haml--haml/lib/hamlit/whitespace_handler.rb

module Hamlit
  class WhitespaceHandler
    def compile_children(node, &block)
      temple = [:multi]
      return temple if node.children.empty?

      temple << :whitespace if prepend_whitespace?(node)
      node.children.each do |n|
        rstrip_whitespace!(temple) if nuke_outer_whitespace?(n)
        temple << yield(n)
        temple << :whitespace if insert_whitespace?(n)
      end
      rstrip_whitespace!(temple) if nuke_inner_whitespace?(node)
      confirm_whitespace(temple)
    end

    private

    def confirm_whitespace(temple)
      temple.map do |exp|
        case exp
        when :whitespace
          [:static, "\n"]
        else
          exp
        end
      end
    end

    def prepend_whitespace?(node)
      return false unless %i[comment tag].include?(node.type)
      !nuke_inner_whitespace?(node)
    end

    def nuke_inner_whitespace?(node)
      return false if node.type != :tag
      node.value[:nuke_inner_whitespace]
    end

    def nuke_outer_whitespace?(node)
      return false if node.type != :tag
      node.value[:nuke_outer_whitespace]
    end

    def rstrip_whitespace!(temple)
      if temple[-1] == :whitespace
        temple.delete_at(-1)
      end
    end

    def insert_whitespace?(node)
      return false if nuke_outer_whitespace?(node)

      case node.type
      when :doctype
        node.value[:type] != 'xml'
      when :plain, :tag, :comment, :filter
        true
      else
        false
      end
    end
  end
end