82 lines
2.4 KiB
Haskell
82 lines
2.4 KiB
Haskell
module Propellor.Property where
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import System.Directory
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import Control.Monad
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import Propellor.Types
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import Propellor.Engine
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import Utility.Monad
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makeChange :: IO () -> IO Result
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makeChange a = a >> return MadeChange
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noChange :: IO Result
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noChange = return NoChange
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{- | Combines a list of properties, resulting in a single property
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- that when run will run each property in the list in turn,
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- and print out the description of each as it's run. Does not stop
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- on failure; does propigate overall success/failure.
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-}
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propertyList :: Desc -> [Property] -> Property
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propertyList desc ps = Property desc $ ensureProperties' ps
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{- | Combines a list of properties, resulting in one property that
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- ensures each in turn, stopping on failure. -}
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combineProperties :: [Property] -> Property
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combineProperties ps = Property desc $ go ps NoChange
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where
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go [] rs = return rs
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go (l:ls) rs = do
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r <- ensureProperty l
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case r of
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FailedChange -> return FailedChange
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_ -> go ls (combineResult r rs)
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desc = case ps of
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(p:_) -> propertyDesc p
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_ -> "(empty)"
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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 -> FilePath -> Property
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flagFile property flagfile = Property (propertyDesc property) $
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go =<< doesFileExist flagfile
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where
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go True = return NoChange
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go False = do
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r <- ensureProperty property
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when (r == MadeChange) $
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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 :: Property -> Property -> Property
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property `onChange` hook = Property (propertyDesc property) $ do
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r <- ensureProperty property
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case r of
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MadeChange -> do
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r' <- ensureProperty hook
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return $ combineResult r r'
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_ -> return r
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{- | Indicates that the first property can only be satisfied once
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- the second is. -}
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requires :: Property -> Property -> Property
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x `requires` y = combineProperties [y, x] `describe` propertyDesc x
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describe :: Property -> Desc -> Property
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describe p d = p { propertyDesc = d }
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(==>) :: Desc -> Property -> Property
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(==>) = flip describe
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infixl 1 ==>
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{- | Makes a Property only be performed when a test succeeds. -}
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check :: IO Bool -> Property -> Property
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check c property = Property (propertyDesc property) $ ifM c
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( ensureProperty property
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, return NoChange
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)
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