42 lines
1.2 KiB
Haskell
42 lines
1.2 KiB
Haskell
{- git-annex deferred parse values
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-
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- Copyright 2015 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU GPL version 3 or higher.
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-}
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{-# LANGUAGE FlexibleInstances #-}
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module Types.DeferredParse where
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import Annex
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import Common
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import Options.Applicative
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-- Some values cannot be fully parsed without performing an action.
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-- The action may be expensive, so it's best to call finishParse on such a
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-- value before using getParsed repeatedly.
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data DeferredParse a = DeferredParse (Annex a) | ReadyParse a
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class DeferredParseClass a where
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finishParse :: a -> Annex a
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getParsed :: DeferredParse a -> Annex a
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getParsed (DeferredParse a) = a
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getParsed (ReadyParse a) = pure a
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instance DeferredParseClass (DeferredParse a) where
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finishParse (DeferredParse a) = ReadyParse <$> a
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finishParse (ReadyParse a) = pure (ReadyParse a)
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instance DeferredParseClass (Maybe (DeferredParse a)) where
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finishParse Nothing = pure Nothing
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finishParse (Just v) = Just <$> finishParse v
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instance DeferredParseClass [DeferredParse a] where
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finishParse v = mapM finishParse v
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-- Use when the Annex action modifies Annex state.
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type GlobalSetter = DeferredParse ()
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type GlobalOption = Parser GlobalSetter
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