export const DINGTALK_APPROVAL_NO_MAX_LENGTH = 64

function isLeapYear(year: number): boolean {
  return year % 400 === 0 || (year % 4 === 0 && year % 100 !== 0)
}

function getDaysInMonth(year: number, month: number): number {
  if (month === 2) {
    return isLeapYear(year) ? 29 : 28
  }

  return [4, 6, 9, 11].includes(month) ? 30 : 31
}

function hasValidDatePrefix(value: string): boolean {
  const year = Number.parseInt(value.slice(0, 4), 10)
  const month = Number.parseInt(value.slice(4, 6), 10)
  const day = Number.parseInt(value.slice(6, 8), 10)

  if (year < 1000 || year > 9999 || month < 1 || month > 12 || day < 1) {
    return false
  }

  return day <= getDaysInMonth(year, month)
}

export function normalizeDingtalkApprovalNo(
  value: string | null | undefined,
): string | null {
  if (typeof value !== 'string') {
    return null
  }

  const normalized = value.trim()
  return normalized || null
}

export function getDingtalkApprovalNoError(
  value: string | null | undefined,
): string | null {
  const normalized = normalizeDingtalkApprovalNo(value)
  if (!normalized) {
    return null
  }

  if (!/^\d+$/.test(normalized)) {
    return '钉钉审批编号只能输入数字'
  }

  if (normalized.length < 9) {
    return '钉钉审批编号需包含8位日期和后续编号'
  }

  if (normalized.length > DINGTALK_APPROVAL_NO_MAX_LENGTH) {
    return `钉钉审批编号不能超过${DINGTALK_APPROVAL_NO_MAX_LENGTH}位`
  }

  if (!hasValidDatePrefix(normalized)) {
    return '钉钉审批编号前8位不是有效日期'
  }

  return null
}

export function validateDingtalkApprovalNo(
  value: string | null | undefined,
): boolean {
  return getDingtalkApprovalNoError(value) === null
}