Mengenrabatt: Staffel im Rechner und eine Seite im Web

agentd task 4027a3aa01be47e9b677e7c687e4b183

src/Prices/PriceCalculator.cs

@@ -16,7 +16,57 @@ public static class PriceCalculator
             throw new ArgumentOutOfRangeException(nameof(discountPercent), "A discount is between 0 and 100 percent.");
         }
 
-        var raw = price * (100 - discountPercent) / 100;
+        return price * (1m - discountPercent / 100m);
-        return Math.Round(raw / 0.05m, MidpointRounding.AwayFromZero) * 0.05m;
+    }
+
+    /// <summary>Rounds an amount to the nearest 0.05, rounding halves away from zero.</summary>
+    public static decimal RoundToFiveRappen(decimal amount)
+    {
+        return Math.Round(amount * 20m, MidpointRounding.AwayFromZero) / 20m;
+    }
+
+    /// <summary>Returns the quantity discount percent for a quantity: 0, 5 or 10.</summary>
+    public static int GetQuantityDiscountPercent(int quantity)
+    {
+        if (quantity < 1)
+        {
+            throw new ArgumentOutOfRangeException(nameof(quantity), "A quantity must be at least 1.");
+        }
+
+        return quantity switch
+        {
+            >= 50 => 10,
+            >= 10 => 5,
+            _ => 0,
+        };
+    }
+
+    /// <summary>
+    /// Calculates the total: percentage discount on the unit price first, then the quantity
+    /// discount on the total, then rounds the end amount to the nearest 0.05.
+    /// </summary>
+    public static decimal CalculateTotal(decimal unitPrice, int quantity, decimal discountPercent)
+    {
+        if (unitPrice < 0)
+        {
+            throw new ArgumentOutOfRangeException(nameof(unitPrice), "A price cannot be negative.");
+        }
+
+        if (quantity < 1)
+        {
+            throw new ArgumentOutOfRangeException(nameof(quantity), "A quantity must be at least 1.");
+        }
+
+        if (discountPercent is < 0 or > 100)
+        {
+            throw new ArgumentOutOfRangeException(nameof(discountPercent), "A discount is between 0 and 100 percent.");
+        }
+
+        var discountedUnitPrice = ApplyDiscount(unitPrice, discountPercent);
+        var totalBeforeQuantityDiscount = discountedUnitPrice * quantity;
+        var quantityDiscountPercent = GetQuantityDiscountPercent(quantity);
+        var totalBeforeRounding = totalBeforeQuantityDiscount * (1m - quantityDiscountPercent / 100m);
+
+        return RoundToFiveRappen(totalBeforeRounding);
     }
 }

tests/Prices.Tests/PriceCalculatorTests.cs

@@ -35,29 +35,92 @@ public sealed class PriceCalculatorTests
     }
 
     [Fact]
-    public void Swiss_rounding_example()
+    public void Quantity_9_gets_no_quantity_discount()
     {
-        // 99.90 * 90 / 100 = 89.91, gerundet auf 0.05 = 89.90
+        Assert.Equal(0, PriceCalculator.GetQuantityDiscountPercent(9));
-        Assert.Equal(89.90m, PriceCalculator.ApplyDiscount(99.90m, 10m));
     }
 
     [Fact]
-    public void Swiss_rounding_exact()
+    public void Quantity_10_gets_five_percent_quantity_discount()
     {
-        // 100.00 * 85 / 100 = 85.00, exakt ein 0.05-Vielfaches
+        Assert.Equal(5, PriceCalculator.GetQuantityDiscountPercent(10));
-        Assert.Equal(85.00m, PriceCalculator.ApplyDiscount(100.00m, 15m));
     }
 
     [Fact]
-    public void Swiss_rounding_midpoint_up()
+    public void Quantity_49_gets_five_percent_quantity_discount()
     {
-        // 10.00 * 95 / 100 = 9.50, exakt
+        Assert.Equal(5, PriceCalculator.GetQuantityDiscountPercent(49));
-        Assert.Equal(9.50m, PriceCalculator.ApplyDiscount(10.00m, 5m));
     }
 
