#!/usr/bin/perl
use warnings;
use strict;
use 5.010; # //

use Tk;

use constant MESSAGE => 'Point a mouse over a bar to see the details';

my $width  = 25;
my $height = 200;
my $space  = 10;


my $input = shift // 'xp.out';
open my $IN, '<', $input or die $!;

my @rectangles;
my ($oldest, $max, $min) = (0, 0, 0);
while (my $line = <$IN>) {
    my ($date, $xp)    = split ' ', $line;
    my ($year, $month) = split /-/, $date;
    my $x = $year * 12 + $month;
    $oldest ||= $x;
    $max = $xp if $xp > $max;
    $min = $xp if $xp < $min;
    push @rectangles, [ $x - $oldest, $xp, $date ];
}
my $step = $height / $max;

my $mw   = 'MainWindow'->new(-title => 'Average XP per month');

my $info = MESSAGE;
$mw->Label(-textvariable => \$info,
           -foreground   => 'black',
           -background   => 'white',
           -relief       => 'ridge',
          )->pack(-pady => 5);

my $canvas = $mw->Canvas(-background => 'white',
                         -width      => $width * (1 + $rectangles[-1][0]),
                         -height     => $height + 2 * $space + $step * abs $min,
                        )->pack(-padx => 10,
                                -pady => 10);

for my $rect (@rectangles) {
    $canvas->createRectangle(
            $rect->[0]   * $width, $space + $step * ($max - $rect->[1]),
            ++$rect->[0] * $width, $space + $height,
            -fill    => (qw/blue cyan green yellow orange red/)
                        [($rect->[1] + abs $min) / ($max + abs $min) * 5],
            -outline => 'black',
            -tag     => "bar$rect->[0]",
        );
    $canvas->bind("bar$rect->[0]",
                  '<Any-Enter>' => sub { $info = "$rect->[2]: $rect->[1]" });

}
$canvas->bind('all', '<Any-Leave>' => sub { $info = MESSAGE });


$mw->Button(-text => 'Quit',
            -command => sub { exit },
           )->pack;


MainLoop();