module TextViewport.Render.RenderBuffer where

import Data.Sequence qualified as Seq
import TextViewport.Buffer.Buffer (Buffer(..))
import TextViewport.Render.CachedRender
import TextViewport.Render.RenderCache
import TextViewport.Render.RenderItem (renderItem)
import TextViewport.Render.RenderedBuffer

renderBuffer :: Int -> Buffer -> RenderCache -> (RenderCache, RenderedBuffer)
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 :: Int -> Int -> Buffer -> RenderCache -> RenderedBuffer -> (RenderCache, RenderedBuffer)
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)