{-# OPTIONS_GHC -Wno-unrecognised-pragmas #-}
module Bus() where

import Clash.Prelude

import Peripherals.Ram(Ram, RamLine, read, RamAddr)
import Peripherals.Uart(UartAddr, read, write)
import Machine(Peripherals(..))
import BusTypes(
    BusError(..),
    TransactionSize(..),
    ReadRequest(..),
    BusResponse(..),
    BusVal(..),
    ReadResponse(..),
    WriteResponse(..)
  )
import Types(Addr,
             Byte, HalfWord, FullWord, DoubleWord, QuadWord)
import Peripherals.Ram(read, bytesInRam)
import Distribution.Types.UnitId (DefUnitId(unDefUnitId))

alignCheck :: Addr -> TransactionSize -> Bool
alignCheck addr SizeByte       = True
alignCheck addr SizeHalfWord   = addr `mod` 2 == 0
alignCheck addr SizeFullWord   = addr `mod` 4 == 0
alignCheck addr SizeDoubleWord = addr `mod` 8 == 0
alignCheck addr SizeQuadWord   = addr `mod` 16 == 0

-- address space follows QEMU behavior for now
(ramStart, ramEnd) = (0x80000000 :: Addr, ramStart + (bytesInRam - 1))
(uartStart, uartEnd) = (0x10000000 :: Addr, uartStart + 7)

-- reading/writing from/to UART is implemented as reading/writing
-- from/to stdin/stdout, so we need IO.
read :: ReadRequest -> Peripherals -> IO ReadResponse
read (Request addr size) peripherals
  | not (alignCheck addr size) = return $ Left UnAligned
  | (addr >= ramStart) && (addr <= ramEnd) =
      return $ Right $ Peripherals.Ram.read size ramAddr (ram peripherals)
  | (addr >= uartStart) && (addr <= uartEnd) =
      Right <$> Peripherals.Uart.read size uartAddr
  | otherwise = return $ Left UnMapped
    where
      ramAddrNoOffset = addr - ramStart
      ramAddr :: RamAddr
      ramAddr = resize ramAddrNoOffset

      uartAddrNoOffset = addr - uartStart
      uartAddr :: UartAddr
      uartAddr = resize uartAddrNoOffset

-- write :: BusVal -> Addr -> Peripherals -> IO WriteResponse
-- write val addr peripherals
--   | (addr >= uartStart) && (addr <= uartEnd) =
--       WriteResponse . Result <$> Peripherals.Uart.write val uartAddr
--     where
--       ramAddrNoOffset = addr - ramStart
--       ramAddr :: RamAddr
--       ramAddr = resize ramAddrNoOffset

--       uartAddrNoOffset = addr - uartStart
--       uartAddr :: UartAddr
--       uartAddr = resize uartAddrNoOffset