# Copyright (c) 2022 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'singleton'
require 'contrast/utils/object_share'

module Contrast
  module Utils
    # Utility methods for building and caching hashes from strings
    class Sha256Builder
      include Singleton

      def initialize
        @sha256_cache = {}
        @gem_hash_cache = {}
      end

      # Return a list of "source" files. Ignore metadata files as well as files
      # in the spec, test or exe directories. Could potentially miss important
      # files but good enough for the time being.
      PATHS = '{lib,bin,ext}/**/*.{rb,c,h,c++,cpp,java,rs}'
      def files path
        if Dir.exist?(path)
          Dir.glob(File.join(path, PATHS))
        else
          []
        end
      end

      # Generate a SHA256 hash of the combined source code of this Gem
      def sha256 path
        return unless path
        return unless File.exist?(path) && !File.directory?(path)

        @sha256_cache[path] ||= Digest::SHA256.file(path).to_s
      end

      def build_from_spec spec
        name = spec.file_name.to_s
        cached = @gem_hash_cache[name]
        return cached if cached

        gem_path = File.join(cache_dir(spec), name)
        hash = sha256(gem_path)

        @gem_hash_cache[name] = hash
        hash
      end

      def cache_dir spec
        gems_dir = spec.gems_dir
        parent_dir = File.dirname(gems_dir)
        File.join(parent_dir, Contrast::Utils::ObjectShare::CACHE)
      end
    end
  end
end