#!/usr/bin/perl

use 5.12.3;

use strict;

use warnings;

use Cwd qw(abs_path cwd);

use IO::Handle qw(autoflush);

use File::Basename qw(basename dirname);

#use File::Slurp qw(read_file);

use diagnostics;

use threads qw(yield);

use threads::shared;

use Thread::Queue;

use Thread::Semaphore;

#use Fcntl qw(:flock);

use POSIX qw(SIGINT);

use POSIX qw(ceil);

chomp(my $cores = `grep -c ^processor /proc/cpuinfo`);

my (@lib, $mode);

# Path to and name of log file to be used for logging.

my $logf = "$ENV{HOME}/md5db.log";

# Delimiter used for database

my $delim = "\t\*\t";

# Array for storing the actual arguments used by the script internally.

# Might be useful for debugging.

my @cmd = (basename($0));

# Name of database file.

my $db = 'md5.db';

# Clear screen command.

my $clear = `clear && echo`;

# Creating a hash that will store the names of files that are

# too big to fit into RAM. We'll process them last.

my %large :shared;

# Creating a few shared variables.

# %err will be used for errors

# $n will be used to count the number of files processed

# %md5h is the database hash

my %err :shared;

my $n :shared = 0;

my %md5h :shared;

my %file_contents :shared;

my $stopping :shared = 0;

my $file_stack :shared = 0;

my $busy :shared = 0;

# This will be used to control access to the logger subroutine.

my $semaphore = Thread::Semaphore->new();

POSIX::sigaction(SIGINT, POSIX::SigAction->new(\&handler))

|| die "Error setting SIGINT handler: $!\n";

# Creating a custom POSIX signal handler.

# First we create a shared variable that will work as a SIGINT switch.

# Then we define the handler subroutine.

# If ^C is pressed for the first time,

# trip the switch and let the current threads finish.

# If ^C is pressed a second time, quit directly.

# Each subroutine to be used for starting threads will have to

# take notice of the state of the $saw_sigint variable.

my $saw_sigint :shared = 0;

sub handler {

}

# Open file handle for the log file

open(my $LOG, '>>', $logf) or die "Can't open '$logf': $!";

# Make the $LOG file handle unbuffered for instant logging.

$LOG->autoflush(1);

# Duplicate STDERR as a regular file handle

open(my $SE, ">&STDERR") or die "Can't duplicate STDERR: $!";

### Subroutine for printing usage instructions

sub usage {

	my $s = basename($0);

	say <<"HELP"

Usage: $s [options] [directory 1] .. [directory N]

	-help Print this help message.

	-double Check database for files that have identical

	hashes.

	-import Import MD5 sums to the database from already existing

	\*.MD5 files in each directory.

	-index Index new files in each directory.

	-test Test the MD5 sums of the files in the database to see if

	they've changed.

HELP

}

# This loop goes through the argument list as passed to the script

# by the user when ran.

foreach my $arg (@ARGV) {

	# If argument starts with a dash '-', interprete it as an option

	if ($arg =~ /^-/) {

		given ($arg) {

			# When '-double', set script mode to 'double', and call

			# the md5double subroutine later.

			when (/^-double$/) {

				if (!$mode) { push(@cmd, $arg); $mode = 'double'; }

			}

			# When '-import', set script mode to 'import', and call

			# the md5import subroutine later.

			when (/^-import$/) {

				if (!$mode) { push(@cmd, $arg); $mode = 'import'; }

			}

			# When '-help', set script mode to 'help', and print

			# usage instructions later.

			when (/^-help$/) {

				if (!$mode) { push(@cmd, $arg); $mode = 'help'; }

			}

			# When '-index', set script mode to 'index', and call

			# the md5index subroutine later.

			when (/^-index$/) {

				if (!$mode) { push(@cmd, $arg); $mode = 'index'; }

			}

			# When '-test', set the script mode to 'test', and call

			# the md5test subroutine later.

			when (/^-test$/) {

				if (!$mode) { push(@cmd, $arg); $mode = 'test'; }

			}

		}

	# If argument is a directory, include it in the @lib array

	} elsif (-d $arg) { push(@lib, $arg); push(@cmd, $arg); }

}

# If no switches were used, print usage instructions

if (!@lib || !$mode || $mode eq 'help')

	{ usage; exit; }

#say "@cmd\n";

