// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "chrome/browser/safe_browsing/extension_telemetry/extension_telemetry_file_processor.h"

#include "base/check.h"
#include "base/containers/fixed_flat_map.h"
#include "base/files/file_enumerator.h"
#include "base/files/file_util.h"
#include "base/metrics/histogram_functions.h"
#include "base/strings/string_number_conversions.h"
#include "base/strings/string_util.h"
#include "base/values.h"
#include "components/safe_browsing/core/common/features.h"
#include "crypto/sha2.h"

namespace safe_browsing {

namespace {
// Max number of files to process per extension.
constexpr int64_t kMaxFilesToProcess = 50;

// Max file size to process - 100KB.
constexpr int64_t kMaxFileSizeBytes = 100 * 1024;

// Max number of files to read per extension.
constexpr int64_t kMaxFilesToRead = 1000;

constexpr base::FilePath::CharType kManifestFilePath[] =
    FILE_PATH_LITERAL("manifest.json");
constexpr base::FilePath::CharType kJSFileSuffix[] = FILE_PATH_LITERAL(".js");
constexpr base::FilePath::CharType kHTMLFileSuffix[] =
    FILE_PATH_LITERAL(".html");
constexpr base::FilePath::CharType kCSSFileSuffix[] = FILE_PATH_LITERAL(".css");

constexpr auto kFileTypePriorityMap =
    base::MakeFixedFlatMap<base::FilePath::StringViewType, int>(
        {{kJSFileSuffix, 3}, {kHTMLFileSuffix, 2}, {kCSSFileSuffix, 1}});

void RecordLargestFileSizeObserved(size_t size) {
  base::UmaHistogramCounts1M(
      "SafeBrowsing.ExtensionTelemetry.FileData.LargestFileSizeObserved", size);
}

void RecordNumFilesFound(int count) {
  base::UmaHistogramCounts1000(
      "SafeBrowsing.ExtensionTelemetry.FileData.NumFilesFound", count);
}

void RecordNumFilesOverProcessingLimit(int count) {
  base::UmaHistogramCounts1000(
      "SafeBrowsing.ExtensionTelemetry.FileData.NumFilesOverProcessingLimit",
      count);
}

void RecordNumFilesOverSizeLimit(int count) {
  base::UmaHistogramCounts1000(
      "SafeBrowsing.ExtensionTelemetry.FileData.NumFilesOverSizeLimit", count);
}

void RecordNumFilesProcessed(int count) {
  base::UmaHistogramCounts1000(
      "SafeBrowsing.ExtensionTelemetry.FileData.NumFilesProcessed", count);
}

void RecordProcessedFileSize(size_t size) {
  base::UmaHistogramCounts1M(
      "SafeBrowsing.ExtensionTelemetry.FileData.ProcessedFileSize", size);
}

void RecordValidExtension(bool valid) {
  base::UmaHistogramBoolean(
      "SafeBrowsing.ExtensionTelemetry.FileData.ValidExtension", valid);
}
}  // namespace

struct ExtensionTelemetryFileProcessor::FileExtensionsComparator {
  bool operator()(const base::FilePath& a, const base::FilePath& b) const {
    return kFileTypePriorityMap.at(base::ToLowerASCII(a.Extension())) >=
           kFileTypePriorityMap.at(base::ToLowerASCII(b.Extension()));
  }
};

ExtensionTelemetryFileProcessor::~ExtensionTelemetryFileProcessor() = default;

ExtensionTelemetryFileProcessor::ExtensionTelemetryFileProcessor()
    : max_files_to_process_(kMaxFilesToProcess),
      max_file_size_(kMaxFileSizeBytes),
      max_files_to_read_(kMaxFilesToRead) {}

base::Value::Dict ExtensionTelemetryFileProcessor::ProcessExtension(
    const base::FilePath& root_dir) {
  DCHECK_CALLED_ON_VALID_SEQUENCE(sequence_checker_);
  if (root_dir.empty()) {
    RecordValidExtension(false);
    return base::Value::Dict();
  }

  // Check if Manifest.json file is valid. If invalid, record in histogram and
  // do not need to process any further.
  base::FilePath manifest_path = root_dir.Append(kManifestFilePath);
  std::string manifest_contents;
  if (!base::ReadFileToString(manifest_path, &manifest_contents) ||
      manifest_contents.empty()) {
    RecordValidExtension(false);
    return base::Value::Dict();
  }