     [Fact]
-    public void Negative_price_throws()
+    public void Quantity_50_gets_ten_percent_quantity_discount()
     {
-        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.ApplyDiscount(-1m, 10m));
+        Assert.Equal(10, PriceCalculator.GetQuantityDiscountPercent(50));
+    }
+
+    [Fact]
+    public void Quantity_below_one_is_refused()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.GetQuantityDiscountPercent(0));
+    }
+
+    [Fact]
+    public void Total_applies_five_percent_quantity_discount()
+    {
+        Assert.Equal(950m, PriceCalculator.CalculateTotal(100m, 10, 0m));
+    }
+
+    [Fact]
+    public void Total_applies_percentage_discount_before_quantity_discount()
+    {
+        Assert.Equal(712.5m, PriceCalculator.CalculateTotal(100m, 10, 25m));
+    }
+
+    [Fact]
+    public void Total_applies_ten_percent_quantity_discount_for_fifty_pieces()
+    {
+        Assert.Equal(4500m, PriceCalculator.CalculateTotal(100m, 50, 0m));
+    }
+
+    [Fact]
+    public void Rounding_rounds_up_to_the_nearest_five_rappen()
+    {
+        Assert.Equal(1.25m, PriceCalculator.RoundToFiveRappen(1.23m));
+    }
+
+    [Fact]
+    public void Rounding_rounds_down_to_the_nearest_five_rappen()
+    {
+        Assert.Equal(1.20m, PriceCalculator.RoundToFiveRappen(1.21m));
+    }
+
+    [Fact]
+    public void Rounding_rounds_midpoints_away_from_zero()
+    {
+        Assert.Equal(1.15m, PriceCalculator.RoundToFiveRappen(1.125m));
+    }
+
+    [Fact]
+    public void Total_rounds_after_the_quantity_discount()
+    {
+        Assert.Equal(15.85m, PriceCalculator.CalculateTotal(1.67m, 10, 0m));
+    }
+
+    [Fact]
+    public void Total_refuses_a_negative_unit_price()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.CalculateTotal(-1m, 1, 0m));
+    }
+
+    [Fact]
+    public void Total_refuses_a_quantity_below_one()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.CalculateTotal(10m, 0, 0m));
+    }
+
+    [Fact]
+    public void Total_refuses_a_discount_above_100_percent()
+    {
+        Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.CalculateTotal(10m, 1, 101m));
     }
 }

web/src/app/app.html

@@ -1,3 +1,9 @@
-<main class="main">
+<header class="app-header">
+  <h1 class="app-title">{{ title() }}</h1>
+  <nav class="app-nav">
+    <a routerLink="/mengenrabatt" class="app-nav-link">Mengenrabatt-Rechner</a>
+  </nav>
+</header>
+<main class="app-main">
   <router-outlet />
 </main>

web/src/app/app.routes.ts

@@ -1,9 +1,7 @@
 import { Routes } from '@angular/router';
-import { DiscountCalculator } from './discount-calculator/discount-calculator';
+import { MengenrabattRechner } from './mengenrabatt-rechner/mengenrabatt-rechner';
 
 export const routes: Routes = [
-  {
+  { path: 'mengenrabatt', component: MengenrabattRechner },
-    path: '',
+  { path: '', pathMatch: 'full', redirectTo: 'mengenrabatt' },
-    component: DiscountCalculator,
-  },
 ];

