
// search_full.cpp

// includes

#include "attack.h"
#include "board.h"
#include "colour.h"
#include "eval.h"
#include "list.h"
#include "move.h"
#include "move_check.h"
#include "move_do.h"
#include "option.h"
#include "piece.h"
#include "pst.h"
#include "pv.h"
#include "search.h"
#include "search_full.h"
#include "see.h"
#include "sort.h"
#include "trans.h"
#include "util.h"
#include "value.h"

#define ABS(x) ((x)<0?-(x):(x))
#define MIN(X, Y)  ((X) < (Y) ? (X) : (Y))


// constants and variables
int ValueDraw;

// main search


// transposition table

static const int TransDepth = 1;


// null move

static /* const */ bool UseNull = true;
static /* const */ bool UseNullEval = true; // true
static const int NullDepth = 2;
static /* const */ int NullReduction = 3;

static /* const */ bool UseVer = true;
static /* const */ bool UseVerEndgame = true; // true
static /* const */ int VerReduction = 5; // was 3

// move ordering

static const int IIDDepth = 3;
static const int IIDReduction = 2;

// extensions

// rebel reduction
static bool use_rebel_reduction = false; // I hope I did this right...

// history pruning

static /* const */ bool UseHistory = true;
static const int HistoryDepth = 3; // was 3
static const int HistoryMoveNb = 3; // was 3
static /* const */ int HistoryValue = 9830; // 60%
static /* const */ int HistoryBound = 2458; // * 16384 + 50) / 100 10%=1638 15%=2458 20%=3277
static /* const */ bool UseExtendedHistory = true;
static bool research_on_beta = true;

// futility pruning

static /* const */ bool UseFutility = true; // false
//static const int FutilityMargin = 100;
static bool quick_futility = false;
static /* const */ int FutilityMargin1 = 100;
static /* const */ int FutilityMargin2 = 300;
static /* const */ int FutilityMargin3 = 950;

// quiescence search

static /* const */ bool UseDelta = true; // false
static /* const */ int DeltaMargin = 50;

static /* const */ int CheckNb = 1;
static /* const */ int CheckDepth = 0; // 1 - CheckNb

// misc

static const int NodeAll = -1;
static const int NodePV  =  0;
static const int NodeCut = +1;

// macros

#define NODE_OPP(type)     (-(type))
#define DEPTH_MATCH(d1,d2) ((d1)>=(d2))

// prototypes

static int  full_root            (list_t * list, board_t * board, int alpha, int beta, int depth, int height, int search_type);

static int  full_search          (board_t * board, int alpha, int beta, int depth, int height, mv_t pv[], int node_type);
static int  full_no_null         (board_t * board, int alpha, int beta, int depth, int height, mv_t pv[], int node_type, int trans_move, int * best_move);

static int  full_quiescence      (board_t * board, int alpha, int beta, int depth, int height, mv_t pv[]);

static int  full_new_depth       (int depth, int move, board_t * board, bool single_reply, bool in_pv, int height);

static bool do_null              (const board_t * board);
static bool do_ver               (const board_t * board);

static void pv_fill              (const mv_t pv[], board_t * board);

static bool move_is_dangerous    (int move, const board_t * board);
static bool capture_is_dangerous (int move, const board_t * board);

static bool simple_stalemate     (const board_t * board);

// functions

// search_full_init()

void search_full_init(list_t * list, board_t * board) {

   const char * string;
   int trans_move, trans_min_depth, trans_max_depth, trans_min_value, trans_max_value;

   ASSERT(list_is_ok(list));
   ASSERT(board_is_ok(board));

   // draw value
   ValueDraw = option_get_int("Contempt Factor");

   // null-move options

   string = option_get_string("NullMove Pruning");

   if (false) {
   } else if (my_string_equal(string,"Always")) {
      UseNull = true;
      UseNullEval = false;
   } else if (my_string_equal(string,"Fail High")) {
      UseNull = true;
      UseNullEval = true;
   } else if (my_string_equal(string,"Never")) {
      UseNull = false;
      UseNullEval = false;
   } else {
      ASSERT(false);
      UseNull = true;
      UseNullEval = true;
   }

   NullReduction = option_get_int("NullMove Reduction");

   string = option_get_string("Verification Search");

   if (false) {
   } else if (my_string_equal(string,"Always")) {
      UseVer = true;
      UseVerEndgame = false;
   } else if (my_string_equal(string,"Endgame")) {
      UseVer = true;
      UseVerEndgame = true;
   } else if (my_string_equal(string,"Never")) {
      UseVer = false;
      UseVerEndgame = false;
   } else {
      ASSERT(false);
      UseVer = true;
      UseVerEndgame = true;
   }

