require 'benchmark'
require 'zlib'
require 'active_support/core_ext/array/extract_options'
require 'active_support/core_ext/array/wrap'
require 'active_support/core_ext/benchmark'
require 'active_support/core_ext/exception'
require 'active_support/core_ext/class/attribute_accessors'
require 'active_support/core_ext/numeric/bytes'
require 'active_support/core_ext/numeric/time'
require 'active_support/core_ext/object/to_param'
require 'active_support/core_ext/string/inflections'

module ActiveSupport
  # See ActiveSupport::Cache::Store for documentation.
  module Cache
    autoload :FileStore, 'active_support/cache/file_store'
    autoload :MemoryStore, 'active_support/cache/memory_store'
    autoload :MemCacheStore, 'active_support/cache/mem_cache_store'
    autoload :NullStore, 'active_support/cache/null_store'

    # These options mean something to all cache implementations. Individual cache
    # implementations may support additional options.
    UNIVERSAL_OPTIONS = [:namespace, :compress, :compress_threshold, :expires_in, :race_condition_ttl]

    module Strategy
      autoload :LocalCache, 'active_support/cache/strategy/local_cache'
    end

    class << self
      # Creates a new CacheStore object according to the given options.
      #
      # If no arguments are passed to this method, then a new
      # ActiveSupport::Cache::MemoryStore object will be returned.
      #
      # If you pass a Symbol as the first argument, then a corresponding cache
      # store class under the ActiveSupport::Cache namespace will be created.
      # For example:
      #
      #   ActiveSupport::Cache.lookup_store(:memory_store)
      #   # => returns a new ActiveSupport::Cache::MemoryStore object
      #
      #   ActiveSupport::Cache.lookup_store(:mem_cache_store)
      #   # => returns a new ActiveSupport::Cache::MemCacheStore object
      #
      # Any additional arguments will be passed to the corresponding cache store
      # class's constructor:
      #
      #   ActiveSupport::Cache.lookup_store(:file_store, "/tmp/cache")
      #   # => same as: ActiveSupport::Cache::FileStore.new("/tmp/cache")
      #
      # If the first argument is not a Symbol, then it will simply be returned:
      #
      #   ActiveSupport::Cache.lookup_store(MyOwnCacheStore.new)
      #   # => returns MyOwnCacheStore.new
      def lookup_store(*store_option)
        store, *parameters = *Array.wrap(store_option).flatten

        case store
        when Symbol
          store_class_name = store.to_s.camelize
          store_class =
            begin
              require "active_support/cache/#{store}"
            rescue LoadError => e
              raise "Could not find cache store adapter for #{store} (#{e})"
            else
              ActiveSupport::Cache.const_get(store_class_name)
            end
          store_class.new(*parameters)
        when nil
          ActiveSupport::Cache::MemoryStore.new
        else
          store
        end
      end

      def expand_cache_key(key, namespace = nil)
        expanded_cache_key = namespace ? "#{namespace}/" : ""

        if prefix = ENV["RAILS_CACHE_ID"] || ENV["RAILS_APP_VERSION"]
          expanded_cache_key << "#{prefix}/"
        end

        expanded_cache_key << retrieve_cache_key(key)
        expanded_cache_key
      end

      private

      def retrieve_cache_key(key)
        case
        when key.respond_to?(:cache_key) then key.cache_key
        when key.is_a?(Array)            then key.map { |element| retrieve_cache_key(element) }.to_param
        else                                  key.to_param
        end.to_s
      end
    end

