Data API Type System

This directory contains the type definitions and utilities for Cherry Studio's Data API system, which provides type-safe IPC communication between renderer and main processes.

Directory Structure

src/shared/data/api/
├── types.ts           # Core request/response types and API utilities
├── paths.ts           # Path template literal type utilities
├── errors.ts          # Error handling: ErrorCode, DataApiError class, factory
└── schemas/
    ├── apiSchemas.ts  # Schema composition (merges all domain schemas)
    └── *.ts           # Domain-specific schemas

File Responsibilities

File	Purpose
types.ts	Core types (DataRequest, DataResponse, ApiClient) and schema utilities
paths.ts	Template literal types for path resolution (/items/:id → /items/${string})
errors.ts	ErrorCode enum, DataApiError class, DataApiErrorFactory, retryability config
schemas/apiSchemas.ts	Composes all domain schemas into ApiSchemas using intersection types
schemas/*.ts	Domain-specific API definitions and DTOs

Schema File Organization

Schema files in schemas/ are organized by the domain of the entity being operated on or returned, not by URL prefix. A parent resource in the path (:topicId, :providerId) only scopes the operation — it does not determine which file the route belongs in.

Route	Returned entity	Lives in
'/topics/:topicId/messages'	Message	messages.ts
'/topics/:topicId/tree'	Tree (Message-derived view)	messages.ts
'/topics/:id/active-node'	ActiveNodeResponse (Topic state)	topics.ts

When a route's URL parent and returned entity disagree, the entity wins.

Import Conventions

Infrastructure Types (direct module imports)

Import infrastructure directly from its module — there is no barrel. Core types, pagination, and query params live in types; errors live in errors; path utilities live in paths:

import type {
  DataRequest,
  DataResponse,
  ApiClient,
  // Pagination types
  OffsetPaginationParams,
  OffsetPaginationResponse,
  CursorPaginationParams,
  CursorPaginationResponse,
  PaginationResponse,
  // Query parameter types
  SortParams,
  SearchParams
} from '@shared/data/api/types'

// Pagination type guards also live in `types`
import { isOffsetPaginationResponse, isCursorPaginationResponse } from '@shared/data/api/types'

import { ErrorCode, DataApiError, DataApiErrorFactory, isDataApiError, toDataApiError } from '@shared/data/api/errors'

Domain DTOs (directly from schema files)

Import domain-specific types directly from their schema files:

// Topic domain
import type { Topic, CreateTopicDto, UpdateTopicDto } from '@shared/data/api/schemas/topics'

// Message domain
import type { Message, CreateMessageDto } from '@shared/data/api/schemas/messages'

Pagination Types

The API system supports two pagination modes with composable query parameters. This section is the type reference only — for mode selection (offset vs cursor), cursor exclusivity semantics, worked examples, and client-side derivations, see the Pagination Guide.

Request Parameters

Type	Fields	Use Case
OffsetPaginationParams	page?, limit?	Traditional page-based navigation
CursorPaginationParams	cursor?, limit?	Infinite scroll, real-time feeds. cursor is an exclusive boundary — the cursor item is not returned (see Pagination Guide)
SortParams	sortBy?, sortOrder?	Sorting (combine as needed)
SearchParams	search?	Text search (combine as needed)

Response Types

Type	Fields	Description
OffsetPaginationResponse<T>	items, total, page	Page-based results
CursorPaginationResponse<T>	items, nextCursor?	Cursor-based results
PaginationResponse<T>	Union of both	When either mode is acceptable; narrow with isOffsetPaginationResponse / isCursorPaginationResponse

Adding a New Domain Schema

1. Create the schema file (e.g., schemas/topic.ts):

import * as z from 'zod'
import type {
  OffsetPaginationParams,
  OffsetPaginationResponse,
  SearchParams,
  SortParams
} from '../apiTypes'

// Field atoms — share between entity, DTO, and query
export const TopicNameSchema = z.string().trim().min(1).max(128)

// Entity schema (z.strictObject rejects unknown fields)
export const TopicSchema = z.strictObject({
  id: z.uuidv4(),
  name: TopicNameSchema,
  createdAt: z.iso.datetime()
})
export type Topic = z.infer<typeof TopicSchema>

// DTO — whitelist pick from entity (see api-design-guidelines.md § Zod Schema & DTO Conventions)
export const CreateTopicSchema = TopicSchema.pick({ name: true })
export type CreateTopicDto = z.infer<typeof CreateTopicSchema>

