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For further +-- documentation, see http://haskell.org/cabal/users-guide/ + +-- The name of the package. +name: reprinter + +-- The package version. See the Haskell package versioning policy (PVP) +-- for standards guiding when and how versions should be incremented. +-- https://wiki.haskell.org/Package_versioning_policy +-- PVP summary: +-+------- breaking API changes +-- | | +----- non-breaking API additions +-- | | | +--- code changes with no API change +version: 0.1.0.0 + +-- A short (one-line) description of the package. +synopsis: Scrap Your Reprinter + +description: A datatype generic algorithm for layout-preserving refactoring + +-- A longer description of the package. +-- description: +license: Apache-2.0 +license-file: LICENSE + +-- The package author(s). +author: Dominic Orchard, Harry Clarke + +-- An email address to which users can send suggestions, bug reports, and +-- patches. +maintainer: d.a.orchard@kent.ac.uk + +-- A copyright notice. +-- copyright: + +category: Text + +build-type: Simple + +-- Constraint on the version of Cabal needed to build this package. +cabal-version: >=1.10 + +source-repository head + type: git + location: https://github.com/camfort/reprinter + +library + -- Modules exported by the library. + exposed-modules: Text.Reprinter + + -- Modules included in this library but not exported. + -- other-modules: + + -- LANGUAGE extensions used by modules in this package. + other-extensions: RankNTypes, DeriveDataTypeable, FlexibleInstances, Rank2Types, GADTs, KindSignatures, ConstraintKinds + + -- Other library packages from which modules are imported. + build-depends: base >=4.9 && <4.10, bytestring >=0.10 && <0.11, transformers >=0.5 && <0.6, syb >=0.6 && <0.7, uniplate >=1.6 && <1.7, mtl >=2.2 && <2.3, syz == 0.2.0.0 + + -- Directories containing source files. + hs-source-dirs: src + + -- Base language which the package is written in. + default-language: Haskell2010 + diff --git a/src/Text/Reprinter.hs b/src/Text/Reprinter.hs new file mode 100644 --- /dev/null +++ b/src/Text/Reprinter.hs @@ -0,0 +1,188 @@ +{-# LANGUAGE RankNTypes #-} +{-# LANGUAGE DeriveDataTypeable #-} + +module Text.Reprinter + ( reprint + , splitBySpan + , Position(..) + , Source + , Reprinting + , initPosition + , catchAll + , genReprinting + , Refactorable(..) + , RefactorType(..) + ) where + +import Data.Generics.Zipper +import Debug.Trace +import qualified Data.ByteString.Char8 as B +import Data.Data +import Control.Monad.Trans.Class (lift) +import Control.Monad.Trans.State.Lazy + +type Source = B.ByteString + +data Position = Position { posColumn :: Int, posLine :: Int } + deriving (Data, Show) + +initPosition = Position { posColumn = 1, posLine = 1 } + +type Reprinting m = + forall b . Typeable b + => b -> m (Maybe (RefactorType, Source, (Position, Position))) + +-- | The reprint algorithm takes a refactoring (parameteric in +-- | some monad m) and turns an arbitrary pretty-printable type 'p' +-- | into a monadic Source transformer. +reprint :: (Monad m, Data p) + => Reprinting m -> p -> Source -> m Source +reprint reprinting tree input + -- If the inupt is null then null is returned + | B.null input = return B.empty + + -- Otherwise go with the normal algorithm + | otherwise = do + -- Initial state comprises start cursor and input source + let state0 = (initPosition, input) + -- Enter the top-node of a zipper for 'tree' + (out, (_, remaining)) <- runStateT (enter reprinting (toZipper tree)) state0 + -- Add to the output source the reamining input source + return $ out `B.append` remaining + +-- The enter, enterDown, enterRight each take a refactoring and a +-- zipper producing a stateful Source transformer with Position +-- state. + +enter, enterDown, enterRight + :: Monad m + => Reprinting m -> Zipper a -> StateT (Position, Source) m Source + +-- `enter` applies the generic refactoring to the current context +-- of the zipper +enter