goplt/docs/requirements.md

Requirements

1️⃣ HIGH‑LEVEL ARCHITECTURAL PRINCIPLES

Principle	Why it matters for a modular platform	How to enforce it
Separation of Concerns (SoC)	Keeps core services (auth, audit, config) independent from business modules.	Use layered or hexagonal/clean‑architecture boundaries.
Domain‑Driven Design (DDD) Bounded Contexts	Allows each module to own its own model & rules while sharing a common identity kernel.	Define a Core Context (Identity, Security, Infrastructure) and Feature Contexts (Billing, CMS, Chat, …).
Modular Monolith → Micro‑service‑ready	Start simple (single process) but keep each module in its own package so you can later split to services if needed.	Package each module as an independent library with its own DI container‑module and routing.
Plug‑in / Extension‑point model	Enables customers or internal teams to drop new features without touching core code.	Export well‑defined interfaces (e.g., IUserProvider, IPermissionResolver, IModuleInitializer).
API‑First	Guarantees that any UI (web, mobile, CLI) can be built on top of the same contract.	Publish OpenAPI/GraphQL schema as part of the build artefact.
Security‑by‑Design	The platform will hold user credentials, roles and possibly PII.	Centralize authentication, authorization, audit, rate‑limiting, CORS, CSP, secure defaults.
Observability	You need to know when a plug‑in crashes or misbehaves.	Provide structured logging, metrics, tracing, health‑checks, central error bus.
CI/CD‑Ready Boilerplate	Keeps the framework maintainable and encourages best‑practice adoption.	Include GitHub Actions / GitLab CI pipelines that run lint, unit, integration, contract tests, and a publish step.
Configuration‑as‑Code	Each module may need its own settings but you want a single source of truth.	Use a hierarchical config system (environment > file > secret store).
Multitenancy (optional)	If you plan SaaS, the core must be ready to isolate data per tenant.	Provide tenant‑aware repository abstractions and tenant‑scoped middlewares.
Versioning & Compatibility	Modules evolve; the core should never break existing plug‑ins.	Adopt semantic versioning + backwards‑compatibility shim layer (e.g., deprecation warnings).

---

2️⃣ LAYERED / HEXAGONAL BLUEPRINT

+---------------------------------------------------+
|                     Presentation                  |
| (REST/GraphQL/ gRPC Controllers, UI SDKs, CLI)    |
+-------------------+-------------------------------+
|        Application Services (Use‑cases)          |
|  - orchestrate core & feature modules            |
|  - enforce policies (RBAC, rate‑limit)           |
+-------------------+-------------------------------+
|            Domain (Business Logic)               |
|  - Core Entities (User, Role, Permission)       |
|  - Domain Services (PasswordPolicy, TokenMgr)   |
+-------------------+-------------------------------+
|           Infrastructure / Adapters              |
|  - Persistence (ORM/NoSQL Repositories)         |
|  - External services (Email, SMS, OIDC)         |
|  - Event bus (Kafka/Rabbit, In‑process)         |
|  - File storage, Cache, Search                  |
+---------------------------------------------------+
|                Platform Core (Kernel)            |
|  - DI container, Module loader, Config manager   |
|  - Cross‑cutting concerns (Logging, Metrics)    |
|  - Security subsystem (AuthN/AuthZ, Token Issuer)|
+---------------------------------------------------+

All layers talk to each other through interfaces defined in the Core kernel. Feature modules implement those interfaces and register themselves at startup.

---

3️⃣ REQUIRED BASE MODULES (THE “CORE KERNEL”)

