-- | 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(..)
, SrcSpan(..)
, SourcePos(..)
, updateSpan
, updateSpans
, linearizeSourcePos
, prettyPrintSourcePos
, split
) where
import Control.Exception ( assert )
import Data.Data ( Data )
import Data.Int ( Int64 )
import Data.List ( genericTake
, sortOn
)
import Data.Text ( Text
, length
, lines
, splitAt
)
import Nix.Expr.Types.Annotated
import Prelude hiding ( length
, lines
, splitAt
)
-- | A span and some text to replace it with.
-- They don't have to be the same length.
data SpanUpdate = SpanUpdate
{ spanUpdateSpan :: SrcSpan
, 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 (spanBegin . 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 (SrcSpan b e) r) t =
let (before, _ ) = split b t
(_ , end) = split e t
in before <> r <> end
-- | Do two spans overlap
overlaps :: SrcSpan -> SrcSpan -> Bool
overlaps (SrcSpan b1 e1) (SrcSpan 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
(fromIntegral (unPos row - 1))
(fromIntegral (unPos col - 1))
)
)
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) =
show (unPos row) <> ":" <> show (unPos column)