--  Programmed by Jedidiah Barber
--  Licensed under the Sunset License v1.0

--  See license.txt for further details


private with

    Ada.Containers.Vectors,
    Ada.Finalization;


generic
    Relation : in Goal;
    Within   : in State;
package Kompsos.Collector is


    State_Not_Found_Error : exception;


    function Has_Next
        return Boolean;

    function Next
        return State;

    function Next
           (Default : in State)
        return State;

    procedure Reset;


private


    type Goal_Access is access all Goal;
    type Constant_Goal_Access is access constant Goal;

    type Graph_Access is access all Goal_Graph;
    type Constant_Graph_Access is access constant Goal_Graph;



    type Eval_Data (Kind : Node_Kind := Unify_Node) is record
        case Kind is
        when Unify_Node =>
            Uni_Offset : Long_Natural  := 0;
        when Disjunct_Node =>
            Dis_Flag   : Boolean       := True;
            Dis_Next1  : Long_Positive := 1;
            Dis_Next2  : Long_Positive := 1;
            Dis_Gone1  : Boolean       := False;
            Dis_Gone2  : Boolean       := False;
        when Conjunct_Node =>
            Con_From   : Long_Positive := 1;
            Con_Base   : State_Access  := null;
            Con_Part   : Goal_Access   := null;
            Con_Next   : Long_Positive := 1;
            Con_Gone   : Boolean       := False;
        when Recurse_Node =>
            Rec_Next   : Long_Positive := 1;
            Rec_Gone   : Boolean       := False;
            Rec_Cache  : Boolean       := True;
        end case;
    end record;



    type Cached_State is record
        Used : Positive     := 1;
        Data : State_Access := null;
    end record;

    package State_Vectors is new Ada.Containers.Vectors
       (Index_Type   => Long_Positive,
        Element_Type => Cached_State);

    type Cache_Entry is record
        Keep : Boolean              := False;
        Data : State_Vectors.Vector := State_Vectors.Empty_Vector;
    end record;

    type Cache_Entry_Access is access Cache_Entry;



    type Book_Node;

    type Book_Node_Access is access Book_Node;

    type Book_Node is record
        Data  : Eval_Data;
        Cache : Cache_Entry_Access := null;
        Next1 : Book_Node_Access   := null;
        Next2 : Book_Node_Access   := null;
    end record;



    type Loose_Book is record
        Used : Positive               := 1;
        Ptr  : Graph_Component_Access := null;
        Book : Book_Node_Access       := null;
    end record;

    package Loose_Book_Vectors is new Ada.Containers.Vectors
       (Index_Type   => Long_Positive,
        Element_Type => Loose_Book);

    package Book_Node_Vectors is new Ada.Containers.Vectors
       (Index_Type   => Long_Positive,
        Element_Type => Book_Node_Access);



    procedure Reset
           (Ptr  : in     Graph_Component_Access;
            Book : in out Book_Node_Access);

    function Get_Next
           (Ptr    : in     Constant_Graph_Access;
            Book   : in out Book_Node_Access;
            Base   : in     State;
            Index  : in     Long_Positive;
            Result :    out State)
        return Boolean;



    type Collector_Final_Controller is new Ada.Finalization.Limited_Controlled with null record;

    overriding procedure Finalize
           (This : in out Collector_Final_Controller);

    Cleanup : Collector_Final_Controller;


end Kompsos.Collector;