# frozen_string_literal: true

module SyntaxTree
  # This visitor transforms the AST into a mermaid flow chart.
  class MermaidVisitor < FieldVisitor
    attr_reader :flowchart, :target

    def initialize
      @flowchart = Mermaid.flowchart
      @target = nil
    end

    def visit_program(node)
      super
      flowchart.render
    end

    private

    def comments(node)
      # Ignore
    end

    def field(name, value)
      case value
      when nil
        # skip
      when Node
        flowchart.link(target, visit(value), name)
      else
        to =
          flowchart.node("#{target.id}_#{name}", value.inspect, shape: :stadium)
        flowchart.link(target, to, name)
      end
    end

    def list(name, values)
      values.each_with_index do |value, index|
        field("#{name}[#{index}]", value)
      end
    end

    def node(node, type)
      previous_target = target

      begin
        @target = flowchart.node("node_#{node.object_id}", type)
        yield
        @target
      ensure
        @target = previous_target
      end
    end

    def pairs(name, values)
      values.each_with_index do |(key, value), index|
        to = flowchart.node("#{target.id}_#{name}_#{index}", shape: :circle)

        flowchart.link(target, to, "#{name}[#{index}]")
        flowchart.link(to, visit(key), "[0]")
        flowchart.link(to, visit(value), "[1]") if value
      end
    end

    def text(name, value)
      field(name, value)
    end
  end
end