feat(filters): move the availability preset into a bar dimension (#188)

frontend/tests/unit/filterDimensions.test.ts

@@ -2,6 +2,7 @@ import { describe, it, expect } from 'vitest';
 import { EMPTY_FILTERS, ItemFilters } from '../../src/filters';
 import type { FilterContext } from '../../src/components/filters/dimension';
 import {
+  availabilityDimension,
   categoryDimension,
   favoritesDimension,
   priceDimension,
@@ -155,3 +156,36 @@ describe('statusDimension', () => {
     expect(state.latest?.status).toBeNull();
   });
 });
+
+describe('availabilityDimension', () => {
+  it('renders in the bar rather than the drawer', () => {
+    expect(availabilityDimension.placement).toBe('bar');
+  });
+
+  // Not sold is the default. A filter nobody chose must not read as one, or it
+  // shows in the tally and in the chip row on a page nobody has filtered.
+  it('reports no chip at the default', () => {
+    expect(availabilityDimension.chips(contextFor({ status: null }).ctx)).toEqual([]);
+    expect(
+      availabilityDimension.chips(contextFor({ status: ['available', 'reserved'] }).ctx)
+    ).toEqual([]);
+  });
+
+  // The behaviour change in #188. This is what lets chips.length serve as both
+  // the tally and the "is anything filtered" predicate the empty state needs.
+  it('reports a chip for Sold and for All', () => {
+    expect(availabilityDimension.chips(contextFor({ status: ['sold'] }).ctx).map((c) => c.label))
+      .toEqual(['Sold']);
+    expect(
+      availabilityDimension
+        .chips(contextFor({ status: ['available', 'reserved', 'sold'] }).ctx)
+        .map((c) => c.label)
+    ).toEqual(['All']);
+  });
+
+  it('returns to the default when removed', () => {
+    const { ctx, state } = contextFor({ status: ['sold'] });
+    availabilityDimension.chips(ctx)[0]?.onRemove();
+    expect(state.latest?.status).toBeNull();
+  });
+});