chore: fix timezone handling

src/localize/datetime.rs

@@ -1,4 +1,5 @@
-use chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime, Utc};
+use chrono::{DateTime, NaiveDate, NaiveDateTime, NaiveTime, TimeZone, Utc};
+use chrono_tz::Tz;
 use once_cell::sync::Lazy;
 use regex::Regex;
 use std::path::Path;
@@ -17,15 +18,25 @@ static DATE_MARKER_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"^\d{8}$").unwr
 /// Regex for validating time marker format (6 digits).
 static TIME_MARKER_REGEX: Lazy<Regex> = Lazy::new(|| Regex::new(r"^\d{6}$").unwrap());
 
+/// Convert a NaiveDateTime to UTC via the given timezone.
+/// Falls back to the earliest local interpretation for ambiguous DST times.
+fn naive_to_utc(dt: NaiveDateTime, tz: Tz) -> Option<DateTime<Utc>> {
+    tz.from_local_datetime(&dt)
+        .single()
+        .or_else(|| tz.from_local_datetime(&dt).earliest())
+        .map(|dt| dt.with_timezone(&Utc))
+}
+
 /// Extract a datetime from a file name in the format YYYYMMDD-HHMMSS.
 ///
 /// The time component is optional and can be 4-6 digits (HHMM, HHMMS, or HHMMSS).
+/// The datetime is interpreted in the given timezone.
 ///
 /// # Examples
-/// - "20230101-123456 Some Text.md" -> DateTime for 2023-01-01 12:34:56
-/// - "20230101 Some Text.md" -> DateTime for 2023-01-01 00:00:00
+/// - "20230101-123456 Some Text.md" -> DateTime for 2023-01-01 12:34:56 in tz
+/// - "20230101 Some Text.md" -> DateTime for 2023-01-01 00:00:00 in tz
 /// - "invalid-file-name.md" -> None
-pub fn extract_datetime_from_file_name(file_name: &str) -> Option<DateTime<Utc>> {
+pub fn extract_datetime_from_file_name(file_name: &str, tz: Tz) -> Option<DateTime<Utc>> {
     let base_name = Path::new(file_name)
         .file_name()
         .and_then(|s| s.to_str())
@@ -48,20 +59,23 @@ pub fn extract_datetime_from_file_name(file_name: &str) -> Option<DateTime<Utc>>
 
     NaiveDateTime::parse_from_str(&datetime_str, "%Y%m%d %H:%M:%S")
         .ok()
-        .map(|dt| dt.and_utc())
+        .and_then(|dt| naive_to_utc(dt, tz))
+}
+
+/// Parse a 14-digit marker string as a NaiveDateTime without timezone conversion.
+fn parse_naive_datetime_from_marker(marker: &str) -> Option<NaiveDateTime> {
+    if !DATETIME_MARKER_REGEX.is_match(marker) {
+        return None;
+    }
+    NaiveDateTime::parse_from_str(marker, "%Y%m%d%H%M%S").ok()
 }
 
 /// Extract a datetime from a marker string in the exact format: YYYYMMDDHHMMSS.
 ///
+/// The datetime is interpreted in the given timezone.
 /// Returns the parsed datetime if the format matches and values are valid.
-pub fn extract_datetime_from_marker(marker: &str) -> Option<DateTime<Utc>> {
-    if !DATETIME_MARKER_REGEX.is_match(marker) {
-        return None;
-    }
-
-    NaiveDateTime::parse_from_str(marker, "%Y%m%d%H%M%S")
-        .ok()
-        .map(|dt| dt.and_utc())
+pub fn extract_datetime_from_marker(marker: &str, tz: Tz) -> Option<DateTime<Utc>> {
+    parse_naive_datetime_from_marker(marker).and_then(|dt| naive_to_utc(dt, tz))
 }
 
 /// Extract a date from a marker string in the exact format: YYYYMMDD.
@@ -90,6 +104,7 @@ pub fn extract_time_from_marker(marker: &str) -> Option<NaiveTime> {
 ///
 /// The function processes markers in reverse order, allowing later markers to override
 /// earlier ones. It combines date-only and time-only markers when both are present.
+/// All naive datetimes (from markers and the inherited fallback) are interpreted in `tz`.
 ///
 /// Rules:
 /// - If a full datetime marker (14 digits) is found, it sets both date and time
@@ -99,6 +114,7 @@ pub fn extract_time_from_marker(marker: &str) -> Option<NaiveTime> {
 pub fn extract_datetime_from_marker_list(
     markers: &[String],
     inherited_datetime: DateTime<Utc>,
+    tz: Tz,
 ) -> DateTime<Utc> {
     let mut shard_time: Option<NaiveTime> = None;
     let mut shard_date: Option<NaiveDate> = None;
@@ -111,34 +127,39 @@ pub fn extract_datetime_from_marker_list(
         if let Some(date) = extract_date_from_marker(marker) {
             shard_date = Some(date);
         }
-        if let Some(datetime) = extract_datetime_from_marker(marker) {
-            shard_date = Some(datetime.naive_utc().date());
-            shard_time = Some(datetime.naive_utc().time());
+        if let Some(naive_dt) = parse_naive_datetime_from_marker(marker) {
+            shard_date = Some(naive_dt.date());
+            shard_time = Some(naive_dt.time());
         }
     }
 
