// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "components/variations/processed_study.h"

#include <cstdint>
#include <set>
#include <string>
#include <string_view>

#include "base/feature_list.h"
#include "base/logging.h"
#include "base/metrics/histogram_functions.h"
#include "base/strings/string_util.h"
#include "base/version.h"
#include "components/variations/proto/study.pb.h"
#include "entropy_provider.h"
#include "third_party/abseil-cpp/absl/container/flat_hash_set.h"
#include "variations_layers.h"

namespace variations {
namespace {

void LogInvalidReason(InvalidStudyReason reason) {
  base::UmaHistogramEnumeration("Variations.InvalidStudyReason", reason);
}

// TODO(crbug.com/41449497): Use
// base::FeatureList::IsValidFeatureOrFieldTrialName once WebRTC trials with ","
// in group names are removed.
bool IsValidExperimentName(const std::string& name) {
  return base::IsStringASCII(name) &&
         name.find_first_of("<*") == std::string::npos;
}

// Validates that all version numbers in the study are valid.
bool ValidateVersionNumbers(const Study& study) {
  if (study.filter().has_min_version() &&
      !base::Version::IsValidWildcardString(study.filter().min_version())) {
    LogInvalidReason(InvalidStudyReason::kInvalidMinVersion);
    DVLOG(1) << study.name()
             << " has invalid min version: " << study.filter().min_version();
    return false;
  }
  if (study.filter().has_max_version() &&
      !base::Version::IsValidWildcardString(study.filter().max_version())) {
    LogInvalidReason(InvalidStudyReason::kInvalidMaxVersion);
    DVLOG(1) << study.name()
             << " has invalid max version: " << study.filter().max_version();
    return false;
  }
  if (study.filter().has_min_os_version() &&
      !base::Version::IsValidWildcardString(study.filter().min_os_version())) {
    LogInvalidReason(InvalidStudyReason::kInvalidMinOsVersion);
    DVLOG(1) << study.name() << " has invalid min os version: "
             << study.filter().min_os_version();
    return false;
  }
  if (study.filter().has_max_os_version() &&
      !base::Version::IsValidWildcardString(study.filter().max_os_version())) {
    LogInvalidReason(InvalidStudyReason::kInvalidMaxOsVersion);
    DVLOG(1) << study.name() << " has invalid max os version: "
             << study.filter().max_os_version();
    return false;
  }
  return true;
}

// Validates that all experiment names in the study are valid.
bool ValidateExperimentNames(const Study& study) {
  absl::flat_hash_set<std::string_view> experiment_names;
  experiment_names.reserve(study.experiment().size());
  for (const auto& experiment : study.experiment()) {
    if (experiment.name().empty()) {
      LogInvalidReason(InvalidStudyReason::kMissingExperimentName);
      DVLOG(1) << study.name() << " is missing an experiment name";
      return false;
    }
    if (!IsValidExperimentName(experiment.name())) {
      LogInvalidReason(InvalidStudyReason::kInvalidExperimentName);
      DVLOG(1) << study.name() << " has a invalid experiment name "
               << experiment.name();
      return false;
    }
    if (!experiment_names.insert(experiment.name()).second) {
      LogInvalidReason(InvalidStudyReason::kRepeatedExperimentName);
      DVLOG(1) << study.name() << " has a repeated experiment name "
               << experiment.name();
      return false;
    }
  }

  // Specifying a default experiment is optional, so finding it in the
  // experiment list is only required when it is specified.
  if (!study.default_experiment_name().empty() &&
      !experiment_names.contains(study.default_experiment_name())) {
    LogInvalidReason(InvalidStudyReason::kMissingDefaultExperimentInList);
    DVLOG(1) << study.name() << " is missing default experiment ("
             << study.default_experiment_name() << ") in its experiment list";
    // The default group was not found in the list of groups. This study is
    // not valid.
    return false;
  }
  return true;
}

