the-biergarten-app/docs/web/architecture.md

Architecture

This document describes the architecture of The Biergarten App.

High-level overview

The Biergarten App is a monorepo split between the backend and the website:

• Backend: .NET 10 Web API with SQL Server, organized as vertical feature slices with MediatR
• Frontend: React 19 + React Router 8 website in web/frontend
• Architecture Style: Vertical-slice backend plus server-rendered React frontend

archive/next-js-web-app/ contains an archived Next.js frontend, kept for reference.

Diagrams

For visual representations, see:

• Vertical Slice - host wiring and project reference diagrams
• Deployment - Docker deployment diagram
• Database Schema - database relationships

Authentication workflow diagrams, one per flow, under diagrams/auth/:

• Registration
• Login
• Refresh Token
• Confirm User
• Resend Confirmation
• Update Username
• Update Email
• Update Password
• Update Profile
• Delete Account
• Error Handling - shared GlobalExceptionFilter mapping used by all flows above

Backend architecture

Vertical-slice architecture pattern

The backend organizes business capabilities as feature slices instead of technical layers.

Each feature (Features.Users, Features.Breweries, Features.Emails, Features.Locations, Features.PhotoUpload) is a single project that owns its own MediatR commands/queries/handlers, validators, and repository end to end.

Features.Emails, Features.Locations, and Features.PhotoUpload have no Controllers/ folder; all three are invoked internally by other slices via MediatR/DI, never over HTTP:

flowchart TB
    subgraph HOST["API.Core (thin host)"]
        direction LR
        H1["Program.cs wiring:<br/>MediatR + AddApplicationPart per slice"]
        H2["Swagger / OpenAPI"]
        H3["JWT auth middleware"]
        H4["GlobalExceptionFilter"]
    end

    subgraph SLICES["Feature Slices"]
        direction LR
        S1["Features.Users<br/>Controllers, Commands/Queries,<br/>Handlers, Repository"]
        S2["Features.Breweries<br/>Controller, Commands/Queries,<br/>Handlers, Repository"]
        S3["Features.Emails<br/>(internal only)<br/>Commands, Handlers,<br/>EmailDispatcher"]
        S4["Features.Locations<br/>(internal only)<br/>Repository"]
        S5["Features.PhotoUpload<br/>(internal only)<br/>Commands, Handlers,<br/>Repository"]
    end

    subgraph SHARED["Shared Projects"]
        direction LR
        SH1["Shared.Contracts<br/>ResponseBody envelope"]
        SH2["Shared.Application<br/>ValidationBehavior"]
    end

    subgraph DOMAIN["Domain Layer"]
        direction LR
        D1["Domain.Entities"]
        D2["Domain.Exceptions"]
    end

    subgraph INFRA["Infrastructure Layer"]
        direction LR
        I1["Database.Connection"]
        I3["Infrastructure.PasswordHashing"]
        I4["Email.Templates"]
    end

    DB[("Database (SQL Server)")]

    HOST -- "discovers controllers via<br/>AddApplicationPart" --> SLICES
    S3 == "ProjectReference<br/>(handles UserRegisteredNotification & ConfirmationEmailResendRequestedNotification)" ==> S1
    S1 -- "ProjectReference<br/>(avatar upload)" --> S5

    SLICES --> SHARED
    SLICES --> DOMAIN
    SLICES --> INFRA

    INFRA --> DB

    style S3 stroke-dasharray: 4 3
    style S4 stroke-dasharray: 4 3
    style S5 stroke-dasharray: 4 3

Layer responsibilities

API layer (API.Core)

Purpose: Thin ASP.NET Core host: no business logic, no controllers of its own

Components:

Component	Description
Program.cs	Thin composition root: builds the host and calls the ServiceCollectionExtensions methods below.
ServiceCollectionExtensions.cs	Registers MediatR (scanning every Features.* assembly), FluentValidation, and uses AddApplicationPart so each slice's controllers are discovered by MVC.
GlobalException.cs	Global exception filter (host-level cross-cutting concern).
Authentication/JwtAuthenticationHandler.cs	JWT auth scheme middleware.
Swagger/OpenAPI documentation, health check endpoints	Host-level documentation and health endpoints.

Dependencies:

• Every Features.* project (for controller/MediatR discovery)
• Shared.Contracts, Shared.Application

Rules:

• No controllers, no business logic, no feature-specific contracts
• Exists purely to host and wire up the feature slices

Feature slices (Features.Users, Features.Breweries, Features.Emails, Features.Locations, Features.PhotoUpload)

Purpose: Each slice is the complete vertical for one business capability

Components (per slice):

Component	Description
Controllers/	HTTP endpoints, binding directly to Command/Query types as the request contract
Commands/<Operation>/ and Queries/<Operation>/	One folder per operation, each containing the Command/Query record, its IRequestHandler, and (for commands) a FluentValidation validator
Repository/	The slice's own Dapper repository implementation
Dtos/	Response shapes returned by query handlers (never the raw domain entity)
DependencyInjection/	An AddFeaturesX() extension method registering the slice's repository/services

Note

Features.Emails has no Controllers/ folder. It's invoked only via MediatR commands sent from other slices, never over HTTP.

