@syncafricabs/kernspark-koa

Koa adapter for the SyncAfrica KernSpark ecosystem. This package provides production-ready Koa middleware, error handlers, and response utilities that integrate the framework-independent @syncafricabs/kernspark-core with Koa.

Table of Contents

• What is it?
• Why it exists
• Features
• Installation
• Quick Start
• Comprehensive Usage
  • Middleware
  • Error Handling
  • Response Adapter
  • Complete Server Example
• API Reference
• Error Handling Reference
• TypeScript Support
• Compatibility Matrix
• Contributing
• License
• Author

What is it?

@syncafricabs/kernspark-koa is a framework adapter that bridges the SyncAfrica KernSpark Core with Koa. It provides:

• KoaIntegration - Maps ApplicationError instances to standardized JSON API responses
• KoaResponseAdapter - Helper methods for sending consistent success and error responses
• koaMiddleware - Request/response logging and correlation ID tracking
• Error handling - Centralized error handling for Koa applications

The adapter follows the adapter pattern: it depends on @syncafricabs/kernspark-core (the framework-independent layer) and Koa only in the adapter layer. The core has zero framework dependencies.

Why it exists

Modern web applications benefit from a KernSpark - a common set of contracts, types, and behaviors shared across bounded contexts. The SyncAfrica KernSpark provides:

1. Standardized API envelopes (ApiSuccess / ApiError)
2. Rich domain error hierarchy (ValidationError, BusinessError, AuthenticationError, etc.)
3. Result types (Result, Ok, Err)
4. Domain primitives (UUID, Money, Entity, ValueObject)

Without adapters, each team would reimplement framework-specific plumbing to use these core types. This adapter eliminates that duplication by providing Koa-specific bindings.

Features

• Middleware support - Drop-in Koa middleware for correlation ID and logging
• Standardized JSON responses - All responses follow the ApiSuccess / ApiError envelope
• Zero-configuration error handling - Centralized error handler for Koa
• Full TypeScript support - Comprehensive type definitions included
• Production-ready - Proper error handling, stack traces, cause chains
• Framework isolation - Core has no Koa dependencies

Installation

npm install @syncafricabs/kernspark-koa @syncafricabs/kernspark-core koa

Or with your preferred package manager:

yarn add @syncafricabs/kernspark-koa @syncafricabs/kernspark-core koa

pnpm add @syncafricabs/kernspark-koa @syncafricabs/kernspark-core koa

Quick Start

import Koa from 'koa';
import { koaMiddleware, koaErrorHandler, KoaResponseAdapter } from '@syncafricabs/kernspark-koa';
import { NotFoundError, ValidationError } from '@syncafricabs/kernspark-core';

const app = new Koa();

app.use(koaMiddleware({
  correlationIdHeader: 'x-correlation-id',
  logRequests: true,
  logResponses: true,
}));

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    koaErrorHandler(error, ctx, () => {});
  }
});

app.get('/users/:id', async (ctx) => {
  const user = findUser(ctx.params.id);

  if (!user) {
    throw new NotFoundError('User not found');
  }

  KoaResponseAdapter.ok(ctx, user, 'User retrieved successfully');
});

app.listen(3000, () => console.log('Server running on port 3000'));

Comprehensive Usage

Middleware

Correlation ID Middleware

The correlation ID middleware generates or propagates a unique identifier for each request.

import { koaMiddleware, KoaMiddlewareOptions } from '@syncafricabs/kernspark-koa';

const options: KoaMiddlewareOptions = {
  correlationIdHeader: 'x-correlation-id',
  logRequests: true,
  logResponses: true,
  logErrors: true,
  sensitiveFields: ['password', 'token', 'secret', 'apiKey', 'creditCard'],
  logger: (meta) => {
    console.log(JSON.stringify(meta));
  },
};

app.use(koaMiddleware(options));

Sample log output:

{
  "method": "GET",
  "url": "/api/users",
  "correlationId": "550e8400-e29b-41d4-a716-446655440000"
}

{
  "method": "POST",
  "url": "/api/users",
  "statusCode": 201,
  "contentLength": 156,
  "responseTime": 45,
  "correlationId": "550e8400-e29b-41d4-a716-446655440000"
}

