frontend/src/modelRecency.js

function parseIsoDateOnly(value) {
  const text = String(value ?? '').trim()
  const isoMatch = text.match(/^(\d{4})-(\d{2})-(\d{2})$/)
  if (!isoMatch) return null

  const year = Number(isoMatch[1])
  const month = Number(isoMatch[2])
  const day = Number(isoMatch[3])
  const date = new Date(Date.UTC(year, month - 1, day))

  if (
    Number.isNaN(date.getTime())
    || date.getUTCFullYear() !== year
    || date.getUTCMonth() !== month - 1
    || date.getUTCDate() !== day
  ) {
    return null
  }

  return date
}

function subtractMonthsUtc(date, months) {
  const year = date.getUTCFullYear()
  const month = date.getUTCMonth()
  const day = date.getUTCDate()
  const base = new Date(Date.UTC(year, month - months, 1))
  const lastDayOfTargetMonth = new Date(
    Date.UTC(base.getUTCFullYear(), base.getUTCMonth() + 1, 0),
  ).getUTCDate()

  base.setUTCDate(Math.min(day, lastDayOfTargetMonth))
  return base
}

export function getFaixaDataRecencyInfo(periodo) {
  const dataFinal = parseIsoDateOnly(periodo?.max ?? periodo?.data_final)
  if (!dataFinal) return { tone: '', label: '' }

  const now = new Date()
  const hojeUtc = new Date(Date.UTC(now.getFullYear(), now.getMonth(), now.getDate()))
  if (dataFinal > hojeUtc) return { tone: '', label: '' }

  if (dataFinal <= subtractMonthsUtc(hojeUtc, 24)) {
    return { tone: '2y', label: '>= 2 anos' }
  }
  if (dataFinal <= subtractMonthsUtc(hojeUtc, 12)) {
    return { tone: '1y', label: '>= 1 ano' }
  }
  if (dataFinal <= subtractMonthsUtc(hojeUtc, 6)) {
    return { tone: '6m', label: '>= 6 meses' }
  }

  return { tone: '', label: '' }
}