Mermaid visitor

Author: kddnewton

lib/syntax_tree.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "cgi"
 require "etc"
 require "fiddle"
 require "json"
@@ -18,6 +19,7 @@
 require_relative "syntax_tree/visitor/field_visitor"
 require_relative "syntax_tree/visitor/json_visitor"
 require_relative "syntax_tree/visitor/match_visitor"
+require_relative "syntax_tree/visitor/mermaid_visitor"
 require_relative "syntax_tree/visitor/mutation_visitor"
 require_relative "syntax_tree/visitor/pretty_print_visitor"
 require_relative "syntax_tree/visitor/environment"

lib/syntax_tree/node.rb

@@ -127,17 +127,19 @@ def format(q)
     end
 
     def pretty_print(q)
-      visitor = Visitor::PrettyPrintVisitor.new(q)
-      visitor.visit(self)
+      accept(Visitor::PrettyPrintVisitor.new(q))
     end
 
     def to_json(*opts)
-      visitor = Visitor::JSONVisitor.new
-      visitor.visit(self).to_json(*opts)
+      accept(Visitor::JSONVisitor.new).to_json(*opts)
     end
 
     def construct_keys
-      PrettierPrint.format(+"") { |q| Visitor::MatchVisitor.new(q).visit(self) }
+      PrettierPrint.format(+"") { |q| accept(Visitor::MatchVisitor.new(q)) }
+    end
+
+    def mermaid
+      accept(Visitor::MermaidVisitor.new)
     end
   end
 

lib/syntax_tree/visitor/mermaid_visitor.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+module SyntaxTree
+  class Visitor
+    # This visitor transforms the AST into a mermaid flow chart.
+    class MermaidVisitor < FieldVisitor
+      attr_reader :output, :target
+
+      def initialize
+        @output = StringIO.new
+        @output.puts("flowchart TD")
+
+        @target = nil
+      end
+
+      def visit_program(node)
+        super
+        output.string
+      end
+
+      private
+
+      def comments(node)
+        # Ignore
+      end
+
+      def field(name, value)
+        case value
+        when Node
+          node_id = visit(value)
+          output.puts("  #{target} -- \"#{name}\" --> #{node_id}")
+        when String
+          node_id = "#{target}_#{name}"
+          output.puts("  #{node_id}([#{CGI.escapeHTML(value.inspect)}])")
+          output.puts("  #{target} -- \"#{name}\" --> #{node_id}")
+        when nil
+          # skip
+        else
+          node_id = "#{target}_#{name}"
+          output.puts("  #{node_id}([\"#{CGI.escapeHTML(value.inspect)}\"])")
+          output.puts("  #{target} -- \"#{name}\" --> #{node_id}")
+        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 = "node_#{node.object_id}"
+
+          yield
+
+          output.puts("  #{@target}[\"#{type}\"]")
+          @target
+        ensure
+          @target = previous_target
+        end
+      end
+
+      def pairs(name, values)
+        values.each_with_index do |(key, value), index|
+          node_id = "#{target}_#{name}_#{index}"
+          output.puts("  #{node_id}((\"&nbsp;\"))")
+          output.puts("  #{target} -- \"#{name}[#{index}]\" --> #{node_id}")
+          output.puts("  #{node_id} -- \"[0]\" --> #{visit(key)}")
+          output.puts("  #{node_id} -- \"[1]\" --> #{visit(value)}") if value
+        end
+      end
+
+      def text(name, value)
+        field(name, value)
+      end
+    end
+  end
+end