Add config for sorted entries cache

optional

src/config.cr

@@ -20,6 +20,8 @@ class Config
   property plugin_path : String = File.expand_path "~/mango/plugins",
     home: true
   property download_timeout_seconds : Int32 = 30
+  property sorted_entries_cache_enable = false
+  property sorted_entries_cache_capacity_kbs = 51200
   property disable_login = false
   property default_username = ""
   property auth_proxy_header_name = ""

src/library/cache.cr

@@ -178,10 +178,16 @@ end
 
 # LRU Cache
 class SortedEntriesCache
-  @@limit : Int128 = Int128.new 1024 * 1024 * 50 # 50MB
+  @@limit : Int128 = Int128.new 0
   # key => entry
   @@cache = {} of String => SortedEntriesCacheEntry
 
+  def self.init
+    enabled = Config.current.sorted_entries_cache_enable
+    cache_size = Config.current.sorted_entries_cache_capacity_kbs
+    @@limit = Int128.new cache_size * 1024 if enabled
+  end
+
   def self.gen_key(book_id : String, username : String,
                    entries : Array(Entry), opt : SortOptions?)
     sig = Digest::SHA1.hexdigest (entries.map &.id).to_s

src/mango.cr

@@ -55,6 +55,7 @@ class CLI < Clim
       Config.load(opts.config).set_current
 
       # Initialize main components
+      SortedEntriesCache.init
       Storage.default
       Queue.default
       Library.default