@opentalon/talon-runtime

Reactive rule engine for Talon — a path-based reactive store that evaluates Talon rules on every state change and dispatches resulting actions to subscribers and registered handlers.

This is the JavaScript runtime, intended for browser and Node applications that want to embed Talon's reactive rule subset (the lexer, parser, evaluator, and TalonStore). For workflow execution, ML primitives, and the full CLI, see the Go implementation in the main repo.

Install

npm install @opentalon/talon-runtime

Quick start

import { TalonStore } from "@opentalon/talon-runtime"

const store = new TalonStore()

store.loadRules(`
  rule "Show delivery address" {
    when "product_type" != "digital"
    do show "delivery_address"
  }

  rule "Recalculate subtotal" {
    when "unit_price" changes or "quantity" changes
    do set "subtotal" to "unit_price" * "quantity"
  }
`)

store.subscribe("*", (actions) => {
  for (const a of actions) {
    console.log(a.rule, a.verb, a.args)
  }
})

store.set("product_type", "physical")
store.set("unit_price", 100)
store.set("quantity", 5)

console.log(store.get("subtotal")) // 500

Features

• Path-based state — flat keys ("unit_price") or nested paths ("booking.items.0.qty").
• Reactive evaluation — every set() re-evaluates affected rules.
• Tagged rule sets — loadRules(src, { tag }) / unloadRules(tag) for dynamic rule swapping.
• Built-in actions — set and validate are handled internally; everything else is dispatched.
• Custom action handlers — store.registerAction("show", (path) => …).
• Prefix subscriptions — store.subscribe("booking.*", …) only fires for matching actions.
• define blocks — name a condition once, reuse it via when is "name".

API

const store = new TalonStore()

store.loadRules(source: string, opts?: { tag?: string }): void
store.unloadRules(tag: string): void

store.set(path: string, value: unknown): void
store.get(path: string): unknown

store.registerAction(verb: string, handler: (...args: any[]) => void): void
store.subscribe(prefix: string, cb: (actions: ActionResult[]) => void): Unsubscribe

Scope

The JS runtime implements the reactive subset of Talon — rules, define, conditions, and actions. Workflows, ML primitives, forecast/detect blocks, and .talon.test files are Go-only. See the main repo for the full language.

License

Apache-2.0