const formatNumber = n => {
  n = n.toString()
  return n[1] ? n : `0${n}`
}

const formatDate = date => {
  const d = date instanceof Date ? date : new Date(date)
  const year = d.getFullYear()
  const month = d.getMonth() + 1
  const day = d.getDate()

  return `${[year, month, day].map(formatNumber).join('-')}`
}

const formatTime = date => {
  const d = date instanceof Date ? date : new Date(date)
  if (Number.isNaN(d.getTime())) {
    return ''
  }

  const year = d.getFullYear()
  const month = d.getMonth() + 1
  const day = d.getDate()
  const hour = d.getHours()
  const minute = d.getMinutes()
  const second = d.getSeconds()

  return `${[year, month, day].map(formatNumber).join('-')} ${[hour, minute, second].map(formatNumber).join(':')}`
}

const today = () => formatDate(new Date())

const parseDate = value => {
  if (value instanceof Date) {
    return new Date(value.getFullYear(), value.getMonth(), value.getDate())
  }
  const text = String(value || '').trim()
  const matched = text.match(/^(\d{4})-(\d{2})-(\d{2})$/)
  if (matched) {
    return new Date(Number(matched[1]), Number(matched[2]) - 1, Number(matched[3]))
  }
  return new Date()
}

const addDays = (value, days) => {
  const date = parseDate(value)
  date.setDate(date.getDate() + toNumber(days))
  return formatDate(date)
}

const uid = prefix => `${prefix}_${Date.now()}_${Math.random().toString(16).slice(2, 8)}`

const toNumber = value => {
  const number = Number(value)
  return Number.isFinite(number) ? number : 0
}

const minutesBetween = (start, end) => {
  const startTime = new Date(start).getTime()
  const endTime = new Date(end).getTime()
  if (!Number.isFinite(startTime) || !Number.isFinite(endTime) || endTime <= startTime) {
    return 0
  }
  return Math.round((endTime - startTime) / 60000)
}

const round = (value, digits = 1) => {
  const base = Math.pow(10, digits)
  return Math.round(toNumber(value) * base) / base
}

const percent = (value, digits = 0) => `${round(value, digits)}%`

const paginate = (rows, page = 1, pageSize = 10) => {
  const safePage = Math.max(1, toNumber(page) || 1)
  const safePageSize = Math.max(1, toNumber(pageSize) || 10)
  const total = rows.length
  const totalPages = Math.max(1, Math.ceil(total / safePageSize))
  const current = Math.min(safePage, totalPages)
  const start = (current - 1) * safePageSize

  return {
    rows: rows.slice(start, start + safePageSize),
    page: current,
    pageSize: safePageSize,
    total,
    totalPages,
  }
}

module.exports = {
  addDays,
  formatDate,
  formatTime,
  formatNumber,
  minutesBetween,
  paginate,
  percent,
  round,
  today,
  toNumber,
  uid,
}