class RuboCop::ResultCache

def self.allow_symlinks_in_cache_location?(config_store)
  config_store.for('.').for_all_cops['AllowSymlinksInCacheRootDirectory']
end

def self.cache_root(config_store)
  root = config_store.for('.').for_all_cops['CacheRootDirectory']
  root ||= if ENV.key?('XDG_CACHE_HOME')
             # Include user ID in the path to make sure the user has write
             # access.
             File.join(ENV['XDG_CACHE_HOME'], Process.uid.to_s)
           else
             File.join(ENV['HOME'], '.cache')
           end
  File.join(root, 'rubocop_cache')
end

def self.cleanup(config_store, verbose, cache_root = nil)
  return if inhibit_cleanup # OPTIMIZE: For faster testing
  cache_root ||= cache_root(config_store)
  return unless File.exist?(cache_root)
  files, dirs = Find.find(cache_root).partition { |path| File.file?(path) }
  return unless requires_file_removal?(files.length, config_store)
  remove_oldest_files(files, dirs, cache_root, verbose)
end

def any_symlink?(path)
  while path != File.dirname(path)
    if File.symlink?(path)
      warn "Warning: #{path} is a symlink, which is not allowed."
      return true
    end
    path = File.dirname(path)
  end
  false
end

def file_checksum(file, config_store)
  digester = Digest::MD5.new
  mode = File.stat(file).mode
  digester.update(
    "#{@pwd}#{file}#{mode}#{config_store.for(file).signature}"
  )
  digester.file(file)
  digester.hexdigest
rescue Errno::ENOENT
  # Spurious files that come and go should not cause a crash, at least not
  # here.
  '_'
end

def initialize(file, options, config_store, cache_root = nil)
  cache_root ||= ResultCache.cache_root(config_store)
  @allow_symlinks_in_cache_location =
    ResultCache.allow_symlinks_in_cache_location?(config_store)
  @path = File.join(cache_root, rubocop_checksum,
                    relevant_options_digest(options),
                    file_checksum(file, config_store))
  @cached_data = CachedData.new(file)
  @pwd = Dir.pwd
end

def load
  @cached_data.from_json(IO.read(@path, encoding: Encoding::UTF_8))
end

def relevant_options_digest(options)
  options = options.reject { |key, _| NON_CHANGING.include?(key) }
  options = options.to_s.gsub(/[^a-z]+/i, '_')
  # We must avoid making file names too long for some filesystems to handle
  # If they are short, we can leave them human-readable
  options.length <= 32 ? options : Digest::MD5.hexdigest(options)
end

def remove_files(files, dirs, remove_count)
  # Batch file deletions, deleting over 130,000+ files will crash
  # File.delete.
  files[0, remove_count].each_slice(10_000).each do |files_slice|
    File.delete(*files_slice)
  end
  dirs.each { |dir| Dir.rmdir(dir) if Dir["#{dir}/*"].empty? }
end

def remove_oldest_files(files, dirs, cache_root, verbose)
  # Add 1 to half the number of files, so that we remove the file if
  # there's only 1 left.
  remove_count = 1 + files.length / 2
  if verbose
    puts "Removing the #{remove_count} oldest files from #{cache_root}"
  end
  sorted = files.sort_by { |path| File.mtime(path) }
  remove_files(sorted, dirs, remove_count)
rescue Errno::ENOENT
  # This can happen if parallel RuboCop invocations try to remove the
  # same files. No problem.
  puts $ERROR_INFO if verbose
end

def requires_file_removal?(file_count, config_store)
  file_count > 1 &&
    file_count > config_store.for('.').for_all_cops['MaxFilesInCache']
end

def rubocop_checksum
  ResultCache.source_checksum ||=
    begin
      lib_root = File.join(File.dirname(__FILE__), '..')
      exe_root = File.join(lib_root, '..', 'exe')
      # These are all the files we have `require`d plus everything in the
      # exe directory. A change to any of them could affect the cop output
      # so we include them in the cache hash.
      source_files = $LOADED_FEATURES + Find.find(exe_root).to_a
      sources = source_files
                .select { |path| File.file?(path) }
                .sort
                .map { |path| IO.read(path, encoding: Encoding::UTF_8) }
      Digest::MD5.hexdigest(sources.join)
    end
end

def save(offenses)
  dir = File.dirname(@path)
  FileUtils.mkdir_p(dir)
  preliminary_path = "#{@path}_#{rand(1_000_000_000)}"
  # RuboCop must be in control of where its cached data is stored. A
  # symbolic link anywhere in the cache directory tree can be an
  # indication that a symlink attack is being waged.
  return if symlink_protection_triggered?(dir)
  File.open(preliminary_path, 'w', encoding: Encoding::UTF_8) do |f|
    f.write(@cached_data.to_json(offenses))
  end
  # The preliminary path is used so that if there are multiple RuboCop
  # processes trying to save data for the same inspected file
  # simultaneously, the only problem we run in to is a competition who gets
  # to write to the final file. The contents are the same, so no corruption
  # of data should occur.
  FileUtils.mv(preliminary_path, @path)
end

def symlink_protection_triggered?(path)
  !@allow_symlinks_in_cache_location && any_symlink?(path)
end

def valid?
  File.exist?(@path)
end