_of_prev_quarter("20110930") eq "20110630");
    ok ( get_last_day_of_prev_quarter("20111030") eq "20110930");
    ok ( get_last_day_of_prev_quarter("20111130") eq "20110930");
    ok ( get_last_day_of_prev_quarter("20111231") eq "20110930");
    ok ( get_last_bus_day_of_prev_quarter("20110901") eq "20110630");
    ok ( get_last_bus_day_of_prev_quarter("20120101") eq "20111230");
}


sub get_last_day_of_prev_quarter
{
    my ($date) = @_;
        
    my $this_quarter          = identify_quarter($date);
    my $quarter               = get_previous_quarter($this_quarter);
    my $last_month_of_quarter = get_last_month_of_quarter($quarter);
    my $ldom                  = last_day_of_month($last_month_of_quarter);

    return $last_month_of_quarter . $ldom;
}
sub get_last_bus_day_of_prev_quarter
{
    my ($date) = @_;
    my $new_date = get_last_day_of_prev_quarter($date);

    my $year  = substr($new_date,0,4);
    my $month = substr($new_date,4,2);
    my $day   = substr($new_date,6,2);

    my $epoch = timelocal(0,0,12,
                          $day,
                          $month-1,
                          $year-1900);

    my @timestuff = localtime($epoch);

    #
    # If the day is a Sunday (0) or a Saturday (6)
    #
    # Subtract 1 or 2 days from the day.

    my $date_diff = 0;
    if ($timestuff[6] == 0)
    {
        $date_diff = 2;
    }
    if ($timestuff[6] == 6)
    {
        $date_diff = 1;
    }
    if ($date_diff > 0)
    {
        $epoch = $epoch - (60*60*24) * $date_diff;
    }

    @timestuff = localtime($epoch);
        
    #
    # Rebuild the YYYYMMDD string from the localtime bits.
    #

    return  $timestuff[5] + 1900 . sprintf( "%02d",$timestuff[4] + 1) . "$timestuff[3]";
}

sub get_last_month_of_quarter
{
    my ($yyyymm) = @_;
    return substr($yyyymm,0,4) . sprintf("%02d",last_month_of_quarter(substr($yyyymm,5,1)));
}
sub last_month_of_quarter
{
    my ($quarter) = @_;
    return $quarter * 3;
}

sub last_day_of_month
{
    # This logic is moronic, but it works. 
    # To get the last day of a given month, first take the first day 
    # of the first month, convert it to epoch seconds, subtract a day
    # (86400 seconds), then re-convert back and pull the "day of month" 
    # element out of the list.

    my ($yyyymm) = @_;
    my $next_day = get_next_month($yyyymm) . "01";
    my $epoch = timelocal(0,0,12,1,
                          substr($next_day,4,2)-1,
                          substr($next_day,0,4)-1900);
    $epoch = $epoch - ( 60*60*24 );
    my @timestuff = localtime($epoch);
    return $timestuff[3];
}
sub get_next_month
{
    my ($yyyymm) = @_;
    my $year  = substr($yyyymm,0,4);
    my $month = substr($yyyymm,4,2);
    if ($month == 12)
    {
        $month = 1;
        $year++;
    }
    else
    {
        $month++;
    }
   
    return $year . sprintf "%02d",$month;
}
sub get_previous_quarter
{
    my ($quarter) = @_;
    my $year = substr($quarter,0,4);
    my $q    = substr($quarter,5,1);

    if ($q == 1)
    {
        $q = 4;
        $year--;
    }
    else
    {
        $q--;
    }
    return "$year" . "Q$q";
}
sub identify_quarter
{
    my ($date) = @_;
    my $year    = substr ($date,0,4);
    my $month   = substr ($date,4,2);
    my $quarter =  int(($month-1) / 3) +1;
    return "$year" . "Q$quarter";
}