// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/histogram_controller.h"

#include "base/bind.h"
#include "base/metrics/histogram_macros.h"
#include "base/process/process_handle.h"
#include "content/browser/histogram_subscriber.h"
#include "content/common/child_process_messages.h"
#include "content/public/browser/browser_child_process_host_iterator.h"
#include "content/public/browser/browser_thread.h"
#include "content/public/browser/child_process_data.h"
#include "content/public/browser/render_process_host.h"
#include "content/public/common/process_type.h"

namespace content {

HistogramController* HistogramController::GetInstance() {
  return base::Singleton<HistogramController>::get();
}

HistogramController::HistogramController() : subscriber_(NULL) {
}

HistogramController::~HistogramController() {
}

void HistogramController::OnPendingProcesses(int sequence_number,
                                             int pending_processes,
                                             bool end) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  if (subscriber_)
    subscriber_->OnPendingProcesses(sequence_number, pending_processes, end);
}

void HistogramController::OnHistogramDataCollected(
    int sequence_number,
    const std::vector<std::string>& pickled_histograms) {
  if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
    BrowserThread::PostTask(
        BrowserThread::UI, FROM_HERE,
        base::Bind(&HistogramController::OnHistogramDataCollected,
                   base::Unretained(this),
                   sequence_number,
                   pickled_histograms));
    return;
  }

  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  if (subscriber_) {
    subscriber_->OnHistogramDataCollected(sequence_number,
                                          pickled_histograms);
  }
}

void HistogramController::Register(HistogramSubscriber* subscriber) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  DCHECK(!subscriber_);
  subscriber_ = subscriber;
}

void HistogramController::Unregister(
    const HistogramSubscriber* subscriber) {
  DCHECK_EQ(subscriber_, subscriber);
  subscriber_ = NULL;
}

void HistogramController::GetHistogramDataFromChildProcesses(
    int sequence_number) {
  DCHECK_CURRENTLY_ON(BrowserThread::IO);

  int pending_processes = 0;
  for (BrowserChildProcessHostIterator iter; !iter.Done(); ++iter) {
    const ChildProcessData& data = iter.GetData();

    // Only get histograms from content process types; skip "embedder" process
    // types.
    if (data.process_type >= PROCESS_TYPE_CONTENT_END)
      continue;

    // In some cases, there may be no child process of the given type (for
    // example, the GPU process may not exist and there may instead just be a
    // GPU thread in the browser process). If that's the case, then the process
    // handle will be base::kNullProcessHandle and we shouldn't ask it for data.
    if (data.handle == base::kNullProcessHandle)
      continue;

    ++pending_processes;
    if (!iter.Send(new ChildProcessMsg_GetChildNonPersistentHistogramData(
            sequence_number))) {
      --pending_processes;
    }
  }

  BrowserThread::PostTask(
      BrowserThread::UI,
      FROM_HERE,
      base::Bind(
          &HistogramController::OnPendingProcesses,
          base::Unretained(this),
          sequence_number,
          pending_processes,
          true));
}

void HistogramController::GetHistogramData(int sequence_number) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);

  int pending_processes = 0;
  for (RenderProcessHost::iterator it(RenderProcessHost::AllHostsIterator());
       !it.IsAtEnd(); it.Advance()) {
    ++pending_processes;
    if (!it.GetCurrentValue()->Send(
            new ChildProcessMsg_GetChildNonPersistentHistogramData(
                sequence_number))) {
      --pending_processes;
    }
  }
  OnPendingProcesses(sequence_number, pending_processes, false);

  BrowserThread::PostTask(
      BrowserThread::IO,
      FROM_HERE,
      base::Bind(&HistogramController::GetHistogramDataFromChildProcesses,
                 base::Unretained(this),
                 sequence_number));
}

}  // namespace content