{-# LANGUAGE DeriveDataTypeable, TemplateHaskell #-}
-- Copyright (C) 2008 JP Bernardy

-- | A normalized API to many buffer operations.

-- The idea is that most operations should be parametric in both
--  * the textual units they work on
--  * the direction towards which they operate (if applicable)

module Yi.Buffer.Normal (TextUnit(Character, Line, VLine, Document, GenUnit),
                         unitSentence, unitEmacsParagraph, unitParagraph,
                         isAnySep, unitSep, unitSepThisLine, isWordChar,
                         -- TextUnit is exported abstract intentionally:
                         -- we'd like to move more units to the GenUnit format.
                         moveB, maybeMoveB,
                         transformB, transposeB,
                         regionOfB, regionOfNonEmptyB, regionOfPartB, 
                         regionOfPartNonEmptyB, regionOfPartNonEmptyAtB,
                         readPrevUnitB, readUnitB,
                         untilB, doUntilB_, untilB_, whileB, doIfCharB,
                         deleteB, genMaybeMoveB,
                         genMoveB, BoundarySide(..), genAtBoundaryB,
                         genEnclosingUnit, genUnitBoundary,
                         , RegionStyle(..)
                         , mkRegionOfStyleB
                         , convertRegionToStyleB
                         , unitWiseRegion
                         , extendRegionToBoundaries
                         , regionStyleA
                         ) where

import Prelude(length, subtract)
import Yi.Prelude

import Data.Binary
import Data.DeriveTH
import Data.List (sort)

import Yi.Buffer.Basic
import Yi.Buffer.Misc
import Yi.Buffer.Region
import Yi.Buffer.TextUnit
import Yi.Dynamic

-- Region styles are relative to the buffer contents.
-- They likely should be considered a TextUnit.
data RegionStyle = LineWise
                 | Inclusive
                 | Exclusive
                 | Block
  deriving (Eq, Typeable, Show)

$(derive makeBinary ''RegionStyle)

-- TODO: put in the buffer state proper.
instance Initializable RegionStyle where
  initial = Inclusive

instance YiVariable RegionStyle

regionStyleA :: Accessor FBuffer RegionStyle
regionStyleA = bufferDynamicValueA

convertRegionToStyleB :: Region -> RegionStyle -> BufferM Region
convertRegionToStyleB r = mkRegionOfStyleB (regionStart r) (regionEnd r)

mkRegionOfStyleB :: Point -> Point -> RegionStyle -> BufferM Region
mkRegionOfStyleB start' stop' regionStyle =
   let [start, stop] = sort [start', stop']
       region = mkRegion start stop in
   case regionStyle of
     LineWise  -> inclusiveRegionB =<< unitWiseRegion Line region
     Inclusive -> inclusiveRegionB region
     Exclusive -> return region
     Block     -> return region

unitWiseRegion :: TextUnit -> Region -> BufferM Region
unitWiseRegion unit = extendRegionToBoundaries unit InsideBound OutsideBound

-- | Extend the given region to boundaries of the text unit.
-- For instance one can extend the selection to complete lines, or
-- paragraphs.
extendRegionToBoundaries :: TextUnit -> BoundarySide -> BoundarySide -> Region -> BufferM Region
extendRegionToBoundaries unit bs1 bs2 region = savingPointB $ do
  moveTo $ regionStart region
  genMaybeMoveB unit (Backward, bs1) Backward
  start <- pointB
  moveTo $ regionEnd region
  genMaybeMoveB unit (Forward, bs2) Forward
  stop <- pointB
  return $ mkRegion' (regionDirection region) start stop