    # An abstract cache store class. There are multiple cache store
    # implementations, each having its own additional features. See the classes
    # under the ActiveSupport::Cache module, e.g.
    # ActiveSupport::Cache::MemCacheStore. MemCacheStore is currently the most
    # popular cache store for large production websites.
    #
    # Some implementations may not support all methods beyond the basic cache
    # methods of +fetch+, +write+, +read+, +exist?+, and +delete+.
    #
    # ActiveSupport::Cache::Store can store any serializable Ruby object.
    #
    #   cache = ActiveSupport::Cache::MemoryStore.new
    #
    #   cache.read("city")   # => nil
    #   cache.write("city", "Duckburgh")
    #   cache.read("city")   # => "Duckburgh"
    #
    # Keys are always translated into Strings and are case sensitive. When an
    # object is specified as a key and has a +cache_key+ method defined, this
    # method will be called to define the key.  Otherwise, the +to_param+
    # method will be called. Hashes and Arrays can also be used as keys. The
    # elements will be delimited by slashes, and the elements within a Hash
    # will be sorted by key so they are consistent.
    #
    #   cache.read("city") == cache.read(:city)   # => true
    #
    # Nil values can be cached.
    #
    # If your cache is on a shared infrastructure, you can define a namespace
    # for your cache entries. If a namespace is defined, it will be prefixed on
    # to every key. The namespace can be either a static value or a Proc. If it
    # is a Proc, it will be invoked when each key is evaluated so that you can
    # use application logic to invalidate keys.
    #
    #   cache.namespace = lambda { @last_mod_time }  # Set the namespace to a variable
    #   @last_mod_time = Time.now  # Invalidate the entire cache by changing namespace
    #
    #
    # Caches can also store values in a compressed format to save space and
    # reduce time spent sending data. Since there is overhead, values must be
    # large enough to warrant compression. To turn on compression either pass
    # <tt>:compress => true</tt> in the initializer or as an option to +fetch+
    # or +write+. To specify the threshold at which to compress values, set the
    # <tt>:compress_threshold</tt> option. The default threshold is 16K.
    class Store

      cattr_accessor :logger, :instance_writer => true

      attr_reader :silence, :options
      alias :silence? :silence

      # Create a new cache. The options will be passed to any write method calls except
      # for :namespace which can be used to set the global namespace for the cache.
      def initialize(options = nil)
        @options = options ? options.dup : {}
      end

      # Silence the logger.
      def silence!
        @silence = true
        self
      end

      # Silence the logger within a block.
      def mute
        previous_silence, @silence = defined?(@silence) && @silence, true
        yield
      ensure
        @silence = previous_silence
      end

      # Set to true if cache stores should be instrumented. Default is false.
      def self.instrument=(boolean)
        Thread.current[:instrument_cache_store] = boolean
      end

      def self.instrument
        Thread.current[:instrument_cache_store] || false
      end