Module	Core responsibilities	Public API / Extension points
Identity‑Management	- User CRUD (local + federation) - Password hashing, reset flow - Email/Phone verification	IUserRepository, IUserService, IExternalIdpProvider
Roles & Permissions	- Role hierarchy (role → permission set) - Permission definitions (string, enum, policy) - Dynamic permission evaluation (ABAC)	IPermissionResolver, IRoleService
Authentication	- JWT / OAuth2 Access & Refresh tokens - OpenID Connect Provider (optional) - Session Management (stateless + optional stateful)	IAuthService, ITokenProvider
Authorization Middleware	- Enforce RBAC/ABAC on each request - Policy DSL (e.g., hasPermission('project.read') && resource.ownerId == user.id)	IAuthorizationHandler
Audit & Activity Log	- Immutable log of security‑relevant actions - Correlation IDs, actor, target, timestamp	IAuditSink, IAuditService
Configuration	- Hierarchical sources (env, files, secret manager) - Validation schema (JSON‑Schema / Yup / JSR‑380)	IConfigProvider
Health & Metrics	- /healthz, /ready, /metrics endpoints - Export to Prometheus, Grafana, CloudWatch	IHealthCheck, IMetricsRegistry
Error Handling	- Centralized error objects, stack trace masking - Automatic mapping to HTTP status - Exception‑to‑event publishing	IErrorMapper, IErrorBus
Logging	- Structured JSON logs (level, requestId, userId) - pluggable sinks (stdout, file, ELK, Cloud Logging)	ILoggerFactory
Notification	- Email, SMS, Push (FCM/APNs), Webhooks - Queue‑backed delivery, retries	INotificationService
File / Blob Storage	- Abstracted bucket API (upload, version, signed URLs)	IBlobStore
Scheduler / Background Jobs	- Cron‑like tasks, queue workers, retry/back‑off policies	IJobScheduler, IJobProcessor
Internationalization (i18n)	- Message catalog, locale negotiation, runtime translation	I18nService
API Gateway (optional)	- Rate‑limit, request/response transformation, API‑key handling, request routing to modules	IGatewayPlugin
Multitenancy (optional)	- Tenant identification (sub‑domain, header, JWT claim) - Tenant‑scoped data isolation primitives	ITenantResolver, ITenantContext

Tip: Pack each module as a separate NPM/ Maven / NuGet / Go module with its own package.json / pom.xml etc. The platform’s bootstrapper loads every module that implements IModuleInitializer (or similar) and calls ConfigureServices / RegisterRoutes.

---

4️⃣ EXTENSION‑POINT DESIGN (HOW PLUG‑INS HOOK IN)

1. Module Manifest – a tiny JSON/YAML file (module.yaml) that declares:

   • Module name, version, dependencies (core ≥ 1.2.0, other modules)
   • Public routes (e.g., /api/v1/blog/**)
   • Required permissions (auto‑generated from source annotations)
   • UI assets (static folder, React component entry point)

2. Bootstrap Interface

   export interface IModuleInitializer {
       /**
        * Called during platform start‑up.
        * Register services, routes, policies, background jobs.
        */
       init(app: IApplicationBuilder, container: IServiceContainer): Promise<void>;
   }
   

3. Dependency Injection (DI) Conventions

   • Core registers contracts (IUserRepository, IPermissionResolver) as singletons.
   • Modules register implementations with a named scope (e.g., UserRepository:Local).
   • Override is possible via module ordering or explicit container.override(...).

4. Policy/Permission Extension

   // core lib
   export type Permission = `${string}.${string}`; // e.g., "blog.post.create"
   
   // module
   export const BLOG_PERMS = {
       POST_CREATE: 'blog.post.create',
       POST_READ:   'blog.post.read',
       POST_UPDATE: 'blog.post.update',
       POST_DELETE: 'blog.post.delete',
   } as const;
   

5. Event Bus & Hooks

   • Central topic: platform.* (user.created, role.assigned, tenant.created)
   • Modules can publish and subscribe via IEventBus.
   • Provide synchronous guard hooks (beforeUserCreate, afterRoleDelete) for validation & side‑effects.

6. UI Plug‑in System

   • Serve a manifest at /modules that front‑end bundles read to render navigation.
   • Encourage Web Component / Module Federation pattern for SPA integration.

---

5️⃣ SAMPLE REPOSITORY LAYOUT (language‑agnostic)

/platform-root
│
├─ /core                                   # ---- Kernel / Base modules ----
│   ├─ /auth
│   │   ├─ src/
│   │   └─ package.json
│   ├─ /identity
│   ├─ /authorization
│   ├─ /audit
│   ├─ /config
│   ├─ /logging
│   ├─ /metrics
│   └─ index.ts (exports all core APIs)
│
├─ /modules                                # ---- Feature plug‑ins ----
│   ├─ /blog
│   │   ├─ module.yaml                     # manifest
│   │   ├─ src/
│   │   │   ├─ BlogController.ts
│   │   │   ├─ BlogService.ts
│   │   │   └─ BlogModule.ts (implements IModuleInitializer)
│   │   └─ package.json
│   │
│   ├─ /billing
│   └─ /chat
│
├─ /infra                                   # ---- Infrastructure adapters ----
│   ├─ /orm (typeorm/hibernate/EFCore etc.)
│   ├─ /cache (redis)
│   ├─ /queue (rabbit/kafka)
│   └─ /storage (s3/azure‑blob)
│
├─ /gateway (optional API‑gateway layer)
│
├─ /scripts                                 # build / lint / test helpers
│
├─ /ci
│   └─ github-actions.yml
│
├─ /docs
│   └─ architecture.md
│
├─ package.json (or pom.xml / go.mod)
└─ README.md

