1 files changed, 154 insertions, 0 deletions
diff --git a/toolkit/components/glean/api/src/private/quantity.rs b/toolkit/components/glean/api/src/private/quantity.rs
new file mode 100644
index 0000000000..cce42c4aea
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+++ b/toolkit/components/glean/api/src/private/quantity.rs
@@ -0,0 +1,154 @@
+// 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 inherent::inherent;
+
+use glean::traits::Quantity;
+
+use super::CommonMetricData;
+
+use crate::ipc::need_ipc;
+use crate::private::MetricId;
+
+/// A quantity metric.
+///
+/// Records a single numeric value of a specific unit.
+#[derive(Clone)]
+pub enum QuantityMetric {
+    Parent(glean::private::QuantityMetric),
+    Child(QuantityMetricIpc),
+}
+#[derive(Clone, Debug)]
+pub struct QuantityMetricIpc;
+
+impl QuantityMetric {
+    /// Create a new quantity metric.
+    pub fn new(_id: MetricId, meta: CommonMetricData) -> Self {
+        if need_ipc() {
+            QuantityMetric::Child(QuantityMetricIpc)
+        } else {
+            QuantityMetric::Parent(glean::private::QuantityMetric::new(meta))
+        }
+    }
+
+    #[cfg(test)]
+    pub(crate) fn child_metric(&self) -> Self {
+        match self {
+            QuantityMetric::Parent(_) => QuantityMetric::Child(QuantityMetricIpc),
+            QuantityMetric::Child(_) => panic!("Can't get a child metric from a child metric"),
+        }
+    }
+}
+
+#[inherent]
+impl Quantity for QuantityMetric {
+    /// Set the value. Must be non-negative.
+    ///
+    /// # Arguments
+    ///
+    /// * `value` - The value. Must be non-negative.
+    ///
+    /// ## Notes
+    ///
+    /// Logs an error if the `value` is negative.
+    pub fn set(&self, value: i64) {
+        match self {
+            QuantityMetric::Parent(p) => {
+                p.set(value);
+            }
+            QuantityMetric::Child(_) => {
+                log::error!("Unable to set quantity metric in non-parent process. Ignoring.");
+                // TODO: Record an error.
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Get the currently stored value.
+    /// This doesn't clear the stored value.
+    ///
+    /// ## Arguments
+    ///
+    /// * `ping_name` - the storage name to look into.
+    ///
+    /// ## Return value
+    ///
+    /// Returns the stored value or `None` if nothing stored.
+    pub fn test_get_value<'a, S: Into<Option<&'a str>>>(&self, ping_name: S) -> Option<i64> {
+        let ping_name = ping_name.into().map(|s| s.to_string());
+        match self {
+            QuantityMetric::Parent(p) => p.test_get_value(ping_name),
+            QuantityMetric::Child(_) => {
+                panic!("Cannot get test value for quantity metric in non-parent process!",)
+            }
+        }
+    }
+
+    /// **Test-only API.**
+    ///
+    /// Gets the number of recorded errors for the given metric and error type.
+    ///
+    /// # Arguments
+    ///
+    /// * `error` - The type of error
+    /// * `ping_name` - represents the optional name of the ping to retrieve the
+    ///   metric for. Defaults to the first value in `send_in_pings`.
+    ///
+    /// # Returns
+    ///
+    /// The number of errors reported.
+    pub fn test_get_num_recorded_errors(&self, error: glean::ErrorType) -> i32 {
+        match self {
+            QuantityMetric::Parent(p) => {
+                p.test_get_num_recorded_errors(error)
+            }
+            QuantityMetric::Child(_) => panic!(
+                "Cannot get the number of recorded errors for quantity metric in non-parent process!"
+            ),
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use crate::{common_test::*, ipc, metrics};
+
+    #[test]
+    fn sets_quantity_metric() {
+        let _lock = lock_test();
+
+        let metric = &metrics::test_only_ipc::a_quantity;
+        metric.set(14);
+
+        assert_eq!(14, metric.test_get_value("store1").unwrap());
+    }
+
+    #[test]
+    fn quantity_ipc() {
+        // QuantityMetric doesn't support IPC.
+        let _lock = lock_test();
+
+        let parent_metric = &metrics::test_only_ipc::a_quantity;
+
+        parent_metric.set(15);
+
+        {
+            let child_metric = parent_metric.child_metric();
+
+            // scope for need_ipc RAII
+            let _raii = ipc::test_set_need_ipc(true);
+
+            // Instrumentation calls do not panic.
+            child_metric.set(30);
+
+            // (They also shouldn't do anything,
+            // but that's not something we can inspect in this test)
+        }
+
+        assert!(ipc::replay_from_buf(&ipc::take_buf().unwrap()).is_ok());
+
+        assert_eq!(15, parent_metric.test_get_value(None).unwrap());
+    }
+}