add KeyVariety type

Where before the "name" of a key and a backend was a string, this makes
it a concrete data type.

This is groundwork for allowing some varieties of keys to be disabled
in file2key, so git-annex won't use them at all.

Benchmarks ran in my big repo:

old git-annex info:

real	0m3.338s
user	0m3.124s
sys	0m0.244s

new git-annex info:

real	0m3.216s
user	0m3.024s
sys	0m0.220s

new git-annex find:

real	0m7.138s
user	0m6.924s
sys	0m0.252s

old git-annex find:

real	0m7.433s
user	0m7.240s
sys	0m0.232s

Surprising result; I'd have expected it to be slower since it now parses
all the key varieties. But, the parser is very simple and perhaps
sharing KeyVarieties uses less memory or something like that.

This commit was supported by the NSF-funded DataLad project.

Types/Key.hs

@@ -7,13 +7,15 @@
 
 module Types.Key where
 
+import Utility.PartialPrelude
+
 import System.Posix.Types
 
 {- A Key has a unique name, which is derived from a particular backend,
  - and may contain other optional metadata. -}
 data Key = Key
 	{ keyName :: String
-	, keyBackendName :: String
+	, keyVariety :: KeyVariety
 	, keySize :: Maybe Integer
 	, keyMtime :: Maybe EpochTime
 	, keyChunkSize :: Maybe Integer
@@ -22,3 +24,85 @@ data Key = Key
 
 {- A filename may be associated with a Key. -}
 type AssociatedFile = Maybe FilePath
+
+{- There are several different varieties of keys. -}
+data KeyVariety
+	= SHA2Key HashSize HasExt
+	| SHA3Key HashSize HasExt
+	| SKEINKey HashSize HasExt
+	| SHA1Key HasExt
+	| MD5Key HasExt
+	| WORMKey
+	| URLKey
+ 	-- Some repositories may contain keys of other varieties,
+	-- which can still be processed to some extent.
+	| OtherKey String
+	deriving (Eq, Ord, Read, Show)
+
+{- Some varieties of keys may contain an extension at the end of the
+ - keyName -}
+newtype HasExt = HasExt Bool
+	deriving (Eq, Ord, Read, Show)
+
+newtype HashSize = HashSize Int
+	deriving (Eq, Ord, Read, Show)
+
+hasExt :: KeyVariety -> Bool
+hasExt (SHA2Key _ (HasExt b)) = b
+hasExt (SHA3Key _ (HasExt b)) = b
+hasExt (SKEINKey _ (HasExt b)) = b
+hasExt (SHA1Key (HasExt b)) = b
+hasExt (MD5Key (HasExt b)) = b
+hasExt WORMKey = False
+hasExt URLKey = False
+hasExt (OtherKey s) =  end s == "E"
+
+sameExceptExt :: KeyVariety -> KeyVariety -> Bool
+sameExceptExt (SHA2Key sz1 _) (SHA2Key sz2 _) = sz1 == sz2
+sameExceptExt (SHA3Key sz1 _) (SHA3Key sz2 _) = sz1 == sz2
+sameExceptExt (SKEINKey sz1 _) (SKEINKey sz2 _) = sz1 == sz2
+sameExceptExt (SHA1Key _) (SHA1Key _) = True
+sameExceptExt (MD5Key _) (MD5Key _) = True
+sameExceptExt _ _ = False
+
+formatKeyVariety :: KeyVariety -> String
+formatKeyVariety v = case v of
+	SHA2Key sz e -> adde e (addsz sz "SHA")
+	SHA3Key sz e -> adde e (addsz sz "SHA3_")
+	SKEINKey sz e -> adde e (addsz sz "SKEIN")
+	SHA1Key e -> adde e "SHA1"
+	MD5Key e -> adde e "MD5"
+	WORMKey -> "WORM"
+	URLKey -> "URL"
+	OtherKey s -> s
+  where
+	adde (HasExt False) s = s
+	adde (HasExt True) s = s ++ "E"
+	addsz (HashSize n) s =  s ++ show n
+
+parseKeyVariety :: String -> KeyVariety
+parseKeyVariety "SHA256"    =  SHA2Key (HashSize 256) (HasExt False)
+parseKeyVariety "SHA256E"   = SHA2Key (HashSize 256) (HasExt True)
+parseKeyVariety "SHA512"    = SHA2Key (HashSize 512) (HasExt False)
+parseKeyVariety "SHA512E"   = SHA2Key (HashSize 512) (HasExt True)
+parseKeyVariety "SHA224"    = SHA2Key (HashSize 224) (HasExt False)
+parseKeyVariety "SHA224E"   = SHA2Key (HashSize 224) (HasExt True)
+parseKeyVariety "SHA384"    = SHA2Key (HashSize 384) (HasExt False)
+parseKeyVariety "SHA384E"   = SHA2Key (HashSize 384) (HasExt True)
+parseKeyVariety "SHA3_512"  = SHA3Key (HashSize 512) (HasExt False)
+parseKeyVariety "SHA3_512E" = SHA3Key (HashSize 512) (HasExt True)
+parseKeyVariety "SHA3_384"  = SHA3Key (HashSize 384) (HasExt False)
+parseKeyVariety "SHA3_384E" = SHA3Key (HashSize 384) (HasExt True)
+parseKeyVariety "SHA3_256"  = SHA3Key (HashSize 256) (HasExt False)
+parseKeyVariety "SHA3_256E" = SHA3Key (HashSize 256) (HasExt True)
+parseKeyVariety "SHA3_224"  = SHA3Key (HashSize 224) (HasExt False)
+parseKeyVariety "SHA3_224E" = SHA3Key (HashSize 224) (HasExt True)
+parseKeyVariety "SKEIN512"  = SKEINKey (HashSize 512) (HasExt False)
+parseKeyVariety "SKEIN512E" = SKEINKey (HashSize 512) (HasExt True)
+parseKeyVariety "SKEIN256"  = SKEINKey (HashSize 256) (HasExt False)
+parseKeyVariety "SKEIN256E" = SKEINKey (HashSize 256) (HasExt True)
+parseKeyVariety "SHA1"      = SHA1Key (HasExt False)
+parseKeyVariety "MD5"       = MD5Key (HasExt False)
+parseKeyVariety "WORM"      = WORMKey
+parseKeyVariety "URL"       = URLKey
+parseKeyVariety s           = OtherKey s