Module: JSON::LD::Compact

Includes:
Utils
Included in:
API
Defined in:
lib/json/ld/compact.rb

Constant Summary collapse

CONTAINER_MAPPING_LANGUAGE_INDEX_ID_TYPE =

The following constant is used to reduce object allocations in #compact below

Set.new(%w[@language @index @id @type]).freeze
EXPANDED_PROPERTY_DIRECTION_INDEX_LANGUAGE_VALUE = 
%w[@direction @index @language @value].freeze

Instance Method Summary collapse

Methods included from Utils

#add_value, #as_array, #as_resource, #blank_node?, #compare_values, #graph?, #has_value?, #index?, #list?, #node?, #node_or_ref?, #node_reference?, #property?, #simple_graph?, #value?

Instance Method Details

#compact(element, base: nil, property: nil, log_depth: nil) ⇒ Array, Hash

This algorithm compacts a JSON-LD document, such that the given context is applied. This must result in shortening any applicable IRIs to terms or compact IRIs, any applicable keywords to keyword aliases, and any applicable JSON-LD values expressed in expanded form to simple values such as strings or numbers.

Parameters:

  • element (Array, Hash)
  • base (String, RDF::URI) (defaults to: nil) —

    (nil) Ensure output objects have keys ordered properly

  • property (String) (defaults to: nil) —

    (nil) Extra validatation

Returns:



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# File 'lib/json/ld/compact.rb', line 21

def compact(element,
            base: nil,
            property: nil,
            log_depth: nil)
  # log_debug("compact", depth: log_depth.to_i) {"element: #{element.inspect}, ec: #{context.inspect}"}

  # If the term definition for active property itself contains a context, use that for compacting values.
  input_context = context

  case element
  when Array
    # log_debug("") {"Array #{element.inspect}"}
    result = element.map do |item|
      compact(item, base: base, property: property, log_depth: log_depth.to_i + 1)
    end.compact

    # If element has a single member and the active property has no
    # @container mapping to @list or @set, the compacted value is that
    # member; otherwise the compacted value is element
    if result.length == 1 &&
       !context.as_array?(property) && @options[:compactArrays]
      # log_debug("=> extract single element", depth: log_depth.to_i) {result.first.inspect}
      result.first
    else
      # log_debug("=> array result", depth: log_depth.to_i) {result.inspect}
      result
    end
  when Hash
    # Otherwise element is a JSON object.

    # @null objects are used in framing
    return nil if element.key?('@null')

    # Revert any previously type-scoped (non-preserved) context
    if context.previous_context && !element.key?('@value') && element.keys != %w[@id]
      # log_debug("revert ec", depth: log_depth.to_i) {"previous context: #{context.previous_context.inspect}"}
      self.context = context.previous_context
    end

    # Look up term definintions from property using the original type-scoped context, if it exists, but apply them to the now current previous context
    td = input_context.term_definitions[property] if property
    if td && !td.context.nil?
      self.context = context.parse(td.context,
        override_protected: true)
      # log_debug("prop-scoped", depth: log_depth.to_i) {"context: #{self.context.inspect}"}
    end

    if (element.key?('@id') || element.key?('@value')) && !element.key?('@annotation')
      result = context.compact_value(property, element, base: @options[:base])
      if !result.is_a?(Hash) || context.coerce(property) == '@json'
        # log_debug("", depth: log_depth.to_i) {"=> scalar result: #{result.inspect}"}
        return result
      end
    end

    # If expanded property is @list and we're contained within a list container, recursively compact this item to an array
    if list?(element) && context.container(property).include?('@list')
      return compact(element['@list'], base: base,
        property: property,
        log_depth: log_depth.to_i + 1)
    end

    inside_reverse = property == '@reverse'
    result = {}
    nest_result = nil

    # Apply any context defined on an alias of @type
    # If key is @type and any compacted value is a term having a local context, overlay that context.
    Array(element['@type'])
      .map { |expanded_type| context.compact_iri(expanded_type, vocab: true) }
      .sort
      .each do |term|
      term_context = input_context.term_definitions[term].context if input_context.term_definitions[term]
      self.context = context.parse(term_context, propagate: false) unless term_context.nil?
      # log_debug("type-scoped", depth: log_depth.to_i) {"context: #{self.context.inspect}"}
    end

    element.keys.opt_sort(ordered: @options[:ordered]).each do |expanded_property|
      expanded_value = element[expanded_property]
      # log_debug("", depth: log_depth.to_i) {"#{expanded_property}: #{expanded_value.inspect}"}

