package Step2;
use strict;
use File::Copy;

################################################################################################################
## This subroutine computes the cross correlation between each 1-day file                                     ##
##	1. all the sac files contained in the current folder are listed                                       ##
##	2. a FTN90 program determines the output names, following this model: YYYYDDD.NW1.ST1.NW2.ST2.CHN.sac ##
##	3. SAC is run and feeded with the file created by the FTN program                                     ##
################################################################################################################
sub cross {
	my($workpath) = @_;
	my @files;
	my $files;
	my ($nbcross, $nbcrosscor);
	my ($i, $j);

	print("\n_______________________________________________________________________________________________________\n");
	print("Cross-correlation process\n\n");

	print("Changing to folder: $workpath\n");
	chdir($workpath);

	opendir(FOLD,"$workpath");
		unlink("liste");
		unlink("crosslist");
		@files = readdir(FOLD);
	closedir(FOLD);

	open(LISTE,">liste") or die("\n\nCouldn't create the new 'liste' file, cross correlation module: $1\n");
	foreach $files (@files) {
		chomp($files);
		if($files =~ /sac$/) {
			print(LISTE "$files");
			print(LISTE "\n");
		}
	}
	print(LISTE "liste");
	close(LISTE);

	open(NAMES,"|dontgivemenames") or die("\n\nCouldn't open the naming program, cross correlation module: $1\n");
	close(NAMES);
	print("\n\n");

	open(CROSSLISTE,"crosslist");
		@files = <CROSSLISTE>;
	close(CROSSLISTE);

	# We are here determining the number of iteration for the cross-correlating loop.
	# The filenames inside of the crosslist file go by 3: the two files to cross-correlate, and the name of the output
	# file.
	# As the perl language is begining any count by 0, I have to add 1 to the number of items in the list. The
	# operations are very simple, but it's much safer and easier to understand if the steps are separated.
	$nbcross = $#files;
	$nbcross = $nbcross + 1;
	$nbcross = $nbcross / 3;
	$nbcrosscor = $nbcross - 1;

	mkdir("norm_files");

	# Here is the part where SAC is used
	open(SAC, "|sac"); # SAC is opened at the beginning of the loops
	print(SAC "echo on commands\n");
	for($i = 0; $i < $nbcross; $i++) {
		$j = 3*$i;
		chomp($files[$j]);
		chomp($files[$j+1]);
		chomp($files[$j+2]);

		print(SAC "*** $i / $nbcrosscor ***\n");

		print(SAC "read ".$files[$j]." ".$files[$j+1]."\n"); # The pair of files which have to be cross-correlated are loaded into memory
		#print("read ".$files[$j]." ".$files[$j+1]."\n");
		
		print(SAC "correlate master 1\n");
		#print("correlate master 1\n");

		print(SAC "write trash ".$files[$j+2]."\n"); # The auto-correlation is useless, the cross-correlation is saved
		print(SAC "deletechannel all\n"); # Memory is emptied.

	}
	print(SAC "quit\n");
	close(SAC); # The loops are over, therefore SAC is closed as well

	open(LISTE,"liste");
		@files = <LISTE>;
	close(LISTE);
	foreach $files (@files) {
		if($files  =~ /sac$/) {
			chomp($files);
			File::Copy::move("$files","norm_files/$files") or die("\nCouldn't move the files, module cross: $!\n");
		}
	}


	
}
1;