export type Subscription = {
  id: string
  key: string
  pubkey: string
  email: string
  frequency: string
  hour: number
  minute: number
  day_of_week?: number
  timezone: string
  created_at: number
  confirmed_at?: number
  unsubscribed_at?: number
  last_digest_at?: number
  last_confirm_sent_at?: number
}

export const getSubscriptionError = (sub: Subscription) => {
  if (!sub.email?.includes('@')) {
    return 'Please provide a valid email address'
  }

  if (!['daily', 'weekly'].includes(sub.frequency)) {
    return 'Frequency must be "daily" or "weekly"'
  }

  if (sub.hour < 0 || sub.hour > 23 || !Number.isInteger(sub.hour)) {
    return 'Hour must be an integer between 0 and 23'
  }

  if (sub.minute < 0 || sub.minute > 59 || !Number.isInteger(sub.minute)) {
    return 'Minute must be an integer between 0 and 59'
  }

  if (sub.frequency === 'weekly') {
    if (sub.day_of_week === undefined || sub.day_of_week === null) {
      return 'dayOfWeek is required for weekly frequency'
    }
    const dow = sub.day_of_week
    if (dow < 0 || dow > 7 || !Number.isInteger(dow)) {
      return 'dayOfWeek must be an integer between 0 and 7 (1=Mon, 7=Sun, 0=Sun)'
    }
  }

  if (!sub.timezone || typeof sub.timezone !== 'string') {
    return 'A valid IANA timezone is required'
  }

  try {
    Intl.DateTimeFormat(undefined, { timeZone: sub.timezone })
  } catch {
    return `"${sub.timezone}" is not a valid IANA timezone`
  }
}

export const getCronExpression = (frequency: string, hour = 17, minute = 0, dayOfWeek?: number) => {
  if (frequency === 'daily') {
    return `0 ${minute} ${hour} * * *`
  }
  // Weekly: default to Monday (1) when not specified
  return `0 ${minute} ${hour} * * ${dayOfWeek ?? 1}`
}