      if expanded_property == '@id'
        compacted_value = as_array(expanded_value).map do |expanded_id|
          if node?(expanded_id) && @options[:rdfstar]
            # This can only really happen for valid RDF-star
            compact(expanded_id, base: base,
              property: '@id',
              log_depth: log_depth.to_i + 1)
          else
            context.compact_iri(expanded_id, base: @options[:base])
          end
        end

        kw_alias = context.compact_iri('@id', vocab: true)
        as_array = compacted_value.length > 1
        compacted_value = compacted_value.first unless as_array
        result[kw_alias] = compacted_value
        next
      end

      if expanded_property == '@type'
        compacted_value = Array(expanded_value).map do |expanded_type|
          input_context.compact_iri(expanded_type, vocab: true)
        end

        kw_alias = context.compact_iri('@type', vocab: true)
        as_array = compacted_value.length > 1 ||
                   (context.as_array?(kw_alias) &&
                    !value?(element) &&
                    context.processingMode('json-ld-1.1'))
        add_value(result, kw_alias, compacted_value, property_is_array: as_array)
        next
      end

      if expanded_property == '@reverse'
        compacted_value = compact(expanded_value, base: base,
          property: '@reverse',
          log_depth: log_depth.to_i + 1)
        # log_debug("@reverse", depth: log_depth.to_i) {"compacted_value: #{compacted_value.inspect}"}
        # handle double-reversed properties
        compacted_value.each do |prop, value|
          next unless context.reverse?(prop)

          add_value(result, prop, value,
            property_is_array: context.as_array?(prop) || !@options[:compactArrays])
          compacted_value.delete(prop)
        end

        unless compacted_value.empty?
          al = context.compact_iri('@reverse', vocab: true)
          # log_debug("", depth: log_depth.to_i) {"remainder: #{al} => #{compacted_value.inspect}"}
          result[al] = compacted_value
        end
        next
      end

      if expanded_property == '@preserve'
        # Compact using `property`
        compacted_value = compact(expanded_value, base: base,
          property: property,
          log_depth: log_depth.to_i + 1)
        # log_debug("@preserve", depth: log_depth.to_i) {"compacted_value: #{compacted_value.inspect}"}

        result['@preserve'] = compacted_value unless compacted_value.is_a?(Array) && compacted_value.empty?
        next
      end

      if expanded_property == '@index' && context.container(property).include?('@index')
        # log_debug("@index", depth: log_depth.to_i) {"drop @index"}
        next
      end

      # Otherwise, if expanded property is @direction, @index, @value, or @language:
      if EXPANDED_PROPERTY_DIRECTION_INDEX_LANGUAGE_VALUE.include?(expanded_property)
        al = context.compact_iri(expanded_property, vocab: true)
        # log_debug(expanded_property, depth: log_depth.to_i) {"#{al} => #{expanded_value.inspect}"}
        result[al] = expanded_value
        next
      end

      if expanded_value.empty?
        item_active_property =
          context.compact_iri(expanded_property,
            value: expanded_value,
            vocab: true,
            reverse: inside_reverse)

        if (nest_prop = context.nest(item_active_property))
          result[nest_prop] ||= {}
          add_value(result[nest_prop], item_active_property, [],
            property_is_array: true)
        else
          add_value(result, item_active_property, [],
            property_is_array: true)
        end
      end

      # At this point, expanded value must be an array due to the Expansion algorithm.
      expanded_value.each do |expanded_item|
        item_active_property =
          context.compact_iri(expanded_property,
            value: expanded_item,
            vocab: true,
            reverse: inside_reverse)

        nest_result = if (nest_prop = context.nest(item_active_property))
          # FIXME??: It's possible that nest_prop will be used both for nesting, and for values of @nest
          result[nest_prop] ||= {}
        else
          result
        end

        container = context.container(item_active_property)
        as_array = !@options[:compactArrays] || context.as_array?(item_active_property)

        value = if list?(expanded_item)
          expanded_item['@list']
        elsif graph?(expanded_item)
          expanded_item['@graph']
        else
          expanded_item
        end

        compacted_item = compact(value, base: base,
          property: item_active_property,
          log_depth: log_depth.to_i + 1)
        # log_debug("", depth: log_depth.to_i) {" => compacted key: #{item_active_property.inspect} for #{compacted_item.inspect}"}

        # handle @list
        if list?(expanded_item)
          compacted_item = as_array(compacted_item)
          if container.include?('@list')
            add_value(nest_result, item_active_property, compacted_item,
              value_is_array: true, allow_duplicate: true)
            next
          else
            al = context.compact_iri('@list', vocab: true)
            compacted_item = { al => compacted_item }
            if expanded_item.key?('@index')
              key = context.compact_iri('@index', vocab: true)
              compacted_item[key] = expanded_item['@index']
            end
          end
        end