Features.PhotoUpload also has no Controllers/ folder; its UploadPhotoCommand is sent by other features' handlers (for example, a future brewery photo upload command) rather than bound to an HTTP route directly.

Dependencies:

• Domain.Entities, Domain.Exceptions
• Database.Connection (generic ADO.NET connection/command plumbing) plus whichever infrastructure project the slice needs (Infrastructure.PasswordHashing for Users, Infrastructure.Email.Templates for Emails)
• Shared.Contracts, Shared.Application
• No other Features.* project, with two exceptions: Features.Users references Features.PhotoUpload directly for avatar uploads, and Features.Emails references Features.Users directly to handle UserRegisteredNotification and ConfirmationEmailResendRequestedNotification

Rules:

• All business logic for that feature lives in its command/query handlers
• No direct controller-to-repository calls; everything flows through MediatR
• Read endpoints return a dedicated Dto, never the domain entity directly

Shared projects (Shared.Contracts, Shared.Application)

Purpose: The minimum cross-slice surface area required because every slice needs it, or because duplicating it four times would be worse than sharing it

Components:

Project	Purpose
Shared.Contracts	ResponseBody<T>/ResponseBody, the API response envelope every controller returns
Shared.Application	ValidationBehavior<TRequest,TResponse>, the MediatR pipeline behavior that runs FluentValidation before a handler executes

Rules:

• Kept deliberately small: this is the exception to "no slice depends on another slice".

Infrastructure layer

Purpose: Technical capabilities and external integrations, shared by whichever slices need them

Components:

Project	Description
Database.Connection	Generic ADO.NET connection/command plumbing (DefaultSqlConnectionFactory, the abstract DapperRepository base class), not domain-specific; each slice's own Repository/ folder builds on this.
Infrastructure.PasswordHashing	Argon2id password hashing.
Infrastructure.Email.Templates	Email template rendering (Razor components).

Dependencies:

• Domain entities
• External libraries (ADO.NET, JWT, Argon2, MailKit, AWSSDK.S3, and so on)

Rules:

• Implements technical concerns only, no business logic
• Reusable across slices

Domain layer (Domain.Entities)

Purpose: Core business entities and models

Components:

Entity	Description
UserAccount	User profile data.
UserCredential	Authentication credentials.
UserVerification	Account verification state.
BreweryPost	A user-submitted brewery listing.
BreweryPostLocation	A brewery's address and coordinates.
City	A city referenced by a brewery location.
StateProvince	A state/province referenced by a city.
Country	A country referenced by a state/province.
BeerStyle	A beer style/category (schema table exists; no repository yet).
BeerPost	A beer listing tied to a brewery and style (schema table exists; no repository yet).
Photo	A photo uploaded by a user account, written via Features.PhotoUpload's IPhotoUploadRepository.

Dependencies:

• None (pure domain)

Rules:

• Plain Old CLR Objects (POCOs)
• No framework dependencies
• No infrastructure references
• Represents business concepts

Design patterns

Vertical slice + MediatR

Purpose: Organize code by feature instead of by technical layer, so everything needed to understand or change one capability lives in one project

Implementation:

• Each HTTP write operation is a Command (for example, CreateBreweryCommand in Features.Breweries/Commands/CreateBrewery/); each read operation is a Query (for example, GetBreweryByIdQuery)
• Controllers generally bind directly to the Command/Query as the request body; there is no separate request DTO + mapping step for writes
  • The exception to this is for authenticated routes, when the current user id needs to be extracted from the authentication token to be used in a command.
• A single shared ValidationBehavior<TRequest,TResponse> (Shared.Application/Behaviors/) runs FluentValidation validators in the MediatR pipeline before any handler executes
• Query handlers map to a dedicated response Dto, so domain entities never leak

Example:

public record CreateBreweryCommand(Guid PostedById, string BreweryName, string Description, ...)
    : IRequest<BreweryDto>;

public class CreateBreweryHandler(IBreweryRepository repository) : IRequestHandler<CreateBreweryCommand, BreweryDto>
{
    public async Task<BreweryDto> Handle(CreateBreweryCommand request, CancellationToken cancellationToken) { ... }
}

Repository pattern

Purpose: Abstract database access behind interfaces

Implementation: each slice owns its own repository, scoped to that feature only:

