1 files changed, 40 insertions, 0 deletions
diff --git a/apps/web/src/components/grid/cellAtCoord.ts b/apps/web/src/components/grid/cellAtCoord.ts
new file mode 100644
index 0000000..dd594a4
--- /dev/null
+++ b/apps/web/src/components/grid/cellAtCoord.ts
@@ -0,0 +1,40 @@
+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;
+}