Remove value-level hash algorithms.

We can use NamedHashAlgorithm to get a name where relevant, and soon
the pair of (recursive, Proxy) :: (Bool, Proxy algo) will be replaced
with a separate type which will let us drop the proxies.

Also, we drop logic from addToStore in the remote impl that was copied
from C++ compatibility code for very old daemon versions.

Author: shlevy

hnix-store-core/src/System/Nix/Hash.hs

@@ -4,10 +4,9 @@ Description : Cryptographic hashes for hnix-store.
 module System.Nix.Hash (
     HNix.Digest
 
-  , HNix.HashAlgorithm
-  , HNix.HashAlgorithm'(..)
-  , HNix.AlgoVal(..)
+  , HNix.HashAlgorithm(..)
   , HNix.HasDigest(..)
+  , HNix.NamedAlgo(..)
   , HNix.hash
   , HNix.hashLazy
 

hnix-store-core/src/System/Nix/Internal/Hash.hs

@@ -39,14 +39,11 @@ import           GHC.TypeLits
 -- | A tag for different hashing algorithms
 --   Also used as a type-level tag for hash digests
 --   (e.g. @Digest SHA256@ is the type for a sha256 hash)
---
---  When used at the type level, `n` is `Nat`
-data HashAlgorithm' n
+data HashAlgorithm
   = MD5
   | SHA1
   | SHA256
-  | Truncated n (HashAlgorithm' n)
-  deriving (Eq, Show)
+  | Truncated Nat HashAlgorithm
 
 class NamedAlgo a where
   algoName :: Text
@@ -60,8 +57,6 @@ instance NamedAlgo 'SHA1 where
 instance NamedAlgo 'SHA256 where
   algoName = "sha256"
 
-type HashAlgorithm = HashAlgorithm' Nat
-
 -- | Types with kind @HashAlgorithm@ may be a @HasDigest@ instance
 --   if they are able to hash bytestrings via the init/update/finalize
 --   API of cryptonite
@@ -191,20 +186,3 @@ truncateDigest (Digest c) = Digest $ BS.pack $ map truncOutputByte [0.. n-1]
 
 digits32 :: V.Vector Char
 digits32 = V.fromList "0123456789abcdfghijklmnpqrsvwxyz"
-
-
--- | Convert type-level @HashAlgorithm@ into the value level
-class AlgoVal (a :: HashAlgorithm) where
-  algoVal :: HashAlgorithm' Integer
-
-instance AlgoVal MD5 where
-  algoVal = MD5
-
-instance AlgoVal SHA1 where
-  algoVal = SHA1
-
-instance AlgoVal SHA256 where
-  algoVal = SHA256
-
-instance forall a n.(AlgoVal a, KnownNat n) => AlgoVal (Truncated n a) where
-  algoVal = Truncated (natVal (Proxy @n)) (algoVal @a)

hnix-store-core/src/System/Nix/Path.hs

@@ -20,7 +20,7 @@ module System.Nix.Path
   ) where
 
 import           System.Nix.Hash           (Digest(..),
-                                            HashAlgorithm'(Truncated, SHA256))
+                                            HashAlgorithm(Truncated, SHA256))
 import           System.Nix.Internal.Hash
 import qualified Data.ByteString           as BS
 import qualified Data.ByteString.Char8     as BSC

hnix-store-remote/app/Main.hs

@@ -1,4 +1,5 @@
 {-# LANGUAGE OverloadedStrings   #-}
+{-# LANGUAGE DataKinds   #-}
 import qualified Data.ByteString.Lazy as LBS
 import qualified Data.HashSet         as HS
 import           Data.Maybe
@@ -10,6 +11,7 @@ import qualified System.Nix.GC                as GC
 import           System.Nix.Path              (PathHashAlgo)
 import           System.Nix.Store.Remote
 import           System.Nix.Store.Remote.Util
+import           System.Nix.Hash
 
 noSuchPath = fromJust $ mkPath "blah"
 
@@ -24,7 +26,7 @@ main = do
     -- (Just path2) <-  addTextToStore "hnix-store2" "test2" (HS.fromList [])  False
     path2 <- addToStore "hi-test-file"
       "/home/greghale/code/hnix-store/hnix-store-remote/hi"
-      False (Proxy :: Proxy PathHashAlgo) (const True) False
+      False (Proxy :: Proxy 'SHA256) (const True) False
 
     valid <- isValidPathUncached path
     valid2 <- isValidPathUncached path2

hnix-store-remote/src/System/Nix/Store/Remote.hs

@@ -175,16 +175,10 @@ type Source = () -- abstract binary source
 addToStoreNar :: ValidPathInfo -> Source -> RepairFlag -> CheckSigsFlag -> MonadStore ()
 addToStoreNar = undefined  -- XXX
 
-printHashType :: HashAlgorithm' Integer -> T.Text
-printHashType MD5             = "MD5"
-printHashType SHA1            = "SHA1"
-printHashType SHA256          = "SHA256"
-printHashType (Truncated _ a) = printHashType a
-
 type PathFilter = Path -> Bool
 
 addToStore
-  :: forall a. (HasDigest a, AlgoVal a)
+  :: forall a. (HasDigest a, NamedAlgo a)
   => LBS.ByteString
   -> FilePath
   -> Bool
@@ -199,14 +193,12 @@ addToStore name pth recursive algoProxy pfilter repair = do
 
   runOpArgs AddToStore $ do
     putByteStringLen name
-    if algoVal @a `elem` [SHA256, Truncated 20 SHA256] && recursive
-      then putInt 0
-      else putInt 1
+    putInt 1
     if recursive
       then putInt 1
       else putInt 0
 
-    putByteStringLen (T.encodeUtf8 . T.toLower . printHashType $ algoVal @a)
+    putByteStringLen (T.encodeUtf8 . T.toLower . T.fromStrict $ algoName @a)
 
     B.putLazyByteString bs