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October 18, 2025 00:45
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| #!/usr/bin/env node | |
| function readStdin(callback) { | |
| let data = ""; | |
| process.stdin.setEncoding("utf8"); | |
| process.stdin.on("data", (chunk) => (data += chunk)); | |
| process.stdin.on("end", () => callback(data.trim())); | |
| } | |
| function getMoonInfo(date = new Date()) { | |
| // --- Julian Day --- | |
| const y = date.getUTCFullYear(); | |
| const m = date.getUTCMonth() + 1; | |
| const d = date.getUTCDate(); | |
| let yy = y, mm = m; | |
| if (m < 3) { yy--; mm += 12; } | |
| const a = Math.floor(yy / 100); | |
| const b = Math.floor(a / 4); | |
| const c = 2 - a + b; | |
| const e = Math.floor(365.25 * (yy + 4716)); | |
| const f = Math.floor(30.6001 * (mm + 1)); | |
| const jd = c + d + e + f - 1524.5; | |
| // --- Phase and age --- | |
| const daysSinceNew = jd - 2451550.1; | |
| const newMoons = daysSinceNew / 29.53058867; | |
| const phase = newMoons - Math.floor(newMoons); | |
| const age = phase * 29.53058867; | |
| let phaseName = ""; | |
| if (age < 1.0) phaseName = "New Moon"; | |
| else if (age < 7.4) phaseName = "Waxing Crescent"; | |
| else if (age < 8.6) phaseName = "First Quarter"; | |
| else if (age < 14.8) phaseName = "Waxing Gibbous"; | |
| else if (age < 15.8) phaseName = "Full Moon"; | |
| else if (age < 22.1) phaseName = "Waning Gibbous"; | |
| else if (age < 23.8) phaseName = "Last Quarter"; | |
| else phaseName = "Waning Crescent"; | |
| // --- Illumination --- | |
| const illum = (1 - Math.cos((age / 29.53058867) * 2 * Math.PI)) / 2; | |
| const percentLit = Math.round(illum * 100); | |
| // --- Days until full/new --- | |
| let daysToFull = 14.77 - age; | |
| if (daysToFull < 0) daysToFull += 29.53; | |
| let daysToNew = 29.53 - age; | |
| if (daysToNew < 0) daysToNew += 29.53; | |
| // --- Zodiac sign (approximate) --- | |
| const T = (jd - 2451545.0) / 36525.0; | |
| let Lm = (218.3164477 + 481267.88123421 * T) % 360; | |
| if (Lm < 0) Lm += 360; | |
| const zodiacNames = [ | |
| "Aries","Taurus","Gemini","Cancer","Leo","Virgo", | |
| "Libra","Scorpio","Sagittarius","Capricorn","Aquarius","Pisces" | |
| ]; | |
| const sign = zodiacNames[Math.floor(Lm / 30)]; | |
| // --- Distance (rough, km) --- | |
| const a_km = 384400; | |
| const ecc = 0.0549; // renamed from e → ecc | |
| const M = (age / 29.53058867) * 2 * Math.PI; | |
| let E = M; | |
| for (let i = 0; i < 5; i++) E -= (E - ecc * Math.sin(E) - M) / (1 - ecc * Math.cos(E)); | |
| const v = 2 * Math.atan(Math.sqrt((1 + ecc) / (1 - ecc)) * Math.tan(E / 2)); | |
| const dist = a_km * (1 - ecc * ecc) / (1 + ecc * Math.cos(v)); | |
| const distK = Math.round(dist / 1000); | |
| return { | |
| phaseName, | |
| percentLit, | |
| daysToFull: daysToFull.toFixed(1), | |
| daysToNew: daysToNew.toFixed(1), | |
| sign, | |
| distK | |
| }; | |
| } | |
| readStdin((input) => { | |
| let date = new Date(); | |
| if (input && /^\d{4}-\d{2}-\d{2}$/.test(input)) | |
| date = new Date(input + "T00:00:00Z"); | |
| const { phaseName, percentLit, daysToFull, daysToNew, sign, distK } = getMoonInfo(date); | |
| const output = `${phaseName}, ${percentLit}% lit, Full in ${daysToFull}d, New in ${daysToNew}d, in ${sign}, Dist ${distK}k km`; | |
| process.stdout.write(output); | |
| }); |
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