   VerReduction = option_get_int("Verification Reduction");

   // rebel reduction options
   use_rebel_reduction = option_get_bool("Rebel Reductions");

   // history-pruning options

   UseHistory = option_get_bool("History Pruning");
   HistoryValue = (option_get_int("History Threshold") * 16384 + 50) / 100;
   research_on_beta = option_get_bool("History Research on Beta");
 
   // futility-pruning options

   UseFutility = option_get_bool("Futility Pruning");
   quick_futility = option_get_bool("Quick Futility eval");
   FutilityMargin1 = option_get_int("Futility Margin");
   FutilityMargin2 = option_get_int("Extended Futility Margin");


   // delta-pruning options

   UseDelta = option_get_bool("Delta Pruning");
   DeltaMargin = option_get_int("Delta Margin");

   // quiescence-search options

   CheckNb = option_get_int("Quiescence Check Plies");
   CheckDepth = 1 - CheckNb;

   // standard sort

   list_note(list);
   list_sort(list);

   // basic sort

   trans_move = MoveNone;
   trans_retrieve(Trans,board->key,&trans_move,&trans_min_depth,&trans_max_depth,&trans_min_value,&trans_max_value);

   note_moves(list,board,0,trans_move);
   list_sort(list);
}

// search_full_root()

int search_full_root(list_t * list, board_t * board, int depth, int search_type) {

   int value, a, b;

   ASSERT(list_is_ok(list));
   ASSERT(board_is_ok(board));
   ASSERT(depth_is_ok(depth));
   ASSERT(search_type==SearchNormal||search_type==SearchShort);

   ASSERT(list==SearchRoot->list);
   ASSERT(!LIST_IS_EMPTY(list));
   ASSERT(board==SearchCurrent->board);
   ASSERT(board_is_legal(board));
   ASSERT(depth>=1);

   if (SearchBest[SearchCurrent->multipv].value == 0){
	   a = -ValueInf;
	   b = +ValueInf;
   }
   else{
	   a = SearchBest[SearchCurrent->multipv].value - 40;
	   b = SearchBest[SearchCurrent->multipv].value + 40;
   }

   if (SearchInput->multipv > 0){
	   a = -ValueInf;
       b = +ValueInf;
   }

   value = full_root(list,board,a,b,depth,0,search_type);

   ASSERT(value_is_ok(value));
   ASSERT(LIST_VALUE(list,0)==value);

   return value;
}

// full_root()

static int full_root(list_t * list, board_t * board, int alpha, int beta, int depth, int height, int search_type) {

   int old_alpha;
   int value, best_value[MultiPVMax];
   int i, move, j;
   int new_depth;
   undo_t undo[1];
   mv_t new_pv[HeightMax];
   bool found;

   ASSERT(list_is_ok(list));
   ASSERT(board_is_ok(board));
   ASSERT(range_is_ok(alpha,beta));
   ASSERT(depth_is_ok(depth));
   ASSERT(height_is_ok(height));
   ASSERT(search_type==SearchNormal||search_type==SearchShort);

   ASSERT(list==SearchRoot->list);
   ASSERT(!LIST_IS_EMPTY(list));
   ASSERT(board==SearchCurrent->board);
   ASSERT(board_is_legal(board));
   ASSERT(depth>=1);

   // init

   SearchStack[height].best_move = MoveNone;
   SearchStack[height].move = MoveNone;
   SearchStack[height].threat_move = MoveNone;
   SearchStack[height].reduced = false;

   SearchCurrent->node_nb++;
   SearchInfo->check_nb--;

   if (SearchCurrent->multipv == 0)
	  for (i = 0; i < LIST_SIZE(list); i++) list->value[i] = ValueNone;

   old_alpha = alpha;
   best_value[SearchCurrent->multipv] = ValueNone;

   // move loop

   for (i = 0; i < LIST_SIZE(list); i++) {

      move = LIST_MOVE(list,i);

	  if (SearchCurrent->multipv > 0){
		  found = false;
		  for (j = 0; j < SearchCurrent->multipv; j++){
			  if (SearchBest[j].pv[0] == move){
				  found = true;
				  break;
			  }
		  }
		  if (found == true)
				continue;
	  }
	  SearchStack[height].move = move;

