# encoding: utf-8
# frozen_string_literal: true
# rubocop:disable Metrics/LineLength

module Carbon
  module Core
    module Pointer
      # Methods that perform accesses on pointers.  This is essentially
      # dereferencing and indexing.  This defines the following functions:
      #
      # - `Carbon::Pointer<T>.value(self): T`
      # - `Carbon::Pointer<T>.value=(self, value: T): T`
      # - `Carbon::Pointer<T>.[]<I: Carbon::Numeric>(self, index: I): T`
      # - `Carbon::Pointer<T>.[]=<I: Carbon::Numeric>(self, index: I, value: T): T`
      #
      # @api private
      module Access
        # Define all of the access functions.  This iterates over all of the
        # integers, defining the array get/set functions in terms of each
        # integer type.  It then defines the value get/set functions.
        #
        # @return [void]
        def define_access_functions
          Ints.each do |int|
            next if int.size == 1
            define_array_get_function(int)
            define_array_set_function(int)
          end
          define_value_get_function
          define_value_set_function
        end

        # Defines the value set function.  This function (named `value=`) sets
        # the value at the pointer.  This is the same as calling the array
        # set function with an index of zero (0).
        #
        # @return [void]
        def define_value_set_function
          function_name = PTYPE.call(:value=, [PTYPE, PTYPEGEN])
          Core.define(function: function_name) do |function|
            function[:return] = PTYPEGEN
            define_value_set_definition(function[:definition])
          end
        end

        # Defines the value get function.  This function (named `value`) gets
        # the value at the pointer.  This is the same as calling the array
        # get function with an index of zero (0).
        #
        # @return [void]
        def define_value_get_function
          function_name = PTYPE.call(:value, [PTYPE])
          Core.define(function: function_name) do |function|
            function[:return] = PTYPEGEN
            define_value_get_definition(function[:definition])
          end
        end

        # Defines the array set function.  This function (named `[]=`) sets
        # the value a given distance away from the pointer.
        #
        # @param int [Core::Int] The integer type for the index.
        # @return [void]
        def define_array_set_function(int)
          function_name = PTYPE.call(:[]=, [PTYPE, int.name, PTYPEGEN])
          Core.define(function: function_name) do |function|
            function[:return] = PTYPEGEN
            define_array_set_definition(int, function[:definition])
          end
        end

        # Defines the array get function.  This function (named `[]`) gets the
        # value at a given distance away from the pointer.
        #
        # @param int [Core::Int] The integer type for the index.
        # @return [void]
        def define_array_get_function(int)
          function_name = PTYPE.call(:[], [PTYPE, int.name])
          Core.define(function: function_name) do |function|
            function[:return] = PTYPEGEN
            define_array_get_definition(int, function[:definition])
          end
        end

      private

        def define_array_set_definition(int, definition)
          entry = definition.add("entry").build
          this, index, value = definition.params
          this.name, index.name, value.name = %w(self index value)

          gep = entry.gep(this, index).as(Carbon::Type("Carbon::UInt64"))
          entry.store(gep, value)
          entry.ret(value)
        end

        def define_array_get_definition(_int, definition)
          entry = definition.add("entry").build
          this, index = definition.params
          this.name, index.name = %w(self index)

          gep = entry.gep(this, index).as(Carbon::Type("Carbon::UInt64"))
          load = entry.load(gep).as(PTYPEGEN)
          entry.ret(load)
        end

        def define_value_set_definition(definition)
          entry = definition.add("entry").build
          this, value = definition.params
          this.name, value.name = %w(self value)

          entry.store(this, value)
          entry.ret(value)
        end

        def define_value_get_definition(definition)
          entry = definition.add("entry").build
          this = definition.params[0]
          this.name = "self"

          entry.ret(entry.load(this).as(PTYPEGEN))
        end
      end
    end
  end
end