panchangam 0.2.0

High-precision Vedic Panchangam calculations using Swiss Ephemeris
Documentation 
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//! Sunrise/Sunset calculations using Swiss Ephemeris
//! Accounts for atmospheric refraction and elevation

use swiss_eph::safe::{self, RiseTransFlags, Planet, GeoPos};

/// Calculate sunrise time for a given date and location
/// Returns Unix timestamp in milliseconds
/// Accounts for atmospheric refraction
pub fn calculate_sunrise(year: i32, month: u32, day: u32, lat: f64, lon: f64, altitude: f64) -> f64 {
    // Start search from midnight to find today's sunrise
    let jd_start = safe::julday(year, month as i32, day as i32, 0.0);
    
    // Standard sunrise (with refraction)
    let flags = RiseTransFlags::new().with_rise();
    let geopos = GeoPos { longitude: lon, latitude: lat, altitude };
    
    match safe::rise_trans(jd_start, Planet::Sun, None, geopos, flags) {
        Ok(jd_rise) => jd_to_unix_ms(jd_rise),
        Err(_) => {
            // Fallback for polar regions - return 6:00 AM
            // Consistent with previous implementation behavior
            let jd_fallback = safe::julday(year, month as i32, day as i32, 6.0);
            jd_to_unix_ms(jd_fallback)
        }
    }
}

/// Calculate sunset time for a given date and location
/// Returns Unix timestamp in milliseconds
pub fn calculate_sunset(year: i32, month: u32, day: u32, lat: f64, lon: f64, altitude: f64) -> f64 {
    // Start search from noon to find today's sunset (usually after noon)
    // If we start at midnight, we might find yesterday's sunset if it was late? 
    // No, `rise_trans` searches forward. 
    // But safely, noon is good.
    let jd_start = safe::julday(year, month as i32, day as i32, 12.0);
    
    let flags = RiseTransFlags::new().with_set();
    let geopos = GeoPos { longitude: lon, latitude: lat, altitude };
    
    match safe::rise_trans(jd_start, Planet::Sun, None, geopos, flags) {
        Ok(jd_set) => jd_to_unix_ms(jd_set),
        Err(_) => {
            // Fallback for polar regions - return 6:00 PM
            let jd_fallback = safe::julday(year, month as i32, day as i32, 18.0);
            jd_to_unix_ms(jd_fallback)
        }
    }
}

/// Convert Julian Day to Unix timestamp in milliseconds
fn jd_to_unix_ms(jd: f64) -> f64 {
    // Unix epoch = JD 2440587.5
    (jd - 2440587.5) * 86400000.0
}

/// Convert Unix timestamp to Julian Day
pub fn unix_ms_to_jd(unix_ms: f64) -> f64 {
    unix_ms / 86400000.0 + 2440587.5
}