Mengenrabatt: Staffel im Rechner und eine Seite im Web

agentd task 4027a3aa01be47e9b677e7c687e4b183

src/Prices/PriceCalculator.cs

@@ -16,6 +16,57 @@ public static class PriceCalculator
             throw new ArgumentOutOfRangeException(nameof(discountPercent), "A discount is between 0 and 100 percent.");
         }
 
-        return price - discountPercent;
+        return price * (1m - discountPercent / 100m);
+    }
+
+    /// <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

@@ -33,4 +33,94 @@ public sealed class PriceCalculatorTests
     {
         Assert.Throws<ArgumentOutOfRangeException>(() => PriceCalculator.ApplyDiscount(100m, 101m));
     }
+
+    [Fact]
+    public void Quantity_9_gets_no_quantity_discount()
+    {
+        Assert.Equal(0, PriceCalculator.GetQuantityDiscountPercent(9));
+    }
+
+    [Fact]
+    public void Quantity_10_gets_five_percent_quantity_discount()
+    {
+        Assert.Equal(5, PriceCalculator.GetQuantityDiscountPercent(10));
+    }
+
+    [Fact]
+    public void Quantity_49_gets_five_percent_quantity_discount()
+    {
+        Assert.Equal(5, PriceCalculator.GetQuantityDiscountPercent(49));
+    }
+
+    [Fact]
+    public void Quantity_50_gets_ten_percent_quantity_discount()
+    {
+        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/.editorconfig

@@ -0,0 +1,17 @@
+# Editor configuration, see https://editorconfig.org
+root = true
+
+[*]
+charset = utf-8
+indent_style = space
+indent_size = 2
+insert_final_newline = true
+trim_trailing_whitespace = true
+
+[*.ts]
+quote_type = single
+ij_typescript_use_double_quotes = false
+
+[*.md]
+max_line_length = off
+trim_trailing_whitespace = false

web/.gitignore

@@ -0,0 +1,44 @@
+# See https://docs.github.com/get-started/getting-started-with-git/ignoring-files for more about ignoring files.
+
+# Compiled output
+/dist
+/tmp
+/out-tsc
+/bazel-out
+
+# Node
+/node_modules
+npm-debug.log
+yarn-error.log
+
+# IDEs and editors
+.idea/
+.project
+.classpath
+.c9/
+*.launch
+.settings/
+*.sublime-workspace
+
+# Visual Studio Code
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
+!.vscode/launch.json
+!.vscode/extensions.json
+!.vscode/mcp.json
+.history/*
+
+# Miscellaneous
+/.angular/cache
+.sass-cache/
+/connect.lock
+/coverage
+/libpeerconnection.log
+testem.log
+/typings
+__screenshots__/
+
+# System files
+.DS_Store
+Thumbs.db

web/.prettierrc

@@ -0,0 +1,12 @@
+{
+  "printWidth": 100,
+  "singleQuote": true,
+  "overrides": [
+    {
+      "files": "*.html",
+      "options": {
+        "parser": "angular"
+      }
+    }
+  ]
+}

web/.vscode/extensions.json

@@ -0,0 +1,4 @@
+{
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=827846
+  "recommendations": ["angular.ng-template"]
+}

web/.vscode/launch.json

@@ -0,0 +1,20 @@
+{
+  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
+  "version": "0.2.0",
+  "configurations": [
+    {
+      "name": "ng serve",
+      "type": "chrome",
+      "request": "launch",
+      "preLaunchTask": "npm: start",
+      "url": "http://localhost:4200/"
+    },
+    {
+      "name": "ng test",
+      "type": "chrome",
+      "request": "launch",
+      "preLaunchTask": "npm: test",
+      "url": "http://localhost:9876/debug.html"
+    }
+  ]
+}

web/.vscode/tasks.json

@@ -0,0 +1,42 @@
+{
+  // For more information, visit: https://go.microsoft.com/fwlink/?LinkId=733558
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "type": "npm",
+      "script": "start",
+      "isBackground": true,
+      "problemMatcher": {
+        "owner": "typescript",
+        "pattern": "$tsc",
+        "background": {
+          "activeOnStart": true,
+          "beginsPattern": {
+            "regexp": "Changes detected"
+          },
+          "endsPattern": {
+            "regexp": "bundle generation (complete|failed)"
+          }
+        }
+      }
+    },
+    {
+      "type": "npm",
+      "script": "test",
+      "isBackground": true,
+      "problemMatcher": {
+        "owner": "typescript",
+        "pattern": "$tsc",
+        "background": {
+          "activeOnStart": true,
+          "beginsPattern": {
+            "regexp": "Changes detected"
+          },
+          "endsPattern": {
+            "regexp": "bundle generation (complete|failed)"
+          }
+        }
+      }
+    }
+  ]
+}

