# @repo/cms-client -- Dual-Mode Payload Client

## Purpose

Provides a typed, uniform interface for accessing Payload CMS data via either the Local API (direct in-process calls) or the HTTP REST API (network requests). The consuming app chooses the mode at startup and injects the Payload instance -- this package never imports it.

## **NEVER import from `@repo/cms-core`, `@repo/core`, or any `apps/*` package.**

This package is completely standalone. The Payload instance is INJECTED at app startup, never imported by this package.

## File Structure

```
packages/cms-client/
  src/
    types.ts          # FindOptions, PayloadClientResult, PayloadClient interface
    client.ts         # createPayloadClient() factory -- returns Local or HTTP client
    local-client.ts   # LocalPayloadClient class -- wraps Payload Local API
    http-client.ts    # HTTPPayloadClient class -- wraps Payload REST API via fetch
    index.ts          # Package entry: re-exports factory, classes, and types
  package.json
  AGENTS.md
```

## Dual-Mode Initialization

### Local Mode (primary -- used for server-side code with direct DB access)

Local mode wraps the Payload Local API. It requires a live `Payload` instance, which is obtained via `getPayload()` in the consuming app:

```typescript
// Example: apps/web-next/src/lib/payload.ts
import { getPayload } from "payload";
import config from "@repo/cms-core/src/payload.config";
import { createPayloadClient } from "@repo/cms-client";

const payload = await getPayload({ config });
const client = createPayloadClient({ mode: "local", payload });

// Now use client.find(), client.create(), etc.
const articles = await client.find("articles", {
  where: { status: { equals: "published" } },
  sort: "-publishedAt",
  limit: 10,
});
```

### HTTP Mode (fallback -- used for external services without direct DB access)

HTTP mode makes REST calls to the Payload API. It only needs the base URL:

```typescript
import { createPayloadClient } from "@repo/cms-client";

const client = createPayloadClient({
  mode: "http",
  baseURL: "http://localhost:3001",
});

// Same API surface as local mode
const articles = await client.find("articles", {
  where: { status: { equals: "published" } },
  limit: 10,
});
```

## Initialization Table

| App / Context | Mode | How initialized | Why this mode |
|---|---|---|---|
| `apps/cms` (server-side) | Local | `getPayload({ config })` from `@repo/cms-core` | Same process as Payload, direct DB access |
| `apps/web-next` (server components/actions) | Local | `getPayload({ config })` from `@repo/cms-core` | Server-side rendering needs fast DB access |
| `apps/web-tanstack` (server loaders) | Local | `getPayload({ config })` from `@repo/cms-core` | Server-side data loading needs fast DB access |
| Client-side (browser) | N/A | Does not use this package directly | Browser goes through tRPC, server handles CMS access |
| External services / microservices | HTTP | `createPayloadClient({ mode: "http", baseURL })` | No access to Payload instance, only REST API |

## PayloadClient API Reference

All methods are available on both Local and HTTP clients via the `PayloadClient` interface.

### `find<T>(collection, options?): Promise<PayloadClientResult<T>>`

Paginated query for documents in a collection.

```typescript
const result = await client.find<Article>("articles", {
  where: { status: { equals: "published" } },
  sort: "-publishedAt",
  limit: 10,
  page: 1,
  depth: 2,
  locale: "en",
});
// result.docs, result.totalDocs, result.totalPages, etc.
```

### `findByID<T>(collection, id, options?): Promise<T>`

Fetch a single document by ID.

```typescript
const article = await client.findByID<Article>("articles", "abc123", {
  depth: 2,
});
```

### `create<T>(collection, data, options?): Promise<T>`

Create a new document.

```typescript
const newArticle = await client.create<Article>("articles", {
  title: "My Article",
  content: "...",
  author: "user-id-123",
  status: "draft",
}, { depth: 1 });
```

### `update<T>(collection, id, data, options?): Promise<T>`

Update an existing document (partial update).

```typescript
const updated = await client.update<Article>("articles", "abc123", {
  status: "published",
  publishedAt: new Date().toISOString(),
});
```

### `delete<T>(collection, id): Promise<T>`

Delete a document by ID.

```typescript
const deleted = await client.delete<Article>("articles", "abc123");
```

## FindOptions Interface

```typescript
interface FindOptions {
  where?: Record<string, unknown>;   // Payload query operators ({ field: { equals: value } })
  sort?: string;                     // Field name, prefix with "-" for descending
  limit?: number;                    // Max documents per page (default: 10)
  page?: number;                     // Page number (1-based)
  depth?: number;                    // Relationship population depth (default: 1)
  locale?: string;                   // Locale for localized fields
}
```

## PayloadClientResult Interface

```typescript
interface PayloadClientResult<T> {
  docs: T[];                  // Array of documents for current page
  totalDocs: number;          // Total matching documents across all pages
  limit: number;              // Max docs per page (as requested)
  totalPages: number;         // Total number of pages
  page: number;               // Current page number (1-based)
  pagingCounter: number;      // Index of first doc on current page
  hasPrevPage: boolean;       // Whether a previous page exists
  hasNextPage: boolean;       // Whether a next page exists
  prevPage: number | null;    // Previous page number, or null
  nextPage: number | null;    // Next page number, or null
}
```

## App Startup Pattern

The Payload instance is always created in the consuming app, then injected into the client:

```typescript
// apps/web-next/src/lib/payload.ts
import { getPayload } from "payload";
import config from "@repo/cms-core/src/payload.config";
import { createPayloadClient, type PayloadClient } from "@repo/cms-client";

let cachedClient: PayloadClient | null = null;

export async function getPayloadClient(): Promise<PayloadClient> {
  if (cachedClient) return cachedClient;

  const payload = await getPayload({ config });
  cachedClient = createPayloadClient({ mode: "local", payload });
  return cachedClient;
}
```

This pattern ensures:
1. The Payload instance is created once and reused
2. The cms-client package never imports config or Payload itself
3. Each app controls its own initialization

## Type Generation

Payload generates TypeScript types from your collection/global definitions:

```bash
cd apps/cms && pnpm generate:types
# Runs: payload generate:types
# Outputs to: packages/cms-core/src/payload-types.ts (configured in payload.config.ts)
```

After adding or modifying collections/globals in `@repo/cms-core`, re-run type generation to keep types in sync.

## Dependencies

| Dependency | Purpose |
|---|---|
| `payload` | `Payload` type for the Local API client constructor (type-only at build time) |

## Cross-References

- **CMS configuration:** `packages/cms-core/` -- see `packages/cms-core/AGENTS.md`
- **CMS app (where getPayload is called):** `apps/cms/` -- see `apps/cms/AGENTS.md`
- **Core use cases (consumers of this client):** `packages/core/` -- see `packages/core/AGENTS.md`