/** `datetime-local` 控件用：本地时间的 `YYYY-MM-DDTHH:mm:ss` */
export function occurredOnToLocalInputValue(d: Date | string | number): string {
  const date = d instanceof Date ? d : new Date(d)
  if (Number.isNaN(date.getTime())) {
    return ''
  }
  const pad = (n: number) => String(n).padStart(2, '0')
  return `${date.getFullYear()}-${pad(date.getMonth() + 1)}-${pad(date.getDate())}T${pad(date.getHours())}:${pad(date.getMinutes())}:${pad(date.getSeconds())}`
}

/** 解析 `datetime-local`（按用户本地时区构造瞬间，再交给 `toISOString()` 发给服务端） */
export function parseLocalDatetimeInput(s: string): Date {
  const m = /^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2})(?::(\d{2}))?/.exec(s.trim())
  if (!m) {
    throw new Error('invalid datetime-local')
  }
  const y = Number(m[1])
  const mo = Number(m[2])
  const day = Number(m[3])
  const h = Number(m[4])
  const mi = Number(m[5])
  const sec = m[6] !== undefined ? Number(m[6]) : 0
  return new Date(y, mo - 1, day, h, mi, sec, 0)
}

/** 列表 / 公开页展示：年月日 星期 时:分:秒（24 小时） */
export function formatOccurredOnDisplay(d: Date | string | number, locale = 'zh-CN'): string {
  const date = d instanceof Date ? d : new Date(d)
  if (Number.isNaN(date.getTime())) {
    return '—'
  }
  return new Intl.DateTimeFormat(locale, {
    year: 'numeric',
    month: 'long',
    day: 'numeric',
    weekday: 'short',
    hour: '2-digit',
    minute: '2-digit',
    second: '2-digit',
    hour12: false,
  }).format(date)
}

export function occurredOnToIsoAttr(d: Date | string | number): string {
  const date = d instanceof Date ? d : new Date(d)
  if (Number.isNaN(date.getTime())) {
    return ''
  }
  return date.toISOString()
}

/** 文章列表：发布日期（年月日 + 星期） */
export function formatPublishedDateOnly(
  d: Date | string | number | null | undefined,
  locale = 'zh-CN',
): string {
  if (d == null) {
    return ''
  }
  const date = d instanceof Date ? d : new Date(d)
  if (Number.isNaN(date.getTime())) {
    return '—'
  }
  return new Intl.DateTimeFormat(locale, {
    year: 'numeric',
    month: 'long',
    day: 'numeric',
    weekday: 'short',
  }).format(date)
}