require_relative 'expression_tree_node'

module RailsServersideDatatables
  class Expression
    attr_reader :expression

    def to_s
      expression.to_s
    end

    protected
    def raw( expr )
      ExprTreeNode.raw(expr )
    end
  end

  class IfThen < Expression

    def initialize( testexpr, comparison_val, thenexpr, elseexpr )
      expression = ExprTreeNode.new('', Type::OPERATOR ) # Concat the statements only

      expression.add_argument raw( 'CASE' )
      expression.add_argument testexpr

      if comparison_val.nil?
        expression.add_argument raw( 'IS NULL' )
        comparison_val = raw( true )
      end

      expression.add_argument raw( 'WHEN' )
      expression.add_argument comparison_val
      expression.add_argument raw( 'THEN' )
      expression.add_argument thenexpr
      expression.add_argument raw( 'ELSE' )
      expression.add_argument elseexpr
      expression.add_argument raw( 'END' )

      @expression = expression
    end
  end

  class FirstNotNull < Expression
    def initialize( test_value, *default )
      f = ExprTreeNode.new(:coalesce, Type::FUNCTION )
      f.add_argument test_value

      default.each { |d|  f.add_argument d }
      @expression = f
    end
  end

  class CastToText < Expression
    def initialize( expression )
      f = ExprTreeNode.new('::', Type::OPERATOR )
      f.add_argument expression
      f.add_argument raw( 'text' )
      @expression = f
    end
  end

  class CastToNumeric < Expression
    def initialize( expression )
      f = ExprTreeNode.new('::', Type::OPERATOR )
      f.add_argument expression
      f.add_argument raw( 'numeric' )
      @expression = f
    end
  end

  class ExpressionAlias < Expression
    def initialize( expression, name )
      f = ExprTreeNode.new('AS', Type::OPERATOR, false )
      f.add_argument expression
      f.add_argument name

      @expression = f
    end
  end

  class FilterByText < Expression
    def initialize( expression, query )
      f = ExprTreeNode.new('ILIKE', Type::OPERATOR, false )
      f.add_argument CastToText.new( expression )
      f.add_argument "%#{query}%"

      @expression = f
    end
  end

  class OrderBy < Expression
    def initialize( expression, direction = :ASC )
      f = ExprTreeNode.new('', Type::OPERATOR, false )
      f.add_argument expression
      f.add_argument ExprTreeNode.raw( direction.to_s.downcase == 'desc' ? 'DESC' : 'ASC' )

      @expression = f
    end
  end

  class ExpressionList < Expression
    def initialize( expressions )
      f = ExprTreeNode.new(',', Type::OPERATOR, false )
      expressions.each { |expr| f.add_argument expr }

      @expression = f
    end
  end

  class NumOp < Expression
    def initialize( a, op, b )
      f = ExprTreeNode.new( op.to_s, Type::OPERATOR )
      f.add_argument CastToNumeric.new( a )
      f.add_argument CastToNumeric.new( b )

      @expression = f
    end
  end
end