# The Biergarten App — Vertical Slice Architecture

Two diagrams, split by concern: which host wires up which slice at startup, and
which projects each slice actually compiles against. Mixing DI wiring and
compile-time references in one graph is what made the old diagram unreadable.

## Host wiring

Each host (`API.Core`, `Database.Seed`) decides for itself which `Features.*`
assemblies to register — there's no shared bootstrap. `Database.Migrations`
doesn't wire up any slice; it applies schema directly.

```mermaid
--8<-- "web/diagrams/vertical-slice/host-wiring.mmd"
```

## Project reference dependencies

Solid arrows are compile-time project references. Dashed arrows are the two
places slices talk to each other without a direct reference: the email MediatR
contract routed through `Shared.Application`, and the one place that pattern is
broken outright. Every DB-backed slice depends on the same three foundation
projects (`Shared.Contracts`, `Domain.Entities`, `Database.Connection`) — drawn
as one box instead of fifteen separate arrows; see the notes for what else each
of those foundation projects pulls in.

```mermaid
--8<-- "web/diagrams/vertical-slice/project-references.mmd"
```

## Notes

- **API.Core**: Program.cs wiring only
  - MediatR + `AddApplicationPart` per HTTP-exposed `Features.*` assembly
  - Swagger/OpenAPI, health checks, JWT auth middleware, global exception filter
  - Only `Features.Users` and `Features.Breweries` get `AddApplicationPart`
    (controllers)
  - `Features.PhotoUpload` and `Features.Emails` scanned for MediatR handlers
    only
  - `Features.Locations` and `Features.Beers` not referenced by `API.Core` at
    all

- **Feature slices**: each owns its own controller (where present),
  commands/queries + handlers, validators, and Dapper repository
  - `Features.Users` covers auth (`Commands/Authentication`), account management
    (`Commands/Account`), and profile/avatar (`Commands/Profile`)
    - internally namespaced `Features.Auth`, despite project name
      `Features.Users`
  - `Features.Emails` and `Features.PhotoUpload` have no controller — invoked
    only via MediatR commands sent from other slices
  - `Features.Locations` has no controller; one MediatR handler
    (`GetOrCreateCityHandler`) registered by `Database.Seed` only — `API.Core`
    never scans it
  - `Features.Beers` is scaffolded (project + references only, no source files
    yet)

- **The one exception to slice isolation**: `Features.Users` takes a direct
  project reference to `Features.PhotoUpload`
  - sends its `UploadPhotoCommand` via MediatR from `UploadAvatarHandler`
  - unlike the email flow, the command type lives in the target slice itself,
    not in `Shared.Application`

- **Shared.Application**:
  - `ValidationBehavior` (MediatR pipeline)
  - Cross-slice email commands (`SendRegistrationEmailCommand`,
    `SendResendConfirmationEmailCommand`)
  - MediatR command contract (not project reference)
  - Every slice (including `Features.Emails`) references it for the pipeline
    behavior alone

- **Domain.Entities**:
  - `UserAccount`, `UserCredential`, `UserVerification`, `UserProfile`,
    `UserAvatar`
  - `BreweryPost`, `BreweryPostLocation`
  - `City`, `StateProvince`, `Country`
  - `BeerPost`, `BeerStyle`, `Photo` (schema tables exist for
    `BeerPost`/`BeerStyle`; no repository yet since `Features.Beers` has no
    code)

- **Database.Connection**: the shared connection-factory project
  - each slice's own repository issues inline SQL via Dapper against it
  - no ORM, no stored procedures
  - Replaces the old `Infrastructure.Sql` project

- **Database.Migrations**: separate console app
  - `schema.dbml` + SQL scripts
  - applies DDL directly
  - distinct from `Database.Seed`, which loads data through the feature slices'
    own DI extensions

- **Database.Seed**:
  - calls each slice's `AddFeatures*()` DI extension directly
  - builds its own MediatR registration
  - no API host, no shared pipeline with `API.Core`

- **Omitted from the diagram**:
  - `Domain.Exceptions` (referenced by nearly every project directly, including
    all of `Shared.Contracts`, `Infrastructure.Jwt`, and each feature slice)
  - `Infrastructure.Configuration` (the shared options-binding project
    referenced by `Database.Connection`, `Infrastructure.Email`,
    `Infrastructure.FileUpload`, and `Features.Emails` directly)
  - both are plumbing-level dependencies of nearly everything above, and drawing
    them would just add a second copy of the same fan-in