{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE Rank2Types #-}

module Yi.Tab
 (
  Tab,
  TabRef,
  tabWindowsA,
  tabLayoutManagerA,
  tabDividerPositionA,
  tkey,
  tabMiniWindows,
  tabFocus,
  forceTab,
  mapWindows,
  tabLayout,
  tabFoldl,
  makeTab,
  makeTab1,
 )  where

import Prelude hiding (foldr, foldl)
import Control.Lens
import qualified Data.Binary as Binary
import Data.Default
import Data.Typeable
import Data.Foldable
import qualified Data.List.PointedList as PL
import Control.Applicative

import Yi.Buffer.Basic(WindowRef)
import Yi.Layout
import Yi.Window

type TabRef = Int

-- | A tab, containing a collection of windows.
data Tab = Tab {
  tkey             :: !TabRef,                  -- ^ For UI sync; fixes #304
  tabWindows       :: !(PL.PointedList Window), -- ^ Visible windows
  tabLayout        :: !(Layout WindowRef),      -- ^ Current layout. Invariant: must be the layout generated by 'tabLayoutManager', up to changing the 'divPos's.
  tabLayoutManager :: !AnyLayoutManager -- ^ layout manager (for regenerating the layout when we add/remove windows)
  }
 deriving Typeable

tabFocus :: Tab -> Window
tabFocus = PL._focus . tabWindows

-- | Returns a list of all mini windows associated with the given tab
tabMiniWindows :: Tab -> [Window]
tabMiniWindows = Prelude.filter isMini . toList . tabWindows

-- | Accessor for the windows. If the windows (but not the focus) have changed when setting, then a relayout will be triggered to preserve the internal invariant.
tabWindowsA :: Functor f =>
    (PL.PointedList Window -> f (PL.PointedList Window)) -> Tab -> f Tab
tabWindowsA f s = (`setter` s) <$> f (getter s)
  where
    setter ws t = relayoutIf (toList ws /= toList (tabWindows t)) (t { tabWindows = ws})
    getter = tabWindows

-- | Accessor for the layout manager. When setting, will trigger a relayout if the layout manager has changed.
tabLayoutManagerA :: Functor f =>
    (AnyLayoutManager -> f AnyLayoutManager) -> Tab -> f Tab
tabLayoutManagerA f s = (`setter` s) <$> f (getter s)
  where
    setter lm t = relayoutIf (lm /= tabLayoutManager t) (t { tabLayoutManager = lm })
    getter = tabLayoutManager

-- | Gets / sets the position of the divider with the given reference. The caller must ensure that the DividerRef is valid, otherwise an error will (might!) occur.
tabDividerPositionA :: DividerRef -> Lens' Tab DividerPosition
tabDividerPositionA ref = lens tabLayout (\ t l -> t{tabLayout = l}) . dividerPositionA ref

relayoutIf :: Bool -> Tab -> Tab
relayoutIf False t = t
relayoutIf True t = relayout t

relayout :: Tab -> Tab
relayout t = t { tabLayout = buildLayout (tabWindows t) (tabLayoutManager t) (tabLayout t) }

instance Binary.Binary Tab where
  put (Tab tk ws _ _) = Binary.put tk >> Binary.put ws
  get = makeTab <$> Binary.get <*> Binary.get


-- | Equality on tab identity (the 'tkey')
instance Eq Tab where
  (==) t1 t2 = tkey t1 == tkey t2

instance Show Tab where
  show t = "Tab " ++ show (tkey t)

-- | A specialised version of "fmap".
mapWindows :: (Window -> Window) -> Tab -> Tab
mapWindows f = over tabWindowsA (fmap f)

-- | Forces all windows in the tab
forceTab :: Tab -> Tab
forceTab t = foldr seq t (t ^. tabWindowsA)

-- | Folds over the windows in the tab
tabFoldl :: (a -> Window -> a) -> a -> Tab -> a
tabFoldl f z t = foldl f z (t ^. tabWindowsA)

-- -- | Run the layout on the given tab, for the given aspect ratio
buildLayout :: PL.PointedList Window -> AnyLayoutManager -> Layout WindowRef -> Layout WindowRef
buildLayout ws m l = pureLayout m l . fmap wkey . Prelude.filter (not . isMini) . toList $ ws

-- | Make a tab from multiple windows
makeTab :: TabRef -> PL.PointedList Window -> Tab
makeTab key ws = Tab key ws (buildLayout ws def def) def

-- | Make a tab from one window
makeTab1 :: TabRef -> Window -> Tab
makeTab1 key win = makeTab key (PL.singleton win)