# Subroutine for controlling the log file

# Applying a semaphore so multiple threads won't try to

# access it at once, just in case ;-)

sub logger {

	$semaphore->down();

	my($arg, $sw, @fn, $n);

	# Creating a variable to hold the current time.

	my $now = localtime(time);

	# Array of accepted switches to this subroutine

	my @larg = qw{start int gone corr diff end};

	# Loop through all the arguments passed to this subroutine

	# Perform checks that decide which variable the arguments are to

	# be assigned to.

	CHECK: while (@_) {

			$arg = shift(@_);

			# If $arg is a switch, set the $sw variable and start

			# the next iteration of the CHECK loop.

			foreach (@larg) {

				if ($_ eq $arg) { $sw = $arg; next CHECK; }

			}

			# If $arg is a number assign it to $n, if it's a file

			# add it to @fn.

			if ($arg =~ /^[0-9]*$/) { $n = $arg; }

			else { push(@fn, $arg); }

	}

	given ($sw) {

		# Starts writing the log.

		when ('start') {

			say $LOG "\n**** Logging started on $now ****\n";

			say $LOG "Running script in '$mode' mode.\n";

		}

		# When the script is interrupted by user pressing ^C,

		# say so in STDOUT, close the log.

		when ('int') {

			say "\nInterrupted by user!\n";

			say $LOG $n . " file(s) were tested.";

			say $LOG "\n**** Logging ended on $now ****\n";

			close $LOG or die "Can't close '$LOG': $!";

		}

		# Called when file has been deleted or moved.

		when ('gone') {

			say $LOG $fn[0] . "\n\t" . "has been (re)moved.\n";

			$err{$fn[0]} = "has been (re)moved.\n";

		}

		# Called when file has been corrupted.

		when ('corr') {

			say $LOG $fn[0] . "\n\t" .

			"has been corrupted.\n";

			$err{$fn[0]} = "has been corrupted.\n";

		}

		when ('diff') {

			say $LOG $fn[0] . "\n\t" .

				"doesn't match the hash in database.\n";

			$err{$fn[0]} = "doesn't match the hash in database.\n";

		}

		# Called when done, and to close the log.

		# If no errors occurred write "Everything is OK!" to the log.

		# If errors occurred print the %err hash.

		# Either way, print number of files processed.

		when ('end') {

			if (!%err) {

				say $LOG "\nEverything is OK!\n";

			} else {

				say "\n**** Errors Occurred ****\n";

				foreach my $fn (sort keys %err) {

					say $SE $fn . "\n\t" . $err{$fn};

				}

			}

			say $LOG $n . " file(s) were tested.\n" if ($n);

			say $LOG "\n**** Logging ended on $now ****\n";

			close $LOG or die "Can't close '$LOG': $!";

		}

	}

	$semaphore->up();

}

# Subroutine for reading a database file into the database hash.

# This is the first subroutine that will be executed and all others

# depend upon it, cause without it we don't have a

# database hash to work with.

sub file2hash {

	# The format string which is used for parsing the database file

	my $format = qr/^.*\t\*\t[[:alnum:]]{32}$/;

	my (@dbfile, @gone);

	# Open the database file and read it into the @dbfile variable

	open(MD5DB, '<', $db) or die "Can't open '$db': $!";

	chomp (@dbfile = (<MD5DB>));

	close(MD5DB) or die "Can't close '$db': $!";

	# Loop through all the lines in the database file and split

	# them before storing in the database hash.

	# Also, print each line to STDOUT for debug purposes

	foreach my $line (@dbfile) {

		# If current line matches the proper database file format,

		# continue.

		if ($line =~ /$format/) {

			my ($fn, $hash) = (split(/\Q$delim/, $line));

			# If $fn is a real file and not already in the hash,

			# continue.

			if (-f $fn && ! $md5h{$fn}) {

					$md5h{$fn} = $hash;

					say "$fn". "$delim" . "$hash";

			# Saves the names of deleted or moved files in '@gone'

			# for printing at the end of this subroutine.

			} else { push(@gone, $fn); }

		}

	}

	# Clears the screen, thereby scrolling past the database file print

	print $clear;

	# Loops through the @gone array and logs every file name

	# that's been deleted or moved.

	foreach my $fn (@gone) { logger('gone', $fn); }

}

# Subroutine for printing the database hash to the database file

sub hash2file {

	open(MD5DB, '>', "$db") or die "Can't open '$db': $!";

