package Whatpm::CSS::Cascade;
use strict;

require Whatpm::CSS::Parser; ## NOTE: For property definitions.
require Whatpm::CSS::SelectorsSerializer;
use Scalar::Util qw/refaddr/;

## Cascading and value computations

sub new ($$) {
  my $self = bless {style_sheets => []}, shift;
  $self->{document} = shift;
  return $self;
} # new

## NOTE: This version does not support dynamic addition --- style
## sheets must be added before any other operation.
## NOTE: The $ss argument must be a value that can be interpreted as
## an array reference of CSSStyleSheet objects.
## NOTE: |type| and |media| attributes are not accounted by this
## method (and any others in the class); CSSStyleSheet objects must
## be filtered before they are passed to this method.
sub add_style_sheets ($$) {
  my ($self, $ss) = @_;

  push @{$self->{style_sheets}}, @$ss;
} # add_style_sheets

## TODO: non-CSS presentation hints
## TODO: style=""

sub ___associate_rules ($) {
  my $self = shift;

  my $selectors_to_elements;

  for my $sheet (@{$self->{style_sheets}}) {
    ## TODO: @media
    ## TODO: @import
    ## TODO: style sheet sources

    for my $rule (@{$sheet->css_rules}) {
      next if $rule->type != 1; # STYLE_RULE

      my $elements_to_specificity = {};

      for my $selector (@{$$rule->{_selectors}}) {
        my $selector_str = Whatpm::CSS::SelectorsSerializer->serialize_test
            ([$selector]);
        unless ($selectors_to_elements->{$selector_str}) {
          $selectors_to_elements->{$selector_str}
              = $self->{document}->___query_selector_all ([$selector]);
        }
        next unless @{$selectors_to_elements->{$selector_str}};

        my $selector_specificity
            = Whatpm::CSS::SelectorsParser->get_selector_specificity
                ($selector);
        for (@{$selectors_to_elements->{$selector_str}}) {
          my $current_specificity = $elements_to_specificity->{refaddr $_};
          if (not defined $current_specificity or ## "*"-only case.
              $selector_specificity->[0] > $current_specificity->[0] or
              $selector_specificity->[1] > $current_specificity->[1] or
              $selector_specificity->[2] > $current_specificity->[2] or
              $selector_specificity->[3] > $current_specificity->[3]) {
            $elements_to_specificity->{refaddr $_} = $selector_specificity;
          }
        }
      }

      my $sd = $rule->style;
      for (keys %$elements_to_specificity) {
        push @{$self->{element_to_sds}->{$_} ||= []},
            [$sd, $elements_to_specificity->{$_}];
      }
    }
  }

  for my $eid (keys %{$self->{element_to_sds} or {}}) {
    $self->{element_to_sds}->{$eid} = [sort {
      $a->[1]->[0] <=> $b->[1]->[0] or
      $a->[1]->[1] <=> $b->[1]->[1] or
      $a->[1]->[2] <=> $b->[1]->[2] or 
      $a->[1]->[3] <=> $b->[1]->[3]
      ## NOTE: Perl |sort| is stable.
    } @{$self->{element_to_sds}->{$eid} or []}];
  }
} # associate_rules

sub get_cascaded_value ($$$) {
  my ($self, $element, $prop_name) = @_;
  return undef unless $Whatpm::CSS::Parser::Prop->{$prop_name};

  my $key = $Whatpm::CSS::Parser::Prop->{$prop_name}->{key};
  return undef unless defined $key; ## Shorthand property or some.

  my $value;
  for my $sds (reverse @{$self->{element_to_sds}->{refaddr $element} or []}) {
    my $vp = ${$sds->[0]}->{$key};
    if (defined $vp->[1] and $vp->[1] eq 'important') {
      return $vp->[0];
    } else {
      $value = $vp->[0] unless defined $value;
    }
  }

  return $value; # might be |undef|.
} # get_cascaded_value

sub get_specified_value ($$$) {
  my ($self, $element, $prop_name) = @_;

  ## TODO: Remove {specified_value} caching, once we implement most
  ## of CSS 2.1 properties and confirm that it makes almost non sence
  ## because of its duplication with {computed_value} caching.
  
  my $eid = refaddr $element;
  unless (exists $self->{specified_value}->{$eid}->{$prop_name}) {
    my $cascaded = $self->get_cascaded_value ($element, $prop_name);
    $self->{specified_value}->{$eid}->{$prop_name} = $cascaded;
    
    unless (defined $cascaded) {
      my $prop_def = $Whatpm::CSS::Parser::Prop->{$prop_name};
      if (defined $prop_def) {
        if ($prop_def->{inherited}) {
          my $parent_element = $element->manakai_parent_element;
          if (defined $parent_element) {
            $self->{specified_value}->{$eid}->{$prop_name}
                = $self->get_computed_value ($parent_element, $prop_name);
          } else {
            $self->{specified_value}->{$eid}->{$prop_name}
                = $prop_def->{initial};
          }
        } else {
          $self->{specified_value}->{$eid}->{$prop_name}
              = $prop_def->{initial};
        }
      } else {
        $self->{specified_value}->{$eid}->{$prop_name} = undef;
      }
    }
  }

  ## NOTE: Always |undef| for shorthand properties.

  return $self->{specified_value}->{$eid}->{$prop_name};
} # get_specified_value

sub get_computed_value ($$$) {
  my ($self, $element, $prop_name) = @_;

  my $eid = refaddr $element;
  unless (exists $self->{computed_value}->{$eid}->{$prop_name}) {
    my $prop_def = $Whatpm::CSS::Parser::Prop->{$prop_name};
    if (defined $prop_def) {
      my $specified = $self->get_specified_value ($element, $prop_name);
      if (defined $specified and $specified->[0] eq 'INHERIT') {
        ## ISSUE: CSS 2.1 does not say to resolve computed value of the parent.
        ## However, it is necessary for some cases (see
        ## <http://suika.fam.cx/gate/2005/sw/inherit>).  In addition,
        ## the initial value is not a computed value for some properties.
        my $parent_element = $element->manakai_parent_element;
        if (defined $parent_element) {
          $specified = $self->get_computed_value ($parent_element, $prop_name);
        } else {
          $specified = $prop_def->{compute}->($self, $element, $prop_name,
                                              $prop_def->{initial});
        }
        ## NOTE: Because of this handling, {compute} codes must be
        ## idempotent.
      }
       
      $self->{computed_value}->{$eid}->{$prop_name}
          = $prop_def->{compute}->($self, $element, $prop_name, $specified);
    } else {
      $self->{computed_value}->{$eid}->{$prop_name} = undef;
    }
  }

  ## NOTE: Always |undef| for shorthand properties.

  return $self->{computed_value}->{$eid}->{$prop_name};
} # get_computed_value

1;
## $Date: 2008/01/02 07:39:21 $