#!/usr/bin/perl
use strict;
use warnings;
use Date::Parse qw/ str2time /;
use POSIX qw/ strftime /;

chomp(my @line = split /,/, <DATA>);
my @data = \@line;

my $beg = str2time("@line[0,1]");
$beg = int($beg / 3600) * 3600; # truncate minutes and seconds

my $end = $beg + 12 * 60 * 60; # add 12 hours

printf "%s  -+-  %s\n",
	map {strftime "%Y-%m-%d %H:%M:%S", localtime $_} $beg,$end;

while (<DATA>) {
	chomp(my @line = split /,/);
	my $date = str2time("@line[0,1]");
	$date = int($date / 3600) * 3600; # truncate minutes and seconds
	
	if ($date < $end) {
		push @data, \@line;	
	}
	else {
		process(@data);
		
		@data = \@line;
		$end = $date + 12 * 60 * 60;
		
		printf "%s  -+-  %s\n",
			map {strftime "%Y-%m-%d %H:%M:%S", localtime $_} $date, $end;
	}
}

process(@data);

sub process {
	my @data = @_;
	# do somthing with data
	my @sum;
	my @idx = 2 .. 5;
	for my $line (@data) {
		for my $col (@idx) {
			$sum[$col] += $line->[$col];
		}
	}
	printf "Avg of %d lines", scalar @data;
	print +(map {sprintf "%10.5f", $sum[$_] / @data} @idx), "\n";
}

__DATA__
2011.01.13,21:25,1.33508,1.33524,1.33470,1.33494,391
2011.01.13,21:30,1.33494,1.33506,1.33447,1.33453,318
2011.01.13,21:35,1.33453,1.33483,1.33417,1.33434,426
2011.01.13,21:40,1.33434,1.33468,1.33417,1.33467,309
2011.01.13,21:45,1.33471,1.33493,1.33465,1.33465,233
2011.01.13,21:50,1.33465,1.33475,1.33443,1.33463,184
2011.01.13,21:55,1.33463,1.33519,1.33463,1.33493,344
2011.01.13,22:00,1.33494,1.33563,1.33489,1.33524,318
2011.01.13,22:05,1.33524,1.33551,1.33512,1.33549,182
2011.01.14,22:05,1.33524,1.33551,1.33512,1.33549,182