User-defined business rules evaluated safely in isolated JS runtimes.

This is the canonical use case for embedding JS in an Elixir app: letting users write custom logic (pricing formulas, validation rules, data transformations) that runs inside your application with strict sandboxing.

Each rule is a JS source string that gets its own QuickBEAM runtime:

• apis: false — no fetch, no setTimeout, no filesystem, no DOM
• Memory limits — OOM returns {:error, %QuickBEAM.JSError{}}
• Timeouts — infinite loops get interrupted
• Handlers — rules can only access what you explicitly expose via Beam.call()
• Isolation — rules can't see each other's globals

Rules are managed dynamically via DynamicSupervisor + Registry: load, unload, reload, and call them at runtime.

{:ok, _} = RuleEngine.start_link()

# Load a rule with a handler
RuleEngine.load(:pricing, """
  async function calculate(sku, qty) {
    const product = await Beam.call("lookup", sku)
    return product.price * qty
  }
""", handlers: %{
  "lookup" => fn [sku] -> Products.get(sku) end
})

# Call it
{:ok, total} = RuleEngine.call(:pricing, "calculate", ["SKU-001", 3])

# Hot-reload with new logic
RuleEngine.reload(:pricing, new_source)

# Clean up
RuleEngine.unload(:pricing)

mix deps.get
mix run run.exs

mix test