How it boots

// platform-root/src/main.ts
import { createApp } from '@core/app';
import { loadModules } from '@core/module-loader';
import { CoreModule } from '@core';

async function bootstrap() {
  const app = await createApp();

  // 1️⃣ Load core kernel (DI, config, logger)
  await app.register(CoreModule);

  // 2️⃣ Dynamically discover all `module.yaml` under /modules
  const modules = await loadModules(__dirname + '/modules');

  // 3️⃣ Initialise each module (order can be defined in manifest)
  for (const mod of modules) {
    await mod.instance.init(app.builder, app.container);
  }

  // 4️⃣ Start HTTP / gRPC server
  await app.listen(process.env.PORT || 3000);
}

bootstrap().catch(err => {
  console.error('❌ Platform failed to start', err);
  process.exit(1);
});

---

6️⃣ KEY DECISIONS YOU MUST TAKE EARLY

Decision	Options	Implications
Language / Runtime	Node.js (NestJS, Fastify), Java (Spring Boot), .NET (ASP.NET Core), Go (Gin/Fiber), Python (FastAPI)	Affects DI framework, module packaging, community libs for auth/OIDC, testing.
Persistence Strategy	Relational (PostgreSQL, MySQL) + optional NoSQL (Mongo, Dynamo)	Choose an ORM/Repository pattern that can be swapped per module.
Auth Protocol	JWT + Refresh, OAuth2 Authorization Server, OpenID Connect Provider, or integrate with external IdP (Keycloak, Auth0)	Influences token lifetimes, revocation strategy, multi‑tenant support.
Event Bus	In‑process EventEmitter (for monolith) → Kafka/Rabbit for scaling	Must expose both sync and async hooks.
Module Packaging	NPM packages (private registry) / Maven artifacts / Docker images (for micro‑service extraction)	Define a semantic version policy (core ≥ 1.0.0 never forces breaking changes on plug‑ins).
Multitenancy Model	Single DB with tenant_id column (shared), Schema‑per‑tenant, or DB‑per‑tenant	Affects repository base class and migrations tooling.
Internationalisation	i18next (frontend) + ICU messages in backend, or .NET Resource files	Choose a format that can be merged from modules at build time.
CI/CD	GitHub Actions + Docker Buildx + semantic‑release	Automate publishing of core + modules to same artifact registry.
Testing Strategy	Unit (Jest, JUnit, xUnit), Integration (Testcontainers), Contract (Pact)	Provide a core testing harness that loads a dummy module and asserts the contract of each extension point.

---

7️⃣ COMMON PITFALLS & HOW TO AVOID THEM

Pitfall	Symptoms	Fix / Guardrail
Tight coupling of modules to core implementation	Module imports internal ORM classes, fails on core upgrade.	Expose only interfaces (IUserRepository) from core and keep the concrete implementation as a private package.
Hard‑coded permission strings	Duplicate names across modules, typos cause silent authorisation bypass.	Provide a Permission Builder DSL (Permission.define('blog.post', ['create', 'read'])) that generates constants and registers them automatically.
Global state in modules	Tests interfere with each other, memory leaks when hot‑reloading.	Enforce stateless services; keep per‑request scoped data (e.g., via DI context).
Schema migrations clash	Two modules try to add the same column or foreign key.	Adopt a central migration orchestrator (e.g., Flyway/DBMate) that loads migration scripts from each module in alphabetical order.
Authorization checks omitted in new routes	Security hole for new plug‑in routes.	Provide a base controller class that auto‑applies Authorize filter, or a compile‑time lint rule that checks every exported route for a permission annotation.
Vendor lock‑in to a particular IdP	Hard to replace Keycloak later.	Keep IdP adapters behind a IIdentityProvider interface; ship at least two (local DB + OIDC).
Unbounded background jobs	Queue overflow, OOM, duplicate processing.	Use a job‑scheduler abstraction that caps concurrency, persists state, and provides @Retry decorator.
Insufficient observability	You can’t tell which module caused latency spikes.	Tag every log/metric with module=<moduleName> automatically via middleware.
Version drift between core and modules	Module built against core 1.0 fails on core 1.5.	Publish a core compatibility matrix and enforce peerDependencies in package.json; CI should fail on mismatched ranges.

