A simple, non-performance-optimized way to keep a Set, Map, etc in a Signal

complex-signal.ts

import { signal } from '@preact/signals'

export type ComplexSignal<T> = {
  value: T
  peek: T
  subscribe: (cb: (t: T) => void) => () => void
  update: (cb: (t: T) => void) => void
}

export function complexSignal<T>(initialValue: T): ComplexSignal<T> {
  const sig = signal<{ inner: T }>({ inner: initialValue })

  const update = (cb: (t: T) => void): void => {
    cb(sig.value.inner)
    sig.value = { inner: sig.value.inner }
  }

  return {
    get value() {
      return sig.value.inner
    },
    get peek() {
      return sig.peek().inner
    },
    subscribe(cb) {
      return sig.subscribe(({ inner }) => cb(inner))
    },
    update
  }
}