• Features.Users/Repository/IUserListRepository.cs, Features.Users/Repository/IUserProfileRepository.cs
• Features.Breweries/Repository/IBreweryRepository.cs
• Features.PhotoUpload/Repository/IPhotoUploadRepository.cs
• Database.Connection/DefaultSqlConnectionFactory.cs: the generic connection factory every slice's repository builds on
• Database.Connection/DapperRepository.cs: shared abstract base class every repository extends, providing CreateConnection() and a RollbackQuietlyAsync() helper that rolls back a transaction while swallowing any exception the rollback itself raises, so the exception that triggered the rollback is what propagates

Benefits:

• Testable (easy to mock)
• Each slice's data access logic is self-contained

Example:

public interface IUserListRepository
{
    Task<UserAccount?> GetByIdAsync(Guid id);
    Task<IEnumerable<UserAccount>> GetAllAsync(int? limit, int? offset);
}

Dependency injection

Purpose: Loose coupling and testability

Configuration: Program.cs wires up MediatR/FluentValidation across every Features.* assembly; each slice exposes its own AddFeaturesX() extension method that registers its repository and slice-internal services

Lifetimes:

• Scoped: Repositories, slice-internal services (per request)
• Singleton: DefaultSqlConnectionFactory
• Transient: Utilities, helpers

Direct SQL via Dapper/ADO.NET

Purpose: Keep data access explicit and colocated with the slice that owns it

Strategy:

• Each repository issues inline SQL through Dapper, which handles parameter binding.
• Proximity search (GET /api/brewery/locations/nearby) filters and orders rows server-side with Coordinates.STDistance(@Origin) <= @RangeInMetres, avoiding a client-side distance calculation over every row.
• Referential checks (for example, "does this CityId exist?") are explicit SELECT 1 ... existence checks in the repository method, run inside the same transaction as the write
• Optimistic concurrency uses each table's RowVersion (ROWVERSION) column, checked in the UPDATE ... WHERE ... AND RowVersion = @RowVersion clause
• Repositories throw Domain.Exceptions types (NotFoundException, ConflictException, ...) directly when a check fails; API.Core's GlobalExceptionFilter maps those exception types to HTTP status codes
• Application focuses on orchestration; the database enforces integrity via keys, CHECK constraints, and cascades

See Database for the schema and the app's SQL error-handling approach in more detail.

Frontend architecture

Website (web/frontend)

The website is a React Router 8 application with server-side rendering enabled.

web/frontend/
├── app/
│   ├── components/      Shared UI: Navbar, FormField, SubmitButton, ToastProvider,
│   │                    RouteErrorState, ClientOnly (defers client-only children,
│   │                    for example Leaflet maps, past hydration)
│   ├── features/        One folder per feature slice, each owning its own
│   │                    routes/, components/, hooks/, schemas, and server-side
│   │                    loader helpers:
│   │                      - account    profile/dashboard management
│   │                      - auth       login, register, confirm, logout
│   │                      - breweries  index/directory/detail routes, Leaflet
│   │                                   map components, nearby-search resource
│   │                                   route, distance/address utils
│   │                      - catalog    beers, beer styles
│   │                      - home       landing page
│   │                      - theme      theme switcher/guide
│   ├── hooks/            Shared hooks not tied to one feature, for example useMediaQuery
│   ├── routes.ts         Route table (React Router 8 config-based routing)
│   ├── root.tsx          App shell and global providers
│   └── app.css           Theme tokens and global styling
├── .storybook/          Storybook config and preview setup
├── stories/             Storybook stories for shared UI and themes
├── tests/playwright/    Storybook Playwright coverage
└── package.json         Frontend scripts and dependencies

Frontend responsibilities

• Render brewery discovery routes (/breweries index, /breweries/directory, /breweries/:id) with Leaflet-powered maps and geolocation-based "nearby" search
• Render the auth demo, account dashboard, and theme guide routes
• Manage cookie-backed website session state
• Call the .NET API for login, registration, token refresh, confirmation, and brewery/location data
• Provide shared UI building blocks for forms, navigation, themes, and toasts
• Supply Storybook documentation and browser-based component verification

Theme system

The website uses semantic DaisyUI theme tokens backed by four Biergarten themes:

• Biergarten Lager
• Biergarten Stout
• Biergarten Cassis
• Biergarten Weizen

All component styling should prefer semantic tokens such as primary, success, surface, and highlight instead of hard-coded color values.

Archived frontend

archive/next-js-web-app/ contains an archived Next.js frontend, kept for reference. Product and engineering documentation points to web/frontend.

