// Copyright 2013 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 "chrome/browser/extensions/api/system_info/system_info_api.h"

#include <set>

#include "base/bind.h"
#include "base/lazy_instance.h"
#include "base/memory/scoped_ptr.h"
#include "base/memory/singleton.h"
#include "base/strings/string_util.h"
#include "base/values.h"
#include "chrome/browser/browser_process.h"
#include "chrome/browser/extensions/api/system_storage/storage_info_provider.h"
#include "chrome/browser/extensions/event_router_forwarder.h"
#include "chrome/browser/storage_monitor/removable_storage_observer.h"
#include "chrome/browser/storage_monitor/storage_info.h"
#include "chrome/browser/storage_monitor/storage_monitor.h"
#include "chrome/common/extensions/api/system_display.h"
#include "chrome/common/extensions/api/system_storage.h"
#include "ui/gfx/display_observer.h"

#if defined(USE_ASH)
#include "ash/screen_ash.h"
#include "ash/shell.h"
#endif

namespace extensions {

using api::system_storage::StorageUnitInfo;
using content::BrowserThread;

namespace system_display = api::system_display;
namespace system_storage = api::system_storage;

namespace {

bool IsDisplayChangedEvent(const std::string& event_name) {
  return event_name == system_display::OnDisplayChanged::kEventName;
}

// Event router for systemInfo API. It is a singleton instance shared by
// multiple profiles.
class SystemInfoEventRouter : public gfx::DisplayObserver,
                              public RemovableStorageObserver {
 public:
  static SystemInfoEventRouter* GetInstance();

  SystemInfoEventRouter();
  virtual ~SystemInfoEventRouter();

  // Add/remove event listener for the |event_name| event.
  void AddEventListener(const std::string& event_name);
  void RemoveEventListener(const std::string& event_name);

 private:
  // gfx::DisplayObserver:
  virtual void OnDisplayBoundsChanged(const gfx::Display& display) OVERRIDE;
  virtual void OnDisplayAdded(const gfx::Display& new_display) OVERRIDE;
  virtual void OnDisplayRemoved(const gfx::Display& old_display) OVERRIDE;

  // RemovableStorageObserver implementation.
  virtual void OnRemovableStorageAttached(const StorageInfo& info) OVERRIDE;
  virtual void OnRemovableStorageDetached(const StorageInfo& info) OVERRIDE;

  // Called from any thread to dispatch the systemInfo event to all extension
  // processes cross multiple profiles.
  void DispatchEvent(const std::string& event_name,
      scoped_ptr<base::ListValue> args);

  // Called to dispatch the systemInfo.display.onDisplayChanged event.
  void OnDisplayChanged();

  // Used to record the event names being watched.
  std::multiset<std::string> watching_event_set_;

  DISALLOW_COPY_AND_ASSIGN(SystemInfoEventRouter);
};

static base::LazyInstance<SystemInfoEventRouter>::Leaky
  g_system_info_event_router = LAZY_INSTANCE_INITIALIZER;

// static
SystemInfoEventRouter* SystemInfoEventRouter::GetInstance() {
  return g_system_info_event_router.Pointer();
}

SystemInfoEventRouter::SystemInfoEventRouter() {
  StorageMonitor::GetInstance()->AddObserver(this);
}

SystemInfoEventRouter::~SystemInfoEventRouter() {
  if (StorageMonitor* storage_monitor = StorageMonitor::GetInstance())
    storage_monitor->RemoveObserver(this);
}

void SystemInfoEventRouter::AddEventListener(const std::string& event_name) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  watching_event_set_.insert(event_name);
  if (watching_event_set_.count(event_name) > 1)
    return;

  // For systemInfo.display event.
  if (IsDisplayChangedEvent(event_name)) {
#if defined(USE_ASH)
    ash::Shell::GetScreen()->AddObserver(this);
#endif
  }
}

void SystemInfoEventRouter::RemoveEventListener(
    const std::string& event_name) {
  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));

  std::multiset<std::string>::iterator it =
      watching_event_set_.find(event_name);
  if (it != watching_event_set_.end())
    watching_event_set_.erase(it);

  if (watching_event_set_.count(event_name) > 0)
    return;

  if (IsDisplayChangedEvent(event_name)) {
#if defined(USE_ASH)
    ash::Shell::GetScreen()->RemoveObserver(this);
#endif
  }
}

void SystemInfoEventRouter::OnRemovableStorageAttached(
    const StorageInfo& info) {
  StorageUnitInfo unit;
  systeminfo::BuildStorageUnitInfo(info, &unit);
  scoped_ptr<base::ListValue> args(new base::ListValue);
  args->Append(unit.ToValue().release());
  DispatchEvent(system_storage::OnAttached::kEventName, args.Pass());
}

void SystemInfoEventRouter::OnRemovableStorageDetached(
    const StorageInfo& info) {
  scoped_ptr<base::ListValue> args(new base::ListValue);
  args->Append(new base::StringValue(StorageMonitor::GetInstance()->
                   GetTransientIdForDeviceId(info.device_id())));

  DispatchEvent(system_storage::OnDetached::kEventName, args.Pass());
}

void SystemInfoEventRouter::OnDisplayBoundsChanged(
    const gfx::Display& display) {
  OnDisplayChanged();
}

void SystemInfoEventRouter::OnDisplayAdded(const gfx::Display& new_display) {
  OnDisplayChanged();
}

void SystemInfoEventRouter::OnDisplayRemoved(const gfx::Display& old_display) {
  OnDisplayChanged();
}

void SystemInfoEventRouter::OnDisplayChanged() {
  scoped_ptr<base::ListValue> args(new base::ListValue());
  DispatchEvent(system_display::OnDisplayChanged::kEventName, args.Pass());
}

void SystemInfoEventRouter::DispatchEvent(const std::string& event_name,
                                          scoped_ptr<base::ListValue> args) {
  g_browser_process->extension_event_router_forwarder()->
      BroadcastEventToRenderers(event_name, args.Pass(), GURL());
}

}  // namespace

static base::LazyInstance<ProfileKeyedAPIFactory<SystemInfoAPI> >
    g_factory = LAZY_INSTANCE_INITIALIZER;

// static
ProfileKeyedAPIFactory<SystemInfoAPI>* SystemInfoAPI::GetFactoryInstance() {
  return &g_factory.Get();
}

SystemInfoAPI::SystemInfoAPI(Profile* profile) : profile_(profile) {
  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
      this, system_storage::OnAttached::kEventName);
  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
      this, system_storage::OnDetached::kEventName);
  ExtensionSystem::Get(profile_)->event_router()->RegisterObserver(
      this, system_display::OnDisplayChanged::kEventName);
}

SystemInfoAPI::~SystemInfoAPI() {
}

void SystemInfoAPI::Shutdown() {
  ExtensionSystem::Get(profile_)->event_router()->UnregisterObserver(this);
}

void SystemInfoAPI::OnListenerAdded(const EventListenerInfo& details) {
  SystemInfoEventRouter::GetInstance()->AddEventListener(details.event_name);
}

void SystemInfoAPI::OnListenerRemoved(const EventListenerInfo& details) {
  SystemInfoEventRouter::GetInstance()->RemoveEventListener(details.event_name);
}

}  // namespace extensions