71 lines
2.1 KiB
Haskell
71 lines
2.1 KiB
Haskell
{- git autocorrection using Damerau-Levenshtein edit distance
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-
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- Copyright 2012 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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module Git.AutoCorrect where
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import Common
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import Git.Types
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import qualified Git.Config
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import Text.EditDistance
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import Control.Concurrent
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{- These are the same cost values as used in git. -}
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gitEditCosts :: EditCosts
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gitEditCosts = EditCosts
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{ deletionCosts = ConstantCost 4
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, insertionCosts = ConstantCost 1
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, substitutionCosts = ConstantCost 2
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, transpositionCosts = ConstantCost 0
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}
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{- Git's source calls this "an empirically derived magic number" -}
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similarityFloor :: Int
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similarityFloor = 7
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{- Finds inexact matches for the input among the choices.
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- Returns an ordered list of good enough matches, or an empty list if
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- nothing matches well. -}
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fuzzymatches :: String -> (c -> String) -> [c] -> [c]
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fuzzymatches input showchoice choices = fst $ unzip $
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sortBy comparecost $ filter similarEnough $ zip choices costs
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where
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distance = restrictedDamerauLevenshteinDistance gitEditCosts input
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costs = map (distance . showchoice) choices
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comparecost a b = compare (snd a) (snd b)
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similarEnough (_, cst) = cst < similarityFloor
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{- Takes action based on git's autocorrect configuration, in preparation for
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- an autocorrected command being run. -}
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prepare :: String -> (c -> String) -> [c] -> Maybe Repo -> IO ()
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prepare input showmatch matches r =
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case readish . Git.Config.get "help.autocorrect" "0" =<< r of
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Just n
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| n == 0 -> list
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| n < 0 -> warn
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| otherwise -> sleep n
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Nothing -> list
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where
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list = error $ unlines $
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[ "Unknown command '" ++ input ++ "'"
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, ""
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, "Did you mean one of these?"
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] ++ map (\m -> "\t" ++ showmatch m) matches
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warn =
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hPutStr stderr $ unlines
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[ "WARNING: You called a command named '" ++
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input ++ "', which does not exist."
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, "Continuing under the assumption that you meant '" ++
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showmatch (Prelude.head matches) ++ "'"
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]
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sleep n = do
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warn
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hPutStrLn stderr $ unwords
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[ "in"
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, show (fromIntegral n / 10 :: Float)
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, "seconds automatically..."]
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threadDelay (n * 100000) -- deciseconds to microseconds
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