From 8ee9728595a4ad8f77837033dd5de17fdedce00a Mon Sep 17 00:00:00 2001
From: Isaac Seymour <i.seymour@oxon.org>
Date: Tue, 8 Nov 2016 10:55:52 +0000
Subject: [PATCH] Limit the size of usage of the session store to ~1KB

Very approximate, but bounds the cookie usage to leave about 75% for
other things.
---
 lib/analytical/session_command_store.rb       | 15 +++++++++----
 spec/analytical/session_command_store_spec.rb | 22 +++++++++++++++----
 2 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/lib/analytical/session_command_store.rb b/lib/analytical/session_command_store.rb
index fa6d1f7..9a96d93 100644
--- a/lib/analytical/session_command_store.rb
+++ b/lib/analytical/session_command_store.rb
@@ -6,18 +6,21 @@ def initialize(session, module_key, initial_list=nil)
       @session = session
       @module_key = module_key
       @session_key = ('analytical_'+module_key.to_s).to_sym
-      ensure_session_setup!(initial_list)
+      assign(initial_list || [])
     end
 
     def assign(v)
       self.commands = v
+      trim_commands!
     end
 
     def commands
+      trim_commands!
       @session[@session_key]
     end
     def commands=(v)
       @session[@session_key] = v
+      trim_commands!
     end
 
     def flush
@@ -30,13 +33,17 @@ def remove(processed_commands)
 
     # Pass any array methods on to the internal array
     def method_missing(method, *args, &block)
-      commands.send(method, *args, &block)
+      commands.send(method, *args, &block).tap { trim_commands! }
     end
 
     private
 
-    def ensure_session_setup!(initial_list=nil)
-      self.commands ||= (initial_list || [])
+    # Make sure to not exceed ~1KB of session storage use (max cookie is 4KB)
+    def trim_commands!
+      serialized_length = @session[@session_key].inspect.length
+      return unless serialized_length > 1000
+      @session[@session_key] = @session[@session_key][0..-2]
+      trim_commands!
     end
 
   end
diff --git a/spec/analytical/session_command_store_spec.rb b/spec/analytical/session_command_store_spec.rb
index aa43bc2..bb5a837 100644
--- a/spec/analytical/session_command_store_spec.rb
+++ b/spec/analytical/session_command_store_spec.rb
@@ -1,12 +1,12 @@
 require 'spec_helper'
 
 describe Analytical::SessionCommandStore do
-  
+
   describe 'with a session hash' do
     before(:each) do
       @session = {}
     end
-    
+
     it 'should add elements' do
       @store = Analytical::SessionCommandStore.new @session, :some_module, ['a']
       @store << 'b'
@@ -30,7 +30,21 @@
 
     it 'should set up the :analytical session hash' do
       @store = Analytical::SessionCommandStore.new @session, :some_module, ['a', 'b']
-      @session[:analytical_some_module].should_not be_nil   
+      @session[:analytical_some_module].should_not be_nil
+    end
+
+    it 'should discard older items when the store is full' do
+      large_item = [
+        "set",
+        {
+          "I have some key" => "and a long param",
+          "and more key" => "and some more value",
+          "so much key" => "such such value",
+        },
+      ]
+      @store = Analytical::SessionCommandStore.new @session, :some_module, [large_item] * 100
+      @session[:analytical_some_module].should_not be_nil
+      @session[:analytical_some_module].inspect.length.should be < 1000
     end
 
     describe 'when flushing' do
@@ -55,5 +69,5 @@
       end
     end
   end
-  
+
 end