const refMap = new WeakMap<object, string>()
let refCounter = 0

/**
 * Generates a stable, unique string key for any JS value.
 *
 * - null / undefined => 'null' / 'undefined'
 * - string / number / boolean => `${type}:${value}` (e.g. 'string:hello', 'number:42',
 *   'boolean:false')
 * - registered symbols (`Symbol.for('foo')`) => 'symbol:foo'
 * - objects / functions / non-registered symbols => one-time ID (e.g. 'ref:1', 'ref:2', etc.)
 *
 * @param value - Any JavaScript value.
 * @returns A string that uniquely and consistently identifies the value.
 */
export function getKey(value: unknown): string {
  if (value === null) return 'null'
  if (value === undefined) return 'undefined'

  if (typeof value === 'string' || typeof value === 'number' || typeof value === 'boolean') {
    return `${typeof value}:${value}`
  }

  if (typeof value === 'symbol') {
    const registryKey = Symbol.keyFor(value)
    if (registryKey !== undefined) {
      return `symbol:${registryKey}`
    }
  }

  let id = refMap.get(value)
  if (!id) {
    id = `ref:${++refCounter}`
    refMap.set(value, id)
  }
  return id
}