require 'bindata/base_primitive'

module BinData
  # Defines a number of classes that contain a floating point number.
  # The float is defined by precision and endian.

  module FloatingPoint #:nodoc: all
    class << self
      def define_methods(float_class, precision, endian)
        float_class.module_eval <<-END
          def do_num_bytes
            #{create_num_bytes_code(precision)}
          end

          #---------------
          private

          def sensible_default
            0.0
          end

          def value_to_binary_string(val)
            #{create_to_binary_s_code(precision, endian)}
          end

          def read_and_return_value(io)
            #{create_read_code(precision, endian)}
          end
        END
      end

      def create_num_bytes_code(precision)
        (precision == :single) ? 4 : 8
      end

      def create_read_code(precision, endian)
        if precision == :single
          unpack = (endian == :little) ? 'e' : 'g'
          nbytes = 4
        else # double_precision
          unpack = (endian == :little) ? 'E' : 'G'
          nbytes = 8
        end

        "io.readbytes(#{nbytes}).unpack('#{unpack}').at(0)"
      end

      def create_to_binary_s_code(precision, endian)
        if precision == :single
          pack = (endian == :little) ? 'e' : 'g'
        else # double_precision
          pack = (endian == :little) ? 'E' : 'G'
        end

        "[val].pack('#{pack}')"
      end
    end
  end


  # Single precision floating point number in little endian format
  class FloatLe < BinData::BasePrimitive
    register_self
    FloatingPoint.define_methods(self, :single, :little)
  end

  # Single precision floating point number in big endian format
  class FloatBe < BinData::BasePrimitive
    register_self
    FloatingPoint.define_methods(self, :single, :big)
  end

  # Double precision floating point number in little endian format
  class DoubleLe < BinData::BasePrimitive
    register_self
    FloatingPoint.define_methods(self, :double, :little)
  end

  # Double precision floating point number in big endian format
  class DoubleBe < BinData::BasePrimitive
    register_self
    FloatingPoint.define_methods(self, :double, :big)
  end
end