+    // Interpret the inherited datetime in the configured timezone for fallback values
+    let inherited_local = inherited_datetime.with_timezone(&tz).naive_local();
+
     // Combine date and time, applying defaults as needed
-    let final_date = shard_date.unwrap_or_else(|| inherited_datetime.naive_utc().date());
+    let final_date = shard_date.unwrap_or_else(|| inherited_local.date());
     let final_time = match (shard_date, shard_time) {
         // If we have a date but no time, use midnight
         (Some(_), None) => NaiveTime::from_hms_opt(0, 0, 0).unwrap(),
         // Otherwise use the shard time or inherit
-        _ => shard_time.unwrap_or_else(|| inherited_datetime.naive_utc().time()),
+        _ => shard_time.unwrap_or_else(|| inherited_local.time()),
     };
 
-    NaiveDateTime::new(final_date, final_time).and_utc()
+    let naive = NaiveDateTime::new(final_date, final_time);
+    naive_to_utc(naive, tz).unwrap_or_else(|| inherited_datetime)
 }
 
 #[cfg(test)]
 mod tests {
     use super::*;
     use chrono::TimeZone;
+    use chrono_tz::UTC;
 
     #[test]
     fn test_extract_date_from_file_name_valid() {
         let file_name = "20230101-123456 Some Text.md";
         assert_eq!(
-            extract_datetime_from_file_name(file_name),
+            extract_datetime_from_file_name(file_name, UTC),
             Some(Utc.with_ymd_and_hms(2023, 1, 1, 12, 34, 56).unwrap())
         );
     }
@@ -146,14 +167,14 @@ mod tests {
     #[test]
     fn test_extract_date_from_file_name_invalid() {
         let file_name = "invalid-file-name.md";
-        assert_eq!(extract_datetime_from_file_name(file_name), None);
+        assert_eq!(extract_datetime_from_file_name(file_name, UTC), None);
     }
 
     #[test]
     fn test_extract_date_from_file_name_without_time() {
         let file_name = "20230101 Some Text.md";
         assert_eq!(
-            extract_datetime_from_file_name(file_name),
+            extract_datetime_from_file_name(file_name, UTC),
             Some(Utc.with_ymd_and_hms(2023, 1, 1, 0, 0, 0).unwrap())
         );
     }
@@ -162,7 +183,7 @@ mod tests {
     fn test_extract_date_from_file_name_short_time() {
         let file_name = "20230101-1234 Some Text.md";
         assert_eq!(
-            extract_datetime_from_file_name(file_name),
+            extract_datetime_from_file_name(file_name, UTC),
             Some(Utc.with_ymd_and_hms(2023, 1, 1, 12, 34, 0).unwrap())
         );
     }
@@ -170,41 +191,61 @@ mod tests {
     #[test]
     fn test_extract_date_from_file_name_empty_string() {
         let file_name = "";
-        assert_eq!(extract_datetime_from_file_name(file_name), None);
+        assert_eq!(extract_datetime_from_file_name(file_name, UTC), None);
     }
 
     #[test]
     fn test_extract_date_from_file_name_with_full_path() {
         let file_name = "/path/to/20230101-123456 Some Text.md";
         assert_eq!(
-            extract_datetime_from_file_name(file_name),
+            extract_datetime_from_file_name(file_name, UTC),
             Some(Utc.with_ymd_and_hms(2023, 1, 1, 12, 34, 56).unwrap())
         );
     }
 
+    #[test]
+    fn test_extract_date_from_file_name_with_timezone_offset() {
+        // Europe/Berlin is UTC+1 in January (CET)
+        let file_name = "20230101-120000 Some Text.md";
+        assert_eq!(
+            extract_datetime_from_file_name(file_name, chrono_tz::Europe::Berlin),
+            Some(Utc.with_ymd_and_hms(2023, 1, 1, 11, 0, 0).unwrap())
+        );
+    }
+
     #[test]
     fn test_extract_datetime_from_marker_valid() {
         let marker = "20250101150000";
         assert_eq!(
-            extract_datetime_from_marker(marker),
+            extract_datetime_from_marker(marker, UTC),
             Some(Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap())
         );
     }
 