Error Handling

Basic Setup

import { koaErrorHandler } from '@syncafricabs/kernspark-koa';

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    koaErrorHandler(error, ctx, () => {});
  }
});

Custom Error Handler Configuration

import { createKoaErrorHandler, KoaErrorHandlerOptions } from '@syncafricabs/kernspark-koa';

const options: KoaErrorHandlerOptions = {
  logErrors: true,
  logStack: true,
  includeCause: true,
  includeStack: process.env.NODE_ENV === 'development',
  defaultStatusCode: 500,
  logger: (error, ctx) => {
    console.error({
      correlationId: ctx.correlationId,
      method: ctx.method,
      url: ctx.url,
      error: error.message,
      stack: error.stack,
    });
  },
};

app.use(async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    createKoaErrorHandler(options)(error, ctx, () => {});
  }
});

Throwing Errors from Route Handlers

import {
  ValidationError,
  MissingFieldsError,
  BusinessError,
  ConflictError,
  NotFoundError,
  AuthenticationError,
  InvalidTokenError,
  AuthorizationError,
  PermissionDeniedError,
  InfrastructureError,
  ExternalServiceError,
} from '@syncafricabs/kernspark-core';

app.post('/users', async (ctx) => {
  const { name, email } = ctx.request.body;

  if (!name || !email) {
    throw new MissingFieldsError('Name and email are required');
  }

  if (!isValidEmail(email)) {
    throw new ValidationError('INVALID_EMAIL', 'Email format is invalid');
  }

  if (userExists(email)) {
    throw new ConflictError('User with this email already exists');
  }

  const user = createUser(ctx.request.body);
  KoaResponseAdapter.created(ctx, user, 'User created successfully');
});

app.get('/users/:id', async (ctx) => {
  const user = findUser(ctx.params.id);
  if (!user) {
    throw new NotFoundError('User not found');
  }
  KoaResponseAdapter.ok(ctx, user);
});

app.delete('/users/:id', async (ctx) => {
  if (!ctx.state.user) {
    throw new InvalidTokenError('Invalid or expired token');
  }

  if (!ctx.state.user.canDeleteUsers) {
    throw new PermissionDeniedError('You do not have permission to delete users');
  }

  deleteUser(ctx.params.id);
  KoaResponseAdapter.noContent(ctx, 'User deleted successfully');
});

Response Adapter

Success Responses

import { KoaResponseAdapter } from '@syncafricabs/kernspark-koa';

// 200 OK with data
KoaResponseAdapter.ok(ctx, user, 'User retrieved');

// 201 Created with data
KoaResponseAdapter.created(ctx, user, 'User created');

// 204 No Content
KoaResponseAdapter.noContent(ctx);

// Send raw ApiSuccess
const success = { status: 200, success: true, data: users, message: 'OK' };
KoaResponseAdapter.sendSuccess(ctx, success);

Error Responses

import { KoaResponseAdapter } from '@syncafricabs/kernspark-koa';

KoaResponseAdapter.badRequest(ctx, 'MISSING_FIELDS', 'Email and password are required');
KoaResponseAdapter.unauthorized(ctx, 'INVALID_CREDENTIALS', 'Invalid email or password');
KoaResponseAdapter.forbidden(ctx, 'PERMISSION_DENIED', 'You do not have permission');
KoaResponseAdapter.notFound(ctx, 'NOT_FOUND', 'User not found');
KoaResponseAdapter.conflict(ctx, 'CONFLICT', 'Resource already exists');
KoaResponseAdapter.unprocessableEntity(ctx, 'INVALID_DATA', 'Invalid request data');
KoaResponseAdapter.tooManyRequests(ctx, 'RATE_LIMIT_EXCEEDED', 'Too many requests');
KoaResponseAdapter.internalServerError(ctx, 'INTERNAL_ERROR', 'An unexpected error occurred');
KoaResponseAdapter.badGateway(ctx, 'BAD_GATEWAY', 'Upstream service error');
KoaResponseAdapter.serviceUnavailable(ctx, 'SERVICE_UNAVAILABLE', 'Service temporarily unavailable');
KoaResponseAdapter.gatewayTimeout(ctx, 'GATEWAY_TIMEOUT', 'Upstream service timeout');

