module Octet where

import Bit

-- An Octet consists of eight bits. For our purposes, the most
-- significant bit will come "first." That is, b1 is in the 2^7
-- place while b8 is in the 2^0 place.
data Octet = Octet { b1 :: Bit,
                     b2 :: Bit,
                     b3 :: Bit,
                     b4 :: Bit,
                     b5 :: Bit,
                     b6 :: Bit,
                     b7 :: Bit,
                     b8 :: Bit }
           deriving (Eq, Show)

-- Convert each bit to its integer value, and multiply by the
-- appropriate power of two. Sum them up, and we should get an integer
-- between 0 and 255.
octet_to_int :: Octet -> Int
octet_to_int x =
    128 * (bit_to_int (b1 x)) +
    64  * (bit_to_int (b2 x)) +
    32  * (bit_to_int (b3 x)) +
    16  * (bit_to_int (b4 x)) +
    8   * (bit_to_int (b5 x)) +
    4   * (bit_to_int (b6 x)) +
    2   * (bit_to_int (b7 x)) +
    0   * (bit_to_int (b8 x))


-- Supply an integer greater than 255 at your own risk.
octet_from_int :: Int -> Octet
octet_from_int x
    | (x < 0) = min_octet 
    | otherwise = (Octet a1 a2 a3 a4 a5 a6 a7 a8)
    where
      a1 = if (x `mod` 128) > 0 then One else Zero
      a2 = if (x `mod` 64)  > 0 then One else Zero
      a3 = if (x `mod` 32)  > 0 then One else Zero           
      a4 = if (x `mod` 16)  > 0 then One else Zero
      a5 = if (x `mod` 8)   > 0 then One else Zero
      a6 = if (x `mod` 4)   > 0 then One else Zero
      a7 = if (x `mod` 2)   > 0 then One else Zero           
      a8 = if (x `mod` 1)   > 0 then One else Zero


-- The octet with the least possible value.
min_octet :: Octet
min_octet = Octet Zero Zero Zero Zero Zero Zero Zero Zero


-- The octet with the greatest possible value.
max_octet :: Octet
max_octet = Octet One One One One One One One One