module Nunes
  class Adapter
    # Private: Wraps a given object with the correct adapter/decorator.
    #
    # client - The thing to be wrapped.
    #
    # Returns Nunes::Adapter instance.
    def self.wrap(client)
      raise ArgumentError, "client cannot be nil" if client.nil?
      return client if client.is_a?(self)

      adapter = adapters.detect { |adapter| adapter.wraps?(client) }

      if adapter.nil?
        raise ArgumentError,
          "I have no clue how to wrap what you've given me (#{client.inspect})"
      end

      adapter.new(client)
    end

    # Private
    def self.wraps?(client)
      client.respond_to?(:increment) && client.respond_to?(:timing)
    end

    # Private
    def self.adapters
      [Nunes::Adapter, *subclasses]
    end

    # Private
    attr_reader :client

    # Internal: Sets the client for the adapter.
    #
    # client - The thing being adapted to a simple interface.
    def initialize(client)
      @client = client
    end

    # Internal: Increment a metric by a value. Override in subclass if client
    # interface does not match.
    def increment(metric, value = 1)
      @client.increment prepare(metric), value
    end

    # Internal: Record a metric's duration. Override in subclass if client
    # interface does not match.
    def timing(metric, duration)
      @client.timing prepare(metric), duration
    end

    # Private: What Ruby uses to separate namespaces.
    ReplaceRegex = /[^a-z0-9\-_]+/i

    # Private: The default metric namespace separator.
    Separator = "."

    RegexSeparator = Regexp.escape(Separator)

    # Private: Regex to match metric ending with separator.
    StartsOrEndsWithSeparator = /\A#{RegexSeparator}|#{RegexSeparator}\Z/

    # Private
    Nothing = ""

    # Private: Prepare a metric name before it is sent to the adapter's client.
    def prepare(metric)
      metric = metric.to_s.gsub(ReplaceRegex, Separator)
      metric.squeeze!(Separator)
      metric.gsub!(StartsOrEndsWithSeparator, Nothing)
      metric
    end
  end
end