-- WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF         --
-- MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR  --
-- ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES   --
-- WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN    --
-- ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF  --
-- OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.           --
------------------------------------------------------------------------------

with Ada.Unchecked_Deallocation;

package body Natools.Smaz_Tools is

   package Sx renames Natools.S_Expressions;

   function Build_Node
     (Map : Dictionary_Maps.Map;
      Empty_Value : Natural)
     return Trie_Node;

   procedure Set_Map
     (Map : in out Dictionary_Maps.Map;
      List : in String_Lists.List);
      --  Set Map contents to match List by index number

   procedure Free is new Ada.Unchecked_Deallocation
     (Trie_Node, Trie_Node_Access);


   ------------------------------
   -- Local Helper Subprograms --
   ------------------------------

   function Build_Node
     (Map : Dictionary_Maps.Map;
      Empty_Value : Natural)
     return Trie_Node
   is
      function First_Character (S : String) return Character
        is (S (S'First));
      function Is_Current (Cursor : Dictionary_Maps.Cursor; C : Character)
        return Boolean
        is (Dictionary_Maps.Has_Element (Cursor)
            and then First_Character (Dictionary_Maps.Key (Cursor)) = C);

      function Suffix (S : String) return String;

      function Suffix (S : String) return String is
      begin
         return S (S'First + 1 .. S'Last);
      end Suffix;

      use type Ada.Containers.Count_Type;
      Cursor : Dictionary_Maps.Cursor;
      Result : Trie_Node
        := (Ada.Finalization.Controlled with
            Is_Leaf => False,
            Index => Empty_Value,
            Children => (others => null));
   begin
      pragma Assert (Dictionary_Maps.Length (Map) >= 1);

      Cursor := Dictionary_Maps.Find (Map, "");

      if Dictionary_Maps.Has_Element (Cursor) then
         Result.Index := Dictionary_Maps.Element (Cursor);
      end if;

      for C in Character'Range loop
         Cursor := Dictionary_Maps.Ceiling (Map, (1 => C));

         if Is_Current (Cursor, C) then
            if not Is_Current (Dictionary_Maps.Next (Cursor), C)
              and then Dictionary_Maps.Key (Cursor) = (1 => C)
            then
               Result.Children (C)
                 := new Trie_Node'(Ada.Finalization.Controlled with
                     Is_Leaf => True,
                     Index => Dictionary_Maps.Element (Cursor));
            else
               declare
                  New_Map : Dictionary_Maps.Map;
               begin
                  loop
                     Dictionary_Maps.Insert
                       (New_Map,
                        Suffix (Dictionary_Maps.Key (Cursor)),
                        Dictionary_Maps.Element (Cursor));
                     Dictionary_Maps.Next (Cursor);
                     exit when not Is_Current (Cursor, C);
                  end loop;

                  Result.Children (C)
                    := new Trie_Node'(Build_Node (New_Map, Empty_Value));
               end;
            end if;
         end if;
      end loop;

      return Result;
   end Build_Node;


   procedure Set_Map
     (Map : in out Dictionary_Maps.Map;
      List : in String_Lists.List)
   is
      I : Natural := 0;
   begin
      Dictionary_Maps.Clear (Map);

      for S of List loop
         Dictionary_Maps.Insert (Map, S, I);
         I := I + 1;
      end loop;
   end Set_Map;



   ----------------------
   -- Public Interface --
   ----------------------

   procedure Read_List

               exit Read_Loop;
         end case;

         Descriptor.Next (Event);
      end loop Read_Loop;
   end Read_List;



   ---------------------------------
   -- Dynamic Dictionary Searches --
   ---------------------------------

   overriding procedure Adjust (Node : in out Trie_Node) is
   begin
      if not Node.Is_Leaf then
         for C in Node.Children'Range loop
            if Node.Children (C) /= null then
               Node.Children (C) := new Trie_Node'(Node.Children (C).all);
            end if;
         end loop;
      end if;
   end Adjust;


   overriding procedure Finalize (Node : in out Trie_Node) is
   begin
      if not Node.Is_Leaf then
         for C in Node.Children'Range loop
            Free (Node.Children (C));
         end loop;
      end if;
   end Finalize;


   procedure Initialize
     (Trie : out Search_Trie;
      List : in String_Lists.List)
   is
      Map : Dictionary_Maps.Map;
      Not_Found : constant Natural := Natural (String_Lists.Length (List));
   begin
      Set_Map (Map, List);

