module Denko
  class Board
    I2C_FREQUENCIES = {
      100000  => 0x00,
      400000  => 0x01,
      1000000 => 0x02,
      3400000 => 0x03,
    }

    # Might make this bigger based on board maps later, but stick with the lowest limit of the AVR boards for now.
    def i2c_limit
      32
    end

    def i2c_convert_frequency(freq)
      # Default to 100 kHz.
      freq = 100000 unless freq

      unless I2C_FREQUENCIES.include?(freq)
        raise ArgumentError, "I2C frequency must be in: #{I2C_FREQUENCIES.keys.inspect}" 
      end
      I2C_FREQUENCIES[freq]
    end

    # CMD = 33
    def i2c_search
      write Message.encode command: 33
    end

    # CMD = 34
    def i2c_write(address, bytes, frequency=100000, repeated_start=false)
      bytes = [bytes] unless bytes.class == Array
      raise ArgumentError, "I2C write must be 1..#{i2c_limit} bytes long" if (bytes.length > i2c_limit || bytes.length < 1)
      
      # Use top bit of address to select stop condition (1), or repated start (0).
      send_stop = repeated_start ? 0 : 1
      frequency = i2c_convert_frequency(frequency)
      
      write Message.encode  command:     34,
                            pin:         address | (send_stop << 7),
                            value:       bytes.length,
                            aux_message: pack(:uint8, frequency) + pack(:uint8, bytes)
    end

    # CMD = 35
    def i2c_read(address, register, read_length, frequency=100000, repeated_start=false)
      raise ArgumentError, "I2C read must be 1..#{i2c_limit} bytes long" if (read_length > i2c_limit || read_length < 1)

      # Use top bit of address to select stop condition (1), or repated start (0).
      send_stop = repeated_start ? 0 : 1
      frequency = i2c_convert_frequency(frequency)

      # A register address starting register address can be given (up to 4 bytes)
      if register
        register = [register].flatten
        raise ArgumentError, 'maximum 4 byte register address for I2C read' if register.length > 4
        register_packed = pack(:uint8, [register.length] + register)
      else
        register_packed = pack(:uint8, [0])
      end

      write Message.encode  command:      35,
                            pin:          address | (send_stop << 7),
                            value:        read_length,
                            aux_message:  pack(:uint8, frequency) + register_packed
    end
  end
end