    -- |
    -- Module      : Basement.Runtime
    -- License     : BSD-style
    -- Maintainer  : foundation
    --
    -- Global configuration environment
    module Basement.Runtime
        where

    import           Basement.Compat.Base
    import           Basement.Types.OffsetSize
    import           System.Environment
    import           System.IO.Unsafe (unsafePerformIO)
    import           Text.Read        (readMaybe)

    -- | Defines the maximum size in bytes of unpinned arrays.
    --
    -- You can change this value by setting the environment variable
    -- @HS_FOUNDATION_UARRAY_UNPINNED_MAX@ to an unsigned integer number.
    --
    -- Note: We use 'unsafePerformIO' here. If the environment variable
    -- changes during runtime and the runtime system decides to recompute
    -- this value, referential transparency is violated (like the First
    -- Order violated the Galactic Concordance!).
    --
    -- TODO The default value of 1024 bytes is arbitrarily chosen for now.
    unsafeUArrayUnpinnedMaxSize :: CountOf Word8
    unsafeUArrayUnpinnedMaxSize = unsafePerformIO $ do
        maxSize <- (>>= readMaybe) <$> lookupEnv "HS_FOUNDATION_UARRAY_UNPINNED_MAX"
        pure $ maybe (CountOf 1024) CountOf maxSize
    {-# NOINLINE unsafeUArrayUnpinnedMaxSize #-}