web/src/components/grid/cellAtCoord.ts


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import Coord from "../../math/Coord";
import { CellRef } from "../../types";
import { RenderedGrid, RenderedRow } from "./renderGrid";

function rowAtCoord(grid: RenderedGrid, coord: Coord): RenderedRow | undefined {
  if (coord.y <= grid.rect.topLeft.y) {
    return grid.renderedRows[0];
  }

  if (coord.y >= grid.rect.bottomRight.y) {
    return grid.renderedRows.at(-1);
  }

  return grid.renderedRows.find((row) =>
    row.rect.verticallyContainsCoord(coord),
  );
}

export default function cellAtCoord(
  grid: RenderedGrid,
  x: number,
  y: number,
): CellRef | undefined {
  const coord = new Coord(x, y);
  const row = rowAtCoord(grid, coord);

  if (!row) return;

  if (x <= row.rect.topLeft.x) {
    return row.renderedCells[0]?.cellRef;
  }

  if (x >= row.rect.bottomRight.x) {
    return row.renderedCells.at(-1)?.cellRef;
  }

  return row.renderedCells.find((cell) =>
    cell.rect.horizontallyContainsCoord(coord),
  )?.cellRef;
}