{-# LANGUAGE DeriveDataTypeable #-}
-- | This module deals with updating spans of characters in values of type Text.
--
-- It defines some helper types and functions to apply these "updates".
module Update.Span
( SpanUpdate(..)
, SourcePos(..)
, SourceSpan(..)
, updateSpan
, updateSpans
, linearizeSourcePos
, prettyPrintSourcePos
) where
import Control.Exception (assert)
import Data.Data (Data)
import Data.Int (Int64)
import Data.List (genericTake, sortOn)
import Data.Monoid ((<>))
import Data.Text (Text, length, lines, splitAt)
import Prelude hiding (length, lines, splitAt)
-- | A position in a text file
data SourcePos = SourcePos{ sourcePosRow :: Int64,
sourcePosColumn :: Int64
}
deriving (Show, Eq, Ord, Data)
-- | A span of characters with a beginning and an end.
--
-- 'spanEnd' must be greater than 'spanBegin'
data SourceSpan = SourceSpan{ sourceSpanBegin :: SourcePos
, sourceSpanEnd :: SourcePos
}
deriving (Show, Data)
-- | A span and some text to replace it with.
-- They don't have to be the same length.
data SpanUpdate = SpanUpdate{ spanUpdateSpan :: SourceSpan
, spanUpdateContents :: Text
}
deriving (Show, Data)
-- | Update many spans in a file. They must be non-overlapping.
updateSpans :: [SpanUpdate] -> Text -> Text
updateSpans us t =
let sortedSpans = sortOn (sourceSpanBegin . spanUpdateSpan) us
anyOverlap = any (uncurry overlaps)
(zip <*> tail $ spanUpdateSpan <$> sortedSpans)
in
assert (not anyOverlap)
(foldr updateSpan t sortedSpans)
-- | Update a single span of characters inside a text value. If you're updating
-- multiples spans it's best to use 'updateSpans'.
updateSpan :: SpanUpdate -> Text -> Text
updateSpan (SpanUpdate (SourceSpan b e) r) t =
let (before, _) = split b t
(_, end) = split e t
in before <> r <> end
-- | Do two spans overlap
overlaps :: SourceSpan -> SourceSpan -> Bool
overlaps (SourceSpan b1 e1) (SourceSpan b2 e2) =
b2 >= b1 && b2 < e1 || e2 >= b1 && e2 < e1
-- | Split some text at a particular 'SourcePos'
split :: SourcePos -> Text -> (Text, Text)
split (SourcePos row col) t =
splitAt (fromIntegral (linearizeSourcePos t row col)) t
-- | Go from a line and column representation to a single character offset from
-- the beginning of the text.
--
-- This probably fails on crazy texts with multi character line breaks.
linearizeSourcePos :: Text -- ^ The string to linearize in
-> Int64 -- ^ The line offset
-> Int64 -- ^ The column offset
-> Int64 -- ^ The character offset
linearizeSourcePos t l c = fromIntegral lineCharOffset + c
where lineCharOffset = sum . fmap ((+1) . length) . genericTake l . lines $ t
prettyPrintSourcePos :: SourcePos -> String
prettyPrintSourcePos (SourcePos row column) =
"line " <> show row <> " column " <> show column