// Validates that all feature names in the study are valid.
bool ValidateFeatureNames(const Study& study) {
  for (const auto& experiment : study.experiment()) {
    if (!experiment.has_feature_association()) {
      continue;
    }
    for (const auto& feature :
         experiment.feature_association().enable_feature()) {
      if (!base::FeatureList::IsValidFeatureOrFieldTrialName(feature)) {
        LogInvalidReason(InvalidStudyReason::kInvalidFeatureName);
        DVLOG(1) << study.name() << " has an invalid feature name " << feature;
        return false;
      }
    }
    for (const auto& feature :
         experiment.feature_association().disable_feature()) {
      if (!base::FeatureList::IsValidFeatureOrFieldTrialName(feature)) {
        LogInvalidReason(InvalidStudyReason::kInvalidFeatureName);
        DVLOG(1) << study.name() << " has an invalid feature name " << feature;
        return false;
      }
    }
    if (!base::FeatureList::IsValidFeatureOrFieldTrialName(
            experiment.feature_association().forcing_feature_on())) {
      LogInvalidReason(InvalidStudyReason::kInvalidFeatureName);
      DVLOG(1) << study.name() << " has an invalid feature name "
               << experiment.feature_association().forcing_feature_on();
      return false;
    }
    if (!base::FeatureList::IsValidFeatureOrFieldTrialName(
            experiment.feature_association().forcing_feature_off())) {
      LogInvalidReason(InvalidStudyReason::kInvalidFeatureName);
      DVLOG(1) << study.name() << " has an invalid feature name "
               << experiment.feature_association().forcing_feature_off();
      return false;
    }
  }
  return true;
}

// Validates and computes the total probability and whether all assignments are
// to a single group.
bool ValidateAndComputeTotalProbability(
    const Study& study,
    base::FieldTrial::Probability* total_probability,
    bool* all_assignments_to_one_group) {
  base::FieldTrial::Probability divisor = 0;
  bool multiple_assigned_groups = false;

  for (const auto& experiment : study.experiment()) {
    if (experiment.has_google_web_experiment_id() &&
        experiment.has_google_web_trigger_experiment_id()) {
      LogInvalidReason(InvalidStudyReason::kTriggerAndNonTriggerExperimentId);
      DVLOG(1) << study.name() << " has experiment (" << experiment.name()
               << ") with a google_web_experiment_id and a "
               << "web_trigger_experiment_id.";
      return false;
    }

    if (experiment.has_google_web_experiment_id() ||
        experiment.has_google_web_trigger_experiment_id() ||
        experiment.has_google_app_experiment_id()) {
      if (study.activation_type() == Study::STICKY_AFTER_QUERY) {
        LogInvalidReason(InvalidStudyReason::kExperimentIdInStickyStudy);
        DVLOG(1) << study.name() << " with sticky activation has experiment ("
                 << experiment.name() << ") with an experiment ID.";
        return false;
      } else if (study.activation_type() == Study::ACTIVATE_ON_QUERY) {
        LogInvalidReason(
            InvalidStudyReason::kExperimentIdInActivateOnQueryStudy);
        DVLOG(1) << study.name() << " with query activation has experiment ("
                 << experiment.name() << ") with an experiment ID.";
        return false;
      }
    }

    if (!experiment.has_forcing_flag() && experiment.probability_weight() > 0) {
      // If |divisor| is not 0, there was at least one prior non-zero group.
      if (divisor != 0) {
        multiple_assigned_groups = true;
      }

      if (experiment.probability_weight() >
          std::numeric_limits<base::FieldTrial::Probability>::max()) {
        LogInvalidReason(InvalidStudyReason::kExperimentProbabilityOverflow);
        DVLOG(1) << study.name() << " has an experiment (" << experiment.name()
                 << ") with a probability weight of "
                 << experiment.probability_weight()
                 << " that exceeds the maximum supported value";
        return false;
      }

      if (divisor + experiment.probability_weight() >
          std::numeric_limits<base::FieldTrial::Probability>::max()) {
        LogInvalidReason(InvalidStudyReason::kTotalProbabilityOverflow);
        DVLOG(1) << study.name() << "'s total probability weight exceeds the "
                 << "maximum supported value";
        return false;
      }
      divisor += experiment.probability_weight();
    }
  }
  *total_probability = divisor;
  *all_assignments_to_one_group = !multiple_assigned_groups;
  return true;
}