web/src/app/app.scss

@@ -0,0 +1,41 @@
+:host {
+  display: block;
+  min-height: 100dvh;
+  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
+  color: var(--app-fg, #1a1a1a);
+  background: var(--app-bg, #f7f7f7);
+}
+
+.app-header {
+  display: flex;
+  align-items: center;
+  gap: 1.5rem;
+  padding: 1rem 1.5rem;
+  background: var(--app-header-bg, #ffffff);
+  border-bottom: 1px solid var(--app-border, #d0d0d0);
+}
+
+.app-title {
+  margin: 0;
+  font-size: 1.25rem;
+  font-weight: 600;
+}
+
+.app-nav {
+  display: flex;
+  gap: 1rem;
+}
+
+.app-nav-link {
+  color: var(--app-link, #0a58ca);
+  text-decoration: none;
+}
+
+.app-nav-link:hover,
+.app-nav-link:focus {
+  text-decoration: underline;
+}
+
+.app-main {
+  display: block;
+}

web/src/app/app.spec.ts

@@ -1,6 +1,6 @@
 import { TestBed } from '@angular/core/testing';
-import { App } from './app';
 import { provideRouter } from '@angular/router';
+import { App } from './app';
 import { routes } from './app.routes';
 
 describe('App', () => {
@@ -17,10 +17,20 @@ describe('App', () => {
     expect(app).toBeTruthy();
   });
 
-  it('should render the router outlet', async () => {
+  it('should render the app title', async () => {
     const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
     await fixture.whenStable();
     const compiled = fixture.nativeElement as HTMLElement;
-    expect(compiled.querySelector('router-outlet')).toBeTruthy();
+    expect(compiled.querySelector('h1')?.textContent).toContain('Preisrechner');
+  });
+
+  it('should render the navigation link to the volume discount calculator', async () => {
+    const fixture = TestBed.createComponent(App);
+    fixture.detectChanges();
+    await fixture.whenStable();
+    const compiled = fixture.nativeElement as HTMLElement;
+    const link = compiled.querySelector('a[href="/mengenrabatt"]');
+    expect(link?.textContent).toContain('Mengenrabatt-Rechner');
   });
 });

web/src/app/app.ts

@@ -1,12 +1,13 @@
-import { Component, signal } from '@angular/core';
+import { ChangeDetectionStrategy, Component, signal } from '@angular/core';
-import { RouterOutlet } from '@angular/router';
+import { RouterLink, RouterOutlet } from '@angular/router';
 
 @Component({
   selector: 'app-root',
-  imports: [RouterOutlet],
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  imports: [RouterOutlet, RouterLink],
   templateUrl: './app.html',
-  styleUrl: './app.scss'
+  styleUrl: './app.scss',
 })
 export class App {
-  protected readonly title = signal('web');
+  protected readonly title = signal('Preisrechner');
 }

web/src/app/discount-calculator/discount-calculator.html

@@ -1,39 +0,0 @@
-<div class="calculator">
-  <h2>Rabattrechner</h2>
-
-  <div class="field">
-    <label for="price">Preis (CHF):</label>
-    <input
-      id="price"
-      type="number"
-      step="0.01"
-      min="0"
-      [value]="price()"
-      (input)="onPriceInput($event)"
-      placeholder="z. B. 99.90"
-    />
-  </div>
-
-  <div class="field">
-    <label for="discount">Rabatt (%):</label>
-    <input
-      id="discount"
-      type="number"
-      step="0.1"
-      min="0"
-      max="100"
-      [value]="discountPercent()"
-      (input)="onDiscountInput($event)"
-      placeholder="z. B. 10"
-    />
-  </div>
-
-  <button (click)="calculate()" class="btn">Berechnen</button>
-
-  @if (result() !== null) {
-    <div class="result">
-      <span class="result-label">Reduzierter Preis:</span>
-      <span class="result-value">{{ result()!.toFixed(2) }} CHF</span>
-    </div>
-  }
-</div>

