// Copyright 2025 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_RESOLVER_H_
#define COMPONENTS_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_RESOLVER_H_

#include <optional>
#include <string_view>
#include <vector>

#include "base/memory/raw_ref.h"
#include "components/keyed_service/core/keyed_service.h"
#include "components/regional_capabilities/regional_capabilities_country_id.h"
#include "components/search_engines/keyword_web_data_service.h"

struct TemplateURLData;
class PrefService;

namespace regional_capabilities {
class RegionalCapabilitiesService;
}

namespace TemplateURLPrepopulateData {

struct PrepopulatedEngine;

// Provides context on TemplateURLPrepopulateData's data set.
struct BuiltinKeywordsMetadata {
  // Country for which we are selecting the built-in prepopulate data.
  regional_capabilities::CountryIdHolder country_id;

  // Version of the built-in prepopulated keywords data.
  int data_version;

  // The migration state of the database, indicating which prepopulated engine
  // migrations have been applied.
  KeywordTable::PrepopulatedEngineMigrationSet
      prepopulated_engines_migration_state;
};

// Resolves prepopulated engines using on various information from the browser
// context, like country, state of some prefs, etc.
// Use this service instead directly calling functions from
// `TemplateURLPrepopulateData`.
class Resolver : public KeyedService {
 public:
  Resolver(PrefService& prefs,
           regional_capabilities::RegionalCapabilitiesService&
               regional_capabilities);

  // Returns the prepopulated URLs for the profile country.
  std::vector<std::unique_ptr<TemplateURLData>> GetPrepopulatedEngines() const;

  // Returns the prepopulated search engine with the given `prepopulated_id`
  // from the profile country's known prepopulated search engines, or `nullptr`
  // if it's not known there.
  std::unique_ptr<TemplateURLData> GetPrepopulatedEngine(
      int prepopulated_id) const;

  // Returns the prepopulated search engine with the given `prepopulated_id`
  // from the full list of known prepopulated search engines, or `nullptr` if
  // it's not known there.
  std::unique_ptr<TemplateURLData> GetEngineFromFullList(
      int prepopulated_id) const;

  // Returns the prepopulated search engine with the given `keyword` from the
  // full list of known prepopulated search engines, or `nullptr` if it's not
  // known there.
  std::unique_ptr<TemplateURLData> GetEngineFromFullList(
      std::u16string_view keyword) const;

  // Returns the fallback default search provider, currently hardcoded to be
  // Google, or whichever one is the first of the list if Google is not in the
  // list of prepopulated search engines.
  // May return `nullptr` if for some reason there are no prepopulated search
  // engines available.
  std::unique_ptr<TemplateURLData> GetFallbackSearch() const;

  // Computes whether updates relative to prepopulated search engines need to be
  // made in the local search engines database.
  //
  // Returns `std::nullopt` when no updates are needed, or a `Metadata`
  // providing country and data version info about the data to be merged in.
  std::optional<BuiltinKeywordsMetadata> ComputeDatabaseUpdateRequirements(
      const WDKeywordsResult::Metadata& keywords_database_metadata) const;

  // Granular reasons for TemplateURLs to match (or not). See `IsMatch` to
  // interpret the values.
  // TODO(crbug.com/507355138): Remove the enum and revert to just using bool.
  // LINT.IfChange(MigrationMatch)
  enum class MigrationMatch {
    kExactMatch = 0,
    kHostMatch = 1,
    kIdsDontMatch = 2,
    kInvalidCheckedUrl = 3,
    kUrlMismatch = 4,
    kMaxValue = kUrlMismatch,
  };
  // LINT.ThenChange(/tools/metrics/histograms/metadata/omnibox/enums.xml:MigrationMatch)

  // Interprets the output of `CompareEngineUnderMigration(checked_data,
  // deprecated_engine)`.
  // Returns true if `match` indicates that `deprecated_engine`'s migration
  // instruction can be applied to `checked_data`.
  static bool IsMatch(MigrationMatch match);

  // Returns whether `deprecated_engine`'s migration instruction can be applied
  // to `checked_data`. This needs to be checked to ensure that we are not
  // incorrectly migrating custom or variant engine definitions.
  // Use `IsMatch(MigrationMatch)` to interpret the output.
  MigrationMatch CompareEngineUnderMigration(
      const TemplateURLData& checked_data,
      const PrepopulatedEngine* deprecated_engine) const;

  // Searches the prepopulated engines for the newest representation of an
  // engine under migration that could match `pre_migration_engine`.
  // The returned `TemplateURLData` is the prepopulated data (see
  // `GetPrepopulatedEngine(int)`) representing the new version of the engine
  // that the prepopulated representation of `pre_migration_engine` points to
  // through `PrepopulatedEngine::migrate_to_id`.
  std::unique_ptr<TemplateURLData> TryGetMigratedEngine(
      const TemplateURLData& pre_migration_engine) const;

 private:
  raw_ref<PrefService> profile_prefs_;
  raw_ref<regional_capabilities::RegionalCapabilitiesService>
      regional_capabilities_;
};

}  // namespace TemplateURLPrepopulateData

#endif  // COMPONENTS_SEARCH_ENGINES_TEMPLATE_URL_PREPOPULATE_DATA_RESOLVER_H_