extract Cacher class from Sparkline logic. It's now easy to replace t…

…he Filesystem cacher with something more interesting

lib/rack-sparklines.rb

@@ -1,5 +1,4 @@
 require 'spark_pr'
-require 'time'
 
 module Rack
   # Render sparkline graphs dynamically from datapoints in a matching CSV file 
@@ -8,11 +7,11 @@ class Sparklines
     DEFAULT_SPARK_OPTIONS = {:has_min => true, :has_max => true, 'has_last' => 'true', 'height' => '40', :step => 10, :normalize => 'logarithmic'}
 
     # Options:
-    #   :spark     - Hash of sparkline options.  See spark_pr.rb
-    #   :prefix    - URL prefix for handled requests.  Setting it to "/sparks"
+    #   :spark   - Hash of sparkline options.  See spark_pr.rb
+    #   :prefix  - URL prefix for handled requests.  Setting it to "/sparks"
     #     treats requests like "/sparks/stats.csv" as dynamic sparklines.
-    #   :directory - local directory that cached PNG files are stored.
-    #   :handler   - Handler instances know how to fetch data and pass them 
+    #   :cacher  - Cachers know how to store and stream sparkline PNG data.
+    #   :handler - Handler instances know how to fetch data and pass them 
     #     to the Sparklines library.
     def initialize(app, options = {})
       @app, @options   = app, options
@@ -27,35 +26,29 @@ def _call(env)
       if env['PATH_INFO'][@options[:prefix]] == @options[:prefix]
         @data_path = env['PATH_INFO'][@options[:prefix].size+1..-1]
         @data_path.sub! /\.png$/, ''
-        @png_path   = @data_path + ".png"
-        @cache_file = ::File.join(@options[:directory], @png_path)
-        @handler    = @options[:handler].set(@data_path)
+        @png_path = @data_path + ".png"
+        @cacher   = @options[:cacher].set(@png_path)
+        @handler  = @options[:handler].set(@data_path)
         if !@handler.exists?
           return @app.call(env)
         end
-        if !@handler.already_cached?(@cache_file)
+        if !@handler.already_cached?(@cacher)
           @handler.fetch do |data|
-            ::File.open(@cache_file, 'wb') do |png|
-              png << Spark.plot(data, @options[:spark])
-            end
+            @cacher.save(data, @options[:spark])
           end
         end
        [200, {
-          "Last-Modified"  => ::File.mtime(@cache_file).rfc822,
+          "Last-Modified"  => @cacher.updated_at.rfc822,
           "Content-Type"   => "image/png",
-          "Content-Length" => ::File.size(@cache_file).to_s
+          "Content-Length" => @cacher.size.to_s
         }, self]
       else
         @app.call(env)
       end
     end
 
     def each
-      ::File.open(@cache_file, "rb") do |file|
-        while part = file.read(8192)
-          yield part
-        end
-      end
+      @cacher.stream { |part| yield part }
     end
   end
 end

lib/rack-sparklines/cachers/filesystem.rb

@@ -0,0 +1,57 @@
+require 'rack-sparklines'
+require 'time'
+
+class Rack::Sparklines
+  module Cachers
+    # Reads sparkline data from CSV files.  Only the first line of numbers are 
+    # read.  Requests for "/sparks/stats.csv" will pass a data_path of "stats.csv"
+    class Filesystem
+      attr_accessor :png_path
+      attr_accessor :directory
+
+      def initialize(directory)
+        @directory = directory
+        @size, @updated_at = nil
+      end
+
+      # Setting the png_path returns a duplicate of this object that has any
+      # custom instance variables (configuration settings, for example).
+      def set(png_path)
+        cacher = dup
+        cacher.png_path = png_path
+        cacher
+      end
+
+      def png_path=(s)
+        @cache_file = File.join(@directory, s)
+        @png_path   = s
+      end
+
+      def size
+        @size ||= File.size(@cache_file)
+      end
+
+      def exists?
+        File.file?(@cache_file)
+      end
+
+      def updated_at
+        @updated_at ||= File.mtime(@cache_file)
+      end
+
+      def save(data, options)
+        File.open(@cache_file, 'wb') do |png|
+          png << Spark.plot(data, options)
+        end
+      end
+
+      def stream
+        ::File.open(@cache_file, "rb") do |file|
+          while part = file.read(8192)
+            yield part
+          end
+        end
+      end
+    end
+  end
+end

lib/rack-sparklines/handlers/abstract_data.rb

@@ -15,8 +15,8 @@ def set(data_path)
         data
       end
 
-      def already_cached?(cache_file)
-        if cache_time = File.file?(cache_file) && File.mtime(cache_file)
+      def already_cached?(cacher)
+        if cache_time = cacher.exists? && cacher.updated_at
           cache_time > updated_at
         end
       end

test/rack-sparklines_test.rb

@@ -8,25 +8,27 @@
 require 'rack-sparklines'
 require 'rack-sparklines/handlers/stubbed_data'
 require 'rack-sparklines/handlers/csv_data'
+require 'rack-sparklines/cachers/filesystem'
 
 class SparklinesTest < Test::Unit::TestCase
   include Rack::Test::Methods
 
-  $data_dir = File.join(File.dirname(__FILE__), 'data')
+  $data_dir     = File.join(File.dirname(__FILE__), 'data')
+  $stubbed_data = {:updated => Time.utc(2009, 1, 1), :contents => [47, 43, 24, 47, 16, 28, 38, 57, 50, 76, 42, 20, 98, 34, 53, 1, 55, 74, 63, 38, 31, 98, 89]}
   FileUtils.rm_rf   $data_dir
   FileUtils.mkdir_p $data_dir
   File.open File.join($data_dir, 'stats.csv'), 'wb' do |csv|
-    csv << "47,43,24,47,16,28,38,57,50,76,42,20,98,34,53,1,55,74,63,38,31,98,89"
+    csv << $stubbed_data[:contents].join(",")
   end
   sleep 1
 
   def app
-    stubbed_data = {:updated => Time.utc(2009, 1, 1), :contents => [47, 43, 24, 47, 16, 28, 38, 57, 50, 76, 42, 20, 98, 34, 53, 1, 55, 74, 63, 38, 31, 98, 89]}
+
     Rack::Sparklines.new \
       Proc.new {|env| [200, {"Content-Type" => "text/html"}, "booya"] },
-      :handler   => Rack::Sparklines::Handlers::StubbedData.new('stats.csv' => stubbed_data),
-      :prefix    => '/sparks',
-      :directory => $data_dir
+      :handler => Rack::Sparklines::Handlers::StubbedData.new('stats.csv' => $stubbed_data),
+      :cacher  => Rack::Sparklines::Cachers::Filesystem.new($data_dir),
+      :prefix  => '/sparks'
   end
 
   def setup
@@ -66,8 +68,8 @@ class SparklinesCSVTest < SparklinesTest
   def app
     Rack::Sparklines.new \
       Proc.new {|env| [200, {"Content-Type" => "text/html"}, "booya"] },
-      :handler   => Rack::Sparklines::Handlers::CsvData.new($data_dir),
-      :prefix    => '/sparks',
-      :directory => $data_dir
+      :handler => Rack::Sparklines::Handlers::CsvData.new($data_dir),
+      :cacher  => Rack::Sparklines::Cachers::Filesystem.new($data_dir),
+      :prefix  => '/sparks'
   end
 end