Add icu_preferences util

Cargo.toml

@@ -42,6 +42,7 @@ members = [
     "utils/fixed_decimal",
     "utils/litemap",
     "utils/pattern",
+    "utils/preferences",
     "utils/tinystr",
     "utils/uniset",
     "utils/writeable",

components/datetime/src/options/preferences.rs

@@ -23,6 +23,8 @@
 //! let prefs = preferences::Bag::from_hour_cycle(preferences::HourCycle::H23);
 //! ```
 use crate::fields;
+use icu_locid::{unicode_ext_value, extensions::unicode};
+use core::convert::TryFrom;
 
 #[cfg(feature = "serde")]
 use serde::{Deserialize, Serialize};
@@ -122,3 +124,22 @@ impl HourCycle {
         }
     }
 }
+
+const H11: unicode::Value = unicode_ext_value!("h11");
+const H12: unicode::Value = unicode_ext_value!("h12");
+const H23: unicode::Value = unicode_ext_value!("h23");
+const H24: unicode::Value = unicode_ext_value!("h24");
+
+impl TryFrom<&unicode::Value> for HourCycle {
+    type Error = ();
+
+    fn try_from(value: &unicode::Value) -> Result<Self, Self::Error> {
+        match value {
+            _ if value == &H11 => Ok(Self::H11),
+            _ if value == &H12 => Ok(Self::H12),
+            _ if value == &H23 => Ok(Self::H23),
+            _ if value == &H24 => Ok(Self::H24),
+            _ => Err(())
+        }
+    }
+}

utils/preferences/Cargo.toml

@@ -0,0 +1,28 @@
+# This file is part of ICU4X. For terms of use, please see the file
+# called LICENSE at the top level of the ICU4X source tree
+# (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
+
+[package]
+name = "icu_preferences"
+description = "API for resolving user preferences against unicode extensions"
+version = "0.0.1"
+authors = ["The ICU4X Project Developers"]
+edition = "2021"
+readme = "README.md"
+repository = "https://github.com/unicode-org/icu4x"
+license-file = "LICENSE"
+categories = ["internationalization"]
+# Keep this in sync with other crates unless there are exceptions
+include = [
+    "src/**/*",
+    "examples/**/*",
+    "benches/**/*",
+    "tests/**/*",
+    "Cargo.toml",
+    "LICENSE",
+    "README.md"
+]
+
+[dev-dependencies]
+icu_locid = { version = "0.6", path = "../../components/locid" }
+icu_datetime = { version = "0.6", path = "../../components/datetime" }

utils/preferences/src/lib.rs

@@ -0,0 +1,32 @@
+#[macro_use]
+mod macros;
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use icu_datetime::options::preferences::HourCycle;
+    use icu_locid::{unicode_ext_key, Locale};
+
+    preferences!(
+        Preferences,
+        ResolvedPreferences,
+        {
+            hour_cycle => Option<HourCycle>, HourCycle, Some(unicode_ext_key!("hc"))
+        }
+    );
+
+    #[test]
+    fn it_works() {
+        let l: Locale = "en-US-u-hc-h23".parse().unwrap();
+
+        let prefs = Preferences { hour_cycle: None };
+
+        let defaults = ResolvedPreferences {
+            hour_cycle: HourCycle::H12,
+        };
+
+        let resolved_prefs = ResolvedPreferences::try_from((&prefs, &l, &defaults)).unwrap();
+
+        assert_eq!(resolved_prefs.hour_cycle, HourCycle::H23);
+    }
+}

