module Interop.Exports (
    hsComputeStats,
    hsFreeString,
    hsMakeMessage,
) where

import Foreign.C.String (CString, newCString, peekCString)
import Foreign.C.Types (CInt (..))
import Foreign.Marshal.Alloc (free)
import Foreign.Ptr (Ptr, nullPtr)
import Foreign.Storable (poke)
import Interop.Shared (SharedStats, calculateSummary, formatHaskellMessage, summaryToSharedStats)

hsComputeStats :: CInt -> CInt -> Ptr SharedStats -> IO CInt
hsComputeStats left right outStats
    | outStats == nullPtr = pure 1
    | otherwise = do
        poke outStats $
            summaryToSharedStats $
                calculateSummary (fromIntegral left) (fromIntegral right)
        pure 0

hsMakeMessage :: CString -> CInt -> CInt -> IO CString
hsMakeMessage namePtr left right
    | namePtr == nullPtr = newCString "Haskell received a null name pointer"
    | otherwise = do
        name <- peekCString namePtr
        let summary = calculateSummary (fromIntegral left) (fromIntegral right)
        newCString (formatHaskellMessage name summary)

hsFreeString :: CString -> IO ()
hsFreeString ptr
    | ptr == nullPtr = pure ()
    | otherwise = free ptr

foreign export ccall "hs_compute_stats" hsComputeStats :: CInt -> CInt -> Ptr SharedStats -> IO CInt
foreign export ccall "hs_make_message" hsMakeMessage :: CString -> CInt -> CInt -> IO CString
foreign export ccall "hs_free_string" hsFreeString :: CString -> IO ()