Natools

   function Trie_Search (Value : String) return Natural;
      --  Function and data source for trie-based search that can be
      --  used with Dictionary.Hash.

   type String_Count is range 0 .. 2 ** 31 - 1;
      --  Type for a number of substring occurrences

   package Methods is
      type Enum is (Encoded, Frequency, Gain);
   end Methods;
      --  Evaluation methods to select words to remove or include

   type Word_Counter is private;
      --  Accumulate frequency/occurrence counts for a set of strings

   procedure Add_Word
     (Counter : in out Word_Counter;
      Word : in String;
      Count : in String_Count := 1);

      Corpus_Entry : in String;
      Compressed_Size : in out Ada.Streams.Stream_Element_Count;
      Counts : in out Dictionary_Counts);
      --  Compress all strings of Corpus, returning the total number of
      --  compressed bytes and the number of uses for each dictionary
      --  element.

   function Worst_Index
     (Dict : in Dictionary;
      Counts : in Dictionary_Counts;
      Method : in Methods.Enum)
     return Ada.Streams.Stream_Element;
      --  Return the element with worst score


   type Score_Value is range 0 .. 2 ** 31 - 1;

   function Length
     (Dict : in Dictionary;
      E : in Ada.Streams.Stream_Element)
     return Score_Value
     is (Natools.Smaz.Dict_Entry (Dict, E)'Length);
      --  Length of a dictionary entry

   function Score_Encoded
     (Dict : in Dictionary;
      Counts : in Natools.Smaz.Tools.Dictionary_Counts;
      E : Ada.Streams.Stream_Element)
     return Score_Value
     is (Score_Value (Counts (E)) * Length (Dict, E));
      --  Score value using the amount of encoded data using E

   function Score_Frequency
     (Dict : in Dictionary;
      Counts : in Natools.Smaz.Tools.Dictionary_Counts;
      E : Ada.Streams.Stream_Element)
     return Score_Value
     is (Score_Value (Counts (E)));
      --  Score value using the number of times E was used

   function Score_Gain
     (Dict : in Dictionary;
      Counts : in Natools.Smaz.Tools.Dictionary_Counts;
      E : Ada.Streams.Stream_Element)
     return Score_Value
     is (Score_Value (Counts (E)) * (Length (Dict, E) - 1));
      --  Score value using the number of bytes saved using E

   function Score
     (Dict : in Dictionary;
      Counts : in Natools.Smaz.Tools.Dictionary_Counts;
      E : in Ada.Streams.Stream_Element;
      Method : in Methods.Enum)
     return Score_Value
     is (case Method is
         when Methods.Encoded => Score_Encoded (Dict, Counts, E),
         when Methods.Frequency => Score_Frequency (Dict, Counts, E),
         when Methods.Gain => Score_Gain (Dict, Counts, E));
      --  Scare value with dynamically chosen method

private

   package Word_Maps is new Ada.Containers.Indefinite_Ordered_Maps
     (String, String_Count);

   type Word_Counter is record
      Map : Word_Maps.Map;
   end record;


   type Score_Value is range 0 .. 2 ** 31 - 1;

   type Scored_Word (Size : Natural) is record
      Word : String (1 .. Size);
      Score : Score_Value;
   end record;

   function "<" (Left, Right : Scored_Word) return Boolean
     is (Left.Score > Right.Score