1 files changed, 97 insertions, 0 deletions
diff --git a/web/src/components/grid/drawSelection.ts b/web/src/components/grid/drawSelection.ts
new file mode 100644
index 0000000..e1024a8
--- /dev/null
+++ b/web/src/components/grid/drawSelection.ts
@@ -0,0 +1,97 @@
+import { RangeSelection, Selection } from "../../selection";
+import { CellRef } from "../../types";
+import excursion from "./excursion";
+import { getRenderedCell, RenderedCell, RenderedGrid } from "./renderGrid";
+
+export interface SelectionStyles {
+  activeCellStroke: string;
+  selectionRangeFill: string;
+  selectionRangeStroke: string;
+}
+
+function strokeActiveCell(
+  ctx: CanvasRenderingContext2D,
+  styles: SelectionStyles,
+  grid: RenderedGrid,
+  cell: RenderedCell,
+) {
+  excursion(ctx, () => {
+    const isLastCell = cell.rect.bottomRight.x === grid.rect.bottomRight.x;
+    const isLastRow = cell.rect.bottomRight.y === grid.rect.bottomRight.y;
+
+    ctx.strokeStyle = styles.activeCellStroke;
+    ctx.lineWidth = 2;
+
+    ctx.strokeRect(
+      cell.rect.topLeft.x + 1,
+      cell.rect.topLeft.y + 1,
+      isLastCell ? cell.rect.width - 2 : cell.rect.width - 1,
+      isLastRow ? cell.rect.height - 2 : cell.rect.height - 1,
+    );
+  });
+}
+
+function drawCellRange(
+  ctx: CanvasRenderingContext2D,
+  styles: SelectionStyles,
+  grid: RenderedGrid,
+  start: CellRef,
+  end: CellRef,
+  { stroke }: { stroke: boolean },
+) {
+  excursion(ctx, () => {
+    const startCell = getRenderedCell(grid, start);
+    const endCell = getRenderedCell(grid, end);
+
+    if (!startCell || !endCell) return;
+
+    const rect = startCell.rect.extend(endCell.rect);
+
+    const isRightEdge = rect.bottomRight.x === grid.rect.bottomRight.x;
+    const isBottomEdge = rect.bottomRight.y === grid.rect.bottomRight.y;
+
+    ctx.fillStyle = styles.selectionRangeFill;
+
+    ctx.fillRect(
+      rect.topLeft.x + 1,
+      rect.topLeft.y + 1,
+      isRightEdge ? rect.width - 2 : rect.width - 1,
+      isBottomEdge ? rect.height - 2 : rect.height - 1,
+    );
+
+    if (!stroke) return;
+
+    ctx.strokeStyle = styles.selectionRangeStroke;
+
+    ctx.strokeRect(
+      rect.topLeft.x + 0.5,
+      rect.topLeft.y + 0.5,
+      isRightEdge ? rect.width - 1 : rect.width,
+      isBottomEdge ? rect.height - 1 : rect.height,
+    );
+  });
+}
+
+export default function drawSelection(
+  ctx: CanvasRenderingContext2D,
+  styles: SelectionStyles,
+  grid: RenderedGrid,
+  selection: Selection | undefined,
+  { pending }: { pending: boolean },
+) {
+  ctx.clearRect(0, 0, grid.rect.width, grid.rect.height);
+
+  if (!selection) return;
+
+  const activeCell = getRenderedCell(grid, selection.activeCellRef);
+
+  if (!activeCell) return;
+
+  if (selection instanceof RangeSelection) {
+    drawCellRange(ctx, styles, grid, selection.range[0], selection.range[1], {
+      stroke: !pending,
+    });
+  }
+
+  strokeActiveCell(ctx, styles, grid, activeCell);
+}