Security architecture

Authentication flow

Flow	Details
Registration	User submits credentials; password is hashed with Argon2id; user account is created as unverified and a confirmation email is dispatched via Features.Emails.
Email confirmation	User follows the confirmation link/token from the email; Features.Users' ConfirmUser command marks the account as verified.
Login	User submits credentials; password is verified against the hash; access and refresh JWTs are issued and returned to the client; neither is stored server-side.
Token refresh	Client exchanges a valid, unexpired refresh token for a new access/refresh pair via Features.Users' RefreshToken command; refresh tokens are stateless JWTs, not tracked server-side, and the previous refresh token remains usable until its own expiration.
API requests	Client sends the access JWT in the Authorization header; JwtAuthenticationHandler validates the token; request proceeds if valid.

Password security

Algorithm: Argon2id

Setting	Value
Memory	64MB
Iterations	4
Parallelism	2 (hardcoded, to avoid thread-pool exhaustion)
Salt	128-bit (16 bytes)
Hash	256-bit (32 bytes)

JWT tokens

Algorithm: HS256 (HMAC-SHA256)

Claims:

Claim	Meaning
sub	User ID
unique_name	Username
jti	Unique token ID
iat	Issued at timestamp
exp	Expiration timestamp

Configuration (appsettings.json):

{
  "Jwt": {
    "ExpirationMinutes": 60,
    "Issuer": "biergarten-api",
    "Audience": "biergarten-users"
  }
}

This block exists in appsettings.json, but nothing in the code currently reads it: actual token lifetimes come from the hardcoded TokenServiceExpirationHours constants, and JwtInfrastructure hardcodes ValidateIssuer/ValidateAudience to false, so Issuer/Audience are not enforced.

Database architecture

For the table-by-table schema and the custom SQL error code scheme, see Database.

SQL-first philosophy

Principles:

1. Database is source of truth
2. Queries live in the owning repository, not scattered across the app
3. Database handles referential integrity
4. Application orchestrates, database executes

Benefits:

• Performance optimization via execution plans
• Query logic scoped to the repository that owns it, not spread across layers
• Version-controlled schema (migrations)
• Easier query profiling and tuning

Migration strategy

Tool: DbUp

Process:

1. Write a SQL script under Database.Migrations/scripts/
2. Embed it in the Database.Migrations project
3. Database.Migrations runs each script against the target database on startup, tracked so a script never re-runs once applied

Migration Files:

scripts/
└── 01-schema/
    ├── 01-UserAccount.sql
    ├── 02-Photo.sql
    ├── ...
    ├── 16-UserProfile.sql
    └── 17-UserAvatar.sql        # one script per CREATE TABLE

Each table has its own script, numbered so a table's foreign keys always point at an earlier-numbered script. As the schema evolves, new numbered scripts get added rather than editing an existing one in place, so DbUp's already-applied tracking stays valid.

Data seeding

Purpose: Populate development/test databases with realistic data

Implementation: Database.Seed project, using data produced by the C++ pipeline under tooling/pipeline/ (see Pipeline README)

Seed Data:

• Countries, state/provinces, and cities (via Features.Locations' ILocationRepository, which creates Country/StateProvince rows on demand while resolving a city)
• User accounts (via Features.Users' repository)
• Brewery posts with locations (via Features.Breweries' repository)

Tables that exist in the schema but have no repository yet ( UserFollow, BeerStyle, BeerPost, BeerPostPhoto, BeerPostComment, BreweryPostPhoto) are not seeded either.

Deployment architecture

Docker containerization

Container Structure:

Container	Purpose
sqlserver	SQL Server 2022
database.migrations	Schema migration runner
database.seed	Data seeder
api.core	ASP.NET Core Web API
mailpit	Local dev/test SMTP server + web UI (not used in production)
seaweedfs	S3-compatible object storage for uploaded photos (dev only)

Environments:

Environment	Compose file
Development	docker-compose.dev.yaml
Testing	docker-compose.test.yaml
Production	docker-compose.prod.yaml

For details, see Docker Guide.

Health checks

• SQL Server: Validates database connectivity
• API: Checks service health and dependencies

Configuration:

healthcheck:
  test: ["CMD-SHELL", "sqlcmd health check"]
  interval: 10s
  retries: 12
  start_period: 30s

Testing architecture

Test pyramid

flowchart TB
    IT["Integration Tests<br/>API.Specs (Reqnroll)"]
    UT["Unit Tests (per slice, handler tests)<br/>Features.Users.Tests, Features.Breweries.Tests,<br/>Features.Emails.Tests, Features.PhotoUpload.Tests<br/>(commands/queries/handlers, with repository/service<br/>dependencies mocked via Moq)"]

    IT --- UT

Strategy:

• Many unit tests (fast, isolated)
• Fewer integration tests (slower, e2e)
• Mock external dependencies
• Test database for integration tests

For details, see Testing Guide.