Editor.hs

{-# language
    TemplateHaskell
  , Rank2Types
  , ExistentialQuantification
  , ScopedTypeVariables
  , OverloadedStrings
  #-}

module Rasa.Internal.Editor
  (
  -- * Accessing/Storing state
  Editor
  , HasEditor(..)
  , buffers
  , exiting
  , nextBufId
  , BufRef(..)
  ) where

import Rasa.Internal.Buffer
import Rasa.Internal.Extensions

import Data.Default
import Data.IntMap
import Control.Lens

-- | An opaque reference to a buffer.
-- When operating over a BufRef Rasa checks if the 'Rasa.Internal.Buffer.Buffer' still
-- exists and simply ignores any operations over non-existent buffers; typically returning 'Nothing'
newtype BufRef =
  BufRef Int
  deriving (Show, Eq, Ord)

-- | This is the primary state of the editor.
data Editor = Editor
  { _buffers' :: IntMap Buffer
  , _exiting' :: Bool
  , _extState' :: ExtMap
  , _nextBufId' :: Int
  }
makeLenses ''Editor

instance Show Editor where
  show ed =
    "Buffers==============\n" ++ show (ed^.buffers) ++ "\n\n"
    ++ "Editor Extensions==============\n" ++ show (ed^.exts) ++ "\n\n"
    ++ "---\n\n"

-- | This allows polymorphic lenses over anything that has access to an Editor context
class HasEditor a where
  editor :: Lens' a Editor

-- | A lens over the map of available buffers
buffers :: HasEditor e => Lens' e (IntMap Buffer)
buffers = editor.buffers'

-- | A lens over the exiting status of the editor
exiting :: HasEditor e => Lens' e Bool
exiting = editor.exiting'

-- | A lens over the next buffer id to be allocated
nextBufId :: HasEditor e => Lens' e Int
nextBufId = editor.nextBufId'

instance HasEditor Editor where
  editor = lens id (flip const)

instance HasExts Editor where
  exts = extState'

instance Default Editor where
  def =
    Editor
    { _extState'=def
    , _buffers'=empty
    , _exiting'=False
    , _nextBufId'=0
    }