require 'digest/sha2'

module ImpressionistController
  module ClassMethods
    def impressionist(opts={})
      before_filter { |c| c.impressionist_subapp_filter(opts) }
    end
  end

  module InstanceMethods
    def self.included(base)
      base.before_filter :impressionist_app_filter
    end

    def impressionist(obj,message=nil,opts={})
      if should_count_impression?(opts)
        if obj.respond_to?("impressionable?")
          if unique_instance?(obj, opts[:unique])
            obj.impressions.create(associative_create_statement({:message => message}))
          end
        else
          # we could create an impression anyway. for classes, too. why not?
          raise "#{obj.class.to_s} is not impressionable!"
        end
      end
    end

    def impressionist_app_filter
      @impressionist_hash = Digest::SHA2.hexdigest(Time.now.to_f.to_s+rand(10000).to_s)
    end

    def impressionist_subapp_filter(opts = {})
      if should_count_impression?(opts)
        actions = opts[:actions]
        actions.collect!{|a|a.to_s} unless actions.blank?
        if (actions.blank? || actions.include?(action_name)) && unique?(opts[:unique])
          Impression.create(direct_create_statement)
        end
      end
    end

    protected

    # creates a statment hash that contains default values for creating an impression via an AR relation.
    def associative_create_statement(query_params={})
      query_params.reverse_merge!(
        :controller_name => controller_name,
        :action_name => action_name,
        :user_id => user_id,
        :request_hash => @impressionist_hash,
        :session_hash => session_hash,
        :ip_address => request.remote_ip,
        :referrer => request.referer,
        :params => params_hash
        )
    end

    private

    def bypass
      Impressionist::Bots.bot?(request.user_agent)
    end

    def should_count_impression?(opts)
      !bypass && condition_true?(opts[:if]) && condition_false?(opts[:unless])
    end

    def condition_true?(condition)
      condition.present? ? conditional?(condition) : true
    end

    def condition_false?(condition)
      condition.present? ? !conditional?(condition) : true
    end

    def conditional?(condition)
      condition.is_a?(Symbol) ? self.send(condition) : condition.call
    end

    def unique_instance?(impressionable, unique_opts)
      return unique_opts.blank? || !impressionable.impressions.where(unique_query(unique_opts, impressionable)).exists?
    end

    def unique?(unique_opts)
      return unique_opts.blank? || check_impression?(unique_opts)
    end

    def check_impression?(unique_opts)
      impressions = Impression.where(unique_query(unique_opts - [:params]))
      check_unique_impression?(impressions, unique_opts)
    end

    def check_unique_impression?(impressions, unique_opts)
      impressions_present = impressions.exists?
      impressions_present && unique_opts_has_params?(unique_opts) ? check_unique_with_params?(impressions) : !impressions_present
    end

    def unique_opts_has_params?(unique_opts)
      unique_opts.include?(:params)
    end

    def check_unique_with_params?(impressions)
      request_param = params_hash
      impressions.detect{|impression| impression.params == request_param }.nil?
    end
    
    # creates the query to check for uniqueness
    def unique_query(unique_opts,impressionable=nil)
      full_statement = direct_create_statement({},impressionable)
      # reduce the full statement to the params we need for the specified unique options
      unique_opts.reduce({}) do |query, param|
        query[param] = full_statement[param]
        query
      end
    end

    # creates a statment hash that contains default values for creating an impression.
    def direct_create_statement(query_params={},impressionable=nil)
      query_params.reverse_merge!(
        :impressionable_type => controller_name.singularize.camelize,
        :impressionable_id => impressionable.present? ? impressionable.id : params[:id]
        )
      associative_create_statement(query_params)
    end

    def session_hash
      # # careful: request.session_options[:id] encoding in rspec test was ASCII-8BIT
      # # that broke the database query for uniqueness. not sure if this is a testing only issue.
      # str = request.session_options[:id]
      # logger.debug "Encoding: #{str.encoding.inspect}"
      # # request.session_options[:id].encode("ISO-8859-1")
      request.session_options[:id]
    end

    def params_hash
      request.params.except(:controller, :action, :id)
    end

    #use both @current_user and current_user helper
    def user_id
      user_id = @current_user ? @current_user.id : nil rescue nil
      user_id = current_user ? current_user.id : nil rescue nil if user_id.blank?
      user_id
    end
  end
end