      Trie := (Not_Found => Not_Found,
               Root => Build_Node (Map, Not_Found));
   end Initialize;


   function Linear_Search (Value : String) return Natural is
      Result : Natural := 0;
   begin
      for S of List_For_Linear_Search loop
         exit when S = Value;
         Result := Result + 1;
      end loop;

      return Result;
   end Linear_Search;


   function Map_Search (Value : String) return Natural is
      Cursor : constant Dictionary_Maps.Cursor
        := Dictionary_Maps.Find (Search_Map, Value);
   begin
      if Dictionary_Maps.Has_Element (Cursor) then
         return Natural (Dictionary_Maps.Element (Cursor));
      else
         return Natural (Dictionary_Maps.Length (Search_Map));
      end if;
   end Map_Search;


   function Search (Trie : in Search_Trie; Value : in String) return Natural is
      Index : Positive := Value'First;
      Position : Trie_Node_Access;
   begin
      if Value'Length = 0 then
         return Trie.Not_Found;
      end if;

      Position := Trie.Root.Children (Value (Index));

      loop
         if Position = null then
            return Trie.Not_Found;
         end if;

         Index := Index + 1;

         if Index not in Value'Range then
            return Position.Index;
         elsif Position.Is_Leaf then
            return Trie.Not_Found;
         end if;

         Position := Position.Children (Value (Index));
      end loop;
   end Search;


   procedure Set_Dictionary_For_Map_Search (List : in String_Lists.List) is
   begin
      Set_Map (Search_Map, List);
   end Set_Dictionary_For_Map_Search;


   procedure Set_Dictionary_For_Trie_Search (List : in String_Lists.List) is
   begin
      Initialize (Trie_For_Search, List);
   end Set_Dictionary_For_Trie_Search;


   function Trie_Search (Value : String) return Natural is
   begin
      return Search (Trie_For_Search, Value);
   end Trie_Search;



   -------------------
   -- Word Counting --
   -------------------

   procedure Add_Substrings

------------------------------------------------------------------------------

with Ada.Containers.Indefinite_Doubly_Linked_Lists;
with Natools.S_Expressions;

private with Ada.Containers.Indefinite_Ordered_Maps;
private with Ada.Containers.Indefinite_Ordered_Sets;
private with Ada.Finalization;

package Natools.Smaz_Tools is
   pragma Preelaborate;

   package String_Lists is new Ada.Containers.Indefinite_Doubly_Linked_Lists
     (String);

   procedure Read_List
     (List : out String_Lists.List;
      Descriptor : in out S_Expressions.Descriptor'Class);
      --  Read atoms from Descriptor to fill List


   List_For_Linear_Search : String_Lists.List;
   function Linear_Search (Value : String) return Natural;
      --  Function and data source for inefficient but dynamic function
      --  that can be used with Dictionary.Hash.

   procedure Set_Dictionary_For_Map_Search (List : in String_Lists.List);
   function Map_Search (Value : String) return Natural;
      --  Function and data source for logarithmic search using standard
      --  ordered map, that can be used with Dictionary.Hash.

   type Search_Trie is private;
   procedure Initialize (Trie : out Search_Trie; List : in String_Lists.List);
   function Search (Trie : in Search_Trie; Value : in String) return Natural;
      --  Trie-based search in a dynamic dictionary, for lookup whose
      --  speed-vs-memory is even more skewed towards speed.

   procedure Set_Dictionary_For_Trie_Search (List : in String_Lists.List);
   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;

   function To_Scored_Word
     (Cursor : in Word_Maps.Cursor;
      Method : in Methods.Enum)
     return Scored_Word;

   package Scored_Word_Sets is new Ada.Containers.Indefinite_Ordered_Sets
     (Scored_Word);

   package Dictionary_Maps is new Ada.Containers.Indefinite_Ordered_Maps
     (String, Natural);

   Search_Map : Dictionary_Maps.Map;

   type Trie_Node;
   type Trie_Node_Access is access Trie_Node;
   type Trie_Node_Array is array (Character) of Trie_Node_Access;

   type Trie_Node (Is_Leaf : Boolean) is new Ada.Finalization.Controlled
     with record
      Index : Natural;

      case Is_Leaf is
         when True  => null;
         when False => Children : Trie_Node_Array;
      end case;
   end record;

   overriding procedure Adjust (Node : in out Trie_Node);
   overriding procedure Finalize (Node : in out Trie_Node);

   type Search_Trie is record
      Not_Found : Natural;
      Root : Trie_Node (False);
   end record;

   Trie_For_Search : Search_Trie;

end Natools.Smaz_Tools;