# Host API

## Purpose

The host API is the stable external boundary for:

- the creative web UI
- the existing engineering GUI
- future external show-control adapters such as grandMA

The core rule stays unchanged:

- the API is a control and observation layer
- the realtime engine remains the timing authority
- no surface is allowed to become the LED clock

## Current Implementation

Runtime pieces:

- `crates/infinity_host/src/control.rs`
- `crates/infinity_host/src/scene.rs`
- `crates/infinity_host/src/simulation.rs`
- `crates/infinity_host_api/src/dto.rs`
- `crates/infinity_host_api/src/server.rs`

The network-facing server is started with:

```powershell
cargo run -p infinity_host_api -- --config config/project.example.toml --bind 127.0.0.1:9001
```

Creative web UI V1 is served by the same process at:

```text
http://127.0.0.1:9001/
```

## Versioning

- HTTP and WebSocket routes are versioned under `/api/v1`
- responses include `api_version: "v1"`
- the external DTOs are intentionally not a direct 1:1 dump of internal core structs

## Endpoint Contract

### GET `/api/v1/snapshot`

Returns the current state and preview in one response.

Example:

```json
{
  "api_version": "v1",
  "generated_at_millis": 241,
  "state": {
    "system": {
      "project_name": "Infinity Vis",
      "schema_version": 1,
      "topology_label": "6 nodes / 18 outputs / 106 LEDs"
    },
    "global": {
      "blackout": false,
      "master_brightness": 0.2,
      "selected_pattern": "solid_color",
      "selected_group": null,
      "transition_duration_ms": 150
    },
    "engine": {
      "logic_hz": 120,
      "frame_hz": 60,
      "preview_hz": 15,
      "uptime_ms": 241,
      "frame_index": 14,
      "dropped_frames": 0,
      "active_transition": null
    },
    "active_scene": {
      "preset_id": null,
      "pattern_id": "solid_color",
      "seed": 100,
      "palette": [
        "#ffffff"
      ],
      "parameters": [],
      "target_group": null,
      "blackout": false
    }
  },
  "preview": {
    "generated_at_millis": 241,
    "panels": [
      {
        "node_id": "node-01",
        "panel_position": "top",
        "representative_color_hex": "#33CCFF",
        "sample_led_hex": [
          "#33CCFF",
          "#28A3CC",
          "#1E7A99"
        ],
        "energy_percent": 28,
        "source": "scene"
      }
    ]
  }
}
```

### GET `/api/v1/catalog`

Returns the creative catalog:

- patterns
- presets
- groups

### GET `/api/v1/presets`

Returns only preset summaries.

Example:

```json
{
  "api_version": "v1",
  "presets": [
    {
      "preset_id": "ocean_gradient",
      "pattern_id": "gradient",
      "target_group": null,
      "transition_duration_ms": 320
    }
  ]
}
```

### GET `/api/v1/groups`

Returns only group summaries.

Example:

```json
{
  "api_version": "v1",
  "groups": [
    {
      "group_id": "top_panels",
      "member_count": 6,
      "tags": [
        "row",
        "top"
      ]
    }
  ]
}
```

### POST `/api/v1/command`

Accepts a versioned command envelope.

Example request:

```json
{
  "request_id": "web-1713352662000",
  "command": {
    "type": "set_master_brightness",
    "payload": {
      "value": 0.42
    }
  }
}
```

Example response:

```json
{
  "api_version": "v1",
  "accepted": true,
  "request_id": "web-1713352662000",
  "generated_at_millis": 522,
  "summary": "master brightness set to 42%"
}
```

Errors use a stable error object:

```json
{
  "api_version": "v1",
  "error": {
    "code": "invalid_command",
    "message": "command request was rejected: missing field `enabled`"
  }
}
```

### WS `/api/v1/stream`

The WebSocket stream emits envelopes with a monotonic sequence and a typed payload.

Stream message types:

- `snapshot`
- `preview`
- `event`

Example snapshot envelope:

```json
{
  "api_version": "v1",
  "sequence": 17,
  "generated_at_millis": 875,
  "message": {
    "type": "snapshot",
    "payload": {
      "global": {
        "blackout": false,
        "master_brightness": 0.35,
        "selected_pattern": "gradient",
        "selected_group": "top_panels",
        "transition_duration_ms": 320
      }
    }
  }
}
```

Example preview envelope:

```json
{
  "api_version": "v1",
  "sequence": 18,
  "generated_at_millis": 875,
  "message": {
    "type": "preview",
    "payload": {
      "generated_at_millis": 875,
      "panels": [
        {
          "node_id": "node-01",
          "panel_position": "top",
          "representative_color_hex": "#FF8A5B",
          "sample_led_hex": [
            "#FF8A5B",
            "#F36E43",
            "#D85A2F"
          ],
          "energy_percent": 47,
          "source": "transition"
        }
      ]
    }
  }
}
```

Example event envelope:

```json
{
  "api_version": "v1",
  "sequence": 19,
  "generated_at_millis": 880,
  "message": {
    "type": "event",
    "payload": {
      "kind": "info",
      "message": "preset recalled: ocean_gradient"
    }
  }
}
```

## Supported Commands

The current API command set covers:

- `set_blackout`
- `set_master_brightness`
- `select_pattern`
- `recall_preset`
- `select_group`
- `set_scene_parameter`
- `set_transition_duration_ms`
- `trigger_panel_test`

This is intentionally enough for:

- creative look development in the web UI
- engineering test triggers in the native GUI
- future external show-control translation layers

## Web UI V1

The first creative web UI is intentionally limited to:

- pattern selection
- preset recall
- group selection
- global brightness
- blackout
- transition duration
- scene parameter controls driven from the API schema
- panel preview
- snapshot display
- event feed

It does not absorb mapping, topology, or hardware-diagnostic workflows. Those stay in the native engineering UI.

## Contract Tests

The API contract is currently verified in:

- `crates/infinity_host_api/tests/contract.rs`

Covered paths:

- root web shell
- `GET /api/v1/snapshot`
- `GET /api/v1/catalog`
- `GET /api/v1/presets`
- `GET /api/v1/groups`
- `POST /api/v1/command`
- `WS /api/v1/stream`

## Future Direction

Next adapters should be built on this boundary instead of reaching into the host core directly.

That includes:

- a richer web authoring surface
- remote operator clients
- a grandMA bridge that translates external show control into host API commands