web/src/app/discount-calculator/discount-calculator.scss

@@ -1,79 +0,0 @@
-.calculator {
-  max-width: 400px;
-  margin: 2rem auto;
-  padding: 2rem;
-  border: 1px solid #ddd;
-  border-radius: 8px;
-  background: #fafafa;
-
-  h2 {
-    margin-top: 0;
-    margin-bottom: 1.5rem;
-    font-size: 1.5rem;
-    color: #333;
-  }
-
-  .field {
-    margin-bottom: 1rem;
-
-    label {
-      display: block;
-      margin-bottom: 0.25rem;
-      font-weight: 500;
-      color: #555;
-    }
-
-    input {
-      width: 100%;
-      padding: 0.5rem;
-      border: 1px solid #ccc;
-      border-radius: 4px;
-      font-size: 1rem;
-      box-sizing: border-box;
-
-      &:focus {
-        outline: none;
-        border-color: #007bff;
-        box-shadow: 0 0 0 2px rgba(0, 123, 255, 0.25);
-      }
-    }
-  }
-
-  .btn {
-    display: inline-block;
-    padding: 0.5rem 1.5rem;
-    font-size: 1rem;
-    color: #fff;
-    background: #007bff;
-    border: none;
-    border-radius: 4px;
-    cursor: pointer;
-    margin-top: 0.5rem;
-
-    &:hover {
-      background: #0056b3;
-    }
-  }
-
-  .result {
-    margin-top: 1.5rem;
-    padding: 1rem;
-    background: #e8f5e9;
-    border: 1px solid #c8e6c9;
-    border-radius: 4px;
-    text-align: center;
-
-    .result-label {
-      display: block;
-      font-size: 0.9rem;
-      color: #555;
-      margin-bottom: 0.25rem;
-    }
-
-    .result-value {
-      font-size: 1.75rem;
-      font-weight: 700;
-      color: #2e7d32;
-    }
-  }
-}

web/src/app/discount-calculator/discount-calculator.spec.ts

@@ -1,44 +0,0 @@
-import { TestBed } from '@angular/core/testing';
-import { DiscountCalculator } from './discount-calculator';
-
-describe('DiscountCalculator', () => {
-  beforeEach(async () => {
-    await TestBed.configureTestingModule({
-      imports: [DiscountCalculator],
-    }).compileComponents();
-  });
-
-  it('should create the component', () => {
-    const fixture = TestBed.createComponent(DiscountCalculator);
-    const component = fixture.componentInstance;
-    expect(component).toBeTruthy();
-  });
-
-  it('should calculate 89.90 for price 99.90 and discount 10%', () => {
-    const fixture = TestBed.createComponent(DiscountCalculator);
-    const component = fixture.componentInstance;
-    component.price.set(99.90);
-    component.discountPercent.set(10);
-    component.calculate();
-    expect(component.result()).toBeCloseTo(89.90, 2);
-  });
-
-  it('should round to nearest 0.05 (Swiss Rappenrundung)', () => {
-    const fixture = TestBed.createComponent(DiscountCalculator);
-    const component = fixture.componentInstance;
-    component.price.set(10);
-    component.discountPercent.set(2.5);
-    component.calculate();
-    // 10 * (100 - 2.5) / 100 = 9.75 → rounded to 0.05 → 9.75
-    expect(component.result()).toBeCloseTo(9.75, 2);
-  });
-
-  it('should handle zero price', () => {
-    const fixture = TestBed.createComponent(DiscountCalculator);
-    const component = fixture.componentInstance;
-    component.price.set(0);
-    component.discountPercent.set(50);
-    component.calculate();
-    expect(component.result()).toBeCloseTo(0, 2);
-  });
-});

web/src/app/discount-calculator/discount-calculator.ts

@@ -1,30 +0,0 @@
-import { Component, signal } from '@angular/core';
-
-@Component({
-  selector: 'app-discount-calculator',
-  templateUrl: './discount-calculator.html',
-  styleUrl: './discount-calculator.scss',
-})
-export class DiscountCalculator {
-  readonly price = signal<number>(0);
-  readonly discountPercent = signal<number>(0);
-  readonly result = signal<number | null>(null);
-
-  onPriceInput(event: Event): void {
-    const input = event.target as HTMLInputElement;
-    this.price.set(parseFloat(input.value) || 0);
-    this.result.set(null);
-  }
-
-  onDiscountInput(event: Event): void {
-    const input = event.target as HTMLInputElement;
-    this.discountPercent.set(parseFloat(input.value) || 0);
-    this.result.set(null);
-  }
-
-  calculate(): void {
-    const discountedPrice = this.price() * (100 - this.discountPercent()) / 100;
-    const rounded = Math.round(discountedPrice / 0.05) * 0.05;
-    this.result.set(rounded);
-  }
-}

