/* -*- 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 */