2 files changed, 179 insertions, 0 deletions
diff --git a/third_party/rust/intl-memoizer/src/concurrent.rs b/third_party/rust/intl-memoizer/src/concurrent.rs
new file mode 100644
index 0000000000..95553281b6
--- /dev/null
+++ b/third_party/rust/intl-memoizer/src/concurrent.rs
@@ -0,0 +1,39 @@
+use super::*;
+use std::sync::Mutex;
+
+#[derive(Debug)]
+pub struct IntlLangMemoizer {
+    lang: LanguageIdentifier,
+    map: Mutex<type_map::concurrent::TypeMap>,
+}
+
+impl IntlLangMemoizer {
+    pub fn new(lang: LanguageIdentifier) -> Self {
+        Self {
+            lang,
+            map: Mutex::new(type_map::concurrent::TypeMap::new()),
+        }
+    }
+
+    pub fn with_try_get<I, R, U>(&self, args: I::Args, cb: U) -> Result<R, I::Error>
+    where
+        Self: Sized,
+        I: Memoizable + Sync + Send + 'static,
+        I::Args: Send + Sync + 'static,
+        U: FnOnce(&I) -> R,
+    {
+        let mut map = self.map.lock().unwrap();
+        let cache = map
+            .entry::<HashMap<I::Args, I>>()
+            .or_insert_with(HashMap::new);
+
+        let e = match cache.entry(args.clone()) {
+            Entry::Occupied(entry) => entry.into_mut(),
+            Entry::Vacant(entry) => {
+                let val = I::construct(self.lang.clone(), args)?;
+                entry.insert(val)
+            }
+        };
+        Ok(cb(&e))
+    }
+}
diff --git a/third_party/rust/intl-memoizer/src/lib.rs b/third_party/rust/intl-memoizer/src/lib.rs
new file mode 100644
index 0000000000..8205616a87
--- /dev/null
+++ b/third_party/rust/intl-memoizer/src/lib.rs
@@ -0,0 +1,140 @@
+use std::cell::RefCell;
+use std::collections::hash_map::Entry;
+use std::collections::HashMap;
+use std::hash::Hash;
+use std::rc::{Rc, Weak};
+use unic_langid::LanguageIdentifier;
+
+pub mod concurrent;
+
+pub trait Memoizable {
+    type Args: 'static + Eq + Hash + Clone;
+    type Error;
+    fn construct(lang: LanguageIdentifier, args: Self::Args) -> Result<Self, Self::Error>
+    where
+        Self: std::marker::Sized;
+}
+
+#[derive(Debug)]
+pub struct IntlLangMemoizer {
+    lang: LanguageIdentifier,
+    map: RefCell<type_map::TypeMap>,
+}
+
+impl IntlLangMemoizer {
+    pub fn new(lang: LanguageIdentifier) -> Self {
+        Self {
+            lang,
+            map: RefCell::new(type_map::TypeMap::new()),
+        }
+    }
+
+    pub fn with_try_get<I, R, U>(&self, args: I::Args, cb: U) -> Result<R, I::Error>
+    where
+        Self: Sized,
+        I: Memoizable + 'static,
+        U: FnOnce(&I) -> R,
+    {
+        let mut map = self
+            .map
+            .try_borrow_mut()
+            .expect("Cannot use memoizer reentrantly");
+        let cache = map
+            .entry::<HashMap<I::Args, I>>()
+            .or_insert_with(HashMap::new);
+
+        let e = match cache.entry(args.clone()) {
+            Entry::Occupied(entry) => entry.into_mut(),
+            Entry::Vacant(entry) => {
+                let val = I::construct(self.lang.clone(), args)?;
+                entry.insert(val)
+            }
+        };
+        Ok(cb(&e))
+    }
+}
+
+#[derive(Default)]
+pub struct IntlMemoizer {
+    map: HashMap<LanguageIdentifier, Weak<IntlLangMemoizer>>,
+}
+
+impl IntlMemoizer {
+    pub fn get_for_lang(&mut self, lang: LanguageIdentifier) -> Rc<IntlLangMemoizer> {
+        match self.map.entry(lang.clone()) {
+            Entry::Vacant(empty) => {
+                let entry = Rc::new(IntlLangMemoizer::new(lang));
+                empty.insert(Rc::downgrade(&entry));
+                entry
+            }
+            Entry::Occupied(mut entry) => {
+                if let Some(entry) = entry.get().upgrade() {
+                    entry
+                } else {
+                    let e = Rc::new(IntlLangMemoizer::new(lang));
+                    entry.insert(Rc::downgrade(&e));
+                    e
+                }
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use fluent_langneg::{negotiate_languages, NegotiationStrategy};
+    use intl_pluralrules::{PluralCategory, PluralRuleType, PluralRules as IntlPluralRules};
+
+    struct PluralRules(pub IntlPluralRules);
+
+    impl PluralRules {
+        pub fn new(
+            lang: LanguageIdentifier,
+            pr_type: PluralRuleType,
+        ) -> Result<Self, &'static str> {
+            let default_lang: LanguageIdentifier = "en".parse().unwrap();
+            let pr_lang = negotiate_languages(
+                &[lang],
+                &IntlPluralRules::get_locales(pr_type),
+                Some(&default_lang),
+                NegotiationStrategy::Lookup,
+            )[0]
+            .clone();
+
+            Ok(Self(IntlPluralRules::create(pr_lang, pr_type)?))
+        }
+    }
+
+    impl Memoizable for PluralRules {
+        type Args = (PluralRuleType,);
+        type Error = &'static str;
+        fn construct(lang: LanguageIdentifier, args: Self::Args) -> Result<Self, Self::Error> {
+            Self::new(lang, args.0)
+        }
+    }
+
+    #[test]
+    fn it_works() {
+        let lang: LanguageIdentifier = "en".parse().unwrap();
+
+        let mut memoizer = IntlMemoizer::default();
+        {
+            let en_memoizer = memoizer.get_for_lang(lang.clone());
+
+            let result = en_memoizer
+                .with_try_get::<PluralRules, _, _>((PluralRuleType::CARDINAL,), |cb| cb.0.select(5))
+                .unwrap();
+            assert_eq!(result, Ok(PluralCategory::OTHER));
+        }
+
+        {
+            let en_memoizer = memoizer.get_for_lang(lang.clone());
+
+            let result = en_memoizer
+                .with_try_get::<PluralRules, _, _>((PluralRuleType::CARDINAL,), |cb| cb.0.select(5))
+                .unwrap();
+            assert_eq!(result, Ok(PluralCategory::OTHER));
+        }
+    }
+}