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+-----------------------------------------------------------------------------
+-- |
+-- Module     : Hadrian.Haskell.Cabal
+-- Copyright  : (c) Andrey Mokhov 2014-2017
+-- License    : MIT (see the file LICENSE)
+-- Maintainer : andrey.mokhov@gmail.com
+-- Stability  : experimental
+--
+-- Basic functionality for extracting Haskell package metadata stored in
+-- Cabal files.
+-----------------------------------------------------------------------------
+module Hadrian.Haskell.Cabal (
+    pkgVersion, pkgIdentifier, pkgDependencies, pkgSynopsis
+    ) where
+
+import Development.Shake
+
+import Hadrian.Haskell.Cabal.Parse
+import Hadrian.Package
+import Hadrian.Oracles.TextFile
+
+-- | Read a Cabal file and return the package version. The Cabal file is tracked.
+pkgVersion :: FilePath -> Action String
+pkgVersion cabalFile = version <$> readCabalFile cabalFile
+
+-- | Read a Cabal file and return the package identifier, e.g. @base-4.10.0.0@.
+-- The Cabal file is tracked.
+pkgIdentifier :: FilePath -> Action String
+pkgIdentifier cabalFile = do
+    cabal <- readCabalFile cabalFile
+    return $ if null (version cabal)
+        then name cabal
+        else name cabal ++ "-" ++ version cabal
+
+-- | Read a Cabal file and return the sorted list of the package dependencies.
+-- The current version does not take care of Cabal conditionals and therefore
+-- returns a crude overapproximation of actual dependencies. The Cabal file is
+-- tracked.
+pkgDependencies :: FilePath -> Action [PackageName]
+pkgDependencies cabalFile = dependencies <$> readCabalFile cabalFile
+
+-- | Read a Cabal file and return the package synopsis. The Cabal file is tracked.
+pkgSynopsis :: FilePath -> Action String
+pkgSynopsis cabalFile = synopsis <$> readCabalFile cabalFile