export function deepClone<T>(value: T): T {
  const seen = new WeakMap<any, any>()

  const getRegExpFlags = (r: RegExp) => {
    let flags = ''
    if (r.global) flags += 'g'
    if (r.ignoreCase) flags += 'i'
    if (r.multiline) flags += 'm'
    if (r.dotAll) flags += 's'
    if (r.unicode) flags += 'u'
    if (r.sticky) flags += 'y'
    return flags
  }

  function _clone(v: any): any {
    if (v === null || typeof v !== 'object') {
      return v
    }

    if (seen.has(v)) {
      return seen.get(v)
    }

    if (v instanceof Date) {
      return new Date(v.getTime())
    }

    if (v instanceof RegExp) {
      return new RegExp(v.source, getRegExpFlags(v))
    }

    if (v instanceof ArrayBuffer) {
      return v.slice(0)
    }

    if (ArrayBuffer.isView(v)) {
      if (v instanceof DataView) {
        const buf = _clone(v.buffer)
        return new DataView(buf, v.byteOffset, v.byteLength)
      }

      return new (v.constructor as any)(v)
    }

    if (v instanceof Map) {
      const m = new Map()
      seen.set(v, m)
      for (const [k, val] of v.entries()) {
        m.set(_clone(k), _clone(val))
      }
      return m
    }

    if (v instanceof Set) {
      const s = new Set()
      seen.set(v, s)
      for (const item of v.values()) s.add(_clone(item))
      return s
    }

    if (Array.isArray(v)) {
      const arr: any[] = []
      seen.set(v, arr)
      for (let i = 0; i < v.length; i++) arr[i] = _clone(v[i])
      return arr as any
    }

    if (typeof v === 'function') {
      return v
    }

    const proto = Object.getPrototypeOf(v)
    const out = Object.create(proto)
    seen.set(v, out)

    const descriptors = Object.getOwnPropertyDescriptors(v)
    for (const [key, desc] of Object.entries(descriptors)) {
      if ('value' in desc) desc.value = _clone(desc.value)
      Object.defineProperty(out, key, desc as PropertyDescriptor)
    }

    const symbols = Object.getOwnPropertySymbols(v)
    for (const s of symbols) {
      const sd = Object.getOwnPropertyDescriptor(v, s)!
      if (sd && 'value' in sd) sd.value = _clone(sd.value)
      Object.defineProperty(out, s, sd as PropertyDescriptor)
    }

    return out
  }

  return _clone(value) as T
}