// API Schema — validation happens via AssertValidSchemas in index.ts
export type TopicSchemas = {
  '/topics': {
    GET: {
      query?: OffsetPaginationParams & SortParams & SearchParams
      response: OffsetPaginationResponse<Topic>  // response is required
    }
    POST: {
      body: CreateTopicDto
      response: Topic
    }
  }
  '/topics/:id': {
    GET: {
      params: { id: string }
      response: Topic
    }
  }
}

Validation: Schemas are validated at composition level via AssertValidSchemas in schemas/apiSchemas.ts:

• Ensures only valid HTTP methods (GET, POST, PUT, DELETE, PATCH)
• Requires response field for each endpoint
• Invalid schemas cause TypeScript errors at the composition point

Design Guidelines: Before creating new schemas, review the API Design Guidelines for path naming, HTTP methods, and error handling conventions.

2. Register in schemas/apiSchemas.ts:

import type { TopicSchemas } from './topics'

// AssertValidSchemas provides fallback validation even if ValidateSchema is forgotten
export type ApiSchemas = AssertValidSchemas<TopicSchemas & MessageSchemas>

3. Implement handlers in src/main/data/api/handlers/

Type Safety Features

Path Resolution

The system uses template literal types to map concrete paths to schema paths:

// Concrete path '/topics/abc123' maps to schema path '/topics/:id'
api.get('/topics/abc123')  // TypeScript knows this returns Topic

Exhaustive Handler Checking

ApiImplementation type ensures all schema endpoints have handlers:

// TypeScript will error if any endpoint is missing
const handlers: ApiImplementation = {
  '/topics': {
    GET: async () => { /* ... */ },
    POST: async ({ body }) => { /* ... */ }
  }
  // Missing '/topics/:id' would cause compile error
}

Type-Safe Client

ApiClient provides fully typed methods:

const topic = await api.get('/topics/123')        // Returns Topic
const topics = await api.get('/topics', {
  query: { page: 1, limit: 20, search: 'hello' }
})  // Returns OffsetPaginationResponse<Topic>
await api.post('/topics', { body: { name: 'New' } })  // Body is typed as CreateTopicDto

Error Handling

The error system provides type-safe error handling with automatic retryability detection:

import {
  DataApiError,
  DataApiErrorFactory,
  ErrorCode,
  isDataApiError,
  toDataApiError
} from '@shared/data/api/errors'

// Create errors using the factory (recommended)
throw DataApiErrorFactory.notFound('Topic', id)
throw DataApiErrorFactory.validation({ name: ['Name is required'] })
throw DataApiErrorFactory.timeout('fetch topics', 3000)
throw DataApiErrorFactory.database(originalError, 'insert topic')

// Or create directly with the class
throw new DataApiError(
  ErrorCode.NOT_FOUND,
  'Topic not found',
  404,
  { resource: 'Topic', id: 'abc123' }
)

// Check if error is retryable (for automatic retry logic)
if (error instanceof DataApiError && error.isRetryable) {
  await retry(operation)
}

// Check error type
if (error instanceof DataApiError) {
  if (error.isClientError) {
    // 4xx - issue with the request
  } else if (error.isServerError) {
    // 5xx - server-side issue
  }
}

// Convert any error to DataApiError
const apiError = toDataApiError(unknownError, 'context')

// Serialize for IPC (Main → Renderer)
const serialized = apiError.toJSON()

// Reconstruct from IPC response (Renderer)
const reconstructed = DataApiError.fromJSON(response.error)

Retryable Error Codes

The following errors are automatically considered retryable:

• SERVICE_UNAVAILABLE (503)
• TIMEOUT (504)
• RATE_LIMIT_EXCEEDED (429)
• DATABASE_ERROR (500)
• INTERNAL_SERVER_ERROR (500)
• RESOURCE_LOCKED (423)

Architecture Overview

Renderer                           Main
────────────────────────────────────────────────────
DataApiService  ──IPC──►  IpcAdapter  ──►  ApiServer
     │                                        │
     │                                        ▼
 ApiClient                              MiddlewareEngine
 (typed)                                      │
                                              ▼
                                         Handlers
                                         (typed)

• Renderer: Uses DataApiService with type-safe ApiClient interface
• IPC: Requests serialized via IpcAdapter
• Main: ApiServer routes to handlers through MiddlewareEngine
• Type Safety: End-to-end types from client call to handler implementation