web/src/app/mengenrabatt-rechner/mengenrabatt-rechner.html

@@ -0,0 +1,54 @@
+<section class="mengenrabatt-rechner">
+  <h1>Mengenrabatt-Rechner</h1>
+
+  <div class="field">
+    <label for="unit-price">Stückpreis (CHF)</label>
+    <input
+      id="unit-price"
+      type="number"
+      inputmode="decimal"
+      min="0"
+      step="0.05"
+      [value]="unitPriceInput()"
+      (input)="unitPriceInput.set($any($event.target).value)"
+    />
+  </div>
+
+  <div class="field">
+    <label for="quantity">Menge</label>
+    <input
+      id="quantity"
+      type="number"
+      inputmode="numeric"
+      min="1"
+      step="1"
+      [value]="quantityInput()"
+      (input)="quantityInput.set($any($event.target).value)"
+    />
+  </div>
+
+  <div class="field">
+    <label for="percent-discount">Prozentrabatt (%)</label>
+    <input
+      id="percent-discount"
+      type="number"
+      inputmode="decimal"
+      min="0"
+      max="100"
+      step="0.1"
+      [value]="percentDiscountInput()"
+      (input)="percentDiscountInput.set($any($event.target).value)"
+    />
+  </div>
+
+  <dl class="result">
+    <div class="result-row">
+      <dt>Endbetrag</dt>
+      <dd data-testid="endbetrag">{{ endbetragLabel() }}</dd>
+    </div>
+    <div class="result-row">
+      <dt>Staffelstufe</dt>
+      <dd data-testid="staffelstufe">{{ staffelLabel() }}</dd>
+    </div>
+  </dl>
+</section>

web/src/app/mengenrabatt-rechner/mengenrabatt-rechner.scss

@@ -0,0 +1,55 @@
+.mengenrabatt-rechner {
+  display: grid;
+  gap: 1rem;
+  max-width: 32rem;
+  margin: 2rem auto;
+  padding: 1.5rem;
+  border: 1px solid var(--app-border, #d0d0d0);
+  border-radius: 0.5rem;
+  font-family: inherit;
+}
+
+.mengenrabatt-rechner h1 {
+  margin: 0;
+  font-size: 1.5rem;
+}
+
+.field {
+  display: grid;
+  gap: 0.25rem;
+}
+
+.field label {
+  font-weight: 600;
+}
+
+.field input {
+  padding: 0.5rem 0.75rem;
+  font: inherit;
+  border: 1px solid var(--app-border, #d0d0d0);
+  border-radius: 0.25rem;
+}
+
+.result {
+  display: grid;
+  gap: 0.5rem;
+  margin: 0;
+  padding-top: 1rem;
+  border-top: 1px solid var(--app-border, #d0d0d0);
+}
+
+.result-row {
+  display: flex;
+  justify-content: space-between;
+  align-items: baseline;
+  margin: 0;
+}
+
+.result-row dt {
+  font-weight: 600;
+}
+
+.result-row dd {
+  margin: 0;
+  font-variant-numeric: tabular-nums;
+}