      # Fetches data from the cache, using the given key. If there is data in
      # the cache with the given key, then that data is returned.
      #
      # If there is no such data in the cache (a cache miss), then nil will be
      # returned. However, if a block has been passed, that block will be run
      # in the event of a cache miss. The return value of the block will be
      # written to the cache under the given cache key, and that return value
      # will be returned.
      #
      #   cache.write("today", "Monday")
      #   cache.fetch("today")  # => "Monday"
      #
      #   cache.fetch("city")   # => nil
      #   cache.fetch("city") do
      #     "Duckburgh"
      #   end
      #   cache.fetch("city")   # => "Duckburgh"
      #
      # You may also specify additional options via the +options+ argument.
      # Setting <tt>:force => true</tt> will force a cache miss:
      #
      #   cache.write("today", "Monday")
      #   cache.fetch("today", :force => true)  # => nil
      #
      # Setting <tt>:compress</tt> will store a large cache entry set by the call
      # in a compressed format.
      #
      #
      # Setting <tt>:expires_in</tt> will set an expiration time on the cache.
      # All caches support auto-expiring content after a specified number of
      # seconds. This value can be specified as an option to the constructor
      # (in which case all entries will be affected), or it can be supplied to
      # the +fetch+ or +write+ method to effect just one entry.
      #
      #   cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 5.minutes)
      #   cache.write(key, value, :expires_in => 1.minute)  # Set a lower value for one entry
      #
      # Setting <tt>:race_condition_ttl</tt> is very useful in situations where a cache entry
      # is used very frequently and is under heavy load. If a cache expires and due to heavy load
      # seven different processes will try to read data natively and then they all will try to
      # write to cache. To avoid that case the first process to find an expired cache entry will
      # bump the cache expiration time by the value set in <tt>:race_condition_ttl</tt>. Yes
      # this process is extending the time for a stale value by another few seconds. Because
      # of extended life of the previous cache, other processes will continue to use slightly
      # stale data for a just a big longer. In the meantime that first process will go ahead
      # and will write into cache the new value. After that all the processes will start
      # getting new value. The key is to keep <tt>:race_condition_ttl</tt> small.
      #
      # If the process regenerating the entry errors out, the entry will be regenerated
      # after the specified number of seconds. Also note that the life of stale cache is
      # extended only if it expired recently. Otherwise a new value is generated and
      # <tt>:race_condition_ttl</tt> does not play any role.
      #
      #   # Set all values to expire after one minute.
      #   cache = ActiveSupport::Cache::MemoryStore.new(:expires_in => 1.minute)
      #
      #   cache.write("foo", "original value")
      #   val_1 = nil
      #   val_2 = nil
      #   sleep 60
      #
      #   Thread.new do
      #     val_1 = cache.fetch("foo", :race_condition_ttl => 10) do
      #       sleep 1
      #       "new value 1"
      #     end
      #   end
      #
      #   Thread.new do
      #     val_2 = cache.fetch("foo", :race_condition_ttl => 10) do
      #       "new value 2"
      #     end
      #   end
      #
      #   # val_1 => "new value 1"
      #   # val_2 => "original value"
      #   # sleep 10 # First thread extend the life of cache by another 10 seconds
      #   # cache.fetch("foo") => "new value 1"
      #
      # Other options will be handled by the specific cache store implementation.
      # Internally, #fetch calls #read_entry, and calls #write_entry on a cache miss.
      # +options+ will be passed to the #read and #write calls.
      #
      # For example, MemCacheStore's #write method supports the +:raw+
      # option, which tells the memcached server to store all values as strings.
      # We can use this option with #fetch too:
      #
      #   cache = ActiveSupport::Cache::MemCacheStore.new
      #   cache.fetch("foo", :force => true, :raw => true) do
      #     :bar
      #   end
      #   cache.fetch("foo")  # => "bar"
      def fetch(name, options = nil)
        if block_given?
          options = merged_options(options)
          key = namespaced_key(name, options)
          unless options[:force]
            entry = instrument(:read, name, options) do |payload|
              payload[:super_operation] = :fetch if payload
              read_entry(key, options)
            end
          end
          if entry && entry.expired?
            race_ttl = options[:race_condition_ttl].to_f
            if race_ttl and Time.now.to_f - entry.expires_at <= race_ttl
              entry.expires_at = Time.now + race_ttl
              write_entry(key, entry, :expires_in => race_ttl * 2)
            else
              delete_entry(key, options)
            end
            entry = nil
          end

          if entry
            instrument(:fetch_hit, name, options) { |payload| }
            entry.value
          else
            result = instrument(:generate, name, options) do |payload|
              yield
            end
            write(name, result, options)
            result
          end
        else
          read(name, options)
        end
      end

      # Fetches data from the cache, using the given key. If there is data in
      # the cache with the given key, then that data is returned. Otherwise,
      # nil is returned.
      #
      # Options are passed to the underlying cache implementation.
      def read(name, options = nil)
        options = merged_options(options)
        key = namespaced_key(name, options)
        instrument(:read, name, options) do |payload|
          entry = read_entry(key, options)
          if entry
            if entry.expired?
              delete_entry(key, options)
              payload[:hit] = false if payload
              nil
            else
              payload[:hit] = true if payload
              entry.value
            end
          else
            payload[:hit] = false if payload
            nil
          end
        end
      end

      # Read multiple values at once from the cache. Options can be passed
      # in the last argument.
      #
      # Some cache implementation may optimize this method.
      #
      # Returns a hash mapping the names provided to the values found.
      def read_multi(*names)
        options = names.extract_options!
        options = merged_options(options)
        results = {}
        names.each do |name|
          key = namespaced_key(name, options)
          entry = read_entry(key, options)