core: add System.Nix.DerivedPath

Co-Authored-By: Richard Marko <[email protected]>

Author: cgibbard

hnix-store-core/hnix-store-core.cabal

@@ -64,6 +64,7 @@ library
     , System.Nix.Build
     , System.Nix.ContentAddress
     , System.Nix.Derivation
+    , System.Nix.DerivedPath
     , System.Nix.Hash
     , System.Nix.Hash.Truncation
     , System.Nix.Nar

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

@@ -0,0 +1,80 @@
+{-# LANGUAGE OverloadedStrings #-}
+
+module System.Nix.DerivedPath (
+    OutputsSpec(..)
+  , DerivedPath(..)
+  , parseOutputsSpec
+  , outputsSpecToText
+  , parseDerivedPath
+  , derivedPathToText
+  ) where
+
+import Data.Bifunctor (first)
+import GHC.Generics (Generic)
+import Data.Set (Set)
+import Data.Text (Text)
+import System.Nix.StorePath (StoreDir, StorePath, StorePathName, InvalidPathError)
+
+import qualified Data.Set
+import qualified Data.Text
+import qualified System.Nix.StorePath
+
+data OutputsSpec =
+    OutputsSpec_All
+  | OutputsSpec_Names (Set StorePathName)
+  deriving (Eq, Generic, Ord, Show)
+
+data DerivedPath =
+    DerivedPath_Opaque StorePath
+  | DerivedPath_Built StorePath OutputsSpec
+  deriving (Eq, Generic, Ord, Show)
+
+data ParseOutputsError =
+    ParseOutputsError_InvalidPath InvalidPathError
+  | ParseOutputsError_NoNames
+  deriving (Eq, Ord, Show)
+
+convertError
+  :: Either InvalidPathError a
+  -> Either ParseOutputsError a
+convertError = first ParseOutputsError_InvalidPath
+
+parseOutputsSpec :: Text -> Either ParseOutputsError OutputsSpec
+parseOutputsSpec t
+  | t == "*" = Right OutputsSpec_All
+  | otherwise = do
+  names <- mapM
+             (convertError . System.Nix.StorePath.makeStorePathName)
+             (Data.Text.splitOn "," t)
+  if null names
+    then Left ParseOutputsError_NoNames
+    else Right $ OutputsSpec_Names (Data.Set.fromList names)
+
+outputsSpecToText :: OutputsSpec -> Text
+outputsSpecToText = \case
+  OutputsSpec_All -> "*"
+  OutputsSpec_Names ns ->
+    Data.Text.intercalate "," (fmap System.Nix.StorePath.unStorePathName (Data.Set.toList ns))
+
+parseDerivedPath
+  :: StoreDir
+  -> Text
+  -> Either ParseOutputsError DerivedPath
+parseDerivedPath root p =
+  case Data.Text.breakOn "!" p of
+    (s,r) ->
+      if Data.Text.null r
+      then DerivedPath_Opaque
+           <$> (convertError $ System.Nix.StorePath.parsePathFromText root s)
+      else DerivedPath_Built
+           <$> (convertError $ System.Nix.StorePath.parsePathFromText root s)
+           <*> parseOutputsSpec r
+
+derivedPathToText :: StoreDir -> DerivedPath -> Text
+derivedPathToText root = \case
+  DerivedPath_Opaque p ->
+    System.Nix.StorePath.storePathToText root p
+  DerivedPath_Built p os ->
+    System.Nix.StorePath.storePathToText root p
+    <> "!"
+    <> outputsSpecToText os