Lemmy

# MISSION: Scaffold "Lemmy" Production Architecture
You are an expert Senior Staff Software Architect and Full-Stack Engineer. Your mission is to scaffold and implement a production-grade, highly reliable, and modular codebase following the proven architecture of **Lemmy**.
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## 1. PROJECT SPECIFICATIONS & BENCHMARK
- **Reference Architecture**: Lemmy
- **What It Does**: Lemmy is a decentralised, federated link aggregator and forum similar to Reddit, with a Rust backend on Actix Web, PostgreSQL through Diesel, and ActivityPub federation between independently run instances.
- **Domain & Category**: Federated Link Aggregator & Forum
- **Production Scale**: 20+ people
- **Development Mode**: CLASSIC
- **Architectural Rationale**: Lemmy splits its Rust backend into many small crates (per database view, API, ActivityPub, email) over one PostgreSQL schema with heavy migrations, so federation, the local API and queries evolve separately while a single binary serves an instance.
- **Live Website Reference**: https://join-lemmy.org
- **Source Repository**: https://github.com/LemmyNet/lemmy
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## 2. PRODUCTION TECH STACK
- **Full Stack Array**: Rust, Actix-web, Diesel, PostgreSQL, ActivityPub, Tokio, Prometheus, Docker, Nginx, TypeScript, Jest
- **Primary Language(s)**: Rust, PLpgSQL, TypeScript
- **License of the reference repo**: AGPL-3.0
- **Backend & APIs**: Rust — Backend language for the lemmy_server binary and all workspace crates (edition 2024, Rust 1.92 minimum).; Actix-web — HTTP server for the API, RSS feeds and federation endpoints, with actix-cors, rate limiting and tracing middleware.; ActivityPub — Federation with other instances through the activitypub_federation crate in the crates/apub/* crates.; Lettre — SMTP email with pooled rustls connections; templates are translated with rosetta-i18n.; markdown-it — Renders user Markdown with plugins for spoilers, sub/superscript and ruby text.
- **Data & persistence**: PostgreSQL — Only database; migrations directory holds hundreds of timestamped Diesel migrations, many in PL/pgSQL.; Diesel — ORM and query builder (diesel and diesel-async), with diesel_ltree for comment trees and per-view crates in crates/db_views.; Moka — In-process cache used by the schema and utils crates.
- **Infrastructure & deploy**: Docker — Multi-stage build with cargo-chef layer caching, Debian runner, non-root user, port 8536.; Nginx — Reverse proxy configuration shipped for the Docker Compose deployment.; Prometheus — Metrics exported through actix-web-prom and the prometheus crate in the routes crate.; Woodpecker CI — CI pipeline defined in .woodpecker.yml; no GitHub Actions workflows are present.; Jest — TypeScript API and federation tests in api_tests/ that run several Lemmy instances against each other.
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## 3. KEY ARCHITECTURAL DECISIONS (audited from https://github.com/LemmyNet/lemmy @ 8d83bcf)
1. **Dozens of small crates, one per database view**: The workspace in Cargo.toml lists crates/db_views/post, comment, community, person, notification, modlog, report_combined and many more as separate crates next to db_schema, api, apub and routes, so a change to one query view recompiles only the crates that depend on it.
2. **Federation as its own crate family**: crates/apub/apub, activities, objects and send isolate ActivityPub handling, built on the activitypub_federation crate that crates/server also depends on, so inbound activities, object conversion and outbound delivery are separated from the local API.
3. **PostgreSQL does real work through migrations**: migrations/ contains hundreds of timestamped Diesel migrations from 2019 onwards and PL/pgSQL is the second-largest language in the repository, so counters, triggers and tree logic live in the database; diesel_ltree supports comment trees.
4. **TypeScript types generated from Rust structs**: Crates such as db_schema, routes and utils expose a ts-rs feature, which derives TypeScript definitions from the Rust API types for client libraries, keeping the API contract in one place.
5. **Two API generations served side by side**: crates/api/routes and crates/api/routes_v3 are separate workspace members wired into lemmy_server, so older clients keep working on the v3 routes while the current API evolves.
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## 4. NON-NEGOTIABLE ARCHITECTURAL GUARDRAILS
1. **Monorepo & Modular Separation**:
   - Structure as a Turborepo monorepo with strict package boundaries:
     - `apps/web`: Application UI, routing, layouts, and server endpoints.
     - `packages/ui`: Shared design tokens, CSS variables, and Radix UI primitive components.
     - `packages/db`: Database schemas, client singleton, declarative migrations, and seed scripts.
     - `packages/config`: Shared TypeScript, ESLint, and build configurations.
2. **Strict Type Safety & Zero `any` Policy**:
   - Enable `strict: true`, `noImplicitAny: true`, and `strictNullChecks: true`.
   - Validate ALL external inputs, API request bodies, and query parameters with **Zod** schemas before execution.
3. **Frontend & Rendering Guidelines**:
   - Isolate interactive UI state to leaf components. Keep core pages lightweight and performant.
4. **Design System & Aesthetics**:
   - Keep every color, radius, shadow and font in a single token file (CSS variables) and consume tokens everywhere; never hardcode hex values in components.
   - Prefer crisp 1px borders and one subtle shadow scale over blurry default shadows. Pair one sans-serif for body/headings with one monospace for tags, badges, metrics, and code.
5. **Data Layer & Reliability**:
   - Write declarative schema definitions with foreign keys, composite indexes on queried filters, and automated timestamp triggers.
   - Use connection pooling and prepared statements for serverless database execution.
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## 5. STEP-BY-STEP SCAFFOLDING ROADMAP
- **Phase 1: Workspace & Root Config**: Initialize package manager, monorepo configuration (`turbo.json`, `tsconfig.base.json`, `package.json`).
- **Phase 2: Database Schema & Client**: Set up the data layer (PostgreSQL, Diesel, Moka): client, connection pool, models, and migration scripts.
- **Phase 3: Design Tokens & UI Primitives**: Build accessible `Button`, `Input`, `Card`, `Badge`, and layout wrappers inside `packages/ui`.
- **Phase 4: Core Application Routes & Handlers**: Implement primary authentication, user session handling, and application routes.
- **Phase 5: Quality Assurance & Build Verification**: Run `tsc --noEmit`, ESLint, Prettier, and smoke test suites to ensure zero compilation or runtime errors.
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## 6. EXECUTION INSTRUCTIONS
1. Review all specifications, architectural guardrails, and stack choices above.
2. Present the full monorepo directory tree structure.
3. Systematically generate the complete, production-ready codebase according to the 5-phase roadmap above — starting with the root workspace setup, followed by the database schema, UI design system package, and full-stack application routes until the repository is fully scaffolded and ready to run.