-- Copyright 2006 mutantlemon.com

module Memory where

import Data.Array.IArray
import Data.Word

import RomImage

class MemoryModel a where
  readMem :: a -> Word16 -> Word8
  writeMem :: a -> Word16 -> Word8 -> a

data Memory = Memory {
  memRomImage :: RomImage,
  memRam :: Array Word16 Word8
}

initMemory :: RomImage -> Memory
initMemory ri = Memory {
  memRomImage = ri,
  memRam = listArray (0x8000, 0xFFFF) (replicate 0x8000 0x00)
}


instance MemoryModel Memory where
  readMem m a =
    if a < 0x8000
    then readRomImageByte (memRomImage m) (fromIntegral a)
    else (memRam m) ! a
  
  writeMem m a v =
    if a < 0x8000
    then m
    else m { memRam = (memRam m)//[(a, v)] }