T06c forms date and time: calendar, date, range, time and date-time pickers, month, quarter, year and week pickers, relative ranges, time zones, durations, cron editor

src/forms/date/zone.rs

@@ -0,0 +1,106 @@
+use std::{rc::Rc, sync::LazyLock};
+
+use gpui::{App, ElementId, Entity, IntoElement, RenderOnce, SharedString, Window};
+use jiff::{
+    Timestamp,
+    tz::{self, Offset, TimeZone},
+};
+
+use super::super::{Choice, Combobox, TextInput, options::OnValue};
+use crate::typography::format::MINUS;
+
+/// An offset as "UTC+09:00", with a true minus sign west of Greenwich.
+pub(crate) fn show_offset(offset: Offset) -> String {
+    let seconds = offset.seconds();
+    let sign = if seconds < 0 { MINUS } else { '+' };
+    let minutes = seconds.unsigned_abs() / 60;
+    format!("UTC{sign}{:02}:{:02}", minutes / 60, minutes % 60)
+}
+
+/// Every zone the system knows, by name.
+static ZONES: LazyLock<Vec<(SharedString, TimeZone)>> = LazyLock::new(|| {
+    let mut zones: Vec<(SharedString, TimeZone)> = tz::db()
+        .available()
+        .filter_map(|name| match TimeZone::get(name.as_str()) {
+            Ok(zone) => Some((SharedString::from(name.as_str().to_string()), zone)),
+            Err(error) => {
+                log::error!("timezone select: skipped {}: {error}", name.as_str());
+                None
+            }
+        })
+        .collect();
+    zones.sort_by(|a, b| a.0.cmp(&b.0));
+    log::info!("timezone select: {} zones", zones.len());
+    zones
+});
+
+/// A searchable list of the system's time zones, each with its offset now.
+#[derive(IntoElement)]
+pub struct TimezoneSelect {
+    id: ElementId,
+    state: Entity<TextInput>,
+    selected: Option<SharedString>,
+    on_change: Option<OnValue>,
+}
+
+impl TimezoneSelect {
+    pub fn new(id: impl Into<ElementId>, state: &Entity<TextInput>) -> Self {
+        Self {
+            id: id.into(),
+            state: state.clone(),
+            selected: None,
+            on_change: None,
+        }
+    }
+
+    /// A zone by its IANA name, such as `Asia/Tokyo`.
+    pub fn selected(mut self, zone: impl Into<SharedString>) -> Self {
+        self.selected = Some(zone.into());
+        self
+    }
+
+    pub fn on_change(
+        mut self,
+        handler: impl Fn(&SharedString, &mut Window, &mut App) + 'static,
+    ) -> Self {
+        self.on_change = Some(Rc::new(handler));
+        self
+    }
+}
+
+impl RenderOnce for TimezoneSelect {
+    fn render(self, _: &mut Window, _: &mut App) -> impl IntoElement {
+        let now = Timestamp::now();
+        let zones = ZONES.iter().map(|(name, zone)| {
+            Choice::new(name.clone(), name.clone()).note(show_offset(zone.to_offset(now)))
+        });
+        let mut combo = Combobox::new(self.id, &self.state, zones);
+        if let Some(zone) = self.selected {
+            combo = combo.selected(zone);
+        }
+        if let Some(on_change) = self.on_change {
+            combo = combo.on_change(move |zone, window, cx| on_change(zone, window, cx));
+        }
+        combo
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use jiff::tz::Offset;
+
+    use super::show_offset;
+
+    #[test]
+    fn offsets_read_as_utc_plus_or_minus() {
+        assert_eq!(
+            show_offset(Offset::from_seconds(9 * 3600).unwrap()),
+            "UTC+09:00"
+        );
+        assert_eq!(
+            show_offset(Offset::from_seconds(-(5 * 3600 + 1800)).unwrap()),
+            "UTC\u{2212}05:30"
+        );
+        assert_eq!(show_offset(Offset::UTC), "UTC+00:00");
+    }
+}