      SearchRoot->depth = depth;
      SearchRoot->move = move;
      SearchRoot->move_pos = i;
      SearchRoot->move_nb = LIST_SIZE(list);

      search_update_root();

      new_depth = full_new_depth(depth,move,board,board_is_check(board)&&LIST_SIZE(list)==1,true, height);

      move_do(board,move,undo);

      if (search_type == SearchShort || best_value[SearchCurrent->multipv] == ValueNone) { // first move
         value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NodePV);
		 if (value <= alpha){ // research
			 old_alpha = -ValueInf;
			 value = -full_search(board,-beta,ValueInf,new_depth,height+1,new_pv,NodePV);
		 }
		 else if (value >= beta){ // research
			 value = -full_search(board,-ValueInf,-alpha,new_depth,height+1,new_pv,NodePV);
		 }
			  
      } else { // other moves
         value = -full_search(board,-alpha-1,-alpha,new_depth,height+1,new_pv,NodeCut);
         if (value > alpha) { // && value < beta
            SearchRoot->change = true;
            SearchRoot->easy = false;
            SearchRoot->flag = false;
            search_update_root();
            value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NodePV);
         }
      }

      move_undo(board,move,undo);

      if (value <= alpha) { // upper bound
         list->value[i] = old_alpha;
      } else if (value >= beta) { // lower bound
         list->value[i] = beta;
      } else { // alpha < value < beta => exact value
         list->value[i] = value;
      }

      if (value > best_value[SearchCurrent->multipv] && (best_value[SearchCurrent->multipv] == ValueNone || value > alpha)) {

         SearchBest[SearchCurrent->multipv].move = move;
		 SearchStack[height].best_move = move;
         SearchBest[SearchCurrent->multipv].value = value;
         if (value <= alpha) { // upper bound
            SearchBest[SearchCurrent->multipv].flags = SearchUpper;
         } else if (value >= beta) { // lower bound
            SearchBest[SearchCurrent->multipv].flags = SearchLower;
         } else { // alpha < value < beta => exact value
            SearchBest[SearchCurrent->multipv].flags = SearchExact;
         }
         SearchBest[SearchCurrent->multipv].depth = depth;
         pv_cat(SearchBest[SearchCurrent->multipv].pv,new_pv,move);

         search_update_best();
      }

      if (value > best_value[SearchCurrent->multipv]) {
         best_value[SearchCurrent->multipv] = value;
         if (value > alpha) {
            if (search_type == SearchNormal) alpha = value;
            if (value >= beta) break;
         }
      }
   }

   ASSERT(value_is_ok(best_value));

   list_sort(list);

   ASSERT(SearchBest->move==LIST_MOVE(list,0));
   ASSERT(SearchBest->value==best_value);

   if (best_value[SearchCurrent->multipv] > old_alpha && best_value[SearchCurrent->multipv] < beta) {
      pv_fill(SearchBest[SearchCurrent->multipv].pv,board);
   }

   return best_value[SearchCurrent->multipv];
}

// full_search()

static int full_search(board_t * board, int alpha, int beta, int depth, int height, mv_t pv[], int node_type) {

   bool in_check;
   bool single_reply;
   //bool mate_threat;
   int trans_move, trans_depth, trans_min_depth, trans_max_depth, trans_min_value, trans_max_value;
   int min_value, max_value;
   int old_alpha;
   int value, best_value;
   int move, best_move;
   int new_depth;
   int played_nb;
   int i;
   int opt_value;
   bool reduced;
   bool rebel_reduction;
   int mb;
   attack_t attack[1];
   sort_t sort[1];
   undo_t undo[1];
   mv_t new_pv[HeightMax];
   mv_t played[256];
   int FutilityMargin;
   int margin;

   ASSERT(board!=NULL);
   ASSERT(range_is_ok(alpha,beta));
   ASSERT(depth_is_ok(depth));
   ASSERT(height_is_ok(height));
   ASSERT(pv!=NULL);
   ASSERT(node_type==NodePV||node_type==NodeCut||node_type==NodeAll);

   ASSERT(board_is_legal(board));

   // horizon?

   if (depth <= 0) return full_quiescence(board,alpha,beta,0,height,pv);

   // init

   SearchStack[height].best_move = MoveNone;
   SearchStack[height].move = MoveNone;
   SearchStack[height].threat_move = MoveNone;
   SearchStack[height].reduced = false;
   //mate_threat = false;

   SearchCurrent->node_nb++;
   SearchInfo->check_nb--;
   PV_CLEAR(pv);

   if (height > SearchCurrent->max_depth) SearchCurrent->max_depth = height;

   if (SearchInfo->check_nb <= 0) {
      SearchInfo->check_nb += SearchInfo->check_inc;
      search_check();
   }

   // draw?

   if (board_is_repetition(board)/* || recog_draw(board)*/) return ValueDraw;

