Loc.hs

module Data.Loc.Loc
  ( Loc,

    -- * Constructing
    loc,
    origin,

    -- * Querying
    line,
    column,

    -- * Show and Read
    locShowsPrec,
    locReadPrec,
  )
where

import Data.Loc.Internal.Prelude
import Data.Loc.Pos (Column, Line)
import Integer.Positive (Positive)

-- | Stands for /location/, consists of a 'Line' and a 'Column'
--
-- You can think of a 'Loc' like a caret position in a text editor.
-- Following the normal convention for text editors and such, line
-- and column numbers start with 1.
data Loc = Loc
  { line :: Line,
    column :: Column
  }
  deriving (Eq, Ord)

-- | 'showsPrec' = 'locShowsPrec'
instance Show Loc where
  showsPrec = locShowsPrec

-- | 'readPrec' = 'locReadPrec'
instance Read Loc where
  readPrec = locReadPrec

-- |
--
-- >>> locShowsPrec minPrec (loc 3 14) ""
-- "3:14"
locShowsPrec :: Int -> Loc -> ShowS
locShowsPrec _ (Loc l c) =
  shows l
    . showString ":"
    . shows c

-- |
--
-- >>> readPrec_to_S locReadPrec minPrec "3:14"
-- [(3:14,"")]
locReadPrec :: ReadPrec Loc
locReadPrec =
  Loc
    <$> (fromIntegral <$> readPrec @Positive)
    <* readPrecChar ':'
    <*> (fromIntegral <$> readPrec @Positive)

-- | Create a 'Loc' from a line number and column number.
loc :: Line -> Column -> Loc
loc = Loc

-- | The smallest location: @'loc' 1 1@
--
-- >>> origin
-- 1:1
origin :: Loc
origin = loc 1 1