module TextViewport.Render.RenderCache where

import Data.Sequence (Seq)
import Data.Sequence qualified as Seq
import TextViewport.Buffer.Buffer (Buffer(Buffer))
import TextViewport.Render.CachedRender (CachedRender)


newtype RenderCache a seg = RenderCache { unRenderCache :: Seq (Maybe (CachedRender a seg)) }
  deriving (Eq, Show)

-- | Create an empty cache matching the buffer size
emptyRenderCacheFor :: Buffer a seg -> RenderCache a seg
emptyRenderCacheFor (Buffer xs) =
    RenderCache (Seq.replicate (Seq.length xs) Nothing)

-- | Resize cache to match buffer length
resizeCache :: Buffer a seg -> RenderCache a seg -> RenderCache a seg
resizeCache (Buffer xs) (RenderCache cache) =
    let n = Seq.length xs
        m = Seq.length cache
    in RenderCache $
         if m < n then cache <> Seq.replicate (n - m) Nothing
         else Seq.take n cache

-- | Number of cached items
length :: RenderCache a seg -> Int
length (RenderCache xs) = Seq.length xs