module RequestLogAnalyzer::Tracker
  
  class NumericValue < Base

    attr_reader :categories

    # Sets up the numeric value tracker. It will check whether the value and category
    # options are set that are used to extract and categorize the values during
    # parsing. Two lambda procedures are created for these tasks
    def prepare
      
      raise "No value field set up for numeric tracker #{self.inspect}" unless options[:value]
      raise "No categorizer set up for numeric tracker #{self.inspect}" unless options[:category]

      unless options[:multiple]
        @categorizer = create_lambda(options[:category])
        @valueizer   = create_lambda(options[:value])
      end

      @categories = {}
    end

    # Get the value information from the request and store it in the respective categories.
    #
    # If a request can contain multiple usable values for this tracker, the :multiple option 
    # should be set to true. In this case, all the values and respective categories will be
    # read from the request using the #every method from the fields given in the :value and 
    # :category option.
    #
    # If the request contains only one suitable value and the :multiple is not set, it will
    # read the single value and category from the fields provided in the :value and :category
    # option, or calculate it with any lambda procedure that is assigned to these options. The
    # request will be passed to procedure as input for the calculation.
    #
    # @param [RequestLogAnalyzer::Request] request The request to get the information from.
    def update(request)
      if options[:multiple]
        found_categories = request.every(options[:category])
        found_values     = request.every(options[:value])
        raise "Capture mismatch for multiple values in a request" unless found_categories.length == found_values.length
        
        found_categories.each_with_index do |cat, index| 
          update_statistics(cat, found_values[index]) if cat && found_values[index].kind_of?(Numeric)
        end
        
      else
        category = @categorizer.call(request)
        value    = @valueizer.call(request)
        update_statistics(category, value) if value.kind_of?(Numeric) && category
      end
    end

    # Block function to build a result table using a provided sorting function.
    # <tt>output</tt> The output object.
    # <tt>amount</tt> The number of rows in the report table (default 10).
    # === Options
    #  * </tt>:title</tt> The title of the table
    #  * </tt>:sort</tt> The key to sort on (:hits, :cumulative, :average, :min or :max)
    def report_table(output, sort, options = {}, &block)
      output.puts
      top_categories = output.slice_results(sorted_by(sort))
      output.with_style(:top_line => true) do
        output.table(*statistics_header(:title => options[:title], :highlight => sort)) do |rows|
          top_categories.each { |(cat, info)| rows << statistics_row(cat) }
        end
      end
    end

    # Display a value
    def display_value(value)
      return "- " if value.nil?
      return "0 " if value.zero?

      case [Math.log10(value.abs).floor, 0].max
        when  0...4  then '%d ' % value
        when  4...7  then '%dk' % (value / 1000)
        when  7...10 then '%dM' % (value / 1000_000)
        when 10...13 then '%dG' % (value / 1000_000_000)
        when 13...16 then '%dT' % (value / 1000_000_000_000)
        else              '%dP' % (value / 1000_000_000_000_000)
      end
    end

    # Generate a request report to the given output object
    # By default colulative and average duration are generated.
    # Any options for the report should have been set during initialize.
    # <tt>output</tt> The output object
    def report(output)
      sortings = output.options[:sort] || [:sum, :mean]
      sortings.each do |sorting|
        report_table(output, sorting, :title => "#{title} - by #{sorting}")
      end
      
      if options[:total]
        output.puts
        output.puts "#{output.colorize(title, :white, :bold)} - total: " + output.colorize(display_value(sum_overall), :brown, :bold)
      end
    end

    # Returns the title of this tracker for reports
    def title
      @title ||= begin
        if options[:title]
          options[:title]
        else
          title_builder = ""
          title_builder << "#{options[:value]} " if options[:value].kind_of?(Symbol)
          title_builder << (options[:category].kind_of?(Symbol) ? "per #{options[:category]}" : "per request")
          title_builder
        end
      end
    end

