// Copyright 2018 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/services/app_service/public/cpp/app_registry_cache.h"

#include <utility>

namespace apps {

AppRegistryCache::Observer::Observer(AppRegistryCache* cache) {
  Observe(cache);
}

AppRegistryCache::Observer::Observer() = default;

AppRegistryCache::Observer::~Observer() {
  if (cache_) {
    cache_->RemoveObserver(this);
  }
}

void AppRegistryCache::Observer::Observe(AppRegistryCache* cache) {
  if (cache == cache_) {
    // Early exit to avoid infinite loops if we're in the middle of a callback.
    return;
  }
  if (cache_) {
    cache_->RemoveObserver(this);
  }
  cache_ = cache;
  if (cache_) {
    cache_->AddObserver(this);
  }
}

AppRegistryCache::AppRegistryCache() = default;

AppRegistryCache::~AppRegistryCache() = default;

void AppRegistryCache::AddObserver(Observer* observer) {
  observers_.AddObserver(observer);
}

void AppRegistryCache::RemoveObserver(Observer* observer) {
  observers_.RemoveObserver(observer);
}

void AppRegistryCache::OnApps(std::vector<apps::mojom::AppPtr> deltas) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);

  if (!deltas_in_progress_.empty()) {
    std::move(deltas.begin(), deltas.end(),
              std::back_inserter(deltas_pending_));
    return;
  }

  DoOnApps(std::move(deltas));
  while (!deltas_pending_.empty()) {
    std::vector<apps::mojom::AppPtr> pending;
    pending.swap(deltas_pending_);
    DoOnApps(std::move(pending));
  }
}

void AppRegistryCache::DoOnApps(std::vector<apps::mojom::AppPtr> deltas) {
  // Merge any deltas elements that have the same app_id. If an observer's
  // OnAppUpdate calls back into this AppRegistryCache then we can therefore
  // present a single delta for any given app_id.
  for (auto& delta : deltas) {
    auto d_iter = deltas_in_progress_.find(delta->app_id);
    if (d_iter != deltas_in_progress_.end()) {
      AppUpdate::Merge(d_iter->second, delta.get());
    } else {
      deltas_in_progress_[delta->app_id] = delta.get();
    }
  }

  // The remaining for loops range over the deltas_in_progress_ map, not the
  // deltas vector, so that OnAppUpdate is called only once per unique app_id.

  // Notify the observers for every de-duplicated delta.
  for (const auto& d_iter : deltas_in_progress_) {
    auto s_iter = states_.find(d_iter.first);
    apps::mojom::App* state =
        (s_iter != states_.end()) ? s_iter->second.get() : nullptr;
    apps::mojom::App* delta = d_iter.second;

    for (auto& obs : observers_) {
      obs.OnAppUpdate(AppUpdate(state, delta));
    }
  }

  // Update the states for every de-duplicated delta.
  for (const auto& d_iter : deltas_in_progress_) {
    auto s_iter = states_.find(d_iter.first);
    apps::mojom::App* state =
        (s_iter != states_.end()) ? s_iter->second.get() : nullptr;
    apps::mojom::App* delta = d_iter.second;

    if (state) {
      AppUpdate::Merge(state, delta);
    } else {
      states_.insert(std::make_pair(delta->app_id, delta->Clone()));
    }
  }
  deltas_in_progress_.clear();
}

apps::mojom::AppType AppRegistryCache::GetAppType(const std::string& app_id) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(my_sequence_checker_);

  auto d_iter = deltas_in_progress_.find(app_id);
  if (d_iter != deltas_in_progress_.end()) {
    return d_iter->second->app_type;
  }
  auto s_iter = states_.find(app_id);
  if (s_iter != states_.end()) {
    return s_iter->second->app_type;
  }
  return apps::mojom::AppType::kUnknown;
}

}  // namespace apps