package App::Math::Tutor::Cmd::VulFrac::Cmd::Add;

use warnings;
use strict;

use vars qw(@ISA $VERSION);

=head1 NAME

App::Math::Tutor::Cmd::VulFrac::Cmd::Add - Plugin for addition and subtraction of vulgar fractions

=cut

our $VERSION = '0.004';

use Moo;
use MooX::Cmd;
use MooX::Options;

has template_filename => (
                           is      => "ro",
                           default => "twocols"
                         );

with "App::Math::Tutor::Role::VulFracExercise";

my %result_formats = (
                       keep      => 1,
                       reducable => 1,
                     );

=head1 ATTRIBUTES

=head2 result_format

Allows controlling of accepted format of exercise output

=cut

option result_format => (
    is        => "ro",
    predicate => 1,
    doc       => "Let one specify result format behavior",
    long_doc  => "Let one specify result format behavior, pick one of\n\n"
      . "reducable: result can be reduced, "
      . "keep: keep exercise format (after reducing)",
    coerce => sub {
        defined $_[0] or return {};
        "HASH" eq ref $_[0] and return $_[0];
        my ( @fail, %rf );
        $rf{$_} = defined $result_formats{$_} or push @fail, $_ foreach @{ $_[0] };
        @fail
          and die "Invalid result format: "
          . join( ", ", @fail )
          . ", pick any of "
          . join( ", ", keys %result_formats );
        return \%rf;
    },
    format     => "s@",
    autosplit  => ",",
    repeatable => 1,
    short      => "r",
                        );

sub _build_command_names
{
    return qw(add sub);
}

my $a_plus_b = sub {
    return
      PolyNum->new( operator => $_[0],
                    values   => [ splice @_, 1 ] );
};
my $a_mult_b = sub {
    return
      ProdNum->new( operator => $_[0],
                    values   => [ splice @_, 1 ] );
};

sub _operands_ok
{
    my ( $self, $op, @operands ) = @_;
    $self->has_result_format or return 1;
    my $s = shift @operands;
    while (@operands)
    {
        my $b = shift @operands;
        my $a = $s->_reduce;
        $b = $b->_reduce;
        my $gcd = VulFrac->new(
                                num   => $a->denum,
                                denum => $b->denum
                              )->_gcd;
        my ( $fa, $fb ) = ( $b->{denum} / $gcd, $a->{denum} / $gcd );
        my ( $xa, $xb ) = (
                            VulFrac->new(
                                          num   => int( $a_mult_b->( '*', $a->num,   $fa ) ),
                                          denum => int( $a_mult_b->( '*', $a->denum, $fa ) ),
                                          sign  => $a->sign
                                        ),
                            VulFrac->new(
                                          num   => int( $a_mult_b->( '*', $b->num,   $fb ) ),
                                          denum => int( $a_mult_b->( '*', $b->denum, $fb ) ),
                                          sign  => $b->sign
                                        )
                          );
        $s = VulFrac->new(
                     num   => int( $a_plus_b->( $op, $xa->sign * $xa->num, $xb->sign * $xb->num ) ),
                     denum => $xa->denum );
    }
    my ( $max_num, $max_denum ) = ( @{ $_[0]->format } );
    my %result_format = %{ $self->result_format };
    $s->_gcd > 1 or return 0 if defined $result_format{reducable} and $result_format{reducable};
    $s = $s->_reduce;
    $s->num <= $max_num     or return 0 if defined $result_format{keep} and $result_format{keep};
    $s->denum <= $max_denum or return 0 if defined $result_format{keep} and $result_format{keep};
    return 1;
}

sub _build_exercises
{
    my ($self) = @_;
    my $neg = $self->negativable;

    my (@tasks);
    foreach my $i ( 1 .. $self->quantity )
    {
        my @line;
        foreach my $j ( 0 .. 1 )
        {
          REDO: my ( $a, $b ) = $self->get_vulgar_fractions(2);
            $self->_operands_ok( $j ? '-' : '+', $a, $b ) or goto REDO;
            push @line, [ $a, $b ];
        }
        push @tasks, \@line;
    }

    my $exercises = {
                      section => "Vulgar fraction addition / subtraction",
                      caption => 'Fractions',
                      label   => 'vulgar_fractions_addition',
                      header  => [ [ 'Vulgar Fraction Addition', 'Vulgar Fraction Subtraction' ] ],
                      solutions  => [],
                      challenges => [],
                    };
    # use Text::TabularDisplay;
    # my $table = Text::TabularDisplay->new( 'Bruch -> Dez', 'Dez -> Bruch' );
    foreach my $line (@tasks)
    {
        my ( @solution, @challenge );

        foreach my $i ( 0 .. 1 )
        {
            my ( $a, $b ) = @{ $line->[$i] };
            my $op = $i ? '-' : '+';
            $op eq '-' and $a < $b and ( $b, $a ) = ( $a, $b ) unless $neg;
            push @challenge, sprintf( '$ %s = $', $a_plus_b->( $op, $a, $b ) );

            my @way;    # remember Frank Sinatra :)
            push @way, $a_plus_b->( $op, $a, $b );

            ( $a, $b ) = ( $a->_reduce, $b = $b->_reduce ) and push @way, $a_plus_b->( $op, $a, $b )
              if ( $a->_gcd > 1 or $b->_gcd > 1 );

            my $gcd = VulFrac->new(
                                    num   => $a->denum,
                                    denum => $b->denum
                                  )->_gcd;
            my ( $fa, $fb ) = ( $b->{denum} / $gcd, $a->{denum} / $gcd );

            my ( $xa, $xb ) = (
                                VulFrac->new(
                                              num   => $a_mult_b->( '*', $a->num,   $fa ),
                                              denum => $a_mult_b->( '*', $a->denum, $fa ),
                                              sign  => $a->sign
                                            ),
                                VulFrac->new(
                                              num   => $a_mult_b->( '*', $b->num,   $fb ),
                                              denum => $a_mult_b->( '*', $b->denum, $fb ),
                                              sign  => $b->sign
                                            )
                              );
            push @way, $a_plus_b->( $op, $xa, $xb );
            $xa = VulFrac->new(
                                num   => int( $xa->num ),
                                denum => int( $xa->denum ),
                                sign  => $xa->sign
                              );
            $xb = VulFrac->new(
                                num   => int( $xb->num ),
                                denum => int( $xb->denum ),
                                sign  => $xb->sign
                              );
            push @way, $a_plus_b->( $op, $xa, $xb );

            my $s = VulFrac->new(
                            num   => $a_plus_b->( $op, $xa->sign * $xa->num, $xb->sign * $xb->num ),
                            denum => $xa->denum );

            push @way, $s;
            $s = VulFrac->new(
                               num   => int( $s->num ),
                               denum => $s->denum,
                               sign  => $s->sign
                             );
            push @way, "" . $s;
            $s->_gcd > 1 and $s = $s->_reduce and push @way, $s;

            $s->num > $s->denum and $s->denum > 1 and push @way, $s->_stringify(1);

            push( @solution, '$ ' . join( " = ", @way ) . ' $' );
        }

        push( @{ $exercises->{solutions} },  \@solution );
        push( @{ $exercises->{challenges} }, \@challenge );
    }

    return $exercises;
}

=head1 LICENSE AND COPYRIGHT

Copyright 2010-2014 Jens Rehsack.

This program is free software; you can redistribute it and/or modify it
under the terms of either: the GNU General Public License as published
by the Free Software Foundation; or the Artistic License.

See http://dev.perl.org/licenses/ for more information.

=cut

1;
