#!/usr/bin/perl

use strict;
use warnings;
use POSIX qw(strftime ceil);
use utf8;
use open qw(:std :utf8);
use Encode qw(encode decode);
use Getopt::Std;

@ARGV = map { decode("UTF-8", $_) } @ARGV;

sub usage() {
	print STDERR "usage: $0 -n num -d dir -f string\n";
	print STDERR "\tn: number of hours to collect from the data files\n";
	print STDERR "\td: data directory to look for data files in\n";
	print STDERR "\tf: file template data files are patterned after\n";
}

my %args;
getopt("ndf", \%args);

unless (defined ($args{n}) && ($args{n} =~ /^\d+$/) && $args{n} >= 0 ){
	usage;
	die "invalid number of hours";
}

unless (defined ($args{d}) && -d "$args{d}"){
	usage;
	die "omg! data dir doesn't exist!";
}

unless (defined ($args{f}) && "$args{f}"){
	usage;
	die "filename template should be a non zero length string";
}

my $p_flag = 0;
my $date = time;
my $data_d = "$args{d}";
my $f_tplate = "$args{f}";
my $n_hours = "$args{n}";

my $out_dat_f = "$data_d/$f_tplate.$n_hours"."_hours";
my $out_dat_f_t = "$out_dat_f.tmp";

if (-e $out_dat_f) {
	unlink $out_dat_f or printf "could not delete $out_dat_f\n";
}

if (-e $out_dat_f_t) {
	unlink $out_dat_f_t or printf "could not delete $out_dat_f_t\n";
}

open(OUT, ">>", $out_dat_f) or die "omg! can't open output file: $out_dat_f";
open(OUT_t, ">>", $out_dat_f_t) or die "omg! can't open output file: $out_dat_f_t";

my $date_pat = strftime "%Y%m%d%H", localtime($date - ($n_hours * 3600));
my $date_pat_iso = strftime "%FT%H:", localtime($date - ($n_hours * 3600));

my $calcd_days = ceil($n_hours / 24);
for (my $nday = $calcd_days; $nday >= 0; $nday--) {
	my $date_it = $date - ($nday * 86400);

	my $datey = strftime "%Y", localtime($date_it);
	my $tdatey = strftime "%Y%m%d", localtime($date_it);
	my $tdatey_iso = strftime "%F", localtime($date_it);

	my $in_dat_f = "$data_d/$datey/$f_tplate.$tdatey";
	my $in_dat_f_iso = "$data_d/$datey/$f_tplate.$tdatey_iso";

	if (-e $in_dat_f or -e $in_dat_f_iso) {
		if (-e $in_dat_f) {
			open(IN, "<", $in_dat_f) or die "omg! can't open input file: $in_dat_f";
		} elsif (-e $in_dat_f_iso) {
			open(IN, "<", $in_dat_f_iso) or die "omg! can't open input file: $in_dat_f_iso";
		} else {
			die "omg! couldn't find any input files!";
		}

		while (<IN>) {
			$p_flag = 1 if(/^$date_pat/);
			$p_flag = 1 if(/^$date_pat_iso/);
			print OUT;
			print OUT_t if($p_flag);
		}
		close(IN);
	}
}
close(OUT);
close(OUT_t);

if (-e $out_dat_f_t && -s $out_dat_f_t >= 1000 * $n_hours) {
	rename $out_dat_f_t, $out_dat_f; 
} elsif (-e $out_dat_f_t) {
	unlink $out_dat_f_t or printf "could not delete $out_dat_f_t\n";
}