module Assembler where

import Data.Int
import qualified Data.Binary as B
import qualified Data.Binary.Builder as Bu
import qualified Data.Binary.Put as P
import qualified Data.ByteString.Lazy as BL
import Compiler

-- Binary (huffman) encoding of instructions
-- 0x00 reserver
-- 0x01 Const
-- 0x04 Add
-- 0x05 Sub
-- 0x06 Mult
-- 0x07 Div


type Bytecode = BL.ByteString

version1 :: Bu.Builder
version1 = P.execPut $ B.putWord8 1

toBinary :: Command -> P.Put
toBinary (Const i) = do
    P.putWord8 0x0001
    P.putInt32le ((fromIntegral i)::Int32)
toBinary Add  = P.putWord8 0x0004
toBinary Sub  = P.putWord8 0x0005
toBinary Mult = P.putWord8 0x0006
toBinary Div  = P.putWord8 0x0007

assemble :: [Command] -> Bytecode
assemble cmds = Bu.toLazyByteString $ mconcat $ version1:map (P.execPut . toBinary) cmds