Function resolveDateRange

app/composables/useCharts.ts:290–337

(
    evolutionOptions: EvolutionOptions,
    packageCreatedIso: string | null,
  )

export function useCharts() {
  function resolveDateRange(
    evolutionOptions: EvolutionOptions,
    packageCreatedIso: string | null,
  ): { start: Date; end: Date } {
    const today = new Date()
    const yesterday = new Date(
      Date.UTC(today.getUTCFullYear(), today.getUTCMonth(), today.getUTCDate() - 1),
    )

    const endDateOnly = toDateOnly(evolutionOptions.endDate)
    const end = endDateOnly ? parseIsoDate(endDateOnly) : yesterday

    const startDateOnly = toDateOnly(evolutionOptions.startDate)
    if (startDateOnly) {
      const start = parseIsoDate(startDateOnly)
      return { start, end }
    }

    let start: Date

    if (evolutionOptions.granularity === 'year') {
      if (packageCreatedIso) {
        start = startOfUtcYear(new Date(packageCreatedIso))
      } else {
        start = addDays(end, -(5 * 365) + 1)
      }
    } else if (evolutionOptions.granularity === 'month') {
      const monthCount = evolutionOptions.months ?? 12
      const firstOfThisMonth = startOfUtcMonth(end)
      start = new Date(
        Date.UTC(
          firstOfThisMonth.getUTCFullYear(),
          firstOfThisMonth.getUTCMonth() - (monthCount - 1),
          1,
        ),
      )
    } else if (evolutionOptions.granularity === 'week') {
      const weekCount = evolutionOptions.weeks ?? 52

      // Full rolling weeks ending on `end` (yesterday by default)
      // Range length is exactly weekCount * 7 days (inclusive)
      start = addDays(end, -(weekCount * 7) + 1)
    } else {
      start = addDays(end, -30 + 1)
    }

    return { start, end }
  }

  async function fetchPackageDownloadEvolution(
    packageName: MaybeRefOrGetter<string>,