# Architecture

## Dependency Graph

```
AyCode.Utils (zero dependencies)
    ↑
AyCode.Interfaces → AyCode.Entities → AyCode.Models
    ↑                    ↑                  ↑
AyCode.Core ─────────────┘                  │
    ↑                                       │
AyCode.Database ────────────────────────────┘
    ↑
AyCode.Services ← AyCode.Services.Server
```

**Rule:** Dependencies flow upward only. Lower layers never reference higher layers.

## Project Roles

### Foundation Layer
- **AyCode.Utils** — Zero-dependency utilities. String/DateTime extensions, lock wrappers.
- **AyCode.Interfaces** — Pure interfaces. `IId<T>` is the root abstraction.
- **AyCode.Entities** — Abstract generic entity classes. Never instantiated directly.
- **AyCode.Models** — DTOs and view models for service boundaries.

### Core Layer
- **AyCode.Core** — Serializers (Binary, JSON, Toon), compression (Brotli, GZip, LZ4), logging framework, constants, validation.
- **AyCode.Core.Serializers.SourceGenerator** — Roslyn incremental generator. Targets netstandard2.0. Generates `IGeneratedBinaryWriter` / `IGeneratedBinaryReader` for `[AcBinarySerializable]` types.

### Data Layer
- **AyCode.Database** — EF Core with generic DAL pattern. Session for reads, Transaction for writes. DAL pooling via `PooledDal`.

### Service Layer
- **AyCode.Services** — Client-side: SignalR client, login service, loggers.
- **AyCode.Services.Server** — Server-side: SignalR hub with custom binary protocol, email (SendGrid), JWT auth.
- **AyCode.Models.Server/DynamicMethods** — Reflection-based tag→method dispatch used by the SignalR hub.

> **SignalR Dispatch:** Both directions use a single method `OnReceiveMessage(int messageTag, int? requestId, SignalParams signalParams, SignalData data)` with integer tag-based routing instead of standard Hub methods. `SignalData` wraps `ArrayPool`-backed byte buffers for zero-alloc receive path. See `AyCode.Services/docs/SIGNALR.md` for full details.

### Server Extensions
- **AyCode.Core.Server**, **AyCode.Interfaces.Server**, **AyCode.Entities.Server**, **AyCode.Models.Server** — Server-only additions that don't belong in shared code.

## Serialization Architecture

Three serializers share a common infrastructure but serve different goals:

| Serializer | Primary Goal | Use Case |
|---|---|---|
| **AcBinary** | Speed | Wire protocol, SignalR, storage |
| **AcJson** | Compatibility | REST APIs, debugging, interop |
| **Toon** | LLM Accuracy | AI context, schema documentation |

## Generic Entity Pattern

Entities use composition via generic type parameters:

```csharp
// Interface layer
interface IAcUser<TProfile, TCompany> : IId<Guid> { ... }

// Entity layer (abstract)
abstract class AcUser<TProfile, TCompany, TUserToCompany, TAddress> { ... }

// Consuming project (concrete)
class User : AcUser<Profile, Company, UserToCompany, Address> { ... }
```

This allows the framework to define relationships without knowing concrete types.