#!/usr/bin/perl -w
# use warnings!!! use it use it use it

# basic operations in perl

###### WARM UP ############
# warm up:  use strict definition of variables
# 		use my libraries (or your libraries)
use strict;
use lib '/work/cvogel/scripts_perl/Library_own/';
use lib '/work/cvogel/scripts_perl/Library/';
use lib '/usr/bin/perl/';
use lib '/work/cvogel/alf1/';
use General;

# print everything at once
$|=1;


# tell user how to use the program, and how many arguments to provide
die "perl_101.pl  <tab delimited input file>\n" unless $ARGV[0];
# rename input variable (@ARGV is argument array)
my $file = $ARGV[0];



####### REAL STUFF ##########


# open file and read in every line
# take first element in each line as key to a hash, store second element as value of hash, push third element into array

# define the hash and array for data storage
my %DATA; # hash key = first element, value = second element
my @MORE_DATA; # array of third elements


######## go through each line of file
open (FILE, $file) or die "Can't open $file\n";
while ( my $line = <FILE> )  {

	next if length(chomp $line) == 0;  # accept this line as is
	# this line chops of every nasty end-of-line character of line, and it skips empty (zero length) lines
	
	print "\nREADING LINE $line\n";
	
	my @entries_of_line = split("\t", $line); # split line into array
	print "Number of entries in line\t", scalar(@entries_of_line), "\n";

	$DATA{$entries_of_line[0]} = $entries_of_line[1];  # put first and second element of array into the hash %DATA
	push(@MORE_DATA, $entries_of_line[2]);  # add third element of entries_of_line to array
	
	print "Done with line\n";

} # while ( my $line = <FILE> )  {
close FILE;


#########  'analyze' your data storage variables and produce some output
print "\n\### ANALYSIS ###\n";

# 1. analyze hash ---------------------------
print "Analyzing hash DATA\n";
print "Number of keys\t", scalar(keys(%DATA)), "\n";  # how many keys in hash?
print "Number of values\t", scalar(values(%DATA)), "\n";  # how many values in hash?

# put all keys from hash %DATA into array and print array with delimiter '---'
my @keys = keys(%DATA);
print "All keys\t", join("---", @keys), "\n";

# print each key and corresponding value from hash
print "\tPrinting all HASH entries\n";
foreach my $entry_in_hash ( keys(%DATA) ) {
	
	print "key\t$entry_in_hash\tvalue\t", $DATA{$entry_in_hash}, "\n";
	
}  #  foreach my $entry_in_hash ( keys(%DATA) ) { 

# 2. analyze array  -------------------
print "\nAnalyzing array MORE_DATA\n";
print "Length (number of entries)\t", scalar(@MORE_DATA), "\n";

# two ways of going through array 
# a. similar to above, go through each entry: 
print "Printing all entries -- take ONE\n";
my $count = 0; # have a little counter along with it
foreach my $entry ( @MORE_DATA ) {

	print "entry\t$entry\tcounter\t$count\n";
	$count++; # increase count by one

} # foreach my $entry ( @MORE_DATA ) {

# b. go from first to last element of array:
print "\n";
print "Printing all entries -- take TWO\n";
for ( my $position = 0; $position <= $#MORE_DATA; $position++ )  {

	print "position $position\tentry in MORE_DATA\t$MORE_DATA[$position]\n";

} #