module Take
  class Unit
    class Compiler

      include PredictMatch

      attr_reader :parent

      def initialize(file, tokens)
        @file   = file
        @tokens = tokens
        @enum   = tokens.each
        @parent = nil
      end

      def compile
        @parent ||= begin
          @parent = AST::Parent.new(name: @file.
            gsub(/\..*\z/, "").gsub(/[\W]/, "_"))
          while peek do
            @parent.children << compile_group
          end

          @parent.source = sourcify([0, 0])
          @parent
        end
      end

      def compile_group
        group = match(:group)
        node = AST::Group.new(name: group[1], source: sourcify(group))

        until peek == :group_end
          part = compile_part
          node.children << part if part
        end

        match(:group_end)

        node
      end

      def compile_part
        predict :group  => :group,
                :test   => :test,
                :before => :before,
                :after  => :after,
                :prefix => :prefix,
                :macro  => :macro
      end

      def compile_test
        test = match(:test)
        body = match(:block)
        AST::Test.new(name: test[1],
                      children: [AST::Block.new({
                        body: body[1],
                        source: sourcify(body)
                      })],
                      source: sourcify(test))
      end

      def compile_before
        before = match(:before)
        body = match(:block)

        AST::Before.new(name: before[1],
                        children: [AST::Block.new({
                          body: body[1],
                          source: sourcify(body)
                          })],
                        source: sourcify(before))
      end

      def compile_after
        after = match(:after)
        body = match(:block)

        AST::After.new(name: after[1],
                       children: [AST::Block.new({
                         body: body[1],
                         source: sourcify(body)
                         })],
                       source: sourcify(after))
      end

      def compile_prefix
        prefix = match(:prefix)
        body = match(:block)

        @parent.children << AST::Prefix.new(
          name: prefix[1],
          children: [AST::Block.new({
            body: body[1],
            source: sourcify(body)
          })],
          source: sourcify(prefix))

        nil
      end

      def compile_macro

      end

      private

      def input
        @enum
      end

      def sourcify(token)
        hash = Hash[[:line, :column].zip(token[-2..-1])]
        hash.merge(file: @file)
      end

    end
  end
end