1 files changed, 70 insertions, 0 deletions
diff --git a/intl/l10n/rust/l10nregistry-ffi/src/fetcher.rs b/intl/l10n/rust/l10nregistry-ffi/src/fetcher.rs
new file mode 100644
index 0000000000..aba8a81470
--- /dev/null
+++ b/intl/l10n/rust/l10nregistry-ffi/src/fetcher.rs
@@ -0,0 +1,70 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at https://mozilla.org/MPL/2.0/. */
+
+use l10nregistry::source::{FileFetcher, ResourceId};
+
+use std::{borrow::Cow, io};
+
+pub struct GeckoFileFetcher;
+
+fn try_string_from_box_u8(input: Box<[u8]>) -> io::Result<String> {
+    String::from_utf8(input.into())
+        .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err.utf8_error()))
+}
+
+// For historical reasons we maintain a locale in Firefox with a codename `ja-JP-mac`.
+// This string is an invalid BCP-47 language tag, so we don't store it in Gecko, which uses
+// valid BCP-47 tags only, but rather keep that quirk local to Gecko L10nRegistry file fetcher.
+//
+// Here, if we encounter `ja-JP-macos` (valid BCP-47), we swap it for `ja-JP-mac`.
+//
+// See bug 1726586 for details, and source::get_locale_from_gecko.
+fn get_path_for_gecko<'s>(input: &'s str) -> Cow<'s, str> {
+    if input.contains("ja-JP-macos") {
+        input.replace("ja-JP-macos", "ja-JP-mac").into()
+    } else {
+        input.into()
+    }
+}
+
+#[async_trait::async_trait(?Send)]
+impl FileFetcher for GeckoFileFetcher {
+    fn fetch_sync(&self, resource_id: &ResourceId) -> io::Result<String> {
+        let path = get_path_for_gecko(&resource_id.value);
+        crate::load::load_sync(path).and_then(try_string_from_box_u8)
+    }
+
+    async fn fetch(&self, resource_id: &ResourceId) -> io::Result<String> {
+        let path = get_path_for_gecko(&resource_id.value);
+        crate::load::load_async(path)
+            .await
+            .and_then(try_string_from_box_u8)
+    }
+}
+
+pub struct MockFileFetcher {
+    fs: Vec<(String, String)>,
+}
+
+impl MockFileFetcher {
+    pub fn new(fs: Vec<(String, String)>) -> Self {
+        Self { fs }
+    }
+}
+
+#[async_trait::async_trait(?Send)]
+impl FileFetcher for MockFileFetcher {
+    fn fetch_sync(&self, resource_id: &ResourceId) -> io::Result<String> {
+        for (p, source) in &self.fs {
+            if p == &resource_id.value {
+                return Ok(source.clone());
+            }
+        }
+        Err(io::Error::new(io::ErrorKind::NotFound, "File not found"))
+    }
+
+    async fn fetch(&self, resource_id: &ResourceId) -> io::Result<String> {
+        self.fetch_sync(resource_id)
+    }
+}