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81 lines
2.3 KiB
Haskell
81 lines
2.3 KiB
Haskell
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{-# LANGUAGE
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OverloadedStrings,
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NoImplicitPrelude
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#-}
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module Merge
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(
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merge,
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)
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where
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import BasePrelude
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-- Lenses
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import Lens.Micro.Platform hiding ((&))
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-- Text
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import qualified Data.Text.All as T
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import Data.Text.All (Text)
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import Data.List.Split
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-- Vector
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import qualified Data.Vector as V
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-- Diffing
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import qualified Data.Patch as PV
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-- | An implementation of a 3-way diff and merge.
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merge
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:: Text -- ^ Original text
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-> Text -- ^ Variant A (preferred)
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-> Text -- ^ Variant B
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-> Text -- ^ Merged text
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merge orig a b = T.concat . V.toList $ PV.apply (pa <> pb') orig'
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where
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(orig', a', b') = (orig, a, b) & each %~
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V.fromList . consolidate . map T.toStrict . break' . T.toString
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pa = PV.diff orig' a'
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pb = PV.diff orig' b'
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(_, pb') = PV.transformWith PV.ours pa pb
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-- | Break a string into words, spaces, and special characters.
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break' :: String -> [String]
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break' = split . dropInitBlank . dropFinalBlank . dropInnerBlanks . whenElt $
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\c -> not (isAlphaNum c) && c /= '\''
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-- | Consolidate some of the things into tokens (like links, consecutive
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-- spaces, and Markdown elements).
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consolidate :: [Text] -> [Text]
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-- spaces
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consolidate s@(" ":_) =
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let (l, r) = span (== " ") s
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in T.concat l : consolidate r
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-- breaks between paragraphs
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consolidate s@("\n":_) =
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let (l, r) = span (== "\n") s
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in T.concat l : consolidate r
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-- code block markers
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consolidate s@("~":_) =
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let (l, r) = span (== "~") s
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in if length l >= 3 then T.concat l : consolidate r else l ++ consolidate r
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consolidate s@("`":_) =
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let (l, r) = span (== "`") s
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in if length l >= 3 then T.concat l : consolidate r else l ++ consolidate r
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-- hrules
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consolidate s@("-":_) =
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let (l, r) = span (== "-") s
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in if length l >= 3 then T.concat l : consolidate r else l ++ consolidate r
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-- ellipses
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consolidate (".":".":".":xs) = "..." : consolidate xs
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-- links
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consolidate s@("http":":":"/":"/":_) =
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let (l, r) = span (\x -> x /= ")" && not (isSpace (T.head x))) s
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in T.concat l : consolidate r
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consolidate s@("https":":":"/":"/":_) =
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let (l, r) = span (\x -> x /= ")" && not (isSpace (T.head x))) s
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in T.concat l : consolidate r
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consolidate ("(":"@":"hk":")":xs) = "(" : "@hk" : ")" : consolidate xs
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-- the rest
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consolidate (x:xs) = x : consolidate xs
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consolidate [] = []
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