support for parsing date string with only time

src/lib.rs

@@ -16,6 +16,7 @@
 mod parse_relative_time;
 mod parse_timestamp;
 
+mod parse_time_only_str;
 mod parse_weekday;
 
 use chrono::{
@@ -237,6 +238,11 @@
         }
     }
 
+    // parse time only dates
+    if let Some(date_time) = parse_time_only_str::parse_time_only(date, s.as_ref()) {
+        return Ok(date_time);
+    }
+
     // Default parse and failure
     s.as_ref()
         .parse()

src/parse_time_only_str.rs

@@ -0,0 +1,120 @@
+use chrono::{DateTime, FixedOffset, Local, NaiveTime, TimeZone};
+use regex::Regex;
+
+mod time_only_formats {
+    pub const HH_MM: &str = "%R";
+    pub const HH_MM_SS: &str = "%T";
+    pub const TWELVEHOUR: &str = "%r";
+}
+
+pub(crate) fn parse_time_only(date: DateTime<Local>, s: &str) -> Option<DateTime<FixedOffset>> {
+    let re =
+        Regex::new(r"^(?<time>.*?)(?:(?<sign>\+|-)(?<h>[0-9]{1,2}):?(?<m>[0-9]{0,2}))?$").unwrap();
+    let captures = re.captures(s)?;
+
+    let parsed_offset = match captures.name("h") {
+        Some(hours) if !(hours.as_str().is_empty()) => {
+            let mut offset_in_sec = hours.as_str().parse::<i32>().unwrap() * 3600;
+            match captures.name("m") {
+                Some(minutes) if !(minutes.as_str().is_empty()) => {
+                    offset_in_sec += minutes.as_str().parse::<i32>().unwrap() * 60;
+                }
+                _ => (),
+            };
+            offset_in_sec *= if &captures["sign"] == "-" { -1 } else { 1 };
+            FixedOffset::east_opt(offset_in_sec)
+        }
+        _ => None,
+    };
+
+    for fmt in [
+        time_only_formats::HH_MM,
+        time_only_formats::HH_MM_SS,
+        time_only_formats::TWELVEHOUR,
+    ] {
+        if let Ok(parsed) = NaiveTime::parse_from_str(captures["time"].trim(), fmt) {
+            let parsed_dt = date.date_naive().and_time(parsed);
+            let offset = match parsed_offset {
+                Some(offset) => offset,
+                None => *date.offset(),
+            };
+            return offset.from_local_datetime(&parsed_dt).single();
+        }
+    }
+
+    None
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::parse_time_only_str::parse_time_only;
+    use chrono::{DateTime, Local, TimeZone};
+    use std::env;
+
+    fn get_test_date() -> DateTime<Local> {
+        Local.with_ymd_and_hms(2024, 03, 03, 0, 0, 0).unwrap()
+    }
+
+    #[test]
+    fn test_time_only() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "21:04")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709499840)
+    }
+
+    #[test]
+    fn test_time_with_offset() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "21:04 +0530")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709480040);
+    }
+
+    #[test]
+    fn test_time_with_hour_only_offset() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "22:04 +01")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709499840);
+    }
+
+    #[test]
+    fn test_time_with_hour_only_neg_offset() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "17:04 -04")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709499840);
+    }
+
+    #[test]
+    fn test_time_with_seconds() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "21:04:30")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709499870)
+    }
+
+    #[test]
+    fn test_time_with_seconds_with_offset() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "21:04:30 +0530")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709480070)
+    }
+
+    #[test]
+    fn test_twelve_hour_time() {
+        env::set_var("TZ", "UTC");
+        let parsed_time = parse_time_only(get_test_date(), "9:04:00 PM")
+            .unwrap()
+            .timestamp();
+        assert_eq!(parsed_time, 1709499840)
+    }
+}