digraph_dot_formatter.rb

# converts directed graph to dot string
#
# Usage:
#
# my_digraph = {node1: [:node2, :node3], node2: [:node3], node3: [:node4], node4: []}
# formatter = DigraphDotFormatter.new(my_digraph)
# 
# formatter.set_node_attributes(:node1, label: 'Start', fillcolor: '#0000ff')
# formatter.set_node_attributes(:node4, label: 'End', fillcolor: '#00ff00')
# formatter.set_edge_attributes(:node3, :node4, label: 'Last move')
#
# formatter.to_dot # =>
#   digraph my_graph {
#     /***** GLOBAL SETTINGS *****/
#     graph          [rotate=0, rankdir="LR"]
#     node           [color="white", style="filled",
#                     shape="box", fillcolor="black",
#                     fontcolor="white", fontsize="14"]
#     edge           [color="#666666", arrowhead="open",
#                     fontsize="11"]
#     /***** Nodes *****/
#     _48d5fa06c371 [label="Start", fillcolor="#0000ff"]
#     _302c2aa8b889 
#     _6b8a0b4095d3 
#     _4d2114173780 [label="End", fillcolor="#00ff00"]
#     /***** Edges *****/
#     _48d5fa06c371 -> _302c2aa8b889 
#     _48d5fa06c371 -> _6b8a0b4095d3 
#     _302c2aa8b889 -> _6b8a0b4095d3 
#     _6b8a0b4095d3 -> _4d2114173780 [label="Last move"]
#   }


class DigraphDotFormatter
  class NodeNotFound < StandardError; end

  # DEFAULT SETTINGS
  NODE_COLOR      = 'white'
  NODE_FILLCOLOR  = 'black'
  NODE_STYLE      = 'filled'
  NODE_SHAPE      = 'box'
  NODE_FONTCOLOR  = 'white'
  NODE_FONTSIZE   = '14'

  EDGE_COLOR      = '#666666'
  EDGE_ARROWHED   = 'open'
  EDGE_FONTSIZE   = '11'

  attr_reader :graph, :nodes, :edges

  def initialize(graph)
    @graph = graph
    @nodes = {}
    @edges = {}
    build_nodes
    build_edges
  end

  def set_node_attributes(graph_node, attrs)
    node = nodes[graph_node]
    attrs.each{|attr_name, value| node.send("#{attr_name}=", value)}
  end

  def set_edge_attributes(from, to, attrs)
    edge = edges[{from => to}]
    attrs.each{|attr_name, value| edge.send("#{attr_name}=", value)}
  end

  def to_dot
    <<-DOT
      digraph quest {
        /***** GLOBAL SETTINGS *****/
        graph          [rotate=0, rankdir="LR"]
        node           [color="#{NODE_COLOR}", style="#{NODE_STYLE}",
                        shape="#{NODE_SHAPE}", fillcolor="#{NODE_FILLCOLOR}",
                        fontcolor="#{NODE_FONTCOLOR}", fontsize="#{NODE_FONTSIZE}"]
        edge           [color="#{EDGE_COLOR}", arrowhead="#{EDGE_ARROWHED}",
                        fontsize="#{EDGE_FONTSIZE}"]
        /***** Nodes *****/
        #{nodes_string}
        /***** Edges *****/
        #{edges_string}
      }
    DOT
  end

  private

    def build_nodes
      graph.keys.map{|node| build_node(node)}
    end

    def build_node(node)
      nodes[node] = Node.new
    end

    def build_edges
      graph.map do |node_from, nodes_to|
        nodes_to.each{|node_to| build_edge(node_from, node_to)}
      end
    end

    def build_edge(node_from, node_to)
      raise NodeNotFound if !nodes[node_from] || !nodes[node_to]
      edges[{node_from => node_to}] = Edge.new(nodes[node_from], nodes[node_to])
    end

    def nodes_string
      nodes.values.map(&:to_s).join("\n")
    end

    def edges_string
      edges.values.map(&:to_s).join("\n")
    end


    module OptionsString
      private

      def options_string
        return '' unless values.any?
        "[#{to_h.map{|key, value| value ? "#{key}=\"#{value}\"" : nil}.compact.join(', ')}]"
      end
    end


    Node = Struct.new(:label, :color, :fillcolor, :style, :shape, :fontcolor, :fontsize) do
      include OptionsString
      attr_reader :id

      def initialize(label: nil, color: nil, fillcolor: nil, style: nil, shape: nil, fontcolor: nil, fontsize: nil)
        @id = "_#{SecureRandom.hex(6)}"
        super(label, color, fillcolor, style, shape, fontcolor, fontsize)
      end

      def to_s
        "#{id} #{options_string}"
      end
    end


    Edge = Struct.new(:label, :color, :arrowhead, :fontsize) do
      include OptionsString
      attr_reader :from, :to

      def initialize(from, to, label: nil, color: nil, arrowhead: nil, fontsize: nil)
        @from = from
        @to = to
        super(label, color, arrowhead, fontsize)
      end

      def to_s
        "#{from.id} -> #{to.id} #{options_string}"
      end
    end
end