#!/usr/bin/perl

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

@ARGV = map { decode("UTF-8", $_) } @ARGV;
die "usage: program data_directory filename_template" unless ($#ARGV == 1);

my $p_flag = 0;
my $date = time;
my $data_d = "$ARGV[0]";
my $f_tplate = "$ARGV[1]";

die "omg! data dir doesn't exist!" unless (-d "$data_d");
die "filename template should be a non zero length string" unless ("$f_tplate");

my $out_dat_f = "$data_d/$f_tplate.2-3_day";
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 - (2 * 86400));
my $date_pat_iso = strftime "%FT%H:", localtime($date - (2 * 86400));

for (my $nday = 2; $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 >= 50000) {
	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";
}