feat(shopping): consolidate() fuer g/kg + ml/l Summierung

Implementiert consolidate() in unit-consolidation.ts: summiert Mengen
innerhalb einer Unit-Family (Gewicht g/kg, Volumen ml/l) mit automatischer
Promotion ab Schwellwert; nicht-family-units werden direkt summiert.
quantity=null wird als 0 behandelt; alle-null ergibt null-Ergebnis.
9 neue Tests, alle 14 Tests gruen.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/lib/server/unit-consolidation.ts

@@ -9,3 +9,58 @@ export function unitFamily(unit: string | null | undefined): UnitFamily {
   if (VOLUME_UNITS.has(u)) return 'volume';
   return u;
 }
+
+export interface QuantityInUnit {
+  quantity: number | null;
+  unit: string | null;
+}
+
+function round2(n: number): number {
+  return Math.round(n * 100) / 100;
+}
+
+/**
+ * Konsolidiert mehrere {quantity, unit}-Eintraege derselben Unit-Family
+ * zu einer gemeinsamen Menge + Display-Unit.
+ *
+ * - Gewicht (g, kg): summiert in g, promoted bei >=1000 g auf kg.
+ * - Volumen (ml, l): summiert in ml, promoted bei >=1000 ml auf l.
+ * - Andere: summiert quantity ohne Umrechnung, Display-Unit vom ersten
+ *   Eintrag.
+ *
+ * quantity=null wird als 0 behandelt. Wenn ALLE quantities null sind,
+ * ist die Gesamtmenge ebenfalls null.
+ */
+export function consolidate(rows: QuantityInUnit[]): QuantityInUnit {
+  if (rows.length === 0) return { quantity: null, unit: null };
+
+  const family = unitFamily(rows[0].unit);
+  const firstUnit = rows[0].unit;
+
+  const allNull = rows.every((r) => r.quantity === null);
+
+  if (family === 'weight') {
+    if (allNull) return { quantity: null, unit: firstUnit };
+    const grams = rows.reduce((sum, r) => {
+      const q = r.quantity ?? 0;
+      return sum + (unitFamily(r.unit) === 'weight' && r.unit?.toLowerCase().trim() === 'kg' ? q * 1000 : q);
+    }, 0);
+    if (grams >= 1000) return { quantity: round2(grams / 1000), unit: 'kg' };
+    return { quantity: round2(grams), unit: 'g' };
+  }
+
+  if (family === 'volume') {
+    if (allNull) return { quantity: null, unit: firstUnit };
+    const ml = rows.reduce((sum, r) => {
+      const q = r.quantity ?? 0;
+      return sum + (r.unit?.toLowerCase().trim() === 'l' ? q * 1000 : q);
+    }, 0);
+    if (ml >= 1000) return { quantity: round2(ml / 1000), unit: 'l' };
+    return { quantity: round2(ml), unit: 'ml' };
+  }
+
+  // Non-family: summiere quantity direkt
+  if (allNull) return { quantity: null, unit: firstUnit };
+  const sum = rows.reduce((acc, r) => acc + (r.quantity ?? 0), 0);
+  return { quantity: round2(sum), unit: firstUnit };
+}

tests/unit/unit-consolidation.test.ts

@@ -1,5 +1,5 @@
 import { describe, it, expect } from 'vitest';
-import { unitFamily } from '../../src/lib/server/unit-consolidation';
+import { unitFamily, consolidate } from '../../src/lib/server/unit-consolidation';
 
 describe('unitFamily', () => {
   it('maps g and kg to weight', () => {
@@ -26,3 +26,75 @@ describe('unitFamily', () => {
     expect(unitFamily('   ')).toBe('');
   });
 });
+
+describe('consolidate', () => {
+  it('kombiniert 500 g + 1 kg zu 1,5 kg', () => {
+    const out = consolidate([
+      { quantity: 500, unit: 'g' },
+      { quantity: 1, unit: 'kg' }
+    ]);
+    expect(out).toEqual({ quantity: 1.5, unit: 'kg' });
+  });
+
+  it('bleibt bei g wenn Summe < 1 kg', () => {
+    const out = consolidate([
+      { quantity: 200, unit: 'g' },
+      { quantity: 300, unit: 'g' }
+    ]);
+    expect(out).toEqual({ quantity: 500, unit: 'g' });
+  });
+
+  it('kombiniert ml + l analog (400 ml + 0,5 l → 900 ml)', () => {
+    const out = consolidate([
+      { quantity: 400, unit: 'ml' },
+      { quantity: 0.5, unit: 'l' }
+    ]);
+    expect(out).toEqual({ quantity: 900, unit: 'ml' });
+  });
+
+  it('promoted zu l ab 1000 ml (0,5 l + 0,8 l → 1,3 l)', () => {
+    const out = consolidate([
+      { quantity: 0.5, unit: 'l' },
+      { quantity: 0.8, unit: 'l' }
+    ]);
+    expect(out).toEqual({ quantity: 1.3, unit: 'l' });
+  });
+
+  it('summiert gleiche nicht-family-units (2 Bund + 1 Bund → 3 Bund)', () => {
+    const out = consolidate([
+      { quantity: 2, unit: 'Bund' },
+      { quantity: 1, unit: 'Bund' }
+    ]);
+    expect(out).toEqual({ quantity: 3, unit: 'Bund' });
+  });
+
+  it('behandelt quantity=null als 0', () => {
+    const out = consolidate([
+      { quantity: null, unit: 'TL' },
+      { quantity: 1, unit: 'TL' }
+    ]);
+    expect(out).toEqual({ quantity: 1, unit: 'TL' });
+  });
+
+  it('gibt null zurueck wenn alle quantities null sind', () => {
+    const out = consolidate([
+      { quantity: null, unit: 'Prise' },
+      { quantity: null, unit: 'Prise' }
+    ]);
+    expect(out).toEqual({ quantity: null, unit: 'Prise' });
+  });
+
+  it('rundet Float-Artefakte auf 2 Dezimalen (0,1 + 0,2 kg → 0,3 kg)', () => {
+    const out = consolidate([
+      { quantity: 0.1, unit: 'kg' },
+      { quantity: 0.2, unit: 'kg' }
+    ]);
+    // 0.1 + 0.2 in kg = 0.3 kg, in g = 300 → promoted? 300 < 1000 → 300 g
+    expect(out).toEqual({ quantity: 300, unit: 'g' });
+  });
+
+  it('nimmt unit vom ersten Eintrag bei unbekannter family', () => {
+    const out = consolidate([{ quantity: 5, unit: 'Stück' }]);
+    expect(out).toEqual({ quantity: 5, unit: 'Stück' });
+  });
+});