require 'gir_ffi/base_argument_builder'

module GirFFI
  # Implements building pre- and post-processing statements for arguments.
  class ArgumentBuilder < BaseArgumentBuilder
    def initialize var_gen, arginfo
      super var_gen, arginfo.name, arginfo.argument_type, arginfo.direction
      @arginfo = arginfo
    end

    def inarg
      if has_input_value?
        @array_arg.nil? ? @name : nil
      end
    end

    def retname
      if has_output_value?
        @retname ||= @var_gen.new_var
      end
    end

    def pre
      pr = []
      if has_input_value?
        pr << fixed_array_size_check if needs_size_check?
        pr << array_length_assignment if is_array_length_parameter?
      end
      pr << set_function_call_argument
      pr
    end

    def post
      if has_output_value?
        value = output_value
        ["#{retname} = #{value}"]
      else
        []
      end
    end

    private

    def output_value
      if is_caller_allocated_object?
        callarg
      elsif needs_outgoing_parameter_conversion?
        case specialized_type_tag
        when :enum, :flags
          "#{argument_class_name}[#{output_conversion_arguments}]"
        else
          "#{argument_class_name}.wrap(#{output_conversion_arguments})"
        end
      elsif is_fixed_length_array?
        "#{callarg}.to_sized_array_value #{array_size}"
      else
        "#{callarg}.to_value"
      end
    end

    def is_array_length_parameter?
      @array_arg
    end

    def needs_size_check?
      specialized_type_tag == :c && type_info.array_fixed_size > -1
    end

    def is_fixed_length_array?
      specialized_type_tag == :c
    end

    def fixed_array_size_check
      size = type_info.array_fixed_size
      "GirFFI::ArgHelper.check_fixed_array_size #{size}, #{@name}, \"#{@name}\""
    end

    def has_output_value?
      @direction == :inout || @direction == :out
    end

    def has_input_value?
      @direction == :inout || @direction == :in
    end

    def array_length_assignment
      arrname = @array_arg.name
      "#{@name} = #{arrname}.nil? ? 0 : #{arrname}.length"
    end

    def set_function_call_argument
      value = if @direction == :out
                if is_caller_allocated_object?
                  "#{argument_class_name}.allocate"
                else
                  "GirFFI::InOutPointer.for #{type_specification}"
                end
              else
                if needs_ingoing_parameter_conversion?
                  ingoing_parameter_conversion
                else
                  @name
                end
              end
      "#{callarg} = #{value}"
    end

    def is_caller_allocated_object?
      [:object, :struct].include?(specialized_type_tag) &&
        @arginfo.caller_allocates?
    end

    def needs_outgoing_parameter_conversion?
      [ :array, :enum, :flags, :ghash, :glist, :gslist, :object, :struct,
        :strv ].include?(specialized_type_tag)
    end

    def needs_ingoing_parameter_conversion?
      @direction == :inout ||
        [ :object, :struct, :callback, :utf8, :void, :glist, :gslist, :ghash,
          :array, :c, :zero_terminated, :strv ].include?(specialized_type_tag)
    end

    def ingoing_parameter_conversion
      case specialized_type_tag
      when :enum, :flags
        base = "#{argument_class_name}[#{parameter_conversion_arguments}]"
        "GirFFI::InOutPointer.from #{specialized_type_tag.inspect}, #{base}"
      when :object, :struct, :void, :glist, :gslist, :ghash, :array,
        :zero_terminated, :strv, :callback
        base = "#{argument_class_name}.from(#{parameter_conversion_arguments})"
        if has_output_value?
          if specialized_type_tag == :strv
            "GirFFI::InOutPointer.from #{type_specification}, #{base}"
          else
            "GirFFI::InOutPointer.from :pointer, #{base}"
          end
        else
          base
        end
      when :c, :utf8
        if has_output_value?
          "GirFFI::InOutPointer.from #{parameter_conversion_arguments}"
        else
          "GirFFI::InPointer.from(#{parameter_conversion_arguments})"
        end
      else
        base = "#{parameter_conversion_arguments}"
        "GirFFI::InOutPointer.from #{specialized_type_tag.inspect}, #{base}"
      end
    end

    def output_conversion_arguments
      conversion_arguments "#{callarg}.to_value"
    end

    def parameter_conversion_arguments
      conversion_arguments @name
    end

    def self_t
      type_tag.inspect
    end
  end
end