1 files changed, 99 insertions, 0 deletions
diff --git a/toolkit/components/glean/src/init/upload_pref.rs b/toolkit/components/glean/src/init/upload_pref.rs
new file mode 100644
index 0000000000..737230c16c
--- /dev/null
+++ b/toolkit/components/glean/src/init/upload_pref.rs
@@ -0,0 +1,99 @@
+// 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 std::ffi::CStr;
+use std::os::raw::c_char;
+use std::sync::atomic::{AtomicBool, Ordering};
+
+use nserror::{nsresult, NS_ERROR_FAILURE, NS_OK};
+use nsstring::{nsACString, nsCStr};
+use xpcom::{
+    interfaces::{nsIPrefBranch, nsISupports},
+    RefPtr,
+};
+
+/// Whether the current value of the localhost testing pref is permitting
+/// metric recording (even if upload is disabled).
+static RECORDING_ENABLED: AtomicBool = AtomicBool::new(false);
+
+// Partially cargo-culted from https://searchfox.org/mozilla-central/rev/598e50d2c3cd81cd616654f16af811adceb08f9f/security/manager/ssl/cert_storage/src/lib.rs#1192
+#[xpcom(implement(nsIObserver), atomic)]
+pub(crate) struct UploadPrefObserver {}
+
+#[allow(non_snake_case)]
+impl UploadPrefObserver {
+    pub(crate) fn begin_observing() -> Result<(), nsresult> {
+        // Ensure we begin with the correct current value of RECORDING_ENABLED.
+        let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+        RECORDING_ENABLED.store(recording_enabled, Ordering::SeqCst);
+
+        // SAFETY: Everything here is self-contained.
+        //
+        // * We allocate the pref observer, created by the xpcom macro
+        // * We query the pref service and bail out if it doesn't exist.
+        // * We create a nsCStr from a static string.
+        // * We control all input to `AddObserverImpl`
+        unsafe {
+            let pref_obs = Self::allocate(InitUploadPrefObserver {});
+            let pref_branch: RefPtr<nsIPrefBranch> =
+                xpcom::components::Preferences::service().map_err(|_| NS_ERROR_FAILURE)?;
+            let pref_nscstr =
+                &nsCStr::from("datareporting.healthreport.uploadEnabled") as &nsACString;
+            (*pref_branch)
+                .AddObserverImpl(pref_nscstr, pref_obs.coerce(), false)
+                .to_result()?;
+            let pref_nscstr = &nsCStr::from("telemetry.fog.test.localhost_port") as &nsACString;
+            (*pref_branch)
+                .AddObserverImpl(pref_nscstr, pref_obs.coerce(), false)
+                .to_result()?;
+        }
+
+        Ok(())
+    }
+
+    unsafe fn Observe(
+        &self,
+        _subject: *const nsISupports,
+        topic: *const c_char,
+        pref_name: *const u16,
+    ) -> nserror::nsresult {
+        let topic = CStr::from_ptr(topic).to_str().unwrap();
+        // Conversion utf16 to utf8 is messy.
+        // We should only ever observe changes to one of the two prefs we want,
+        // but just to be on the safe side let's assert.
+
+        // cargo-culted from https://searchfox.org/mozilla-central/rev/598e50d2c3cd81cd616654f16af811adceb08f9f/security/manager/ssl/cert_storage/src/lib.rs#1606-1612
+        // (with a little transformation)
+        let len = (0..).take_while(|&i| *pref_name.offset(i) != 0).count(); // find NUL.
+        let slice = std::slice::from_raw_parts(pref_name, len);
+        let pref_name = match String::from_utf16(slice) {
+            Ok(name) => name,
+            Err(_) => return NS_ERROR_FAILURE,
+        };
+        log::info!("Observed {:?}, {:?}", topic, pref_name);
+        debug_assert!(topic == "nsPref:changed");
+        debug_assert!(
+            pref_name == "datareporting.healthreport.uploadEnabled"
+                || pref_name == "telemetry.fog.test.localhost_port"
+        );
+
+        let upload_enabled = static_prefs::pref!("datareporting.healthreport.uploadEnabled");
+        let recording_enabled = static_prefs::pref!("telemetry.fog.test.localhost_port") < 0;
+        log::info!(
+            "New upload_enabled {}, recording_enabled {}",
+            upload_enabled,
+            recording_enabled
+        );
+        if RECORDING_ENABLED.load(Ordering::SeqCst) && !recording_enabled {
+            // Whenever the test pref goes from permitting recording to forbidding it,
+            // ensure Glean is told to wipe the stores.
+            // This may send a "deletion-request" ping for a client_id that's never sent
+            // any other pings.
+            glean::set_upload_enabled(false);
+        }
+        RECORDING_ENABLED.store(recording_enabled, Ordering::SeqCst);
+        glean::set_upload_enabled(upload_enabled || recording_enabled);
+        NS_OK
+    }
+}