+    #[test]
+    fn test_extract_datetime_from_marker_with_timezone_offset() {
+        // Europe/Berlin is UTC+1 in January (CET)
+        let marker = "20250101150000";
+        assert_eq!(
+            extract_datetime_from_marker(marker, chrono_tz::Europe::Berlin),
+            Some(Utc.with_ymd_and_hms(2025, 1, 1, 14, 0, 0).unwrap())
+        );
+    }
+
     #[test]
     fn test_extract_datetime_from_marker_invalid_format() {
-        assert_eq!(extract_datetime_from_marker("2025010115000"), None); // too short
-        assert_eq!(extract_datetime_from_marker("202501011500000"), None); // too long
-        assert_eq!(extract_datetime_from_marker("2025-01-01T150000"), None); // separators
-        assert_eq!(extract_datetime_from_marker("2025010115000a"), None); // non-digit
-        assert_eq!(extract_datetime_from_marker(""), None);
+        assert_eq!(extract_datetime_from_marker("2025010115000", UTC), None); // too short
+        assert_eq!(extract_datetime_from_marker("202501011500000", UTC), None); // too long
+        assert_eq!(extract_datetime_from_marker("2025-01-01T150000", UTC), None); // separators
+        assert_eq!(extract_datetime_from_marker("2025010115000a", UTC), None); // non-digit
+        assert_eq!(extract_datetime_from_marker("", UTC), None);
     }
 
     #[test]
     fn test_extract_datetime_from_marker_invalid_values() {
-        assert_eq!(extract_datetime_from_marker("20250230120000"), None); // Feb 30
-        assert_eq!(extract_datetime_from_marker("20250101126000"), None); // minute 60
-        assert_eq!(extract_datetime_from_marker("20250101240000"), None); // hour 24
+        assert_eq!(extract_datetime_from_marker("20250230120000", UTC), None); // Feb 30
+        assert_eq!(extract_datetime_from_marker("20250101126000", UTC), None); // minute 60
+        assert_eq!(extract_datetime_from_marker("20250101240000", UTC), None); // hour 24
     }
 
     #[test]
@@ -260,7 +301,10 @@ mod tests {
     #[test]
     fn test_no_markers_inherits_datetime() {
         let inherited = Utc.with_ymd_and_hms(2025, 1, 2, 3, 4, 5).unwrap();
-        assert_eq!(extract_datetime_from_marker_list(&[], inherited), inherited);
+        assert_eq!(
+            extract_datetime_from_marker_list(&[], inherited, UTC),
+            inherited
+        );
     }
 
     #[test]
@@ -273,7 +317,7 @@ mod tests {
             "1234567".to_string(),
         ];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             inherited
         );
     }
@@ -283,7 +327,7 @@ mod tests {
         let inherited = Utc.with_ymd_and_hms(2025, 6, 7, 8, 9, 10).unwrap();
         let markers = vec!["20250101".to_string()];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 0, 0, 0).unwrap()
         );
     }
@@ -293,7 +337,7 @@ mod tests {
         let inherited = Utc.with_ymd_and_hms(2025, 6, 7, 8, 9, 10).unwrap();
         let markers = vec!["150000".to_string()];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 6, 7, 15, 0, 0).unwrap()
         );
     }
@@ -303,7 +347,7 @@ mod tests {
         let inherited = Utc.with_ymd_and_hms(2025, 6, 7, 8, 9, 10).unwrap();
         let markers = vec!["20250101150000".to_string()];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap()
         );
     }
@@ -313,7 +357,7 @@ mod tests {
         let inherited = Utc.with_ymd_and_hms(2025, 6, 7, 8, 9, 10).unwrap();
         let markers = vec!["20250101".to_string(), "150000".to_string()];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap()
         );
     }
@@ -328,7 +372,7 @@ mod tests {
             "160000".to_string(),
         ];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap()
         );
     }
@@ -343,7 +387,7 @@ mod tests {
         ];
         // The first date (20250101) and first time (150000) should win over the later combined datetime
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap()
         );
     }
@@ -358,8 +402,19 @@ mod tests {
             "150000".to_string(),   // valid
         ];
         assert_eq!(
-            extract_datetime_from_marker_list(&markers, inherited),
+            extract_datetime_from_marker_list(&markers, inherited, UTC),
             Utc.with_ymd_and_hms(2025, 1, 1, 15, 0, 0).unwrap()
         );
     }
+
+    #[test]
+    fn test_marker_list_with_timezone_offset() {
+        // Europe/Berlin is UTC+2 in summer (CEST)
+        let inherited = Utc.with_ymd_and_hms(2025, 6, 7, 8, 9, 10).unwrap();
+        let markers = vec!["150000".to_string()];
+        assert_eq!(
+            extract_datetime_from_marker_list(&markers, inherited, chrono_tz::Europe::Berlin),
+            Utc.with_ymd_and_hms(2025, 6, 7, 13, 0, 0).unwrap()
+        );
+    }
 }