// Copyright 2017 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

module metrics.mojom;

import "mojo/public/mojom/base/byte_string.mojom";
import "mojo/public/mojom/base/shared_memory.mojom";

// These values are persisted to logs. Entries should not be renumbered and
// numeric values should never be reused. If you add any entries to this enum,
// you must also update the corresponding enum UmaChildPingStatus at
// tools/metrics/histograms/enums.xml.
enum UmaChildPingStatus {
  BROWSER_SENT_IPC = 0,
  CHILD_RECEIVED_IPC = 1,
  BROWSER_REPLY_CALLBACK = 2,
};

enum UmaPingCallSource {
  PERIODIC,
  SHARED_MEMORY_SET_UP,
};

// Used to 1) pass a shared memory segment where the child process will store
// histograms, and 2) create a ChildHistogramFetcher so that the child process
// can report to the browser process the histograms that could not be stored on
// the shared memory (e.g. they were emitted before it was set up).
interface ChildHistogramFetcherFactory {
  // Creates a ChildHistogram interface that uses shared memory buffer to
  // store histograms that are to be reported by the browser process to UMA.
  CreateFetcher(
      mojo_base.mojom.UnsafeSharedMemoryRegion? shared_memory,
      pending_receiver<ChildHistogramFetcher> child_histogram_fetcher);
};

// Used by the browser process to request non-persistent histograms (i.e., not
// on the shared memory) from a child process.
interface ChildHistogramFetcher {
  // Send to all the child processes to send back histogram data.
  GetChildNonPersistentHistogramData()
      => (array<mojo_base.mojom.ByteString> deltas);

  // Ping-pong mechanism to quantify child process histogram losses. See
  // implementation and call site for details.
  Ping(UmaPingCallSource call_source) => ();
};