require "cgi/escape"
require "cgi/util" unless defined?(CGI::EscapeExt)

module Prism
  # This visitor provides the ability to call Node#to_dot, which converts a
  # subtree into a graphviz dot graph.
  class DotVisitor < Visitor
    class Field # :nodoc:
      attr_reader :name, :value, :port

      def initialize(name, value, port)
        @name = name
        @value = value
        @port = port
      end

      def to_dot
        if port
          "<tr><td align=\"left\" colspan=\"2\" port=\"#{name}\">#{name}</td></tr>"
        else
          "<tr><td align=\"left\">#{name}</td><td>#{CGI.escapeHTML(value || raise)}</td></tr>"
        end
      end
    end

    class Table # :nodoc:
      attr_reader :name, :fields

      def initialize(name)
        @name = name
        @fields = []
      end

      def field(name, value = nil, port: false)
        fields << Field.new(name, value, port)
      end

      def to_dot
        dot = <<~DOT
          <table border="0" cellborder="1" cellspacing="0" cellpadding="4">
            <tr><td colspan="2"><b>#{name}</b></td></tr>
        DOT

        if fields.any?
          "#{dot}  #{fields.map(&:to_dot).join("\n  ")}\n</table>"
        else
          "#{dot}</table>"
        end
      end
    end

    class Digraph # :nodoc:
      attr_reader :nodes, :waypoints, :edges

      def initialize
        @nodes = []
        @waypoints = []
        @edges = []
      end

      def node(value)
        nodes << value
      end

      def waypoint(value)
        waypoints << value
      end

      def edge(value)
        edges << value
      end

      def to_dot
        <<~DOT
          digraph "Prism" {
            node [
              fontname=\"Courier New\"
              shape=plain
              style=filled
              fillcolor=gray95
            ];

            #{nodes.map { |node| node.gsub(/\n/, "\n  ") }.join("\n  ")}
            node [shape=point];
            #{waypoints.join("\n  ")}

            #{edges.join("\n  ")}
          }
        DOT
      end
    end

    private_constant :Field, :Table, :Digraph

    # The digraph that is being built.
    attr_reader :digraph

    # Initialize a new dot visitor.
    def initialize
      @digraph = Digraph.new
    end

    # Convert this visitor into a graphviz dot graph string.
    def to_dot
      digraph.to_dot
    end
    <%- nodes.each do |node| -%>

    # Visit a <%= node.name %> node.
    def visit_<%= node.human %>(node)
      table = Table.new("<%= node.name %>")
      id = node_id(node)
      <%- if (node_flags = node.flags) -%>

      # flags
      table.field("flags", <%= node_flags.human %>_inspect(node))
      <%- end -%>
      <%- node.fields.each do |field| -%>

      # <%= field.name %>
      <%- case field -%>
      <%- when Prism::Template::NodeField -%>
      table.field("<%= field.name %>", port: true)
      digraph.edge("#{id}:<%= field.name %> -> #{node_id(node.<%= field.name %>)};")
      <%- when Prism::Template::OptionalNodeField -%>
      unless (<%= field.name %> = node.<%= field.name %>).nil?
        table.field("<%= field.name %>", port: true)
        digraph.edge("#{id}:<%= field.name %> -> #{node_id(<%= field.name %>)};")
      end
      <%- when Prism::Template::NodeListField -%>
      if node.<%= field.name %>.any?
        table.field("<%= field.name %>", port: true)

        waypoint = "#{id}_<%= field.name %>"
        digraph.waypoint("#{waypoint};")

        digraph.edge("#{id}:<%= field.name %> -> #{waypoint};")
        node.<%= field.name %>.each { |child| digraph.edge("#{waypoint} -> #{node_id(child)};") }
      else
        table.field("<%= field.name %>", "[]")
      end
      <%- when Prism::Template::StringField, Prism::Template::ConstantField, Prism::Template::OptionalConstantField, Prism::Template::UInt8Field, Prism::Template::UInt32Field, Prism::Template::ConstantListField, Prism::Template::IntegerField, Prism::Template::DoubleField -%>
      table.field("<%= field.name %>", node.<%= field.name %>.inspect)
      <%- when Prism::Template::LocationField -%>
      table.field("<%= field.name %>", location_inspect(node.<%= field.name %>))
      <%- when Prism::Template::OptionalLocationField -%>
      unless (<%= field.name %> = node.<%= field.name %>).nil?
        table.field("<%= field.name %>", location_inspect(<%= field.name %>))
      end
      <%- else -%>
      <%- raise -%>
      <%- end -%>
      <%- end -%>

      digraph.nodes << <<~DOT
        #{id} [
          label=<#{table.to_dot.gsub(/\n/, "\n  ")}>
        ];
      DOT

      super
    end
    <%- end -%>

    private

    # Generate a unique node ID for a node throughout the digraph.
    def node_id(node)
      "Node_#{node.object_id}"
    end

    # Inspect a location to display the start and end line and column numbers.
    def location_inspect(location)
      "(#{location.start_line},#{location.start_column})-(#{location.end_line},#{location.end_column})"
    end
    <%- flags.each do |flag| -%>

    # Inspect a node that has <%= flag.human %> flags to display the flags as a
    # comma-separated list.
    def <%= flag.human %>_inspect(node)
      flags = [] #: Array[String]
      <%- flag.values.each do |value| -%>
      flags << "<%= value.name.downcase %>" if node.<%= value.name.downcase %>?
      <%- end -%>
      flags.join(", ")
    end
    <%- end -%>
  end
end
