An attempt to make the Typescript compiler do some basic validation of a petri net, ensuring that only defined places (nodes) can be used, both for the places, and transitions (vertices) of the graph.

represent-petri-net-in-typescript.ts

export {}
// Representing Petri Nets as typed values in Typescript.
type PlaceID = string
type Place<P extends PlaceID = PlaceID> = {
  id: P
}

type Transition<P> = {
  start: P
  end: P
}

type PetriNet<P extends PlaceID = PlaceID> = {
  places: Set<Place<P>>
  transitions: Set<Transition<P>>
}

// This is the first magic:
// See: https://stackoverflow.com/questions/60496276/typescript-derive-union-type-from-array-of-objects
// type Allowed = typeof knownPlaces[number]['id']
function registerPlaces<T extends readonly Place[] & Array<{ id: V }>, V extends string>(...args: T): T {
  return args
}

// Typescript then can ensure only defined placeIDs can be used in transitions and places
function petriNet<Places extends PlaceID>(
  places: readonly Place<Places>[],
  transitions: Transition<Places>[]
): PetriNet<Places> {
  return {
    places: new Set(places),
    transitions: new Set(transitions)
  }
}

// ---------------------------------------------------------------------------------------------------------------
const alphaPlaces = registerPlaces(
  {id: 'a'},
  {id: 'b'},
  {id: 'z'}
)

const alphaNet = petriNet<typeof alphaPlaces[number]['id']>(alphaPlaces, [
  {start: 'a', end: 'b'},
  {start: 'a', end: 'z'}
])

console.log('alphaNet')
console.log(alphaNet)

// -- Bad Transitions
const badNet = petriNet<typeof alphaPlaces[number]['id']>(alphaPlaces, [
  {start: 'a', end: 'b'},
  // TS2322: Type '"c"' is not assignable to type '"a" | "b" | "z"'.
  {start: 'a', end: 'c'}
])

console.log('badNet')
console.log(badNet)



// ---------------------------------------------------------------------------------------------------------------
// -- Bad Places
const otherPlaces = registerPlaces(
  {id: 'b'},
  {id: 'c'}
)

// TS2345: Argument of type '[{ id: "b"; }, { id: "c"; }]' is not assignable to parameter of type 'readonly Place<"a" | "b" | "z">[]'.
// Type '"c"' is not assignable to type '"a" | "b" | "z"'.
const badPlaces = petriNet<typeof alphaPlaces[number]['id']>(otherPlaces, [
    {start: 'c', end: 'b'},
    {start: 'b', end: 'c'}
  ]
)

console.log(badPlaces)