import type { FieldErrors, FieldValues } from 'react-hook-form'

import { texts } from '@/texts'
import { addToast } from '@/lib/toast'

function isPlainObject(value: object): boolean {
  const proto: object | null = Object.getPrototypeOf(value) as object | null

  return proto === Object.prototype || proto === null
}

/**
 * Walk RHF `FieldErrors` for the first non-empty `message`.
 * Skips `ref` (DOM / focus handles — often circular) and non-plain objects
 * so a validation toast can never blow the call stack.
 */
function findFirstErrorMessage(value: unknown, seen: WeakSet<object> = new WeakSet<object>()): string | undefined {
  if (!value || typeof value !== 'object') return undefined
  if (seen.has(value)) return undefined

  if (Array.isArray(value)) {
    seen.add(value)

    for (const item of value) {
      const message = findFirstErrorMessage(item, seen)

      if (message) return message
    }

    return undefined
  }

  // DOM nodes, class instances, etc. — never treat as error trees
  if (!isPlainObject(value)) return undefined

  seen.add(value)

  if ('message' in value && typeof value.message === 'string' && value.message.trim()) {
    return value.message
  }

  for (const [key, nestedValue] of Object.entries(value)) {
    if (key === 'ref') continue

    const message = findFirstErrorMessage(nestedValue, seen)

    if (message) return message
  }

  return undefined
}

/** React Hook Form invalid-submit callback used by user-facing forms. */
export function showFormValidationToast<TFieldValues extends FieldValues = FieldValues>(errors: FieldErrors<TFieldValues>) {
  addToast({
    title: texts.common.formIncomplete,
    description: findFirstErrorMessage(errors) ?? texts.common.formValidationDefault,
    color: 'danger',
  })
}