web/README.md

@@ -0,0 +1,59 @@
+# Web
+
+This project was generated using [Angular CLI](https://github.com/angular/angular-cli) version 22.1.2.
+
+## Development server
+
+To start a local development server, run:
+
+```bash
+ng serve
+```
+
+Once the server is running, open your browser and navigate to `http://localhost:4200/`. The application will automatically reload whenever you modify any of the source files.
+
+## Code scaffolding
+
+Angular CLI includes powerful code scaffolding tools. To generate a new component, run:
+
+```bash
+ng generate component component-name
+```
+
+For a complete list of available schematics (such as `components`, `directives`, or `pipes`), run:
+
+```bash
+ng generate --help
+```
+
+## Building
+
+To build the project run:
+
+```bash
+ng build
+```
+
+This will compile your project and store the build artifacts in the `dist/` directory. By default, the production build optimizes your application for performance and speed.
+
+## Running unit tests
+
+To execute unit tests with the [Vitest](https://vitest.dev/) test runner, use the following command:
+
+```bash
+ng test
+```
+
+## Running end-to-end tests
+
+For end-to-end (e2e) testing, run:
+
+```bash
+ng e2e
+```
+
+Angular CLI does not come with an end-to-end testing framework by default. You can choose one that suits your needs.
+
+## Additional Resources
+
+For more information on using the Angular CLI, including detailed command references, visit the [Angular CLI Overview and Command Reference](https://angular.dev/tools/cli) page.

web/angular.json

@@ -0,0 +1,78 @@
+{
+  "$schema": "./node_modules/@angular/cli/lib/config/schema.json",
+  "version": 1,
+  "cli": {
+    "packageManager": "npm"
+  },
+  "newProjectRoot": "projects",
+  "projects": {
+    "web": {
+      "projectType": "application",
+      "schematics": {
+        "@schematics/angular:component": {
+          "style": "scss"
+        }
+      },
+      "root": "",
+      "sourceRoot": "src",
+      "prefix": "app",
+      "architect": {
+        "build": {
+          "builder": "@angular/build:application",
+          "options": {
+            "browser": "src/main.ts",
+            "tsConfig": "tsconfig.app.json",
+            "inlineStyleLanguage": "scss",
+            "assets": [
+              {
+                "glob": "**/*",
+                "input": "public"
+              }
+            ],
+            "styles": [
+              "src/styles.scss"
+            ]
+          },
+          "configurations": {
+            "production": {
+              "budgets": [
+                {
+                  "type": "initial",
+                  "maximumWarning": "500kB",
+                  "maximumError": "1MB"
+                },
+                {
+                  "type": "anyComponentStyle",
+                  "maximumWarning": "4kB",
+                  "maximumError": "8kB"
+                }
+              ],
+              "outputHashing": "all"
+            },
+            "development": {
+              "optimization": false,
+              "extractLicenses": false,
+              "sourceMap": true
+            }
+          },
+          "defaultConfiguration": "production"
+        },
+        "serve": {
+          "builder": "@angular/build:dev-server",
+          "configurations": {
+            "production": {
+              "buildTarget": "web:build:production"
+            },
+            "development": {
+              "buildTarget": "web:build:development"
+            }
+          },
+          "defaultConfiguration": "development"
+        },
+        "test": {
+          "builder": "@angular/build:unit-test"
+        }
+      }
+    }
+  }
+}

web/package.json

@@ -0,0 +1,32 @@
+{
+  "name": "web",
+  "version": "0.0.0",
+  "scripts": {
+    "ng": "ng",
+    "start": "ng serve",
+    "build": "ng build",
+    "watch": "ng build --watch --configuration development",
+    "test": "ng test"
+  },
+  "private": true,
+  "packageManager": "npm@10.8.3",
+  "dependencies": {
+    "@angular/common": "^22.1.0",
+    "@angular/compiler": "^22.1.0",
+    "@angular/core": "^22.1.0",
+    "@angular/forms": "^22.1.0",
+    "@angular/platform-browser": "^22.1.0",
+    "@angular/router": "^22.1.0",
+    "rxjs": "~7.8.0",
+    "tslib": "^2.3.0"
+  },
+  "devDependencies": {
+    "@angular/build": "^22.1.2",
+    "@angular/cli": "^22.1.2",
+    "@angular/compiler-cli": "^22.1.0",
+    "jsdom": "^28.0.0",
+    "prettier": "^3.8.1",
+    "typescript": "~6.0.2",
+    "vitest": "^4.0.8"
+  }
+}

