Int.hs

-- |
-- Module      : Data.LazyHash.Cache.Int
-- Copyright   : (c) Justus Sagemüller 2017
-- License     : GPL v3
-- 
-- Maintainer  : (@) jsagemue $ uni-koeln.de
-- Stability   : experimental
-- Portability : portable
-- 
-- Identical interface to "Data.LazyHash.Cache", but specialised to hashes of type 'Int'
-- (which are computed with "Data.Hashable"). At only 64 bits, collisions are
-- <https://en.wikipedia.org/wiki/Birthday_problem likely> with this type once you store
-- a considerable number of values, so don't use it for serious applications.

{-# LANGUAGE LambdaCase       #-}
{-# LANGUAGE FlexibleContexts #-}

module Data.LazyHash.Cache.Int (
             -- * The caching actions
               cached, cached'
             -- * Prehashing tools
             , fundamental, (<#>), liftPH2
             -- * Configuration
                               ) where

import Data.LazyHash.Cache hiding (cached, cached')

import Data.LazyHash.Class
import Data.LazyHash.Numerical ()

import qualified Data.Hashable as SH

import Data.Binary
import System.FilePath
import System.Directory

import Data.Typeable

import qualified Data.ByteString.Char8 as BS
import qualified Data.ByteString.Lazy as BS (toStrict)

import Numeric (showHex) 
import Data.Word (Word64) 

import Data.Default.Class
import Lens.Micro

-- | Like 'Data.LazyHash.Cache.cached', but specialised to 'Int' hashes.
cached :: (Binary a, Typeable a) => Prehashed Int a -> IO a
cached = cached' def

-- | Like 'Data.LazyHash.Cache.cached'', but specialised to 'Int' hashes.
cached' :: (Binary a, Typeable a)
                   => CacheAccessConf
                   -> Prehashed Int a -- ^ Value to cache
                   -> IO a
cached' conf (Prehashed h v) = case conf^.cachingLocation of
  Nothing -> do
   tmpRoot <- getTemporaryDirectory
   cached' (conf & cachingLocation .~ Just (tmpRoot</>"hs-lazy-hashed")) (Prehashed h v)
  Just path -> do
   let fname = path </> showHex (fromIntegral (h # typeRep [v]) :: Word64) [] <.> ".lhbs"
   cachedValueInFile conf fname v