# ADR-003: Leptos CSR-Only para Frontend

**Status**: Accepted | Implemented
**Date**: 2024-11-01
**Deciders**: Frontend Architecture Team
**Technical Story**: Selecting WASM framework for client-side Kanban board UI

---

## Decision

Usar **Leptos 0.8.12 en modo Client-Side Rendering (CSR)** para frontend WASM, sin SSR.

---

## Rationale

1. **Fine-Grained Reactivity**: Similar to SolidJS (not virtual DOM), updates only affected nodes
2. **WASM Performance**: Compiles to optimized WebAssembly
3. **Deployment Simplicity**: CSR = static files + API, no server-side rendering complexity
4. **VAPORA is a Platform**: Not a content site, so no SEO requirement

---

## Alternatives Considered

### ❌ Yew
- Virtual DOM model (slower updates)
- Larger bundle size

### ❌ Dioxus
- Promising but less mature ecosystem

### ✅ Leptos CSR (CHOSEN)
- Fine-grained reactivity, excellent performance
- No SEO needed for platform

---

## Trade-offs

**Pros**:
- ✅ Excellent WASM performance
- ✅ Simple deployment (static files)
- ✅ UnoCSS integration for glassmorphism styling
- ✅ Strong type safety in templates

**Cons**:
- ⚠️ No SEO (not applicable for platform)
- ⚠️ Smaller ecosystem than React/Vue
- ⚠️ Leptos SSR available but adds complexity

---

## Implementation

**Leptos Component Example**:
```rust
#[component]
fn ProjectBoard() -> impl IntoView {
    let (projects, set_projects) = create_signal(vec![]);

    view! {
        <div class="grid grid-cols-3 gap-4">
            <For each=projects key=|p| p.id let:project>
                <ProjectCard project />
            </For>
        </div>
    }
}
```

**Key Files**:
- `/crates/vapora-frontend/src/main.rs` (app root)
- `/crates/vapora-frontend/src/pages/` (page components)
- `/crates/vapora-frontend/Cargo.toml` (dependencies)

---

## Verification

```bash
# Build WASM
trunk build --release

# Serve and test
trunk serve

# Check bundle size
ls -lh dist/index_*.wasm
```

**Expected**: WASM bundle < 500KB, components render reactively

---

## Consequences

- Team must learn Leptos reactive system
- SSR not available (acceptable trade-off)
- Maintenance: Leptos updates follow Rust ecosystem

---

## References

- [Leptos Documentation](https://leptos.dev/)
- `/crates/vapora-frontend/src/` (source code)

---

**Related ADRs**: ADR-001 (Workspace)