Recipe Developer Guide

How to create a new recipe for Sowel.

Architecture

A recipe is a reusable automation template. Users instantiate recipes with parameters (slots) to create running automation instances. Recipes are registered at engine startup and exposed via the REST API.

Recipe class (definition)
  -> RecipeManager.register()
    -> GET /api/v1/recipes -> UI shows available recipes
      -> User creates instance with params
        -> RecipeManager.createInstance() -> validate() -> start()
          -> Recipe subscribes to EventBus events and reacts

Creating a Recipe

1. Create the file

Create src/recipes/<recipe-name>.ts extending the Recipe base class:

import type { RecipeSlotDef, RecipeLangPack } from "../shared/types.js";
import { Recipe, type RecipeContext } from "./engine/recipe.js";

export class MyRecipe extends Recipe {
  readonly id = "my-recipe";
  readonly name = "My Recipe"; // English (fallback)
  readonly description = "What it does"; // English (fallback)
  readonly slots: RecipeSlotDef[] = [
    // ...see Slots section below
  ];
  override readonly i18n: Record<string, RecipeLangPack> = {
    // ...see Translations section below
  };

  validate(params: Record<string, unknown>, ctx: RecipeContext): void {
    // Throw if params are invalid
  }

  start(params: Record<string, unknown>, ctx: RecipeContext): void {
    // Subscribe to events, start timers
  }

  stop(): void {
    // Unsubscribe events, clear timers (must be idempotent)
  }
}

2. Register in index.ts

import { MyRecipe } from "./recipes/my-recipe.js";
// ...
recipeManager.register(MyRecipe);

3. Write tests

Create src/recipes/<recipe-name>.test.ts. Follow the pattern in motion-light.test.ts:

• In-memory SQLite with migrations
• Fake timers (vi.useFakeTimers())
• Mock integration registry capturing MQTT publishes
• Test validation, event handling, timer behavior, cleanup

Slots

Slots define the parameters users configure when creating an instance.

interface RecipeSlotDef {
  id: string; // Unique within recipe (e.g. "lights", "timeout")
  name: string; // English label (fallback)
  description: string; // English description (fallback)
  type: "zone" | "equipment" | "number" | "duration" | "time" | "boolean";
  required: boolean;
  list?: boolean; // Allow multiple values (equipment lists)
  defaultValue?: unknown;
  constraints?: {
    equipmentType?: EquipmentType | EquipmentType[]; // Filter equipment selector
    min?: number;
    max?: number;
  };
}

Common slot patterns:

Slot type	UI control	Value format
zone	Auto-filled	Zone UUID
equipment	Dropdown/check	Equipment UUID (or UUID[] if list)
duration	Numeric + min	"10m", "30s", "1h"
number	Numeric input	Numeric value
time	Time picker	"HH:MM" string (24h)
boolean	Toggle	true / false

Translations (i18n)

Translations travel with the recipe, not in the platform locale files. This allows recipes to be hot-loaded without modifying fr.json/en.json.

How it works

Each recipe defines an i18n record mapping language codes to translated names, descriptions, and slot labels:

override readonly i18n: Record<string, RecipeLangPack> = {
  fr: {
    name: "Ma recette",
    description: "Ce qu'elle fait",
    slots: {
      lights: { name: "Lumieres", description: "Lumieres a controler" },
      timeout: { name: "Delai", description: "Delai avant extinction" },
    },
  },
  // Add more languages as needed
};

Type definitions

interface RecipeLangPack {
  name: string;
  description: string;
  slots?: Record<string, RecipeSlotI18n>; // Keyed by slot id
}

interface RecipeSlotI18n {
  name: string;
  description: string;
}

Resolution in the UI

The frontend uses helpers from ui/src/lib/recipe-i18n.ts:

recipeName(recipe, lang); // Recipe name with fallback
recipeDescription(recipe, lang); // Recipe description with fallback
recipeSlotName(recipe, slot, lang); // Slot name with fallback
recipeSlotDescription(recipe, slot, lang); // Slot description with fallback

Fallback chain: i18n[lang].name -> recipe.name (English embedded in class).

Adding a new language

Add a new key to the i18n record in your recipe class. No platform files to modify.

RecipeContext

The ctx object injected into validate() and start() provides:

Property	Type	Purpose
eventBus	EventBus	Subscribe to typed events
equipmentManager	EquipmentManager	Query equipment state, execute orders
zoneManager	ZoneManager	Query zone definitions
zoneAggregator	ZoneAggregator	Query aggregated zone data
state	RecipeStateStore	Persist key-value state (survives restart)
log(msg, level?)	function	Write to recipe execution log
notifyStateChanged()	function	Tell UI that state changed (timers)

Shared Helpers

Reusable utilities in src/recipes/engine/:

Module	Exports
duration.ts	parseDuration(value), formatDuration(ms)
light-helpers.ts	isAnyLightOn(), turnOnLights(), turnOffLights(), setLightsBrightness()

Event Bus Events

Key events recipes typically subscribe to:

Event	Payload
zone.data.changed	{ zoneId, aggregatedData: { motion, luminosity, ... } }
equipment.data.changed	{ equipmentId, alias, value, category }

Lifecycle

1. Registration: recipeManager.register(MyRecipe) -- creates a sample instance to extract metadata
2. Instantiation: User creates via API -> validate() -> persisted to SQLite -> start()
3. Restore: On engine restart, enabled instances are loaded from DB and start() is called
4. Update: stop() -> update params in DB -> validate() -> start() with new params
5. Delete: stop() -> removed from DB (cascades to state + logs)

Existing Recipes

ID	Description
motion-light	Turn on lights on motion, off after timeout
switch-light	Toggle lights on button press, optional failsafe timer

Checklist

• [ ] Recipe class extends Recipe with id, name, description, slots, i18n
• [ ] validate() checks all params, throws on error
• [ ] start() subscribes to events, stores unsubs
• [ ] stop() clears all timers and unsubscribes (idempotent)
• [ ] Registered in src/index.ts
• [ ] Tests written and passing
• [ ] npx tsc --noEmit passes
• [ ] French translations in i18n record