web/src/app/app.config.ts

@@ -0,0 +1,11 @@
+import { ApplicationConfig, provideBrowserGlobalErrorListeners } from '@angular/core';
+import { provideRouter } from '@angular/router';
+
+import { routes } from './app.routes';
+
+export const appConfig: ApplicationConfig = {
+  providers: [
+    provideBrowserGlobalErrorListeners(),
+    provideRouter(routes)
+  ]
+};

web/src/app/app.html

@@ -0,0 +1,9 @@
+<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

@@ -0,0 +1,7 @@
+import { Routes } from '@angular/router';
+import { MengenrabattRechner } from './mengenrabatt-rechner/mengenrabatt-rechner';
+
+export const routes: Routes = [
+  { path: 'mengenrabatt', component: MengenrabattRechner },
+  { path: '', pathMatch: 'full', redirectTo: 'mengenrabatt' },
+];

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

@@ -0,0 +1,36 @@
+import { TestBed } from '@angular/core/testing';
+import { provideRouter } from '@angular/router';
+import { App } from './app';
+import { routes } from './app.routes';
+
+describe('App', () => {
+  beforeEach(async () => {
+    await TestBed.configureTestingModule({
+      imports: [App],
+      providers: [provideRouter(routes)],
+    }).compileComponents();
+  });
+
+  it('should create the app', () => {
+    const fixture = TestBed.createComponent(App);
+    const app = fixture.componentInstance;
+    expect(app).toBeTruthy();
+  });
+
+  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('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

@@ -0,0 +1,13 @@
+import { ChangeDetectionStrategy, Component, signal } from '@angular/core';
+import { RouterLink, RouterOutlet } from '@angular/router';
+
+@Component({
+  selector: 'app-root',
+  changeDetection: ChangeDetectionStrategy.OnPush,
+  imports: [RouterOutlet, RouterLink],
+  templateUrl: './app.html',
+  styleUrl: './app.scss',
+})
+export class App {
+  protected readonly title = signal('Preisrechner');
+}

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 ?? '—');
+}

web/src/index.html

@@ -0,0 +1,13 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <title>Web</title>
+  <base href="/">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <link rel="icon" type="image/x-icon" href="favicon.ico">
+</head>
+<body>
+  <app-root></app-root>
+</body>
+</html>

web/src/main.ts

@@ -0,0 +1,6 @@
+import { bootstrapApplication } from '@angular/platform-browser';
+import { appConfig } from './app/app.config';
+import { App } from './app/app';
+
+bootstrapApplication(App, appConfig)
+  .catch((err) => console.error(err));

web/src/styles.scss

@@ -0,0 +1 @@
+/* You can add global styles to this file, and also import other style files */

web/tsconfig.app.json

@@ -0,0 +1,14 @@
+/* To learn more about Typescript configuration file: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html. */
+/* To learn more about Angular compiler options: https://angular.dev/reference/configs/angular-compiler-options. */
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "types": []
+  },
+  "include": [
+    "src/**/*.ts"
+  ],
+  "exclude": [
+    "src/**/*.spec.ts"
+  ]
+}

web/tsconfig.json

@@ -0,0 +1,31 @@
+/* To learn more about Typescript configuration file: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html. */
+/* To learn more about Angular compiler options: https://angular.dev/reference/configs/angular-compiler-options. */
+{
+  "compileOnSave": false,
+  "compilerOptions": {
+    "noImplicitOverride": true,
+    "noPropertyAccessFromIndexSignature": true,
+    "noImplicitReturns": true,
+    "noFallthroughCasesInSwitch": true,
+    "skipLibCheck": true,
+    "isolatedModules": true,
+    "experimentalDecorators": true,
+    "importHelpers": true,
+    "target": "ES2022",
+    "module": "preserve"
+  },
+  "angularCompilerOptions": {
+    "enableI18nLegacyMessageIdFormat": false,
+    "strictInjectionParameters": true,
+    "strictInputAccessModifiers": true
+  },
+  "files": [],
+  "references": [
+    {
+      "path": "./tsconfig.app.json"
+    },
+    {
+      "path": "./tsconfig.spec.json"
+    }
+  ]
+}

web/tsconfig.spec.json

@@ -0,0 +1,14 @@
+/* To learn more about Typescript configuration file: https://www.typescriptlang.org/docs/handbook/tsconfig-json.html. */
+/* To learn more about Angular compiler options: https://angular.dev/reference/configs/angular-compiler-options. */
+{
+  "extends": "./tsconfig.json",
+  "compilerOptions": {
+    "types": [
+      "vitest/globals"
+    ]
+  },
+  "include": [
+    "src/**/*.d.ts",
+    "src/**/*.spec.ts"
+  ]
+}