	# Loops through all the keys in the database hash and prints

	# the entries (divided by the $delim variable) to the database file.

	foreach my $k (sort keys %md5h) {

		say MD5DB $k . $delim . $md5h{$k};

	}

	close(MD5DB) or die "Can't close '$db': $!";

}

# Subroutine for finding files

# Finds all the files inside the directory name passed to it,

# and sorts the output before storing it in the @files array.

sub getfiles {

	my $dn = shift;

	my @files;

	or die "Can\'t run 'find': $!";

	while (my $fn = (<FIND>)) {

			chomp($fn);

			$fn =~ s($dn/)();

			push(@files, $fn) if (-f $fn && $fn ne basename($db));

	}

	close(FIND) or die "Can't close 'find': $!";

	return @files;

}

sub md5double {

	if (!keys(%md5h)) {

		say "No database file. Run the script in 'index' mode first\n" .

		"to index the files.";

		exit;

	}

	# Loop through the %md5h hash and save the checksums as keys in a

	# new hash called %exists. Each of those keys will hold an

	# anonymous array with the matching file names.

	my %exists;

	foreach my $fn (keys(%md5h)) {

		my $hash = $md5h{$fn};

		if (!$exists{"$hash"}) {

			$exists{"$hash"}->[0] = $fn;

		} else {

			push(@{$exists{"$hash"}}, $fn);

		}

	}

	# Loop through the %exists hash and print files that are identical,

	# if any.

	foreach my $hash (keys(%exists)) {

		if (scalar(@{$exists{"$hash"}}) > 1) {

			say "These files have the same hash (${hash}):";

			foreach my $fn (@{$exists{"$hash"}}) {

				say $fn;

			}

			say "";

		}

	}

}

# Subroutine for finding and parsing *.MD5 files, adding the hashes

# to the database hash and thereby also to the file.

# It takes 1 argument:

# (1) the thread queue

sub md5import {

	my $md5fn = shift;

	my ($fn, $hash, @fields, @lines);

	# The format string which is used for parsing the *.MD5 files.

	my $format = qr/^[[:alnum:]]{32}\s\*.*/;

	# If the file extension is *.MD5 in either upper- or

	# lowercase, continue.

	if ($md5fn =~ /.md5$/i) {

		# Open the *.MD5 file and read its contents to the

		# @lines array.

		open(MD5, '<', $md5fn) or die "Can't open '$md5fn': $!";

		chomp(@lines = (<MD5>));

		close(MD5) or die "Can't close '$md5fn': $!";

		# Loop to check that the format of the *.MD5 file really

		# is correct before proceeding.

		foreach my $line (@lines) {

			# If format string matches the line(s) in the *.MD5

			# file, continue.

			if ($line =~ /$format/) {

				# Split the line so that the hash and file name go

				# into @fields array.

				# After that strip the path (if any) of the file

				# name, and prepend the path of the *.MD5 file to

				# it instead.

				# Store hash and file name in the $hash and $fn

				# variables for readability.

				@fields = split(/\s\Q*/, $line, 2);

				my $path = dirname($md5fn);

				$hash = $fields[0];

				if ($path eq '.') { $fn = basename($fields[1]); }

				else { $fn = dirname($md5fn)

				. '/' . basename($fields[1]); }

				# Convert CR+LF newlines to proper LF to avoid

				# identical file names from being interpreted as

				# different.

				$fn =~ s/\r//;

				# Unless file name already is in the database hash,

				# print a message, add it to the hash.

				if (! $md5h{$fn} && -f $fn) {

					say "$fn" . "\n\t" .

					"Imported MD5 sum from '" .

					basename($md5fn) .

					"'.\n";

					$md5h{$fn} = $hash;

					# If file name is not a real file, write to

					# the log.

					# If file name is in database hash but the

					# MD5 sum from the MD5 file doesn't match,

					# print to the log.

				} elsif (! -f $fn) { logger('gone', $fn); }

				elsif ($md5h{$fn} ne $hash)

				{ logger('diff', $md5fn); }

			}

		}

	}

}

sub md5sum {

	my $fn = shift;

	while ($busy) { yield(); }

	if ($large{$fn}) {

		lock($busy);

		$busy = 1;

		$busy = 0;

		return $hash;

	} else {

# It takes 1 argument:

# (1) the thread queue

	my $q = shift;

	my $tid = threads->tid();

				if ($fn) {

					}

				}