Boundaries (Config & Request Pipeline)

A boundary.ts acts as a folder-scoped configuration and request pipeline in your file-system routing architecture.

Any boundary.ts applies to every route in its folder and all subfolders recursively. Instead of manually registering middleware chains or route guards, placing a boundary.ts configures CORS, Headers, Excluded Paths, Dependency Injection, and an auto-detected request pipeline cleanly scoped to that sub-tree.

Anatomy of a Boundary

A boundary.ts has two distinct, independent parts:

Config — pure data, declared via defineBoundary() (functional) or the @Boundary() class decorator (OOP). It configures CORS, headers, DI providers, timeout, and exclusion rules.
Pipeline — real code, auto-detected by function signature. No manual pipeline registration is needed.

Signature	Detected as	Execution timing
`(req, res, next)`	Chain Step	Runs in file/declaration order, before the route
`(ctx, next)` — default export (functional) or class method `handle(ctx, next)` (OOP)	Request Wrapper	Wraps around all chain steps and the nested route/boundary

1. Functional Paradigm

In functional style, export config = defineBoundary(...), export named middleware functions (req, res, next) for chain steps, and optionally provide a default export function (ctx, next) as an onion-style wrapper.

src/http/admin/boundary.ts

import { defineBoundary } from 'exisjs/router'import type { Request, Response, Next, BoundaryContext } from 'exisjs/router'import { UnauthorizedError } from 'exisjs/error'
// 1. Configuration (CORS, Headers, Exclusions, DI Providers)export const config = defineBoundary({  cors: {    origin: ['https://admin.yourdomain.com'],    credentials: true,  },  headers: {    'X-Admin-Api-Version': '2.0',  },  exclude: [    '/admin/health',    { path: '/admin/public/*', method: 'GET' }  ],})
// 2. Chain Step (auto-detected by (req, res, next) signature)export function requireAuth(req: Request, res: Response, next: Next) {  if (!req.headers['x-api-key']) {    throw new UnauthorizedError('Missing API key')  }  next()}
// 3. Wrapper (auto-detected as default export with (ctx, next) signature)export default async function (ctx: BoundaryContext, next: Next) {  const start = Date.now()  try {    const result = await next()    const duration = Date.now() - start    ctx.res.setHeader('X-Response-Time', `${duration}ms`)    return { success: true, data: result }  } catch (err: any) {    return {      success: false,      error: { message: err.message || 'Internal error' },    }  }}

2. Class-Based (OOP) Paradigm

In OOP style, decorate a class with @Boundary(...). Named methods taking (req, res, next) are auto-detected as chain steps, and a method named handle(ctx, next) serves as the request wrapper.

src/http/admin/boundary.ts

import { Boundary } from 'exisjs/decorators'import type { Request, Response, Next, BoundaryContext } from 'exisjs/router'import { UnauthorizedError } from 'exisjs/error'
@Boundary({  cors: {    origin: ['https://admin.yourdomain.com'],    credentials: true,  },  headers: {    'X-Admin-Api-Version': '2.0',  },  exclude: ['/admin/health'],})export default class AdminBoundary {  // Chain step  requireAuth(req: Request, res: Response, next: Next) {    if (!req.headers['x-api-key']) {      throw new UnauthorizedError('Missing API key')    }    next()  }
  // Wrapper  async handle(ctx: BoundaryContext, next: Next) {    const start = Date.now()    const result = await next()    ctx.res.setHeader('X-Response-Time', `${Date.now() - start}ms`)    return result  }}

Cascading & Inheritance

Boundaries cascade down the directory tree. For instance:

src/http/├── boundary.ts       # Root Boundary (applies to /api/*)└── admin/    ├── boundary.ts   # Admin Boundary (applies to /api/admin/*)    └── users/        └── route.ts  # Handled by both Root Boundary and Admin Boundary

Wrappers & Chain Steps: Outer boundaries execute first. Root wrappers wrap nested wrappers, and root chain steps run before nested chain steps.
CORS & Headers: Sub-boundaries inherit and merge or override parent headers and CORS policies.
Exclusions: When a route matches an exclusion pattern (e.g. /admin/health in exclude), that boundary's chain steps and wrappers are bypassed for the request.

Dependency Injection via Providers

Boundaries also act as IoC module scopes. You can scope providers to a directory tree using providers:

src/http/users/boundary.ts

import { defineBoundary } from 'exisjs/router'import { UsersRepository } from './repository'
export const config = defineBoundary({  providers: [    ['UsersRepository', { useClass: UsersRepository }],  ],})

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