        # Graph object compaction cases:
        if graph?(expanded_item)
          if container.include?('@graph') &&
             (container.include?('@id') || (container.include?('@index') && simple_graph?(expanded_item)))
            # container includes @graph and @id
            map_object = nest_result[item_active_property] ||= {}
            # If there is no @id, create a blank node identifier to use as an index
            map_key = if container.include?('@id') && expanded_item['@id']
              context.compact_iri(expanded_item['@id'], base: @options[:base])
            elsif container.include?('@index') && expanded_item['@index']
              context.compact_iri(expanded_item['@index'], vocab: true)
            else
              context.compact_iri('@none', vocab: true)
            end
            add_value(map_object, map_key, compacted_item,
              property_is_array: as_array)
          elsif container.include?('@graph') && simple_graph?(expanded_item)
            # container includes @graph but not @id or @index and value is a simple graph object
            if compacted_item.is_a?(Array) && compacted_item.length > 1
              # Mutple objects in the same graph can't be represented directly, as they would be interpreted as two different graphs. Need to wrap in @included.
              included_key = context.compact_iri('@included', vocab: true)
              compacted_item = { included_key => compacted_item }
            end
            # Drop through, where compacted_item will be added
            add_value(nest_result, item_active_property, compacted_item,
              property_is_array: as_array)
          else
            # container does not include @graph or otherwise does not match one of the previous cases, redo compacted_item
            al = context.compact_iri('@graph', vocab: true)
            compacted_item = { al => compacted_item }
            if expanded_item['@id']
              al = context.compact_iri('@id', vocab: true)
              compacted_item[al] = context.compact_iri(expanded_item['@id'], vocab: false)
            end
            if expanded_item.key?('@index')
              key = context.compact_iri('@index', vocab: true)
              compacted_item[key] = expanded_item['@index']
            end
            add_value(nest_result, item_active_property, compacted_item,
              property_is_array: as_array)
          end
        elsif container.intersect?(CONTAINER_MAPPING_LANGUAGE_INDEX_ID_TYPE) && !container.include?('@graph')
          map_object = nest_result[item_active_property] ||= {}
          c = container.first
          container_key = context.compact_iri(c, vocab: true)
          compacted_item = if container.include?('@id')
            map_key = compacted_item[container_key]
            compacted_item.delete(container_key)
            compacted_item
          elsif container.include?('@index')
            index_key = context.term_definitions[item_active_property].index || '@index'
            if index_key == '@index'
              map_key = expanded_item['@index']
            else
              index_key = context.expand_iri(index_key, vocab: true)
              container_key = context.compact_iri(index_key, vocab: true)
              map_key, *others = Array(compacted_item.is_a?(Hash) && compacted_item[container_key])
              if map_key.is_a?(String)
                case others.length
                when 0 then compacted_item.delete(container_key) if compacted_item.is_a?(Hash)
                when 1 then compacted_item[container_key] = others.first
                else        compacted_item[container_key] = others
                end
              else
                map_key = context.compact_iri('@none', vocab: true)
              end
            end
            # Note, if compacted_item is a node reference and key is @id-valued, then this could be compacted further.
            compacted_item
          elsif container.include?('@language')
            map_key = expanded_item['@language']
            value?(expanded_item) ? expanded_item['@value'] : compacted_item
          elsif container.include?('@type')
            map_key, *types = Array(compacted_item.is_a?(Hash) && compacted_item[container_key])
            case types.length
            when 0 then compacted_item.delete(container_key) if compacted_item.is_a?(Hash)
            when 1 then compacted_item[container_key] = types.first
            else        compacted_item[container_key] = types
            end

            # if compacted_item contains a single entry who's key maps to @id, then recompact the item without @type
            if compacted_item.is_a?(Hash) && compacted_item.keys.length == 1 && expanded_item.key?('@id')
              compacted_item = compact({ '@id' => expanded_item['@id'] },
                base: base,
                property: item_active_property,
                log_depth: log_depth.to_i + 1)
            end
            compacted_item
          end
          map_key ||= context.compact_iri('@none', vocab: true)
          add_value(map_object, map_key, compacted_item,
            property_is_array: as_array)
        else
          add_value(nest_result, item_active_property, compacted_item,
            property_is_array: as_array)
        end
      end
    end

    result
  else
    # For other types, the compacted value is the element value
    # log_debug("compact", depth: log_depth.to_i) {element.class.to_s}
    element
  end
ensure
  self.context = input_context
end