#!/usr/bin/env perl -w

sub mysort{
    #I'm not actually going to use this function, but this code
    #spells out how the finished sorting procedure ends up working

    if (length $a < length $b){
	return 1; #a is shorter, so b is first;
    } elsif (length $a > length $b){
	return -1; #a is longer, so a is first;
    } else { #lengths are equal, now compare the strings
	if ($a lt $b){
	    return 1; #a is 'less than' b, so b is first
	} elsif ($a gt $b){
	    return -1; #a is 'greater than' b, so a is first
	} else{
	    return 0; #strings are equal, so it doesn't matter
	}
    }
}

#the or operator expects a scalar, so we get the size of @ARGV.  If there
#are no command line arguments, the size is 0, so we evaluate the other part
#of the or statement.
@ARGV or die "You must enter at least one file name on the command line!\n";


#go through each file and try to open it.  We can't use the empty <> operator
#here, because we need to be able to give an appropriate error message
#if the file cannot be opened.
foreach $file (@ARGV){
    if (!open FILE, "$file"){
	print STDERR "Could not open file $file: $!\n";
	next;
    }
    
    #Go through each line, split it on the space character.
    foreach $line (<FILE>){
	chomp $line;
	@words = split / /, $line;
	foreach (@words){
	    #remove anything from the word that's not a letter, number, or '
	    s/[^\w\']//g; 
	    #add this word to the hash, incrementing its count
	    $hash{$_}++;
	}
    }
    close FILE;
}

#Sort the keys of the hash by length, then in reverse ASCIIbetical order
@sorted = sort {length($b) <=> length($a) or $b cmp $a} keys (%hash);

#If I wanted to use the sort function above, I could have instead written:
#@sorted = sort mysort keys (%hash);

#We will now figure out to which set(s) each word belongs
#instead of a foreach with a bunch of push ... if statements, 
#I could have just done 5 grep statements.  But we didn't cover grep before
#the homework was due.
foreach (@sorted){
    push @Capitals, $_ if /^[A-Z]/; #beginning of string, capital letter
    push @lowers, $_ if /^[a-z0-9]/; #beginning of string, lowercase or number
    push @apos, $_ if /\'/; #apostrophe, anywhere in the string
    push @vowels, $_ if /[aeiou]{2}/i; #two of a, e, i, o, u - case insensitive
    push @dups, $_ if /(.)\1/i; #any character, immediately followed by itself
}

#now, for each set, print out every member of the set, followed by 
#its count in the hash
 
print "Words starting with Capitals:\n";
foreach (@Capitals){
    print "\t$_ - $hash{$_}\n";
}
print "\n";

print "Words starting with lowercase letters (or numbers):\n";
foreach (@lowers){
    print "\t$_ - $hash{$_}\n";
}
print "\n";

print "Words containing apostrophes:\n";
foreach (@apos){
    print "\t$_ - $hash{$_}\n";
}
print "\n";

print "Words containing adjacent vowels:\n";
foreach (@vowels){
    print "\t$_ - $hash{$_}\n";
}
print "\n";

print "Words containing adjacent duplicate letters:\n";
foreach (@dups){
    print "\t$_ - $hash{$_}\n";
}
print "\n";