1 files changed, 38 insertions, 5 deletions
diff --git a/web/src/selection.ts b/web/src/selection.ts
index 88d394b..3d18417 100644
--- a/web/src/selection.ts
+++ b/web/src/selection.ts
@@ -1,4 +1,4 @@
-import { CellRef } from "./types";
+import { CellRef, cellRefEquals } from "./types";
 
 export abstract class Selection {
   readonly gridId: string;
@@ -8,12 +8,45 @@ export abstract class Selection {
     this.gridId = gridId;
     this.activeCellRef = activeCellRef;
   }
+
+  abstract extend(cellRef: CellRef): Selection;
+}
+
+export class ActiveCellSelection extends Selection {
+  extend(cellRef: CellRef): Selection {
+    if (cellRefEquals(cellRef, this.activeCellRef)) {
+      return this;
+    }
+
+    return new RangeSelection(this.gridId, this.activeCellRef, [
+      this.activeCellRef,
+      cellRef,
+    ]);
+  }
 }
 
-export class ActiveCellSelection extends Selection {}
+export type CellRange = [CellRef, CellRef];
 
-export class RangeSelection extends Selection {}
+export class RangeSelection extends Selection {
+  #range: CellRange;
 
-export class AllSelection extends Selection {}
+  get range() {
+    return this.#range;
+  }
 
-export class PendingSelection extends Selection {}
+  constructor(gridId: string, activeCellRef: CellRef, range: CellRange) {
+    super(gridId, activeCellRef);
+    this.#range = range;
+  }
+
+  extend(cellRef: CellRef): Selection {
+    if (cellRefEquals(cellRef, this.activeCellRef)) {
+      return new ActiveCellSelection(this.gridId, cellRef);
+    }
+
+    return new RangeSelection(this.gridId, this.activeCellRef, [
+      this.#range[0],
+      cellRef,
+    ]);
+  }
+}