// 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/ui/app_list/recommended_apps.h"

#include <algorithm>
#include <vector>

#include "base/bind.h"
#include "chrome/browser/extensions/extension_ui_util.h"
#include "chrome/browser/profiles/profile.h"
#include "chrome/browser/ui/app_list/recommended_apps_observer.h"
#include "chrome/common/pref_names.h"
#include "extensions/browser/extension_prefs.h"
#include "extensions/browser/extension_registry.h"
#include "extensions/browser/pref_names.h"
#include "extensions/common/extension.h"
#include "extensions/common/extension_set.h"

namespace app_list {

namespace {

struct AppSortInfo {
  AppSortInfo() : app(NULL) {}
  AppSortInfo(const extensions::Extension* app,
              const base::Time& last_launch_time)
      : app(app), last_launch_time(last_launch_time) {}

  const extensions::Extension* app;
  base::Time last_launch_time;
};

bool AppLaunchedMoreRecent(const AppSortInfo& app1, const AppSortInfo& app2) {
  return app1.last_launch_time > app2.last_launch_time;
}

}  // namespace

RecommendedApps::RecommendedApps(Profile* profile)
    : profile_(profile), extension_registry_observer_(this) {
  extensions::ExtensionPrefs* prefs = extensions::ExtensionPrefs::Get(profile_);
  pref_change_registrar_.Init(prefs->pref_service());
  pref_change_registrar_.Add(extensions::pref_names::kExtensions,
                             base::Bind(&RecommendedApps::Update,
                                        base::Unretained(this)));
  extension_registry_observer_.Add(extensions::ExtensionRegistry::Get(profile));
  Update();
}

RecommendedApps::~RecommendedApps() {
}

void RecommendedApps::AddObserver(RecommendedAppsObserver* observer) {
  observers_.AddObserver(observer);
}

void RecommendedApps::RemoveObserver(RecommendedAppsObserver* observer) {
  observers_.RemoveObserver(observer);
}

void RecommendedApps::Update() {
  extensions::ExtensionPrefs* prefs = extensions::ExtensionPrefs::Get(profile_);

  std::vector<AppSortInfo> sorted_apps;
  const extensions::ExtensionSet& extensions =
      extensions::ExtensionRegistry::Get(profile_)->enabled_extensions();
  for (extensions::ExtensionSet::const_iterator app = extensions.begin();
       app != extensions.end();
       ++app) {
    if (!extensions::ui_util::ShouldDisplayInAppLauncher(*app, profile_))
      continue;

    sorted_apps.push_back(
        AppSortInfo(app->get(), prefs->GetLastLaunchTime((*app)->id())));
  }

  std::sort(sorted_apps.begin(), sorted_apps.end(), &AppLaunchedMoreRecent);

  const size_t kMaxRecommendedApps = 4;
  sorted_apps.resize(std::min(kMaxRecommendedApps, sorted_apps.size()));

  Apps new_recommends;
  for (size_t i = 0; i < sorted_apps.size(); ++i)
    new_recommends.push_back(sorted_apps[i].app);

  const bool changed = apps_.size() != new_recommends.size() ||
      !std::equal(apps_.begin(), apps_.end(), new_recommends.begin());
  if (changed) {
    apps_.swap(new_recommends);
    FOR_EACH_OBSERVER(
        RecommendedAppsObserver, observers_, OnRecommendedAppsChanged());
  }
}

void RecommendedApps::OnExtensionWillBeInstalled(
    content::BrowserContext* browser_context,
    const extensions::Extension* extension,
    bool is_update,
    bool from_ephemeral,
    const std::string& old_name) {
  Update();
}

void RecommendedApps::OnExtensionLoaded(
    content::BrowserContext* browser_context,
    const extensions::Extension* extension) {
  Update();
}

void RecommendedApps::OnExtensionUnloaded(
    content::BrowserContext* browser_context,
    const extensions::Extension* extension,
    extensions::UnloadedExtensionInfo::Reason reason) {
  Update();
}

void RecommendedApps::OnExtensionUninstalled(
    content::BrowserContext* browser_context,
    const extensions::Extension* extension) {
  Update();
}

}  // namespace app_list