# 
# [{:op=>"and"},
#  [{:op=>"="}, [{:path=>"hello"}, {:lit=>":ivan"}]],
#  [{:op => "or"},
#    [{:op=>"="}, [{:path=>"test"}, {:lit=>":ivan"}]],
#    [{:op => ">"}, [:path => "test3", {:list => ":ivan"}]]]]
# 
# hello = :ivan and (test = :ivan or test3 = :ivan)
 
class Parser
  def initialize(where_clause, binding)
    @binding = binding
    @tokens = where_clause.scan(/\(|\)|>=|<=|<>|=|>|<|[:?\w\.\*]+/)
    @stack = @top = @current_stack = []
    @previous = nil
  end
  
  def ast
    @tokens.each do |token|
      p token
 
      return nil unless token
      case token
      when "("
        @current_stack << []
        @previous = @current_stack
        @previous_top = @top
        @top = @current_stack = @current_stack.last
      when ")"
        @current_stack = @previous
        @top = @previous_top
      when "or", "and"
        @top.unshift [{:op => token}, @current_stack, []]
      when ">", "<", "<>", "=", ">=", "<="
        first = @current_stack.pop
        @current_stack.push(:op => token)
        @current_stack << []
        @previous = @current_stack
        @current_stack = @current_stack.last
        @current_stack.push first
      when /:[\w\.\*]+/
        @current_stack.push :lit => token
        @current_stack = @previous
      when /[\w\.\*]+/
        @current_stack.push(:path => token)
      end 
 
      
    end
    #@stack.push(@current_stack)
    #@current_stack = []
    @stack 
  end
end