#!/usr/bin/env perl -w
use strict;


if (!@ARGV){ #no command line arguments, so Part A
    my ($file, $dir, $yn, @all_lines);
    #prompt for file name and attempt to open
    print "Enter the name of a file, please:\n";
    chomp ($file = <STDIN>); 

    if (!-e $file){ #file does not exist in this directory
	print "$file does not exist in the current directory\n";
	print "Do you wish to enter a directory where the file can be found? (y/n)\n";
	chomp ($yn = <STDIN>);
	if ($yn eq "n"){ #user doesn't wish to enter directory
	    print "You've chosen not to enter a directory.  Good bye\n";
	    exit;
	}
	#if we got here, user does want to enter a directory.  Take it, and open file
	print "Enter the name of the directory (no trailing slash):\n";
	chomp ($dir = <STDIN>);
	open FILE, "$dir/$file" or die "Cannot open file: $!\n";
    } else { # the file does exist, so open it.
	open FILE, "$file" or die "Cannot open file: $!\n";
    }

    # file is opened (one way or another).  Read from it now and print the info
    @all_lines = <FILE>;
    print "The file $file contains " . @all_lines . " lines\n";
    if (@all_lines){
	print "The first line is:\n";
	print $all_lines[0];
	print "The last line is: \n";
	print $all_lines[-1];
    }

    #Now we want to open a file in the same directory as the original
    #The new file's name is the old file name in all caps

    if ($dir){ # if we entered a directory name
	open OFILE, ">$dir/\U$file\E" or die "Cannot create \U$file\E: $!\n";
    } else {
	open OFILE, "> \U$file\E" or die "Cannot create \U$file\E: $!\n";
    }

    #now we simply print all lines of the original to the new (in lowercase)
    #since we're interpolating, elements will be printed with a space
    #seperating them.  We don't want that.
    $" = '';
    print OFILE "\L@all_lines\E";

    #close both files
    close OFILE;
    close FILE;
} else { #there was at least one command line argument, so Part B
    
    my ($word, @words, %words, $file, $line);
    foreach $file (@ARGV){ # go through each file and open it
	if (!open FILE, $file){
	    print "Cannot open $file: $!\n";
	    next;
	}
	foreach $line (<FILE>){ #split each line in the file into words
	    chomp $line;
	    @words = split / /, $line;
	    foreach (@words){ #use a hash to keep track of which words have been counted
		$words{$_}++;
	    }
	}
	close FILE;
    }
    
    foreach $word (keys %words){ #go through each element of the hash
	print "$word - $words{$word}\n";
    }
    if (keys %words == 0){
	print "All files were empty or invalid\n";
    }
}