#!/usr/bin/perl -w

# Files containing current and max brightness values
my $cur_file = "/sys/class/backlight/intel_backlight/brightness";
my $max_file = "/sys/class/backlight/intel_backlight/max_brightness";
my $last_file = "/home/jpm/.config/blc.last";

sub to_percent {
    my $value = shift;
    if ($value eq "Permission Denied") {
        return $value;
    } else {
        $value = int($value/get_max()*100);
        return $value . '%';
    }
}

sub get_offset {
    return int(get_max()/100);
}

sub get_current {
    open(my $c,'<',"$cur_file");
    my $current = <$c>;
    close $c;
    chomp $current;
    return $current;
}

sub get_max {
    open(my $m,'<',"$max_file");
    my $max = <$m>;
    close $m;
    chomp $max;
    return $max;
}

sub get_min {
    return int((get_max()/100)+2);
}

sub writable {
    if (! -w $cur_file) {
        return 0;
    } else {
        return 1;
    }
}

sub increment {
    if (writable()) {
        my $current = get_current();
        my $max = get_max();
        my $target = $current+get_offset();
        if ($target > $max) {
            $target = $max;
        }
        open(my $c,'>',"$cur_file");
	    print $c $target;
        close $c;
        return $target;
    } else {
        return "Permission Denied";
    }
}

sub decrement {
    if (writable()) {
        my $current = get_current();
        my $min = get_min();
        my $target = $current-get_offset();
        if ($target < $min) {
            $target = $min;
        }
        open(my $c,'>',"$cur_file");
	    print $c $target;
        close $c;
        return $target;
    } else {
        return "Permission Denied";
    }
}

sub set {
    my $value = shift;
    if (writable()) {
        $current = get_current();
        if ($value > $current) {
            for (my $i=$current;$i<=$value;$i++) {
                open(my $c,'>',"$cur_file");
		        print $c $i;
                close $c;
            }
        } else {
            for (my $i=$current;$i>=$value;$i--) {
                open(my $c,'>',"$cur_file");
		        print $c $i;
                close $c;
            }
        }
        return $value;
    } else {
        return "Permission Denied";
    }
}

sub help {
    print "
Backlight Control

Usage: blc.pl [--silent|--notify] [OPTION] [VALUE]

With no option the backlight information is printed as JSON.

Output printed to STDOUT unless:

--silent  Do not display output (overrides --notify)
--notify  Send output to notification daemon. --notify=N will
          change the display duration in ms. Default is 200ms

Output option must preceed the first Action option.

Actions:

= VALUE   Set backlight to specific value. VALUE greater than
          100 will be treated as absolute value. VALUE eqaul to
          or less than 100 will be treated as a percentage
++        Increment by 1%
+= VALUE  Increment by VALUE percent
--        Decrement by 1%
-= VALUE  Decrement by VALUE percent

Actions corrected to 1% or 100% if over or under. All actions
provide output as a percentage, with the % symbol.

Final percentage printed as below, skipping other options.

Print:

==        Print current absolute value
^         Print maximum absolute value
%         Print current percentage (does not include % symbol)
--help    Help (not impacted by --silent or --notify)
--HELP    Advanced help (same as above)

Any other option will be printed literally";
}

sub advanced {
    $current = get_current();
    $max = get_max();
    print ".

Print functions can be strung together but command will exit
with the first non-print option. eg.

    \$ blc.pl == / ^
    21/100
    \$ blc.pl == ++
    ('==' ignored)
    (Backlight incremented)

Escape options with \\ in quotes to display them literally. eg.

    \$ blc.pl == / ^ '\\=' % \'\\%\'
    " . $current . "/" . $max . "=" . int($current/$max*100) . "%

Only one \'\\' is removed per block. eg.

    \$ blc.pl '\\% \\'
    % \\

";
}

my $current = get_current();
my (@output, $target, $silent, $notify);

if (scalar @ARGV) {
    for (my $i=0;$i<scalar @ARGV;$i++) {
        if ($ARGV[$i] eq '++') {
            $target = increment();
            @output = to_percent($target);
            last;
        } elsif ($ARGV[$i] eq '+=') {
            for (my $i=0;$i<scalar @ARGV;$i++) {
                if ($ARGV[$i] eq '+=') {
                    if (defined $ARGV[($i+1)]) {
                        $count = $ARGV[($i+1)];
                        for (my $j=0;$j<$count;$j++) {
                            $target = increment();
                            if ($target eq "Permission Denied") {
                                last;
                            }
                        }
                        @output = to_percent($target);
                    } else {
                        @output = ("No value after $ARGV[$i]");
                    }
                    last;
                }
            }
            last;
        } elsif ($ARGV[$i] eq '--') {
            $target = decrement();
            @output = to_percent($target);
            last;
        } elsif ($ARGV[$i] eq '-=') {
            for (my $i=0;$i<scalar @ARGV;$i++) {
                if ($ARGV[$i] eq '-=') {
                    if (defined $ARGV[($i+1)]) {
                        $count = $ARGV[($i+1)];
                        for (my $j=0;$j<$count;$j++) {
                            $target = decrement();
                            if ($target eq "Permission Denied") {
                                last;
                            }
                        }
                        @output = to_percent($target);
                    } else {
                        @output = ("No value after $ARGV[$i]");
                    }
                    last;
                }
            }
            last;
        } elsif ($ARGV[$i] eq '=') {
            $target = $ARGV[($i+1)];
            if (defined $target) {
                if ($target < 1) {
                    $target = set(get_min());
                } elsif ($target > get_max()) {
                    $target = set(get_max());
                } elsif ($target > 100) {
	                $target = set($target);
                } else {
	                $target = set(int((get_max()*$target/100)+1));
                }
                if ($target eq "Permission Denied") {
                    @output = $target;
                } else {
                    @output = to_percent($target);
                }
                last;
            } else {
                @output = ("No value after $ARGV[$i]");
                last;
            }
        } elsif ($ARGV[$i] eq '%') {
            push @output,int(get_current()/get_max()*100);
        } elsif ($ARGV[$i] eq '^') {
            push @output,get_max();
        } elsif ($ARGV[$i] eq '==') {
            push @output,get_current();
        } elsif ($ARGV[$i] eq '--help') {
            help();
            print " (see --HELP).\n\n";
            exit();
        } elsif ($ARGV[$i] eq '--HELP') {
            help();
            advanced();
            exit();
        } elsif ($ARGV[$i] eq '--silent') {
            $silent = 'TRUE';
        } elsif ($ARGV[$i] =~ /^--notify/) {
            $notify = 'TRUE';
            if ($ARGV[$i] =~ /=[0-9]+$/) {
                $duration = $ARGV[$i];
                $duration =~ s/.*=([0-9]+)/$1/;
            } else {
                $duration = 200;
            }
        } else {
            my $add = $ARGV[$i];
            $add =~ s/\\//;
            push @output,$add;
        }
    }
} else {
    @output = ('{"Backlight":{"Max":"' . get_max() . '","Current":"' . get_current() . '","Percentage","' .  int(get_current()/get_max()*100) . '%"}}');
}


open(my $fh,'>',$last_file);
print $fh get_current();
close($fh);

if ($silent) {
    exit();
} elsif ($notify) {
    # Don't output anything if the value didn't change
    if ($current == get_current()) {
        exit();
    }
    my $concat;
    foreach (@output) {
        $concat .= $_;
    }
    system "notify-send --urgency=normal -i /usr/share/icons/Papirus-Dark-Grey/48x48/status/notification-display-brightness.svg -t $duration \"$concat\"";
    exit();
} else {
    print foreach @output;
    print "\n";
    exit();
}