import { isValidEmail, type WidgetFormField } from '../types/widget'

/** Validate a widget form field with the same value normalization and bounds
 * used by backend/app/api/widget_chat.py before accepting a form submission. */
export function validateWidgetFormField(field: WidgetFormField, value: unknown): string | null {
  const label = field.label || field.name
  const valueString = value === null || value === undefined ? '' : String(value).trim()

  if (field.required && valueString === '') {
    return `${label} 为必填项`
  }
  if (valueString === '') return null

  if (field.type === 'email' && !isValidEmail(valueString)) {
    return '请输入有效的邮箱地址'
  }

  if (field.type === 'tel') {
    const digits = valueString.replace(/\D/g, '')
    if (digits.length < 7 || digits.length > 15) return '请输入有效的电话号码'
  }

  if (field.type === 'text' || field.type === 'textarea') {
    const valueLength = [...valueString].length
    if (field.minLength != null && valueLength < field.minLength) {
      return `${label} 至少需要 ${field.minLength} 个字符`
    }
    // Match the server's text-field contract: maxLength=0 disables the bound.
    if (field.maxLength && valueLength > field.maxLength) {
      return `${label} 不能超过 ${field.maxLength} 个字符`
    }
  }

  if (field.type === 'number') {
    const numberPattern = /^[+-]?(?:(?:\d(?:_?\d)*(?:\.(?:\d(?:_?\d)*)?)?|\.\d(?:_?\d)*)(?:e[+-]?\d(?:_?\d)*)?|inf(?:inity)?|nan)$/i
    if (!numberPattern.test(valueString)) return `${label} 必须是有效数字`

    const specialNumber = /^[+-]?(?:inf(?:inity)?|nan)$/i.test(valueString)
    const lowerValue = valueString.toLowerCase()
    const numberValue = specialNumber
      ? lowerValue.endsWith('nan')
        ? Number.NaN
        : valueString.startsWith('-') ? Number.NEGATIVE_INFINITY : Number.POSITIVE_INFINITY
      : Number(valueString.replace(/_/g, ''))
    const minimum = field.minLength === undefined ? 0 : field.minLength
    const maximum = field.maxLength === undefined ? null : field.maxLength
    if (minimum !== null && numberValue < minimum) {
      return `${label} 不能小于 ${minimum}`
    }
    if (maximum !== null && numberValue > maximum) {
      return `${label} 不能大于 ${maximum}`
    }
  }

  return null
}