---

8️⃣ QUICK START GUIDE (What to Build First)

1. Create the Core Kernel

   • Set up DI container, config loader, logger, health/metrics endpoint.
   • Scaffold IUserRepository, IPermissionResolver, ITokenProvider.

2. Implement Identity & Auth

   • Choose JWT + Refresh + optional OpenID Connect.
   • Add password hashing (bcrypt/argon2) and email verification flow.

3. Add Role/Permission Engine

   • Simple RBAC matrix with an extensible Permission type.
   • Provide a UI admin UI (or API only) to manage roles.

4. Set Up Event Bus & Audit

   • Publish user.created, role.granted events.
   • Store audit entries in an append‑only table (or log to Elastic).

5. Build the Module Loader

   • Scan modules/*/module.yaml, load via require()/classpath.
   • Register each IModuleInitializer.

6. Create a Sample Feature Module – e.g., Blog

   • Define its own entities (Post, Comment).
   • Register routes (/api/v1/blog/posts).
   • Declare required permissions (blog.post.create).

7. Write Integration Tests

   • Spin up an in‑memory DB (SQLite or H2).
   • Load core + blog module, assert that a user without blog.post.create receives 403.

8. Add CI Pipeline

   • Lint → Unit → Integration (Docker Compose with DB + Redis).
   • On tag, publish core and blog packages to your private registry.

9. Document Extension Points

   • Provide a Developer Handbook (README + docs/extension-points.md).

10. Iterate – add Notification, Scheduler, Multitenancy, API‑Gateway as needed.

---

9️⃣ TOOLS & LIBRARIES (starter suggestions per stack)

Stack	Core	Auth	DI / Module	Event Bus	ORM	Validation	Testing
Node (TypeScript)	NestJS (or Fastify + awilix)	@nestjs/passport, passport-jwt, openid-client	NestJS dynamic modules or @nestjs-modules/mailer	@nestjs/event-emitter or KafkaJS	TypeORM / Prisma	class-validator + class-transformer	Jest + supertest, Testcontainers
Java	Spring Boot	Spring Security + spring-boot-starter-oauth2-resource-server	Spring Boot @Configuration + ImportBeanDefinitionRegistrar	Spring Cloud Stream (Kafka)	JPA / Hibernate	Bean Validation (Hibernate Validator)	JUnit5 + Testcontainers
.NET 8	ASP.NET Core	Microsoft.AspNetCore.Authentication.JwtBearer	IHostedService + Scrutor for module discovery	MassTransit (Rabbit/Kafka)	EF Core	FluentValidation	xUnit + DockerTestContainers
Go	Echo / Fiber	golang.org/x/oauth2 + github.com/golang-jwt/jwt/v5	uber-go/fx for DI, module registration	segmentio/kafka-go	GORM / Ent	go-playground/validator	Testify + Dockertest
Python	FastAPI	fastapi-users / Authlib	pluggy (pytest plugins) or custom loader	aiokafka	SQLModel / Tortoise ORM	Pydantic	Pytest + pytest‑asyncio, Testcontainers

Pick the stack you’re most comfortable with; the concepts stay identical.

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🎉 TL;DR – What You Must Deliver

Layer	Must‑have components	Why
Core Kernel	Config, Logger, DI, Health, Metrics, Error Bus	Foundation for any module.
Security	Auth (JWT/OIDC), Authorization (RBAC + ABAC), Audit	Guarantees secure, traceable access.
User & Role Management	User CRUD, Password reset, Role ↔ Permission matrix	The “identity” piece everyone will reuse.
Extension System	IModuleInitializer, module.yaml, EventBus, Permission DSL	Enables plug‑ins without touching core.
Infrastructure Adapters	DB repo, Cache, Queue, Blob storage, Email/SMS	Keeps core agnostic to any concrete tech.
Observability	Structured logs, Prometheus metrics, OpenTelemetry traces	You can monitor each module individually.
DevOps Boilerplate	CI pipelines, Dockerfiles, Semantic‑release, Docs	Makes the framework production‑ready out‑of‑the‑box.
Sample Feature Module	(e.g., Blog) to show how to add routes, permissions, DB entities	Provides a reference implementation for future developers.

When you scaffold those pieces once, any downstream team can drop a new folder that follows the module.yaml contract, implement the initializer, add its own tables & APIs, and instantly get:

• secure authentication,
• role‑based authorization,
• logging/metrics,
• unified config,
• CI‑ready testing,
• optional multi‑tenant isolation.

That’s the foundation of a robust, future‑proof platform boilerplate. Happy building! 🚀