// Validates the study type enums.
bool ValidateStudyTypeEnums(const Study& study) {
  // Note: These enums are specifically defined as `features.enum_type = OPEN`,
  // meaning unknown values are present as integers on the original field. This
  // allows us to validate them using IsValid() without needing to use proto
  // reflection (which is more expensive) on unknown values.
  if (study.has_consistency() &&
      !Study::Consistency_IsValid(study.consistency())) {
    LogInvalidReason(InvalidStudyReason::kUnsupportedStudyConsistency);
    DVLOG(1) << study.name()
             << " has an unsupported consistency: " << study.consistency();
    return false;
  }
  if (study.has_activation_type() &&
      !Study::ActivationType_IsValid(study.activation_type())) {
    LogInvalidReason(InvalidStudyReason::kUnsupportedStudyActivationType);
    DVLOG(1) << study.name() << " has an unsupported activation type: "
             << study.activation_type();
    return false;
  }
  if (study.activation_type() == Study::STICKY_AFTER_QUERY &&
      study.consistency() != Study::PERMANENT) {
    LogInvalidReason(InvalidStudyReason::kInvalidConsistencyForStickyStudy);
    DVLOG(1) << study.name() << " has invalid consistency ("
             << study.consistency()
             << ") for activation type STICKY_AFTER_QUERY";
    return false;
  }
  return true;
}

// Validates the sanity of |study| and computes the total probability and
// whether all assignments are to a single group.
bool ValidateStudyAndComputeTotalProbability(
    const Study& study,
    base::FieldTrial::Probability* total_probability,
    bool* all_assignments_to_one_group) {
  if (study.name().empty()) {
    LogInvalidReason(InvalidStudyReason::kBlankStudyName);
    DVLOG(1) << "study with missing study name";
    return false;
  }

  if (!base::FeatureList::IsValidFeatureOrFieldTrialName(study.name())) {
    LogInvalidReason(InvalidStudyReason::kInvalidStudyName);
    DVLOG(1) << study.name() << " is an invalid experiment name";
    return false;
  }

  if (study.has_expiry_date()) {
    LogInvalidReason(InvalidStudyReason::kUnsupportedExpiryDate);
    DVLOG(1) << study.name() << " uses the unsupported expiry_date field.";
    return false;
  }

  if (!ValidateVersionNumbers(study)) {
    return false;
  }

  if (!ValidateExperimentNames(study)) {
    return false;
  }

  if (!ValidateFeatureNames(study)) {
    return false;
  }

  if (!ValidateStudyTypeEnums(study)) {
    return false;
  }

  for (const auto& experiment : study.experiment()) {
    const auto& flag = experiment.forcing_flag();
    // Forcing flags are passed to CommandLine::HasSwitch. It should be safe to
    // pass invalid flags to that, but we do validation to prevent triggering
    // the DCHECK there.
    if (base::ToLowerASCII(flag) != flag) {
      LogInvalidReason(InvalidStudyReason::kInvalidForcingFlag);
      DVLOG(1) << study.name() << " has an invalid forcing flag " << flag;
      return false;
    }
  }

  return ValidateAndComputeTotalProbability(study, total_probability,
                                            all_assignments_to_one_group);
}

}  // namespace

// static
const char ProcessedStudy::kGenericDefaultExperimentName[] =
    "VariationsDefaultExperiment";

ProcessedStudy::ProcessedStudy() = default;

ProcessedStudy::ProcessedStudy(const ProcessedStudy& other) = default;

ProcessedStudy::~ProcessedStudy() = default;

bool ProcessedStudy::Init(const Study* study) {
  base::FieldTrial::Probability total_probability = 0;
  bool all_assignments_to_one_group = false;
  std::vector<std::string> associated_features;
  if (!ValidateStudyAndComputeTotalProbability(*study, &total_probability,
                                               &all_assignments_to_one_group)) {
    return false;
  }

  study_ = study;
  total_probability_ = total_probability;
  all_assignments_to_one_group_ = all_assignments_to_one_group;
  return true;
}

int ProcessedStudy::GetExperimentIndexByName(const std::string& name) const {
  for (int i = 0; i < study_->experiment_size(); ++i) {
    if (study_->experiment(i).name() == name) {
      return i;
    }
  }

  return -1;
}

const std::string_view ProcessedStudy::GetDefaultExperimentName() const {
  if (study_->default_experiment_name().empty()) {
    return kGenericDefaultExperimentName;
  }

  return study_->default_experiment_name();
}

}  // namespace variations