web/src/app/mengenrabatt-rechner/mengenrabatt-rechner.spec.ts

@@ -0,0 +1,107 @@
+import { TestBed, ComponentFixture } from '@angular/core/testing';
+import { MengenrabattRechner } from './mengenrabatt-rechner';
+
+function setInputs(
+  fixture: ComponentFixture<MengenrabattRechner>,
+  unitPrice: string,
+  quantity: string,
+  percent: string,
+): void {
+  const inputs = fixture.nativeElement.querySelectorAll('input');
+  (inputs[0] as HTMLInputElement).value = unitPrice;
+  inputs[0].dispatchEvent(new Event('input'));
+  (inputs[1] as HTMLInputElement).value = quantity;
+  inputs[1].dispatchEvent(new Event('input'));
+  (inputs[2] as HTMLInputElement).value = percent;
+  inputs[2].dispatchEvent(new Event('input'));
+  fixture.detectChanges();
+}
+
+function compute(unitPrice: string, quantity: string, percent: string): {
+  endbetrag: string;
+  staffelstufe: string;
+} {
+  const fixture = TestBed.createComponent(MengenrabattRechner);
+  fixture.detectChanges();
+  setInputs(fixture, unitPrice, quantity, percent);
+  const compiled = fixture.nativeElement as HTMLElement;
+  return {
+    endbetrag: (compiled.querySelector('[data-testid="endbetrag"]')?.textContent ?? '').trim(),
+    staffelstufe: (compiled.querySelector('[data-testid="staffelstufe"]')?.textContent ?? '').trim(),
+  };
+}
+
+describe('MengenrabattRechner', () => {
+  beforeEach(async () => {
+    await TestBed.configureTestingModule({
+      imports: [MengenrabattRechner],
+    }).compileComponents();
+  });
+
+  describe('quantity tiers', () => {
+    it('uses the 0% tier for 9 pieces', () => {
+      const { endbetrag, staffelstufe } = compute('10', '9', '0');
+      expect(staffelstufe).toBe('0 % (1–9 Stück)');
+      expect(endbetrag).toContain('90.00');
+    });
+
+    it('switches to the 5% tier at 10 pieces', () => {
+      const { endbetrag, staffelstufe } = compute('10', '10', '0');
+      expect(staffelstufe).toBe('5 % (10–49 Stück)');
+      expect(endbetrag).toContain('95.00');
+    });
+
+    it('stays on the 5% tier at 49 pieces', () => {
+      const { endbetrag, staffelstufe } = compute('1', '49', '0');
+      expect(staffelstufe).toBe('5 % (10–49 Stück)');
+      // 1 * 0.95 * 49 = 46.55
+      expect(endbetrag).toContain('46.55');
+    });
+
+    it('switches to the 10% tier at 50 pieces', () => {
+      const { endbetrag, staffelstufe } = compute('1', '50', '0');
+      expect(staffelstufe).toBe('10 % (ab 50 Stück)');
+      // 1 * 0.9 * 50 = 45.00
+      expect(endbetrag).toContain('45.00');
+    });
+  });
+
+  describe('discount pipeline', () => {
+    it('applies percentage discount first, then the quantity tier discount (100/10/25 → 712.50)', () => {
+      const { endbetrag, staffelstufe } = compute('100', '10', '25');
+      // 100 * 0.75 = 75; 75 * 10 = 750; quantity tier 5%: 750 * 0.95 = 712.50
+      expect(endbetrag).toContain('712.50');
+      expect(staffelstufe).toBe('5 % (10–49 Stück)');
+    });
+  });
+
+  describe('rounding to 0.05', () => {
+    it('rounds 1.23 up to 1.25', () => {
+      const { endbetrag } = compute('1.23', '1', '0');
+      // 1 piece is in the 1–9 tier (0%); rounded to 0.05: 1.23 -> 1.25
+      expect(endbetrag).toContain('1.25');
+    });
+  });
+
+  describe('invalid input', () => {
+    it('shows the placeholder when inputs are empty', () => {
+      const { endbetrag, staffelstufe } = compute('', '', '');
+      expect(endbetrag).toBe('—');
+      expect(staffelstufe).toBe('—');
+    });
+
+    it('shows the placeholder for a non-integer quantity', () => {
+      const { endbetrag } = compute('10', '3.5', '0');
+      expect(endbetrag).toBe('—');
+    });
+  });
+
+  describe('DOM output', () => {
+    it('renders the Endbetrag with two decimals and the German Staffelstufe label', () => {
+      const { endbetrag, staffelstufe } = compute('100', '10', '25');
+      expect(endbetrag).toMatch(/\d+\.\d{2}/);
+      expect(endbetrag).toContain('712.50');
+      expect(staffelstufe).toBe('5 % (10–49 Stück)');
+    });
+  });
+});