  // Gather all installed extension files, filter and sort by types.
  SortedFilePaths installed_files = RetrieveFilePaths(root_dir);
  // Record +1 for Manifest.json file.
  RecordNumFilesFound(installed_files.size() + 1);

  // Compute hashes of files until |max_files_to_process_| limit is reached.
  base::Value::Dict extension_data =
      ComputeHashes(root_dir, std::move(installed_files));
  extension_data.Set(manifest_path.BaseName().AsUTF8Unsafe(),
                     std::move(manifest_contents));

  RecordNumFilesProcessed(extension_data.size());
  RecordValidExtension(true);
  return extension_data;
}

ExtensionTelemetryFileProcessor::SortedFilePaths
ExtensionTelemetryFileProcessor::RetrieveFilePaths(
    const base::FilePath& root_dir) {
  base::FileEnumerator enumerator(root_dir, /*recursive=*/true,
                                  base::FileEnumerator::FILES);
  int64_t exceeded_file_size_counter = 0;
  int64_t largest_file_size = 0;
  SortedFilePaths sorted_file_paths;

  // Find all file paths within extension directory and add them to a list.
  for (int read_counter = 0; read_counter < max_files_to_read_;
       read_counter++) {
    base::FilePath full_path = enumerator.Next();
    if (full_path.empty()) {
      break;
    }

    // Skip non-applicable type files.
    if (!IsApplicableType(full_path)) {
      continue;
    }

    // Skip invalid and empty files.
    std::optional<int64_t> file_size = base::GetFileSize(full_path);
    if (!file_size.has_value() || file_size.value() <= 0) {
      continue;
    }

    // Record largest file size observed.
    largest_file_size = std::max(largest_file_size, file_size.value());

    // Add file for processing if within size limit, otherwise, skip and record.
    if (file_size.value() <= max_file_size_) {
      sorted_file_paths.insert(std::move(full_path));
    } else {
      exceeded_file_size_counter++;
    }
  }

  RecordLargestFileSizeObserved(largest_file_size);
  RecordNumFilesOverSizeLimit(exceeded_file_size_counter);
  return sorted_file_paths;
}

base::Value::Dict ExtensionTelemetryFileProcessor::ComputeHashes(
    const base::FilePath& root_dir,
    const SortedFilePaths& file_paths) {
  base::Value::Dict extension_data;

  for (const auto& full_path : file_paths) {
    if (extension_data.size() >= max_files_to_process_) {
      break;
    }

    std::string file_contents;
    base::ReadFileToString(full_path, &file_contents);

    // Use relative path as key since file names can repeat.
    base::FilePath relative_path;
    root_dir.AppendRelativePath(full_path, &relative_path);

    std::string hash = crypto::SHA256HashString(file_contents);
    std::string hex_encode = base::HexEncode(hash);

    extension_data.Set(
        relative_path.NormalizePathSeparatorsTo('/').AsUTF8Unsafe(),
        std::move(hex_encode));

    RecordProcessedFileSize(file_contents.size());
  }

  RecordNumFilesOverProcessingLimit(
      std::max(0, static_cast<int>(file_paths.size() - max_files_to_process_)));
  return extension_data;
}

bool ExtensionTelemetryFileProcessor::IsApplicableType(
    const base::FilePath& file_path) {
  return file_path.MatchesExtension(kJSFileSuffix) ||
         file_path.MatchesExtension(kHTMLFileSuffix) ||
         file_path.MatchesExtension(kCSSFileSuffix);
}

void ExtensionTelemetryFileProcessor::SetMaxFilesToProcessForTest(
    int64_t max_files_to_process) {
  max_files_to_process_ = max_files_to_process;
}
void ExtensionTelemetryFileProcessor::SetMaxFileSizeBytesForTest(
    int64_t max_file_size) {
  max_file_size_ = max_file_size;
}

void ExtensionTelemetryFileProcessor::SetMaxFilesToReadForTest(
    int64_t max_files_to_read) {
  max_files_to_read_ = max_files_to_read;
}

}  // namespace safe_browsing