graphviz_presenter.rb

class GraphvizPresenter < GraphPresenter
  def to_gv
    [
      "digraph MyFlow {",
      '',
      '## LABELS',
      '',
      label_lines,
      '',
      '## EDGES',
      '',
      edge_lines,
      metadata_lines,
      "}"
    ].flatten.join("\n")
  end

  def label_lines
    labels.map do |name, label|
      attrs = {
        label: escape(label),
        shape: "box"
      }
      if is_first?(name)
        attrs.merge!(
          color: "gold1",
          style: "filled"
        )
      elsif is_outcome?(name)
        attrs.merge!(
          color: "aquamarine",
          style: "filled"
        )
      end
      attribute_clause = attrs.map { |k, v| "#{k}=\"#{v}\"" }.join(' ')
      %Q{#{normalize_name(name)} [#{attribute_clause}]}
    end
  end

  def is_first?(node_name)
    @flow.questions.first.name == node_name
  end

  def is_outcome?(node_name)
    @flow.outcomes.map(&:name).include?(node_name)
  end

  def edge_lines
    adjacency_list.map do |name, exits|
      exits.map do |nextnode, label|
        next unless nextnode
        %Q{#{normalize_name(name)}->#{normalize_name(nextnode)} [label="#{label}"];}
      end
    end.flatten
  end

  def metadata_lines
    [
      'overlap=false;',
      'splines=true;',
      %Q{label="#{escape(presenter.title)}";},
      'fontsize=12;'
    ]
  end

  def escape(label)
    map = {
      "\n" => '\n',
      "[" => '\[',
      "]" => '\]',
      '"' => '\''
    }
    label.to_s.gsub(%r{[\n\[\]"]}, map)
  end

  def normalize_name(name)
    name.to_s.gsub(/[^a-zA-Z0-9_]/, "")
  end
end