// Copyright 2019 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 "components/previews/content/previews_optimization_guide_decider.h"

#include <utility>

#include "components/optimization_guide/hints_processing_util.h"
#include "components/optimization_guide/optimization_guide_decider.h"
#include "components/optimization_guide/proto/hints.pb.h"
#include "components/previews/content/previews_user_data.h"
#include "components/previews/core/previews_experiments.h"
#include "components/previews/core/previews_switches.h"
#include "content/public/browser/navigation_handle.h"

namespace previews {

namespace {

// The default max size of the cache holding resource loading hints by URL.
size_t kDefaultMaxResourceLoadingHintsCacheSize = 10;

// Returns base::nullopt if |previews_type| can't be converted.
base::Optional<optimization_guide::proto::OptimizationType>
ConvertPreviewsTypeToOptimizationType(PreviewsType previews_type) {
  switch (previews_type) {
    case PreviewsType::NONE:
      return optimization_guide::proto::OPTIMIZATION_NONE;
    case PreviewsType::NOSCRIPT:
      return optimization_guide::proto::NOSCRIPT;
    case PreviewsType::UNSPECIFIED:
      return optimization_guide::proto::TYPE_UNSPECIFIED;
    case PreviewsType::RESOURCE_LOADING_HINTS:
      return optimization_guide::proto::RESOURCE_LOADING;
    case PreviewsType::LITE_PAGE_REDIRECT:
      return optimization_guide::proto::LITE_PAGE_REDIRECT;
    case PreviewsType::DEFER_ALL_SCRIPT:
      return optimization_guide::proto::DEFER_ALL_SCRIPT;
    default:
      return base::nullopt;
  }
}

// Returns the optimization types to register with the Optimization Guide
// Decider based on which Previews are enabled for the session.
std::unordered_set<optimization_guide::proto::OptimizationType>
GetOptimizationTypesToRegister() {
  std::unordered_set<optimization_guide::proto::OptimizationType>
      optimization_types;

  if (params::IsNoScriptPreviewsEnabled())
    optimization_types.insert(optimization_guide::proto::NOSCRIPT);
  if (params::IsResourceLoadingHintsEnabled())
    optimization_types.insert(optimization_guide::proto::RESOURCE_LOADING);
  if (params::IsLitePageServerPreviewsEnabled())
    optimization_types.insert(optimization_guide::proto::LITE_PAGE_REDIRECT);
  if (params::IsDeferAllScriptPreviewsEnabled())
    optimization_types.insert(optimization_guide::proto::DEFER_ALL_SCRIPT);

  return optimization_types;
}

// Parses |resource_loading_hints| and returns a vector of resource patterns
// that can be blocked.
std::vector<std::string> GetResourcePatternsToBlock(
    const google::protobuf::RepeatedPtrField<
        optimization_guide::proto::ResourceLoadingHint>&
        resource_loading_hints) {
  std::vector<std::string> resource_patterns_to_block;
  for (const auto& resource_loading_hint : resource_loading_hints) {
    if (!resource_loading_hint.resource_pattern().empty() &&
        resource_loading_hint.loading_optimization_type() ==
            optimization_guide::proto::LOADING_BLOCK_RESOURCE) {
      resource_patterns_to_block.push_back(
          resource_loading_hint.resource_pattern());
    }
  }
  return resource_patterns_to_block;
}

}  // namespace

PreviewsOptimizationGuideDecider::PreviewsOptimizationGuideDecider(
    optimization_guide::OptimizationGuideDecider* optimization_guide_decider)
    : optimization_guide_decider_(optimization_guide_decider),
      resource_loading_hints_cache_(kDefaultMaxResourceLoadingHintsCacheSize),
      registered_optimization_types_(GetOptimizationTypesToRegister()) {
  DCHECK(optimization_guide_decider_);

  optimization_guide_decider_->RegisterOptimizationTypes(
      std::vector<optimization_guide::proto::OptimizationType>(
          registered_optimization_types_.begin(),
          registered_optimization_types_.end()));
}

