dplummer/cachext

require "redlock"
require "thread"
require "faraday/error"

module Cachext
  class Configuration
    attr_accessor :raise_errors,       # raise all errors all the time? (for tests)
                  :default_expires_in, # in seconds
                  :cache,              # conform to ActiveSupport::Cache interface
                  :redis,              # redis client for locking
                  :error_logger,       # conform to Honeybadger interface
                  :default_errors,     # array of errors to catch and not reraise
                  :not_found_errors,   # array of errors where we delete the backup and reraise
                  :max_lock_wait,      # time in seconds to wait for a lock
                  :debug,              # output debug messages to STDERR
                  :heartbeat_expires,  # time in seconds for process heardbeat to expire
                  :failure_threshold,  # Number of tries before tripping circuit breaker
                  :breaker_timeout     # time in seconds to wait before switching breaker to half-open

    MissingConfiguration = Class.new(StandardError)

    def self.setup
      config = new
      yield config

      if config.cache.nil?
        raise MissingConfiguration, "Must configure the config.cache. Try config.cache = Rails.cache"
      end

      if config.redis.nil?
        raise MissingConfiguration, "Must configure the config.redis. Try config.redis = Redis.current"
      end

      config.lock_manager

      config
    end

    def initialize
      self.raise_errors = false
      self.default_errors = [
        Faraday::Error::ConnectionFailed,
        Faraday::Error::TimeoutError,
      ]
      self.not_found_errors = [
        Faraday::Error::ResourceNotFound,
      ]
      self.default_expires_in = 60
      self.max_lock_wait = 5
      self.debug = ENV['CACHEXT_DEBUG'] == "true"
      self.heartbeat_expires = 2
      self.failure_threshold = 3
      self.breaker_timeout = 60
      @debug_mutex = Mutex.new
    end

    def lock_manager
      @lock_manager ||= Redlock::Client.new [lock_redis], retry_count: 1
    end

    def lock_redis
      redis
    end

    def log_errors?
      error_logger.present?
    end

    def debug
      if block_given?
        if @debug
          @debug_mutex.synchronize do
            yield
          end
        end
      else
        @debug
      end
    end
  end
end