50 lines
1.7 KiB
Haskell
50 lines
1.7 KiB
Haskell
module Indentation (parseIndentation, indentMarker, outdentMarker, eolMarker) where
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import Data.List
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-- XXX this doesn't handle multi-line strings
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-- XXX or VALOF processes
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-- XXX or tabs
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indentMarker = "__indent"
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outdentMarker = "__outdent"
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eolMarker = "__eol"
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countIndent :: String -> Int
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countIndent (' ':' ':cs) = 1 + (countIndent cs)
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countIndent (' ':cs) = error "Bad indentation"
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countIndent _ = 0
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stripIndent :: String -> String
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stripIndent (' ':cs) = stripIndent cs
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stripIndent cs = cs
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stripComment :: String -> String
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stripComment [] = []
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stripComment ('-':'-':s) = []
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stripComment ('"':s) = '"' : stripCommentInString s
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stripComment (c:s) = c : stripComment s
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stripCommentInString :: String -> String
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stripCommentInString [] = error "In string at end of line"
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stripCommentInString ('"':s) = '"' : stripComment s
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stripCommentInString (c:s) = c : stripCommentInString s
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parseIndentation :: [String] -> String
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parseIndentation ls = concat $ intersperse "\n" $ lines
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where
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(initSuffix, lines) = flatten' ls 0
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rep n i = concat $ take n (repeat i)
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flatten' [] level = ("", [rep level (' ' : outdentMarker)])
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flatten' (s:ss) level
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| isBlankLine = let (suffix, rest) = flatten' ss level in (suffix, "" : rest)
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| newLevel > level = (rep (newLevel - level) (' ' : indentMarker), processed : rest)
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| newLevel < level = (rep (level - newLevel) (' ' : outdentMarker), processed : rest)
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| otherwise = ("", processed : rest)
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where newLevel = countIndent s
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stripped' = stripComment s
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isBlankLine = stripIndent stripped' == ""
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processed = (if isBlankLine then "" else (stripped' ++ (' ' : eolMarker))) ++ suffix
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(suffix, rest) = flatten' ss newLevel
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