module TextViewport.Render.RenderBuffer where

import Data.Hashable (Hashable)
import Data.Sequence qualified as Seq
import Data.Sequences (Index, Textual)
import TextViewport.Buffer.Buffer (Buffer(..))
import TextViewport.Render.CachedRender
import TextViewport.Render.RenderCache
import TextViewport.Render.RenderItem (renderItem)
import TextViewport.Render.RenderedBuffer
import TextViewport.Render.Segmentation (Segmenter)


renderBuffer :: (Segmenter seg a, Hashable a, Textual a, Index a ~ Int) => Int -> Buffer a seg -> RenderCache a seg -> (RenderCache a seg, RenderedBuffer a)
renderBuffer width (Buffer items) (RenderCache cache) =
  let n = Seq.length items
      go i (cAcc, rAcc)
        | i >= n    = (RenderCache cAcc, RenderedBuffer rAcc)
        | otherwise =
            let item     = Seq.index items i
                mOld     = Seq.index cache i
                newEntry = renderItem width i item mOld
                cAcc'    = Seq.update i (Just newEntry) cAcc
                rAcc'    = rAcc Seq.|> crRendered newEntry
            in go (i + 1) (cAcc', rAcc')
  in go 0 (cache, Seq.empty)

updateRenderedItem :: (Segmenter seg a, Hashable a, Textual a, Index a ~ Int) => Int -> Int -> Buffer a seg -> RenderCache a seg -> RenderedBuffer a -> (RenderCache a seg, RenderedBuffer a)
updateRenderedItem width itemIx (Buffer items) (RenderCache cache) (RenderedBuffer rb) =
    let item    = Seq.index items itemIx
        mOld     = Seq.index cache itemIx
        newEntry = renderItem width itemIx item mOld
        newCache = Seq.update itemIx (Just newEntry) cache
        newRB    = Seq.update itemIx (crRendered newEntry) rb
    in (RenderCache newCache, RenderedBuffer newRB)