PreviewsOptimizationGuideDecider::~PreviewsOptimizationGuideDecider() = default;

bool PreviewsOptimizationGuideDecider::IsReady() const {
  // TODO(crbug/969558): Figure out what to do here. The behavior in the old
  // version was to check if the hints were initialized, but that detail is
  // opaque to us at this level.
  return true;
}

bool PreviewsOptimizationGuideDecider::CanApplyPreview(
    PreviewsUserData* previews_data,
    content::NavigationHandle* navigation_handle,
    PreviewsType type) {
  // See if we need to bypass the lite page redirect blacklist.
  if (type == PreviewsType::LITE_PAGE_REDIRECT &&
      params::LitePageRedirectPreviewIgnoresOptimizationGuideFilter()) {
    return true;
  }

  base::Optional<optimization_guide::proto::OptimizationType>
      optimization_type = ConvertPreviewsTypeToOptimizationType(type);
  if (!optimization_type.has_value())
    return false;

  // See if we can apply the optimization. Note that
  // |optimization_guide_decider_| also ensures that the current browser
  // conditions match a painful page load as a prerequisite for returning true.
  optimization_guide::OptimizationMetadata optimization_metadata;
  optimization_guide::OptimizationGuideDecision decision =
      optimization_guide_decider_->CanApplyOptimization(
          navigation_handle,
          optimization_guide::OptimizationTarget::kPainfulPageLoad,
          *optimization_type, &optimization_metadata);

  // Return false if we are even unsure if we can apply the optimization (i.e.
  // hint not loaded yet or just not applicable).
  if (decision != optimization_guide::OptimizationGuideDecision::kTrue)
    return false;

  // If we can apply it, populate information from metadata.
  if (previews_data &&
      optimization_metadata.previews_metadata.has_inflation_percent()) {
    previews_data->set_data_savings_inflation_percent(
        optimization_metadata.previews_metadata.inflation_percent());
  }
  if (optimization_metadata.previews_metadata.resource_loading_hints_size() >
      0) {
    resource_loading_hints_cache_.Put(
        navigation_handle->GetURL(),
        GetResourcePatternsToBlock(
            optimization_metadata.previews_metadata.resource_loading_hints()));
  }

  return true;
}

bool PreviewsOptimizationGuideDecider::MaybeLoadOptimizationHints(
    content::NavigationHandle* navigation_handle,
    base::OnceClosure callback) {
  // We use this method as a way of enforcing some sort of preview ordering.
  // Thus, we check if we can potentially apply any of the client-side previews,
  // and if any of them potentially can be applied, then we return true.
  const std::vector<optimization_guide::proto::OptimizationType>
      optimization_types_to_check = {
          optimization_guide::proto::DEFER_ALL_SCRIPT,
          optimization_guide::proto::RESOURCE_LOADING,
          optimization_guide::proto::NOSCRIPT};

  bool might_have_hint = false;
  for (const auto optimization_type : optimization_types_to_check) {
    // Don't check for the hint if the optimization type is not enabled.
    if (registered_optimization_types_.find(optimization_type) ==
        registered_optimization_types_.end()) {
      continue;
    }

    if (optimization_guide_decider_->CanApplyOptimization(
            navigation_handle,
            optimization_guide::OptimizationTarget::kPainfulPageLoad,
            optimization_type,
            /*optimization_metadata=*/nullptr) !=
        optimization_guide::OptimizationGuideDecision::kFalse) {
      might_have_hint = true;
      break;
    }
  }

  std::move(callback).Run();
  return might_have_hint;
}

bool PreviewsOptimizationGuideDecider::GetResourceLoadingHints(
    const GURL& url,
    std::vector<std::string>* out_resource_patterns_to_block) {
  auto rlh_it = resource_loading_hints_cache_.Get(url);
  if (rlh_it == resource_loading_hints_cache_.end())
    return false;

  *out_resource_patterns_to_block = rlh_it->second;
  return true;
}

void PreviewsOptimizationGuideDecider::LogHintCacheMatch(
    const GURL& url,
    bool is_committed) const {
  // Intentionally unimplemented: This is handled directly by the
  // OptimizationGuideDecider.
}

void PreviewsOptimizationGuideDecider::ClearFetchedHints() {
  // Intentionally unimplemented: This is handled directly by the
  // OptimizationGuideDecider.
}

}  // namespace previews