module TextViewport.Viewport.Position where

import TextViewport.Render.RenderedBuffer (RenderedBuffer)
import TextViewport.Render.RenderedBuffer qualified as RenderedBuffer
import TextViewport.Render.RenderedLine qualified as RenderedLine
import TextViewport.Viewport.Viewport (Viewport)
import TextViewport.Viewport.Viewport qualified as Viewport

lookupPosition
  :: Int
  -> Int
  -> Viewport
  -> RenderedBuffer
  -> Maybe (Int, Int)
lookupPosition x y vp rb =
  let allLines = RenderedBuffer.flatten rb
      idx      = Viewport.vpOffset vp + y
  in case drop idx allLines of
       (rl:_) ->
         let charIx = RenderedLine.rlCharStart rl + x
         in Just (RenderedLine.rlItemIx rl, charIx)
       [] -> Nothing