112 lines
3.3 KiB
Haskell
112 lines
3.3 KiB
Haskell
{-# LANGUAGE PackageImports #-}
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{-# LANGUAGE FlexibleContexts #-}
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module Propellor.Property where
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import System.Directory
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import System.FilePath
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import Control.Monad
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import Data.Monoid
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import Control.Monad.IfElse
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import "mtl" Control.Monad.RWS.Strict
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import Propellor.Types
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import Propellor.Info
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import Utility.Monad
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-- Constructs a Property.
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property :: Desc -> Propellor Result -> Property NoInfo
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property d s = simpleProperty d s mempty
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-- | Makes a perhaps non-idempotent Property be idempotent by using a flag
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-- file to indicate whether it has run before.
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-- Use with caution.
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flagFile :: Property i -> FilePath -> Property i
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flagFile p = flagFile' p . return
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flagFile' :: Property i -> IO FilePath -> Property i
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flagFile' p getflagfile = adjustPropertySatisfy p $ \satisfy -> do
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flagfile <- liftIO getflagfile
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go satisfy flagfile =<< liftIO (doesFileExist flagfile)
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where
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go _ _ True = return NoChange
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go satisfy flagfile False = do
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r <- satisfy
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when (r == MadeChange) $ liftIO $
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unlessM (doesFileExist flagfile) $ do
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createDirectoryIfMissing True (takeDirectory flagfile)
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writeFile flagfile ""
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return r
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--- | Whenever a change has to be made for a Property, causes a hook
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-- Property to also be run, but not otherwise.
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onChange
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:: (Combines (Property x) (Property y))
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=> Property x
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=> Property y
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=> CombinedType (Property x) (Property y)
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onChange = combineWith $ \p hook -> do
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r <- p
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case r of
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MadeChange -> do
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r' <- hook
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return $ r <> r'
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_ -> return r
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(==>) :: IsProp (Property i) => Desc -> Property i -> Property i
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(==>) = flip describe
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infixl 1 ==>
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-- | Makes a Property only need to do anything when a test succeeds.
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check :: IO Bool -> Property i -> Property i
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check c p = adjustPropertySatisfy p $ \satisfy -> ifM (liftIO c)
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( satisfy
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, return NoChange
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)
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-- | Tries the first property, but if it fails to work, instead uses
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-- the second.
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fallback :: (Combines (Property p1) (Property p2)) => Property p1 -> Property p2 -> Property (CInfo p1 p2)
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fallback = combineWith $ \a1 a2 -> do
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r <- a1
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if r == FailedChange
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then a2
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else return r
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-- | Marks a Property as trivial. It can only return FailedChange or
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-- NoChange.
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--
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-- Useful when it's just as expensive to check if a change needs
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-- to be made as it is to just idempotently assure the property is
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-- satisfied. For example, chmodding a file.
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trivial :: Property i -> Property i
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trivial p = adjustPropertySatisfy p $ \satisfy -> do
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r <- satisfy
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if r == MadeChange
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then return NoChange
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else return r
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doNothing :: Property NoInfo
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doNothing = property "noop property" noChange
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-- | Makes a property that is satisfied differently depending on the host's
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-- operating system.
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--
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-- Note that the operating system may not be declared for some hosts.
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withOS :: Desc -> (Maybe System -> Propellor Result) -> Property NoInfo
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withOS desc a = property desc $ a =<< getOS
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-- | Undoes the effect of a property.
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revert :: RevertableProperty -> RevertableProperty
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revert (RevertableProperty p1 p2) = RevertableProperty p2 p1
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makeChange :: IO () -> Propellor Result
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makeChange a = liftIO a >> return MadeChange
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noChange :: Propellor Result
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noChange = return NoChange
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-- | Registers an action that should be run at the very end,
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endAction :: Desc -> (Result -> Propellor Result) -> Propellor ()
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endAction desc a = tell [EndAction desc a]
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