# Domain Entities — Unit 1: master-backend

## Entity Overview

```mermaid
graph TD
    MasterDbCtx["MasterDbContext\n(per-module EF Core DbContext)"]
    CmsInst["CmsInstance\n(aggregate root)"]
    Status["CmsInstanceStatus\n(enum)"]
    Opts["MasterModuleOptions\n(config POCO)"]
    DP["IDataProtector\n(ApiKey encryption)"]
    DTO["CmsInstanceDto\n(API response shape)"]
    CreateReq["CreateCmsInstanceRequest\n(API input)"]
    UpdateReq["UpdateStatusRequest\n(API input)"]
    UpdateRes["UpdateStatusResult\n(API response for status update)"]

    MasterDbCtx -->|"owns"| CmsInst
    CmsInst -->|"has"| Status
    CmsInst -->|"ApiKey encrypted via"| DP
    CmsInst -->|"projected to"| DTO
    CreateReq -->|"creates"| CmsInst
    UpdateReq -->|"mutates status of"| CmsInst
    UpdateRes -->|"returned from UpdateStatusAsync"| CmsInst
    Opts -->|"IntegrityCheckIntervalMinutes"| MasterDbCtx
    Opts -->|"MasterUrl fallback"| MasterDbCtx

    classDef entity fill:#9ae6b4,stroke:#2f855a,stroke-width:2px,color:#000
    classDef infra fill:#63b3ed,stroke:#2b6cb0,stroke-width:1px,color:#000
    classDef dto fill:#FFC107,stroke:#F57F17,stroke-width:1px,color:#000
    classDef config fill:#CE93D8,stroke:#6A1B9A,stroke-width:1px,color:#000
    class CmsInst entity
    class MasterDbCtx,DP infra
    class Status,DTO,CreateReq,UpdateReq,UpdateRes dto
    class Opts config
```

Text alternative: MasterDbContext owns CmsInstance; CmsInstance has a Status enum and its ApiKey is encrypted via IDataProtector; request/response shapes map to and from CmsInstance.

---

## CmsInstance

**Table**: `CmsInstances` (owned by `MasterDbContext`, migrations in `SlpModularCms.Modules.Master`)

| Field | Type | Nullable | Notes |
|-------|------|----------|-------|
| `Id` | `Guid` | No | Primary key |
| `Name` | `string` | No | Friendly display name; required |
| `Url` | `string` | No | Base URL of slave CMS API; must start with `http://` or `https://` |
| `ApiKey` | `string` | No | Encrypted via ASP.NET Core Data Protection before storage; decrypted before HTTP calls |
| `Status` | `CmsInstanceStatus` | No | Default: `Available` on creation |
| `DisableMessage` | `string?` | Yes | Required when `Status = NotAvailable`; null otherwise |
| `LastContactedAt` | `DateTimeOffset?` | Yes | Null = never successfully contacted; set on successful registration or integrity check |
| `LastStatusPushedAt` | `DateTimeOffset?` | Yes | Null = status never successfully pushed; set after successful `PushStatusAsync` |
| `LastIntegrityCheckFailedAt` | `DateTimeOffset?` | Yes | Null = no pending failure; set when integrity check cannot reach slave or re-registration fails; cleared on next successful contact |

---

## CmsInstanceStatus

```csharp
public enum CmsInstanceStatus
{
    Available = 0,
    NotAvailable = 1,
    Inactive = 2,
}
```

| Value | Meaning | Master Contacts Slave? |
|-------|---------|----------------------|
| `Available` | Slave is enabled; normal operation | Yes (status push + integrity checks) |
| `NotAvailable` | Slave is disabled; `DisableMessage` served to end-users | Yes (status push + integrity checks) |
| `Inactive` | Soft-removed; greyed out in UI | **No** — all HTTP contact is halted |

---

## MasterModuleOptions

**Config section**: `"MasterModule"` in `appsettings.json`

| Property | Type | Default | Side | Notes |
|----------|------|---------|------|-------|
| `IntegrityCheckIntervalMinutes` | `int` | `60` | Master | Interval for `IntegrityCheckBackgroundService` |
| `MasterUrl` | `string?` | `null` | Master | Fallback public URL of this master CMS; used by background service when `HttpContext` is unavailable |
| `CacheMinutes` | `int` | `60` | Slave | Slave pull cache interval (used by Unit 2) |
| `ApiKey` | `string?` | `null` | Slave | Slave API key for validating incoming master requests (used by Unit 2) |

---

## CmsInstanceDto (API Response)

**Rule**: `ApiKey` is **never** included (NFR-MASTER-03).

| Property | Type | Notes |
|----------|------|-------|
| `Id` | `Guid` | |
| `Name` | `string` | |
| `Url` | `string` | |
| `Status` | `string` | Serialized as string (`"Available"` / `"NotAvailable"` / `"Inactive"`) |
| `DisableMessage` | `string?` | |
| `LastContactedAt` | `DateTimeOffset?` | |
| `LastStatusPushedAt` | `DateTimeOffset?` | |
| `LastIntegrityCheckFailedAt` | `DateTimeOffset?` | Visible in UI so owner knows which slaves have pending check failures |

---

## CreateCmsInstanceRequest (API Input)

| Property | Type | Validation |
|----------|------|-----------|
| `Name` | `string` | Required, non-empty |
| `Url` | `string` | Required; must start with `http://` or `https://` |
| `ApiKey` | `string` | Required, non-empty |

---

## UpdateStatusRequest (API Input)

| Property | Type | Validation |
|----------|------|-----------|
| `Status` | `CmsInstanceStatus` | Required; must be valid enum value |
| `DisableMessage` | `string?` | Required and non-empty when `Status = NotAvailable`; ignored otherwise |

---

## UpdateStatusResult (Service Return / API Response)

| Property | Type | Notes |
|----------|------|-------|
| `Success` | `bool` | Always `true` when status persisted to DB (DB is the authority) |
| `SlaveContactSuccess` | `bool` | `true` if HTTP push to slave succeeded; `false` if push failed (slave unreachable); not applicable for `Inactive` transitions (returns `true`) |