#!/usr/bin/perl
use Time::Local;
use Digest::MD5  qw(md5_hex);
use File::Basename;


my $trk_dir = "$ENV{HOME}/.trk";

use constant {
	START => 1,
	TIMEFORMAT => 2,
	STOP => 3,
};

sub help
{
	my $code = shift;
	printf("It seems you require assistance\n");

	if ( $code )
	{
		printf("How to start\n") if $code == START;
		printf("How to time\n")  if $code == TIMEFORMAT;
	}
	exit(-1);
}

# Input to parse_time is:
#   * date -> date-string in the form YYYY-MM-DD
#   * time -> time-string in the form HH:MM
# Return value is a unix timestamp, as returned by time()
sub parse_time ($$)
{
	my ( $Y, $M, $D ) = split ("-", shift );
	my ( $h, $m ) = split(":", shift );
	return timelocal(0, $m, $h, $D, ($M-1), $Y);
}

sub gen_puuid (;$)
{
        my $id_length = shift;
        $id_length = 32 if not defined $id_length;

        my $w = time;

        for(my $i=0 ; $i<128;)
        {
                my $tc = chr(int(rand(127)));
                if($tc =~ /[a-zA-Z0-9]/)
                {
                        $w .=$tc;
                        $i++;
                }
        }
        $w = md5_hex( $w );

        while ( length($w) < $id_length )
        {
                $w .= gen_puuid( $id_length - length( $w ) );
        }

        $w = substr( $w, 0, $id_length );
        return $w;
}

sub parse_arguments ($)
{

	my $step = shift;

	my $start_time = time;
	my $title = undef;
	
	if (( $#ARGV >= 1) && ( $ARGV[1] eq "at" ))
	{
		# Start and Activity require a title to be present.
		# All other (stop, main...) do not ^^.
		if ( ($step == START) || ($step == TASK) ) 
		{
			# TODO: Allow no title!
			# If no title is given, read ID of previously used project in stead :)
			help($step) unless $#ARGV > 3;
			$title = join(" ", @ARGV[4..$#ARGV]);
		}
		help(TIMEFORMAT) unless ( $ARGV[2] =~ m/\d\d\d\d-\d\d-\d\d/ && $ARGV[3] =~ m/\d\d:\d\d/);

		$start_time = parse_time( $ARGV[2], $ARGV[3] );
	} 
	elsif ( ($step == START) || ($step == TASK) ) 
	{
		shift(@ARGV);
		$title = join(" ", @ARGV);
	}

	if ( not defined $title )
	{
		return $start_time;
	}
	else
	{
		return ( $start_time, $title );
	}
}

sub get_current_project
{
	return undef if ( ! -f $trk_dir . "/current" );
	open ( CUR, "<" .  $trk_dir . "/current" ) or die ("Unable to read current project file");
	my $id = <CUR>;
	chomp($id);
	close(CUR);
	return $id;
}

sub set_current_project ($)
{
	my $id = shift;
	return undef if ( -f $trk_dir . "/current" );
	open ( CUR, ">" .  $trk_dir . "/current" ) or die ("Unable to write current project file");
	printf(CUR "%s\n", $id );
	close(CUR);

	open ( LAST, ">" .  $trk_dir . "/last" ) or die ("Unable to write last project file");
	printf(LAST "%s\n", $id );
	close(LAST);
}

sub current_task
{
	my $project = get_current_project();
	return undef if not $project;

	open ( CUR, "<" .  $trk_dir . "/current" ) or die ("Unable to read current project file");
	<CUR>;
	my $id = <CUR>;
	chomp($id);
	close(CUR);
	return $id;

}

sub get_projects
{
	my %projects;

	foreach my $d ( <$trk_dir/*> )
	{
		next if not -d $d;
		next if not -f $d . "/info";

		my $id = basename($d);
		my $title = get_project_name( $id );

		$projects{$id} = $title unless not defined $title;
	}

	return \%projects;

}

sub get_project_id ($)
{
	my $title = shift;

	# Get hash of project-id's and -names from get_projects
	my $projects = get_projects();

	# Look up name in list
	foreach my $id ( keys $projects )
	{
		# Return ID for name
		return $id if ( $projects->{$id} eq $title ) 
	}

	# If no match, return undef.
	return undef;
}

sub get_project_name ($)
{
	my $id = shift;
	open(PRO, "<" . $trk_dir . "/" . $id . "/info" ) or die ("Unable to read project medatata file!");
	my $title = undef;
	while (<PRO>)
	{
		next if not $_ =~ /^title:(.*)/;
		$title = $1;
	}
	close(PRO);
	return $title;
}

sub create_project ($)
{
	my $title = shift;

	my $id;
	do
	{
		$id = gen_puuid(8);
	
	} while ( -d $trk_dir . "/" . $id );
	mkdir ( $trk_dir . "/" . $id );

	open(PRO, ">" . $trk_dir . "/" . $id . "/info" ) or die ("Unable to create project medatata file!");
	printf(PRO "title:%s", $title);
	close(PRO);

	return $id;
}

############################################################

if ( ! -d $trk_dir )
{
	mkdir $trk_dir or die("Unable to create data directory");
}

if ( $#ARGV < 0 )
{
	help();
}

my $command = $ARGV[0];

if ( ( $command eq "start") || ($command eq "on" ) )
{
	if ( $#ARGV < 1)
	{
		help(START);
	}

	my ( $start_time, $title ) = parse_arguments(START);

	my $current = get_current_project();
	if ( not $current )
	{
		$current = get_project_id( $title );
		if ( not $current )
		{
			printf("No project by that name! Creating a new one.\n");
			$current = create_project($title);
		}
		else
		{
			printf("Continuing tracking for existing project.\n");
		}
		set_current_project($current);
	}
	else
	{
		printf("A project is being tracked: %s\n", get_project_name( $current ) );
		printf("Stop current tracking before starting a new one\n");
		exit(0);	
	}

	# First iteration is VERY naive: simply add the start time to the bottom of the tracking file
	# Will have to do more logic: if the start point is before one of the times already in the track,
	# the file will have to be manipulated to get coherent tracking!
	open (TRACK, ">>" . $trk_dir . "/" . $current . "/tracking" ) or die ("Unable to open file, $!");
	printf(TRACK "[%s]", $start_time);
	close (TRACK);

	printf("Started tracking of '%s' at %s\n\n", $title, scalar localtime $start_time);
}
elsif ( ( $command eq "stop") || ($command eq "off" ) )
{
	if ( $#ARGV < 0)
	{
		help(STOP);
	}


	my $stop_time = parse_arguments(STOP);

	my $current = get_current_project();
	if ( not $current )
	{
		printf("No project is currently tracked. To stop, please start first\n");
		exit(0);
	}
	my $title = get_project_name( $current );

	die ("Project exists, but tracking file does not!") if ( not -f  $trk_dir . "/" . $current . "/tracking" );

	# First iteration is VERY naive: simply add the stop time to the bottom line of the tracking file
	# Will have to do more logic: if the start point is before one of the times already in the track,
	# the file will have to be manipulated to get coherent tracking!
	# In addtion to this: actually do some file sanity checking!
	open (TRACK, ">>" . $trk_dir . "/" . $current . "/tracking" ) or die ("Unable to open file, $!");
	printf(TRACK " to [%s]\n", $stop_time);
	close (TRACK);

	unlink ( $trk_dir . "/current" );

	printf("Stopped tracking of '%s' at %s\n\n", $title, scalar localtime $stop_time);
}
else
{
	help();
}