web/src/app/mengenrabatt-rechner/mengenrabatt-rechner.ts

@@ -0,0 +1,99 @@
+import { ChangeDetectionStrategy, Component, computed, signal } from '@angular/core';
+
+interface DiscountTier {
+  readonly minQuantity: number;
+  readonly maxQuantity: number | null;
+  readonly percent: number;
+  readonly label: string;
+}
+
+const TIERS: readonly DiscountTier[] = [
+  { minQuantity: 1, maxQuantity: 9, percent: 0, label: '0 % (1–9 Stück)' },
+  { minQuantity: 10, maxQuantity: 49, percent: 5, label: '5 % (10–49 Stück)' },
+  { minQuantity: 50, maxQuantity: null, percent: 10, label: '10 % (ab 50 Stück)' },
+];
+
+const PERCENT_DIVISOR = 100;
+const ROUNDING_STEP = 20; // 1 / 0.05 → multiply before rounding
+
+function tierFor(quantity: number): DiscountTier | null {
+  for (const tier of TIERS) {
+    if (quantity >= tier.minQuantity && (tier.maxQuantity === null || quantity <= tier.maxQuantity)) {
+      return tier;
+    }
+  }
+  return null;
+}
+
+function parseNumber(value: string): number | null {
+  if (value.trim() === '') {
+    return null;
+  }
+  const parsed = Number(value.replace(',', '.'));
+  return Number.isFinite(parsed) ? parsed : null;
+}
+
+function formatChf(value: number): string {
+  return `CHF\u00a0${value.toFixed(2)}`;
+}
+
+@Component({
+  selector: 'app-mengenrabatt-rechner',
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  imports: [],
+  templateUrl: './mengenrabatt-rechner.html',
+  styleUrl: './mengenrabatt-rechner.scss',
+})
+export class MengenrabattRechner {
+  protected readonly unitPriceInput = signal('');
+  protected readonly quantityInput = signal('');
+  protected readonly percentDiscountInput = signal('');
+
+  private readonly unitPrice = computed(() => parseNumber(this.unitPriceInput()));
+  private readonly quantity = computed(() => {
+    const value = parseNumber(this.quantityInput());
+    if (value === null || !Number.isInteger(value) || value <= 0) {
+      return null;
+    }
+    return value;
+  });
+  private readonly percentDiscount = computed(() => {
+    const value = parseNumber(this.percentDiscountInput());
+    if (value === null || value < 0 || value > 100) {
+      return null;
+    }
+    return value;
+  });
+
+  protected readonly tier = computed<DiscountTier | null>(() => {
+    const quantity = this.quantity();
+    return quantity === null ? null : tierFor(quantity);
+  });
+
+  private readonly total = computed<number | null>(() => {
+    const unitPrice = this.unitPrice();
+    const quantity = this.quantity();
+    const percentDiscount = this.percentDiscount();
+    const tier = this.tier();
+    if (
+      unitPrice === null ||
+      unitPrice < 0 ||
+      quantity === null ||
+      percentDiscount === null ||
+      tier === null
+    ) {
+      return null;
+    }
+    const discountedUnit = unitPrice * (1 - percentDiscount / PERCENT_DIVISOR);
+    const subtotal = discountedUnit * quantity;
+    const withTierDiscount = subtotal * (1 - tier.percent / PERCENT_DIVISOR);
+    return Math.round(withTierDiscount * ROUNDING_STEP) / ROUNDING_STEP;
+  });
+
+  protected readonly endbetragLabel = computed<string>(() => {
+    const value = this.total();
+    return value === null ? '—' : formatChf(value);
+  });
+
+  protected readonly staffelLabel = computed<string>(() => this.tier()?.label ?? '—');
+}