const MONTHS_SHORT = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
const MONTHS_LONG = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December']
const WEEKDAYS_SHORT = ['Sun', 'Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat']
const WEEKDAYS_LONG = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday']

export function formatDate(date: Date, format: string): string {
  if (!format) return ''

  const year = date.getFullYear()
  const month = date.getMonth()
  const day = date.getDate()
  const weekday = date.getDay()
  const ordinalSuffix = day >= 11 && day <= 13
    ? 'th'
    : ({ 1: 'st', 2: 'nd', 3: 'rd' } as Record<number, string>)[day % 10] ?? 'th'

  const replacements: [RegExp, string][] = [
    [/YYYY/g, String(year)],
    [/YY/g, String(year).slice(-2)],
    [/MMMM/g, MONTHS_LONG[month]],
    [/MMM/g, MONTHS_SHORT[month]],
    [/MM/g, String(month + 1).padStart(2, '0')],
    [/M/g, String(month + 1)],
    [/dddd/g, WEEKDAYS_LONG[weekday]],
    [/ddd/g, WEEKDAYS_SHORT[weekday]],
    [/Do/g, `${day}${ordinalSuffix}`],
    [/DD/g, String(day).padStart(2, '0')],
    [/D/g, String(day)],
  ]

  let result = format
  const placeholders: string[] = []

  for (let i = 0; i < replacements.length; i++) {
    const [pattern, value] = replacements[i]
    const placeholder = `\x00${i}\x00`
    result = result.replace(pattern, () => {
      placeholders[i] = value
      return placeholder
    })
  }

  for (let i = 0; i < replacements.length; i++) {
    const placeholder = `\x00${i}\x00`
    if (placeholders[i] !== undefined) {
      result = result.split(placeholder).join(placeholders[i])
    }
  }

  return result
}

export function formatTime(date: Date, format: string): string {
  if (!format) return ''

  const hours24 = date.getHours()
  const hours12 = hours24 % 12 || 12
  const minutes = date.getMinutes()
  const seconds = date.getSeconds()
  const isPM = hours24 >= 12

  const replacements: [RegExp, string][] = [
    [/HH/g, String(hours24).padStart(2, '0')],
    [/H/g, String(hours24)],
    [/hh/g, String(hours12).padStart(2, '0')],
    [/h/g, String(hours12)],
    [/mm/g, String(minutes).padStart(2, '0')],
    [/m/g, String(minutes)],
    [/ss/g, String(seconds).padStart(2, '0')],
    [/s/g, String(seconds)],
    [/A/g, isPM ? 'PM' : 'AM'],
    [/a/g, isPM ? 'pm' : 'am'],
  ]

  let result = format
  const placeholders: string[] = []

  for (let i = 0; i < replacements.length; i++) {
    const [pattern, value] = replacements[i]
    const placeholder = `\x00${i}\x00`
    result = result.replace(pattern, () => {
      placeholders[i] = value
      return placeholder
    })
  }

  for (let i = 0; i < replacements.length; i++) {
    const placeholder = `\x00${i}\x00`
    if (placeholders[i] !== undefined) {
      result = result.split(placeholder).join(placeholders[i])
    }
  }

  return result
}