add rust code

Author: devprofile98

GregorianToJalali.rs

@@ -0,0 +1,95 @@
+use std::fmt;
+
+#[derive(Debug)]
+struct JalaliDate {
+    year: usize,
+    month: usize,
+    day: usize,
+}
+impl fmt::Display for JalaliDate {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{:04}-{:02}-{:02}", self.year, self.month, self.day)
+    }
+}
+
+fn gregorian_to_jalali(year: usize, month: usize, day: usize) -> JalaliDate {
+    let mut result = JalaliDate {
+        year: 0,
+        month: 0,
+        day: 0,
+    };
+
+    let days_of_greg_month = [0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334];
+
+    let (adjusted_year, initial_year) = if year <= 1600 {
+        (year - 621, 0)
+    } else {
+        (year - 1600, 979)
+    };
+
+    result.year = initial_year;
+
+    let temp = if adjusted_year > 2 {
+        adjusted_year + 1
+    } else {
+        adjusted_year
+    };
+
+    let mut days = ((temp + 3) / 4) + (365 * adjusted_year) - ((temp + 99) / 100) - 80
+        + days_of_greg_month[month - 1]
+        + ((temp + 399) / 400)
+        + day;
+
+    result.year += 33 * (days / 12053);
+    days %= 12053;
+
+    result.year += 4 * (days / 1461);
+    days %= 1461;
+
+    if days > 365 {
+        result.year += (days - 1) / 365;
+        days = (days - 1) % 365;
+    }
+
+    result.month = if days < 186 {
+        1 + (days / 31)
+    } else {
+        7 + ((days - 186) / 30)
+    };
+
+    result.day = if days < 186 {
+        1 + (days % 31)
+    } else {
+        1 + ((days - 186) % 30)
+    };
+
+    result
+}
+
+fn main() {
+    let date = gregorian_to_jalali(2014, 2, 4);
+    println!("{}", date);
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_gregorian_to_jalali() {
+        let date = gregorian_to_jalali(2025, 3, 20);
+        assert_eq!(date.to_string(), "1403-12-30");
+    }
+
+    #[test]
+    fn test_gregorian_to_jalali_edge_case() {
+        let date = gregorian_to_jalali(2025, 3, 21);
+        assert_eq!(date.to_string(), "1404-01-01");
+    }
+
+    #[test]
+    fn test_display_format() {
+        let date = gregorian_to_jalali(2014, 2, 4);
+        assert_eq!(date.to_string(), "1392-11-15");
+    }
+}