Implement sorted entries cache

sorted_entries cached

src/library/cache.cr

@@ -157,3 +157,90 @@ class InfoCache
     @@cached_sort_opt_previous = {} of String => Hash(String, SortOptions)
   end
 end
+
+private class SortedEntriesCacheEntry
+  getter key : String, atime : Time
+
+  def initialize(@ctime : Time, @key : String, @value : Array(String))
+    @atime = @ctime
+  end
+
+  def value
+    @atime = Time.utc
+    @value
+  end
+
+  def instance_size
+    @value.size * (instance_sizeof(String) + sizeof(String)) +
+      @value.sum(&.size) + instance_sizeof(SortedEntriesCacheEntry)
+  end
+end
+
+# LRU Cache
+class SortedEntriesCache
+  @@limit : Int128 = Int128.new 1024 * 1024 * 50 # 50MB
+  # key => entry
+  @@cache = {} of String => SortedEntriesCacheEntry
+
+  def self.gen_key(book_id : String, username : String,
+                   entries : Array(Entry), opt : SortOptions?)
+    sig = Digest::SHA1.hexdigest (entries.map &.id).to_s
+    user_context = opt && opt.method == SortMethod::Progress ? username : ""
+    Digest::SHA1.hexdigest (book_id + sig + user_context +
+                            (opt ? opt.to_tuple.to_s : "nil"))
+  end
+
+  def self.get(key : String)
+    entry = @@cache[key]?
+    Logger.debug "SortedEntries Cache Hit! #{key}" unless entry.nil?
+    Logger.debug "SortedEntries Cache Miss #{key}" if entry.nil?
+    return ids2entries entry.value unless entry.nil?
+  end
+
+  def self.set(key : String, value : Array(Entry))
+    @@cache[key] = SortedEntriesCacheEntry.new Time.utc, key, value.map &.id
+    Logger.debug "SortedEntries Cached #{key}"
+    remove_victim_cache
+  end
+
+  def self.invalidate(key : String)
+    @@cache.delete key
+  end
+
+  def self.print
+    sum = @@cache.sum { |_, entry| entry.instance_size }
+    Logger.debug "---- Sorted Entries Cache ----"
+    Logger.debug "Size: #{sum} Bytes"
+    Logger.debug "List:"
+    @@cache.each { |k, v| Logger.debug "#{k} | #{v.atime}" }
+    Logger.debug "------------------------------"
+  end
+
+  private def self.ids2entries(ids : Array(String))
+    e_map = Library.default.deep_entries.to_h { |entry| {entry.id, entry} }
+    entries = [] of Entry
+    begin
+      ids.each do |id|
+        entries << e_map[id]
+      end
+      return entries if ids.size == entries.size
+    rescue
+    end
+  end
+
+  private def self.is_cache_full
+    sum = @@cache.sum { |_, entry| entry.instance_size }
+    sum > @@limit
+  end
+
+  private def self.remove_victim_cache
+    while is_cache_full && @@cache.size > 0
+      Logger.debug "SortedEntries Cache Full! Remove LRU"
+      min = @@cache.min_by? { |_, entry| entry.atime }
+      Logger.debug "Target: #{min[0]}, Last Access Time: #{min[1].atime}" if min
+      invalidate min[0] if min
+
+      print if Logger.get_severity == Log::Severity::Debug
+    end
+  end
+end

src/library/entry.cr

@@ -187,6 +187,11 @@ class Entry
     @book.parents.each do |parent|
       InfoCache.invalidate_progress_cache parent.id, username
     end
+    [false, true].each do |ascend|
+      sorted_entries_cache_key = SortedEntriesCache.gen_key @book.id, username,
+        @book.entries, SortOptions.new(SortMethod::Progress, ascend)
+      SortedEntriesCache.invalidate sorted_entries_cache_key
+    end
 
     TitleInfo.new @book.dir do |info|
       if info.progress[username]?.nil?

src/library/library.cr

@@ -61,6 +61,10 @@ class Library
     titles + titles.flat_map &.deep_titles
   end
 
+  def deep_entries
+    titles.flat_map &.deep_entries
+  end
+
   def to_slim_json : String
     JSON.build do |json|
       json.object do

src/library/title.cr

@@ -344,6 +344,10 @@ class Title
   #   use the default (auto, ascending)
   # When `opt` is not nil, it saves the options to info.json
   def sorted_entries(username, opt : SortOptions? = nil)
+    cache_key = SortedEntriesCache.gen_key @id, username, @entries, opt
+    cached_entries = SortedEntriesCache.get cache_key
+    return cached_entries if cached_entries
+
     if opt.nil?
       opt = SortOptions.from_info_json @dir, username
     end
@@ -377,6 +381,7 @@ class Title
 
     ary.reverse! unless opt.not_nil!.ascend
 
+    SortedEntriesCache.set cache_key, ary
     ary
   end
 
@@ -442,6 +447,12 @@ class Title
     parents.each do |parent|
       InfoCache.invalidate_progress_cache parent.id, username
     end
+    [false, true].each do |ascend|
+      sorted_entries_cache_key =
+        SortedEntriesCache.gen_key @id, username, @entries,
+          SortOptions.new(SortMethod::Progress, ascend)
+      SortedEntriesCache.invalidate sorted_entries_cache_key
+    end
 
     selected_entries = ids
       .map { |id|