reprinting z = do + + -- Step 1. + -- Apply a refactoring + refactoringInfo <- lift $ query reprinting z + + -- Step 2. + output <- + case refactoringInfo of + -- No refactoring, so go into the children + Nothing -> enterDown reprinting z + + -- A refactoring was applied + Just (typ, output, (lb, ub)) -> do + (cursor, inp) <- get + case typ of + Replace -> do + -- Get the soure text up to the start of the refactored expr + let (p0, inp') = splitBySpan (cursor, lb) inp + -- Cut out the portion of source text consumed by the refactoring + let (_, inp'') = splitBySpan (lb, ub) inp' + put (ub, inp'') + return $ B.concat [p0, output] + After -> do + -- Get the soure text up to the end of the refactored expr + let (p0, inp') = splitBySpan (cursor, ub) inp + put (ub, inp') + return $ B.concat [p0, output] + Before -> do + -- Get the soure text up to the start of the refactored expr + let (p0, inp') = splitBySpan (cursor, lb) inp + -- Cut out the portion of source text consumed by the refactoring + let (p1, inp'') = splitBySpan (lb, ub) inp' + put (ub, inp'') + return $ B.concat [p0, output, p1] + + -- Part 3. + -- Enter the right sibling of the current context + output' <- enterRight reprinting z + + -- Concat the output for the current context, children, and right sibling + return $ B.concat [output, output'] + +-- `enterDown` navigates to the children of the current context +enterDown reprinting z = + case down' z of + -- Go to children + Just dz -> enter reprinting dz + -- No children + Nothing -> return B.empty + +-- `enterRight` navigates to the right sibling of the current context +enterRight reprinting z = + case right z of + -- Go to right sibling + Just rz -> enter reprinting rz + -- No right sibling + Nothing -> return B.empty + +-- | Given a lower-bound and upper-bound pair of Positions, split the +-- | incoming Source based on the distanceF between the Position pairs +splitBySpan :: (Position, Position) -> Source -> (Source, Source) +splitBySpan (l, u) = subtext (ll, lc) (ll, lc) (ul, uc) + where (Position lc ll) = l + (Position uc ul) = u + +{- + Split a text. + + Returns a tuple containing: + 1. the bit of input text between upper and lower bounds + 2. the remaining input text + + Takes: + 1. current cursor position + 2. lower bound + 3. upper bound + 4. input text +-} +subtext :: (Int, Int) -> (Int, Int) -> (Int, Int) -> B.ByteString -> (B.ByteString, B.ByteString) +subtext cursor (lowerLn, lowerCol) (upperLn, upperCol) = + subtext' B.empty cursor + where + subtext' acc (cursorLn, cursorCol) input + + | cursorLn <= lowerLn && (cursorCol >= lowerCol ==> cursorLn < lowerLn) = + case B.uncons input of + Nothing -> (B.reverse acc, input) + Just ('\n', input') -> subtext' acc (cursorLn+1, 1) input' + Just (_, input') -> subtext' acc (cursorLn, cursorCol+1) input' + + | cursorLn <= upperLn && (cursorCol >= upperCol ==> cursorLn < upperLn) = + case B.uncons input of + Nothing -> (B.reverse acc, input) + Just ('\n', input') -> subtext' (B.cons '\n' acc) (cursorLn+1, 1) input' + Just (x, input') -> subtext' (B.cons x acc) (cursorLn, cursorCol+1) input' + + | otherwise = + (B.reverse acc, input) + +-- Logical implication operator. +(==>) :: Bool -> Bool -> Bool; infix 2 ==> +a ==> b = a <= b + +-- | Specify a refactoring type +data RefactorType = Before | After | Replace + +-- | Infrastructure for building the reprinter "plugins" +class Refactorable t where + isRefactored :: t -> Maybe RefactorType + getSpan :: t -> (Position, Position) + +-- | Essentially wraps the refactorable interface +genReprinting :: (Monad m, Refactorable t, Typeable t) + => (t -> m Source) + -> t -> m (Maybe (RefactorType, Source, (Position, Position))) +genReprinting f z = do + case isRefactored z of + Nothing -> return Nothing + Just refactorType -> do + output <- f z + return $ Just (refactorType, output, getSpan z) + +-- | Catch all generic query +catchAll :: Monad m => a -> m (Maybe b) +catchAll _ = return Nothing