class ERBLint::Cache

def cache_dir_exists?
  File.directory?(@cache_dir)
end

def checksum(filename, file_content)
  digester = Digest::SHA1.new
  mode = File.stat(filename).mode
  digester.update(
    "#{mode}#{config.to_hash}#{ERBLint::VERSION}#{file_content}",
  )
  digester.hexdigest
rescue Errno::ENOENT
  # Spurious files that come and go should not cause a crash, at least not
  # here.
  "_"
end

def clear
  return unless cache_dir_exists?
  puts "Clearing cache by deleting cache directory"
  FileUtils.rm_r(@cache_dir)
end

def close
  prune_cache
end

def get(filename, file_content)
  file_checksum = checksum(filename, file_content)
  begin
    cache_file_contents_as_offenses = JSON.parse(
      File.read(File.join(@cache_dir, file_checksum)),
    ).map do |offense_hash|
      ERBLint::CachedOffense.new(offense_hash)
    end
  rescue Errno::ENOENT
    return false
  end
  @hits.push(file_checksum)
  cache_file_contents_as_offenses
end

def initialize(config, cache_dir = nil)
  @config = config
  @cache_dir = cache_dir || CACHE_DIRECTORY
  @hits = []
  @new_results = []
  puts "Cache mode is on"
end

def prune_cache
  if hits.empty?
    puts "Cache being created for the first time, skipping prune"
    return
  end
  cache_files = Dir.new(@cache_dir).children
  cache_files.each do |cache_file|
    next if hits.include?(cache_file) || new_results.include?(cache_file)
    File.delete(File.join(@cache_dir, cache_file))
  end
end

def set(filename, file_content, offenses_as_json)
  file_checksum = checksum(filename, file_content)
  @new_results.push(file_checksum)
  FileUtils.mkdir_p(@cache_dir)
  File.open(File.join(@cache_dir, file_checksum), "wb") do |f|
    f.write(offenses_as_json)
  end
end