Create Repository Interface

Create Repository Interface

Creates the repository interface that defines data access operations for an entity. Implementations (MockDB, MongoDB, etc.) will implement this interface.

Quick Reference

Location: src/​repositories/​{entity-name}.repository.ts Naming: Singular, kebab-case (e.g., note.repository.ts, course.repository.ts)

Instructions

Step 1: Create the Interface File

Create src/​repositories/​{entity-name}.repository.ts

Step 2: Import Schema Types

import type {
  {Entity}Type,
  Create{Entity}Type,
  Update{Entity}Type,
  {Entity}QueryParamsType,
  {Entity}IdType,
} from "@/​schemas/​{entity-name}.schema";
import type { PaginatedResultType } from "@/​schemas/​shared.schema";
import type { UserIdType } from "@/​schemas/​user.schemas";

Step 3: Define the Interface

export interface I{Entity}Repository {
  findAll(params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;
  findById(id: {Entity}IdType): Promise<{Entity}Type | null>;
  create(data: Create{Entity}Type, createdByUserId: UserIdType): Promise<{Entity}Type>;
  update(id: {Entity}IdType, data: Update{Entity}Type): Promise<{Entity}Type | null>;
  remove(id: {Entity}IdType): Promise<boolean>;
}

Standard CRUD Methods

Every repository interface should include these standard CRUD methods:

Patterns & Rules

Naming Conventions

• Interface name: I{Entity}Repository (e.g., INoteRepository, ICourseRepository)
• File name: {entity-name}.repository.ts (singular, kebab-case)

Return Type Patterns

• Single entity lookups: Return EntityType | null (null if not found)
• List operations: Return PaginatedResultType<EntityType> (always, even if empty)
• Create operations: Return the created EntityType (with generated ID and timestamps)
• Update operations: Return EntityType | null (null if entity doesn't exist)
• Delete operations: Return boolean (true if deleted, false if not found)

Parameter Patterns

• Create method: Takes Create{Entity}Type + createdByUserId: UserIdType
• Update method: Takes id separately (from URL) + Update{Entity}Type (from body)
• Query methods: Take {Entity}QueryParamsType for filtering/​pagination

Import Rules

• Always use path aliases: @/​schemas/​..., @/​repositories/​...
• Import types with import type { ... } for type-only imports
• Import from specific schema files, not barrel exports

Adding Custom Methods

Add custom methods based on your system's requirements. Common patterns include:

Query by Attribute (findByX)

Find entities by a specific attribute:

findByStatus(status: StatusType, params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;
findByOwner(ownerId: UserIdType, params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;
findByCategory(categoryId: CategoryIdType, params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;

Batch Operations

Operate on multiple entities at once:

// Batch queries
findAllByIds(ids: {Entity}IdType[], params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;
findAllByStatus(status: StatusType, params: {Entity}QueryParamsType): Promise<PaginatedResultType<{Entity}Type>>;

// Batch mutations
createMany(data: Create{Entity}Type[], createdByUserId: UserIdType): Promise<{Entity}Type[]>;
updateMany(ids: {Entity}IdType[], data: Update{Entity}Type): Promise<number>; // returns count updated
removeMany(ids: {Entity}IdType[]): Promise<number>; // returns count deleted
removeByOwner(ownerId: UserIdType): Promise<number>; // returns count deleted

Aggregation Operations

Get counts or summaries without fetching full entities:

countByStatus(status: StatusType): Promise<number>;
countByOwner(ownerId: UserIdType): Promise<number>;

Complete Example

import type {
  NoteType,
  CreateNoteType,
  UpdateNoteType,
  NoteQueryParamsType,
  NoteIdType,
} from "@/​schemas/​note.schema";
import type { PaginatedResultType } from "@/​schemas/​shared.schema";
import type { UserIdType } from "@/​schemas/​user.schemas";

export interface INoteRepository {
  // Standard CRUD
  findAll(params: NoteQueryParamsType): Promise<PaginatedResultType<NoteType>>;
  findById(id: NoteIdType): Promise<NoteType | null>;
  create(data: CreateNoteType, createdByUserId: UserIdType): Promise<NoteType>;
  update(id: NoteIdType, data: UpdateNoteType): Promise<NoteType | null>;
  remove(id: NoteIdType): Promise<boolean>;

  // Custom methods (assuming it was needed)
  findAllByIds(
    ids: NoteIdType[],
    params: NoteQueryParamsType,
  ): Promise<PaginatedResultType<NoteType>>;
}

Next Steps

After creating the interface, create an implementation:

• For development/​testing: Use create-mockdb-repository skill
• For production: Use create-mongodb-repository skill

What NOT to Do

• Do NOT include implementation details in the interface
• Do NOT use concrete types (use the interface for dependency injection)
• Do NOT add business logic - repositories only handle data access
• Do NOT throw domain errors - return null/​false and let the service handle it
• Do NOT use plural naming (notes.repository.ts) - use singular (note.repository.ts)