Complete Server Example

import Koa from 'koa';
import { koaMiddleware, koaErrorHandler, KoaResponseAdapter } from '@syncafricabs/kernspark-koa';
import { NotFoundError, ValidationError, ConflictError } from '@syncafricabs/kernspark-core';

const app = new Koa();

// Middleware
app.use(koaMiddleware({
  correlationIdHeader: 'x-correlation-id',
  logRequests: true,
  logResponses: true,
  sensitiveFields: ['password', 'token', 'secret'],
}));

// Error handling
app.use(async (ctx, next) => {
  try {
    await next();
  } catch (error) {
    koaErrorHandler(error, ctx, () => {});
  }
});

// Routes
app.get('/users/:id', async (ctx) => {
  const user = findUser(ctx.params.id);
  if (!user) {
    throw new NotFoundError('User not found');
  }
  KoaResponseAdapter.ok(ctx, user, 'User retrieved successfully');
});

app.post('/users', async (ctx) => {
  const { name, email } = ctx.request.body;

  if (!name || !email) {
    throw new ValidationError('MISSING_FIELDS', 'Name and email are required');
  }

  if (findUserByEmail(email)) {
    throw new ConflictError('User with this email already exists');
  }

  const user = createUser(ctx.request.body);
  KoaResponseAdapter.created(ctx, user, 'User created successfully');
});

app.listen(3000, () => console.log('Server running on port 3000'));

API Reference

koaErrorHandler

Koa error handling middleware. Catches all errors and maps them to standardized JSON responses.

function koaErrorHandler(error: Error, ctx: Context, next: Next): void;

createKoaErrorHandler(options?: KoaErrorHandlerOptions)

Creates a customized error handler.

| Option | Type | Default | Description | |--------|------|---------|-------------| | logErrors | boolean | true | Enable/disable error logging | | logStack | boolean | false | Include stack traces in logs | | includeCause | boolean | true | Include error cause in response | | includeStack | boolean | false | Include stack traces in response (dev only) | | defaultStatusCode | number | 500 | Default status for unknown errors | | logger | function | console.error | Custom logger function |

KoaResponseAdapter

Static utility class for sending responses.

| Method | HTTP Status | Description | |--------|-------------|-------------| | ok(ctx, data?, message?) | 200 | Send success response with data | | created(ctx, data?, message?) | 201 | Send created response with data | | noContent(ctx, message?) | 204 | Send no content response | | sendSuccess(ctx, apiSuccess) | varies | Send raw ApiSuccess | | sendError(ctx, apiError) | varies | Send raw ApiError | | badRequest(ctx, errorCode, message) | 400 | Send bad request error | | unauthorized(ctx, errorCode, message) | 401 | Send unauthorized error | | forbidden(ctx, errorCode, message) | 403 | Send forbidden error | | notFound(ctx, errorCode, message) | 404 | Send not found error | | conflict(ctx, errorCode, message) | 409 | Send conflict error | | unprocessableEntity(ctx, errorCode, message) | 422 | Send unprocessable entity error | | tooManyRequests(ctx, errorCode, message) | 429 | Send too many requests error | | internalServerError(ctx, errorCode, message) | 500 | Send internal server error | | badGateway(ctx, errorCode, message) | 502 | Send bad gateway error | | serviceUnavailable(ctx, errorCode, message) | 503 | Send service unavailable error | | gatewayTimeout(ctx, errorCode, message) | 504 | Send gateway timeout error |

koaMiddleware(options?: KoaMiddlewareOptions)

Koa middleware for correlation ID and request/response logging.

| Option | Type | Default | Description | |--------|------|---------|-------------| | correlationIdHeader | string | 'x-correlation-id' | Header name for correlation ID | | logRequests | boolean | true | Log incoming requests | | logResponses | boolean | true | Log outgoing responses | | logErrors | boolean | true | Log errors | | sensitiveFields | string[] | ['password', 'token', 'secret', ...] | Body fields to redact | | logger | function | console.info | Custom logger function |

