1 files changed, 113 insertions, 0 deletions
diff --git a/toolkit/components/glean/bindings/private/Event.h b/toolkit/components/glean/bindings/private/Event.h
new file mode 100644
index 0000000000..d452ffe316
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+++ b/toolkit/components/glean/bindings/private/Event.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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 http://mozilla.org/MPL/2.0/. */
+
+#ifndef mozilla_glean_GleanEvent_h
+#define mozilla_glean_GleanEvent_h
+
+#include "nsIGleanMetrics.h"
+#include "mozilla/glean/fog_ffi_generated.h"
+#include "mozilla/Tuple.h"
+#include "nsString.h"
+#include "nsTArray.h"
+
+namespace mozilla::glean {
+
+// forward declaration
+class GleanEvent;
+
+namespace impl {
+
+/**
+ * Represents the recorded data for a single event
+ */
+struct RecordedEvent {
+ public:
+  uint64_t mTimestamp;
+  nsCString mCategory;
+  nsCString mName;
+
+  nsTArray<Tuple<nsCString, nsCString>> mExtra;
+};
+
+template <class T>
+class EventMetric {
+  friend class mozilla::glean::GleanEvent;
+
+ public:
+  constexpr explicit EventMetric(uint32_t id) : mId(id) {}
+
+  /**
+   * Record an event.
+   *
+   * @param aExtras The list of (extra key, value) pairs. Allowed extra keys are
+   *                defined in the metric definition.
+   *                If the wrong keys are used or values are too large
+   *                an error is report and no event is recorded.
+   */
+  void Record(const Span<const Tuple<T, nsCString>>& aExtras = {}) const {
+    static_assert(sizeof(T) <= sizeof(int32_t),
+                  "Extra keys need to fit into 32 bits");
+
+    nsTArray<int32_t> extraKeys;
+    nsTArray<nsCString> extraValues;
+    for (auto& entry : aExtras) {
+      extraKeys.AppendElement(static_cast<int32_t>(mozilla::Get<0>(entry)));
+      extraValues.AppendElement(mozilla::Get<1>(entry));
+    }
+
+    fog_event_record(mId, &extraKeys, &extraValues);
+  }
+
+  /**
+   * **Test-only API**
+   *
+   * Get a list of currently stored events for this event metric.
+   *
+   * This function will attempt to await the last parent-process task (if any)
+   * writing to the the metric's storage engine before returning a value.
+   * This function will not wait for data from child processes.
+   *
+   * This doesn't clear the stored value.
+   * Parent process only. Panics in child processes.
+   *
+   * @param aPingName The (optional) name of the ping to retrieve the metric
+   *        for. Defaults to the first value in `send_in_pings`.
+   *
+   * @return value of the stored metric, or Nothing() if there is no value.
+   */
+  Maybe<nsTArray<RecordedEvent>> TestGetValue(
+      const nsACString& aPingName = nsCString()) const {
+    if (!fog_event_test_has_value(mId, &aPingName)) {
+      return Nothing();
+    }
+
+    // TODO(bug 1678567): Implement this.
+    nsTArray<RecordedEvent> empty;
+    return Some(std::move(empty));
+  }
+
+ private:
+  const uint32_t mId;
+};
+
+}  // namespace impl
+
+class GleanEvent final : public nsIGleanEvent {
+ public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIGLEANEVENT
+
+  explicit GleanEvent(uint32_t id) : mEvent(id){};
+
+ private:
+  virtual ~GleanEvent() = default;
+
+  const impl::EventMetric<uint32_t> mEvent;
+};
+
+}  // namespace mozilla::glean
+
+#endif /* mozilla_glean_GleanEvent.h */