utils/preferences/src/macros.rs

@@ -0,0 +1,40 @@
+#[macro_export]
+macro_rules! preferences {
+    ($name:ident, $resolved_name:ident, {$($key:ident => $pref:ty, $resolved:ty, $ue:expr),*}) => (
+        #[derive(Default)]
+        pub struct $name {
+            $(
+                $key: $pref,
+            )*
+        }
+
+        pub struct $resolved_name {
+            $(
+                $key: $resolved,
+            )*
+        }
+
+        impl TryFrom<(&$name, &Locale, &$resolved_name)> for $resolved_name {
+            type Error = ();
+
+            fn try_from(input: (&$name, &Locale, &$resolved_name)) -> Result<Self, Self::Error> {
+                let (prefs, locale, defaults) = input;
+                let keywords = &locale.extensions.unicode.keywords;
+
+                $(
+                    let mut $key = prefs.$key;
+                    if $key.is_none() {
+                        $key = $ue.and_then(
+                            |ue_key| keywords.get(&ue_key).map(TryInto::try_into)
+                        ).transpose()?;
+                    }
+                )*
+                Ok($resolved_name {
+                    $(
+                        $key: $key.unwrap_or(defaults.$key),
+                    )*
+                })
+            }
+        }
+    )
+}

utils/preferences/tests/dtf.rs

@@ -0,0 +1,85 @@
+use icu_datetime::options::preferences::HourCycle;
+use icu_locid::{unicode_ext_key, Locale};
+use icu_preferences::preferences;
+
+#[derive(Clone, Copy)]
+enum Calendar {
+    Gregory,
+}
+
+impl TryFrom<&icu_locid::extensions::unicode::Value> for Calendar {
+    type Error = ();
+
+    fn try_from(_i: &icu_locid::extensions::unicode::Value) -> Result<Self, Self::Error> {
+        Ok(Calendar::Gregory)
+    }
+}
+
+preferences!(
+    DTFPreferences,
+    ResolvedDTFPreferences,
+    {
+        hour_cycle => Option<HourCycle>, HourCycle, Some(unicode_ext_key!("hc")),
+        calendar => Option<Calendar>, Calendar, Some(unicode_ext_key!("ca"))
+    }
+);
+
+struct DateTimeFormat {
+    prefs: ResolvedDTFPreferences,
+}
+
+impl DateTimeFormat {
+    pub fn new(locale: &Locale, prefs: &DTFPreferences) -> Self {
+        let en_us_defaults = ResolvedDTFPreferences {
+            hour_cycle: HourCycle::H12,
+            calendar: Calendar::Gregory,
+        };
+
+        let prefs = ResolvedDTFPreferences::try_from((prefs, locale, &en_us_defaults)).unwrap();
+
+        Self { prefs }
+    }
+
+    pub fn format(&self, _input: u64) -> String {
+        match self.prefs.hour_cycle {
+            HourCycle::H11 => "00:13 am",
+            HourCycle::H12 => "12:13 am",
+            HourCycle::H23 => "00:13",
+            HourCycle::H24 => "24:13",
+        }
+        .to_string()
+    }
+}
+
+#[test]
+fn dtf_default() {
+    let loc: Locale = "en-US".parse().unwrap();
+    let prefs = DTFPreferences {
+        hour_cycle: None,
+        ..Default::default()
+    };
+    let dtf = DateTimeFormat::new(&loc, &prefs);
+    assert_eq!(dtf.format(0), String::from("12:13 am"));
+}
+
+#[test]
+fn dtf_uext() {
+    let loc: Locale = "en-US-u-hc-h11".parse().unwrap();
+    let prefs = DTFPreferences {
+        hour_cycle: None,
+        ..Default::default()
+    };
+    let dtf = DateTimeFormat::new(&loc, &prefs);
+    assert_eq!(dtf.format(0), String::from("00:13 am"));
+}
+
+#[test]
+fn dtf_prefs() {
+    let loc: Locale = "en-US-u-hc-h11".parse().unwrap();
+    let prefs = DTFPreferences {
+        hour_cycle: Some(HourCycle::H24),
+        ..Default::default()
+    };
+    let dtf = DateTimeFormat::new(&loc, &prefs);
+    assert_eq!(dtf.format(0), String::from("24:13"));
+}