# Phase 4: Demo Device Provider & Seed Data

**Status:** ⬜ Not Started
**Parent plan:** [PLAN.md](./PLAN.md)
**Domain:** backend

## Objective
Create a demo device provider that exposes discoverable virtual LED devices, and build a seed data generator that populates the demo data directory with sample entities on first run.

## Tasks

- [ ] Task 1: Create `server/src/wled_controller/core/devices/demo_provider.py` — `DemoDeviceProvider` extending `LEDDeviceProvider`:
  - `device_type = "demo"`
  - `capabilities = {"manual_led_count", "power_control", "brightness_control", "static_color"}`
  - `create_client()` returns a `MockClient` (reuse existing)
  - `discover()` returns 3 pre-defined virtual devices:
    - "Demo LED Strip" (60 LEDs, ip="demo-strip")
    - "Demo LED Matrix" (256 LEDs / 16×16, ip="demo-matrix")
    - "Demo LED Ring" (24 LEDs, ip="demo-ring")
  - `check_health()` always returns online with simulated ~2ms latency
  - `validate_device()` returns `{"led_count": <from url>}`
- [ ] Task 2: Register `DemoDeviceProvider` in `led_client.py` `_register_builtin_providers()`
- [ ] Task 3: Create `server/src/wled_controller/core/demo_seed.py` — seed data generator:
  - Function `seed_demo_data(storage_config: StorageConfig)` that checks if demo data dir is empty and populates it
  - Seed entities: 3 devices (matching discover results), 2 output targets, 2 picture sources (using demo engine), 2 CSS sources (gradient + color_cycle), 1 audio source (using demo engine), 1 scene preset, 1 automation
  - Use proper ID formats matching existing conventions (e.g., `dev_<hex>`, `tgt_<hex>`, etc.)
- [ ] Task 4: Call `seed_demo_data()` during server startup in `main.py` when demo mode is active (before stores are loaded)

## Files to Modify/Create
- `server/src/wled_controller/core/devices/demo_provider.py` — New: DemoDeviceProvider
- `server/src/wled_controller/core/devices/led_client.py` — Register DemoDeviceProvider
- `server/src/wled_controller/core/demo_seed.py` — New: seed data generator
- `server/src/wled_controller/main.py` — Call seed on demo startup

## Acceptance Criteria
- Demo devices appear in discovery results when in demo mode
- Seed data populates `data/demo/` with valid JSON files on first demo run
- Subsequent demo runs don't overwrite existing demo data
- All seeded entities load correctly in stores

## Notes
- Seed data must match the exact schema expected by each store (look at existing JSON files for format)
- Use the entity dataclass `to_dict()` / store patterns to generate valid data
- Demo discovery should NOT appear when not in demo mode

## Review Checklist
- [ ] All tasks completed
- [ ] Code follows project conventions
- [ ] No unintended side effects
- [ ] Build passes
- [ ] Tests pass (new + existing)

## Handoff to Next Phase
<!-- Filled in after completion -->