const [birthdate, lifeExpectancyArg = "90"] = process.argv.slice(2);

if (!birthdate) {
  console.error("Error: birthdate is required (YYYY-MM-DD format)");
  process.exit(1);
}

const lifeExpectancy = parseInt(lifeExpectancyArg, 10);
const WEEKS_PER_YEAR = 52;
const TOTAL_WEEKS = lifeExpectancy * WEEKS_PER_YEAR;

// Parse birthdate
const birth = new Date(birthdate);
if (isNaN(birth.getTime())) {
  console.error("Error: Invalid birthdate format. Use YYYY-MM-DD");
  process.exit(1);
}

const now = new Date();
const ageMs = now.getTime() - birth.getTime();
const ageWeeks = Math.floor(ageMs / (7 * 24 * 60 * 60 * 1000));
const ageYears = ageMs / (365.25 * 24 * 60 * 60 * 1000);
const ageDays = Math.floor(ageMs / (24 * 60 * 60 * 1000));

// Calculate weeks
const weeksLived = Math.min(ageWeeks, TOTAL_WEEKS);
const weeksRemaining = Math.max(0, TOTAL_WEEKS - weeksLived);
const percentageLived = ((weeksLived / TOTAL_WEEKS) * 100).toFixed(1);

// Calculate milestones
const seasonsLived = Math.floor(ageWeeks / 13);
const decadesLived = Math.floor(ageYears / 10);
const yearsLived = Math.floor(ageYears);
const monthsLived = Math.floor(ageYears * 12);

// Calculate next milestone
const nextBirthday = new Date(birth);
nextBirthday.setFullYear(now.getFullYear());
if (nextBirthday < now) {
  nextBirthday.setFullYear(now.getFullYear() + 1);
}
const daysUntilBirthday = Math.ceil(
  (nextBirthday.getTime() - now.getTime()) / (24 * 60 * 60 * 1000)
);

// Format age nicely
const ageYearsWhole = Math.floor(ageYears);
const ageMonthsRemainder = Math.floor((ageYears - ageYearsWhole) * 12);

console.log("Life statistics calculated:");
console.log(`  Age: ${ageYearsWhole} years, ${ageMonthsRemainder} months`);
console.log(`  Weeks lived: ${weeksLived.toLocaleString()} of ${TOTAL_WEEKS.toLocaleString()}`);
console.log(`  Progress: ${percentageLived}%`);

const stats = {
  birthdate,
  lifeExpectancy,
  totalWeeks: TOTAL_WEEKS,
  weeksLived,
  weeksRemaining,
  percentageLived: parseFloat(percentageLived),
  age: {
    years: ageYearsWhole,
    months: monthsLived,
    weeks: weeksLived,
    days: ageDays,
    formatted: `${ageYearsWhole} years, ${ageMonthsRemainder} months`,
  },
  milestones: {
    seasonsLived,
    yearsLived,
    decadesLived,
    daysUntilNextBirthday: daysUntilBirthday,
    nextAge: ageYearsWhole + 1,
  },
};

console.log(JSON.stringify(stats, null, 2));