# frozen_string_literal: true
#
# ronin-code-asm - A Ruby DSL for crafting Assembly programs and shellcode.
#
# Copyright (c) 2007-2022 Hal Brodigan (postmodern.mod3 at gmail.com)
#
# ronin-code-asm is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# ronin-code-asm is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with ronin-code-asm.  If not, see <https://www.gnu.org/licenses/>.
#

require 'ronin/code/asm/register'

module Ronin
  module Code
    module ASM
      #
      # Represents a Memory Operand.
      #
      # @see http://asm.sourceforge.net/articles/linasm.html#Memory
      #
      class MemoryOperand < Struct.new(:base, :offset, :index, :scale, :width)

        #
        # Creates a new Memory Operand.
        #
        # @param [Register, nil] base
        #   The base of the value.
        #
        # @param [Integer] offset
        #   The fixed offset to add to the `base`.
        #
        # @param [Register, nil] index
        #   The variable index to multiple by `scale`, then add to `base.
        #
        # @param [Integer] scale
        #   The scale to multiple `index` by.
        #
        # @param [Integer, nil] width
        #   The optional width of the memory operand.
        #
        # @raise [TypeError]
        #   `base` or `index` was not a {Register} or `nil`.
        #
        def initialize(base=nil,offset=0,index=nil,scale=1,width=nil)
          unless (base.nil? || base.kind_of?(Register))
            raise(TypeError,"base must be a Register or nil")
          end

          unless offset.kind_of?(Integer)
            raise(TypeError,"offset must be an Integer")
          end

          unless (index.nil? || index.kind_of?(Register))
            raise(TypeError,"index must be a Register or nil")
          end

          unless scale.kind_of?(Integer)
            raise(TypeError,"scale must be an Integer")
          end

          if base
            width ||= base.width
          end

          super(base,offset,index,scale,width)
        end

        #
        # Adds to the offset of the Memory Operand.
        #
        # @param [Integer] offset
        #   The offset to add to the Memory Operand.
        #
        # @return [MemoryOperand]
        #   The new Memory Operand.
        #
        def +(offset)
          MemoryOperand.new(
            self.base,
            self.offset + offset,
            self.index,
            self.scale,
            self.width
          )
        end

        #
        # Subtracts from the offset of the Memory Operand.
        #
        # @param [Integer] offset
        #   The offset to subject from the Memory Operand.
        #
        # @return [MemoryOperand]
        #   The new Memory Operand.
        #
        def -(offset)
          MemoryOperand.new(
            self.base,
            self.offset - offset,
            self.index,
            self.scale,
            self.width
          )
        end

      end
    end
  end
end