Error Handling Reference

The error handler maps the following ApplicationError subclasses:

| Error Class | HTTP Status | Error Code | |-------------|-------------|------------| | ValidationError | 400 | Custom (e.g., INVALID, MISSING_FIELDS) | | MissingFieldsError | 400 | MISSING_FIELDS | | BusinessError | Varies | Custom | | ConflictError | 409 | CONFLICT | | InsufficientFundsError | 400 | INSUFFICIENT_FUNDS | | QuotaExceededError | 429 | QUOTA_EXCEEDED | | NotFoundError | 404 | NOT_FOUND | | ExpiredError | 410 | EXPIRED | | TooManyRequestsError | 429 | TOO_MANY_REQUESTS | | PaymentRequiredError | 402 | PAYMENT_REQUIRED | | LockedError | 423 | LOCKED | | AccountSuspendedError | 403 | ACCOUNT_SUSPENDED | | FeatureNotAvailableError | 501 | FEATURE_NOT_AVAILABLE | | DataIntegrityError | 422 | DATA_INTEGRITY_ERROR | | AuthenticationError | 401 | Custom (e.g., INVALID_TOKEN) | | InvalidTokenError | 401 | INVALID_TOKEN | | TokenExpiredError | 401 | TOKEN_EXPIRED | | SessionExpiredError | 401 | SESSION_EXPIRED | | AuthorizationError | Varies | Custom | | PermissionDeniedError | 403 | PERMISSION_DENIED | | NotAllowedError | 403 | NOT_ALLOWED | | InfrastructureError | Varies | Custom | | ExternalServiceError | 502 | EXTERNAL_SERVICE_ERROR | | BadGatewayError | 502 | BAD_GATEWAY | | GatewayTimeoutError | 504 | GATEWAY_TIMEOUT | | ServiceUnavailableError | 503 | SERVICE_UNAVAILABLE | | RequestFailedError | 500 | REQUEST_FAILED | | NotImplementedError | 501 | NOT_IMPLEMENTED | | MaintenanceModeError | 503 | MAINTENANCE_MODE |

Unknown ApplicationError instances use their embedded statusCode. Non-ApplicationError errors return HTTP 500 with INTERNAL_SERVER_ERROR code.

TypeScript Support

Full TypeScript support with strict mode enabled. The adapter extends Koa types:

import { Context, Next } from 'koa';

// Koa context augmentation for correlation ID
declare module 'koa' {
  interface Context {
    correlationId?: string;
  }
}

Strict Mode

This package is compiled with strict: true. Enable strict mode in your project for full type safety:

{
  "compilerOptions": {
    "strict": true,
    "noImplicitAny": true,
    "strictNullChecks": true
  }
}

Compatibility Matrix

| Package Version | Node.js | Koa | @syncafricabs/kernspark-core | |----------------|---------|-----|----------------------------------| | 1.0.0 | >=18.0.0 | ^2.14.0 | ^1.0.0 |

| Feature | Koa 2.14+ | |---------|-------------| | Middleware | Supported | | Error handling | Supported | | Request/response logging | Supported | | Correlation ID propagation | Supported | | TypeScript 5.0+ | Supported |

Contributing

1. Fork the repository
2. Create your feature branch: git checkout -b feature/my-feature
3. Commit your changes: git commit -am 'Add my feature'
4. Push to the branch: git push origin feature/my-feature
5. Submit a pull request

Development Setup

# Clone the repository
git clone https://github.com/iamprovy-dev/kernspark-js.git
cd kernspark/packages/kernspark-koa

# Install dependencies
npm install

# Build
npm run build

# Run lint
npm run lint

# Run tests
npm test

Code Standards

• Use TypeScript with strict mode
• Follow the existing code style (2-space indentation, semicolons)
• Ensure all tests pass before submitting PR

License

Apache-2.0

Author

Providence Chikukwa

• Email: [email protected]
• GitHub: https://github.com/iamprovy-dev
• LinkedIn: https://www.linkedin.com/in/provychikukwa
• Organization: SyncAfrica Business Solutions