    # Returns all the categories and the tracked duration as a hash than can be exported to YAML
    def to_yaml_object
      return nil if @categories.empty?
      @categories
    end
    

    # Update sthe running calculation of statistics with the newly found numeric value.
    # <tt>category</tt>:: The category for which to update the running statistics calculations
    # <tt>number</tt>:: The numeric value to update the calculations with.
    def update_statistics(category, number)
      @categories[category] ||= {:hits => 0, :sum => 0, :mean => 0.0, :sum_of_squares => 0.0, :min => number, :max => number }
      delta = number - @categories[category][:mean]

      @categories[category][:hits]           += 1
      @categories[category][:mean]           += (delta / @categories[category][:hits])
      @categories[category][:sum_of_squares] += delta * (number - @categories[category][:mean])
      @categories[category][:sum]            += number
      @categories[category][:min]             = number if number < @categories[category][:min]
      @categories[category][:max]             = number if number > @categories[category][:max]
    end

    # Get the number of hits of a specific category.
    # <tt>cat</tt> The category
    def hits(cat)
      @categories[cat][:hits]
    end

    # Get the total duration of a specific category.
    # <tt>cat</tt> The category
    def sum(cat)
      @categories[cat][:sum]
    end

    # Get the minimal duration of a specific category.
    # <tt>cat</tt> The category
    def min(cat)
      @categories[cat][:min]
    end

    # Get the maximum duration of a specific category.
    # <tt>cat</tt> The category
    def max(cat)
      @categories[cat][:max]
    end

    # Get the average duration of a specific category.
    # <tt>cat</tt> The category
    def mean(cat)
      @categories[cat][:mean]
    end

    # Get the standard deviation of the duration of a specific category.
    # <tt>cat</tt> The category
    def stddev(cat)
      Math.sqrt(variance(cat))
    end

    # Get the variance of the duration of a specific category.
    # <tt>cat</tt> The category
    def variance(cat)
      return 0.0 if @categories[cat][:hits] <= 1
      (@categories[cat][:sum_of_squares] / (@categories[cat][:hits] - 1))
    end

    # Get the average duration of a all categories.
    def mean_overall
      sum_overall / hits_overall
    end

    # Get the cumlative duration of a all categories.
    def sum_overall
      @categories.inject(0.0) { |sum, (name, cat)| sum + cat[:sum] }
    end

    # Get the total hits of a all categories.
    def hits_overall
      @categories.inject(0) { |sum, (name, cat)| sum + cat[:hits] }
    end

    # Return categories sorted by a given key.
    # <tt>by</tt> The key to sort on. This parameter can be omitted if a sorting block is provided instead
    def sorted_by(by = nil)
      if block_given?
        categories.sort { |a, b| yield(b[1]) <=> yield(a[1]) }
      else
        categories.sort { |a, b| send(by, b[0]) <=> send(by, a[0]) }
      end
    end

    # Returns the column header for a statistics table to report on the statistics result
    def statistics_header(options)
      [
        {:title => options[:title], :width => :rest},
        {:title => 'Hits',   :align => :right, :highlight => (options[:highlight] == :hits),   :min_width => 4},
        {:title => 'Sum',    :align => :right, :highlight => (options[:highlight] == :sum),    :min_width => 6},
        {:title => 'Mean',   :align => :right, :highlight => (options[:highlight] == :mean),   :min_width => 6},
        {:title => 'StdDev', :align => :right, :highlight => (options[:highlight] == :stddev), :min_width => 6},
        {:title => 'Min',    :align => :right, :highlight => (options[:highlight] == :min),    :min_width => 6},
        {:title => 'Max',    :align => :right, :highlight => (options[:highlight] == :max),    :min_width => 6}
      ]
    end

    # Returns a row of statistics information for a report table, given a category
    def statistics_row(cat)
      [cat, hits(cat), display_value(sum(cat)), display_value(mean(cat)), display_value(stddev(cat)),
                display_value(min(cat)), display_value(max(cat))]
    end
  end
end