   // mate-distance pruning


      // lower bound

      value = VALUE_MATE(height+2); // does not work if the current position is mate
      if (value > alpha && board_is_mate(board)) value = VALUE_MATE(height);

      if (value > alpha) {
         alpha = value;
         if (value >= beta) return value;
      }

      // upper bound

      value = -VALUE_MATE(height+1);

      if (value < beta) {
         beta = value;
         if (value <= alpha) return value;
      }
 

   // transposition table

   trans_move = MoveNone;

   if (depth >= TransDepth) {

      if (trans_retrieve(Trans,board->key,&trans_move,&trans_min_depth,&trans_max_depth,&trans_min_value,&trans_max_value)) {

         // trans_move is now updated

         if (node_type != NodePV) {

            
               if (trans_min_value > +ValueEvalInf && trans_min_depth < depth) {
                  trans_min_depth = depth;
               }

               if (trans_max_value < -ValueEvalInf && trans_max_depth < depth) {
                  trans_max_depth = depth;
               }
            

            min_value = -ValueInf;

            if (DEPTH_MATCH(trans_min_depth,depth)) {
               min_value = value_from_trans(trans_min_value,height);
               if (min_value >= beta) return min_value;
            }

            max_value = +ValueInf;

            if (DEPTH_MATCH(trans_max_depth,depth)) {
               max_value = value_from_trans(trans_max_value,height);
               if (max_value <= alpha) return max_value;
            }

            if (min_value == max_value) return min_value; // exact match
         }
      }
   }

   // height limit

   if (height >= HeightMax-1) return eval(board, alpha, beta, false, false);

   // more init

   old_alpha = alpha;
   best_value = ValueNone;
   best_move = MoveNone;
   played_nb = 0;

   attack_set(attack,board);
   in_check = ATTACK_IN_CHECK(attack);

   // null-move pruning

   if (UseNull && depth >= NullDepth && node_type != NodePV) {

      if (!in_check
       && !value_is_mate(beta)
       && do_null(board)
       && (!UseNullEval || depth <= NullReduction+1 || eval(board,alpha, beta, false, in_check) >= beta)) {

         // null-move search
		 
         new_depth = depth - NullReduction - 1;
		 
	     move_do_null(board,undo);
         value = -full_search(board,-beta,-beta+1,new_depth,height+1,new_pv,NODE_OPP(node_type));
         move_undo_null(board,undo);

         // verification search

         if (UseVer && depth > VerReduction) {

            if (value >= beta && (!UseVerEndgame || do_ver(board))) {

               new_depth = depth - VerReduction;
               ASSERT(new_depth>0);

               value = full_no_null(board,alpha,beta,new_depth,height,new_pv,NodeCut,trans_move,&move);

               if (value >= beta) {
                  ASSERT(move==new_pv[0]);
                  played[played_nb++] = move;
                  best_move = move;
				  SearchStack[height].move = move;
				  SearchStack[height].best_move = move;
                  best_value = value;
                  pv_copy(pv,new_pv);
                  goto cut;
               }
            }
         }

         // pruning

         if (value >= beta) {

            if (value > +ValueEvalInf) value = +ValueEvalInf; // do not return unproven mates
            ASSERT(!value_is_mate(value));

            // pv_cat(pv,new_pv,MoveNull);

            best_move = MoveNone;
            best_value = value;
            goto cut;
         }
		 SearchStack[height].threat_move = SearchStack[height+1].best_move;
		 if (SearchStack[height-1].reduced){ // Idea by Tord Romstad 
				if (/* value < alpha - 250 ||*/ MOVE_FROM(SearchStack[height+1].best_move) == MOVE_TO(SearchStack[height-1].move))
					return alpha-1;
					//depth++;
		 }
	  }
   }

   // mate threat 
/*   mate_threat = false;
   if (value <= VALUE_MATE(height+2)){ 
			mate_threat = true;
   } */

   // Internal Iterative Deepening
   
   if (depth >= IIDDepth && node_type == NodePV && trans_move == MoveNone) {

      // new_depth = depth - IIDReduction;
	  new_depth = MIN(depth - IIDReduction,depth/2);
      ASSERT(new_depth>0);

      value = full_search(board,alpha,beta,new_depth,height,new_pv,node_type);
      if (value <= alpha) value = full_search(board,-ValueInf,beta,new_depth,height,new_pv,node_type);

      trans_move = new_pv[0];
   }

   // move generation

   sort_init(sort,board,attack,depth,height,trans_move);

   single_reply = false;
   if (in_check && LIST_SIZE(sort->list) == 1) single_reply = true; // HACK

   // move loop

   opt_value = +ValueInf;

   while ((move=sort_next(sort)) != MoveNone) {

	  SearchStack[height].move = move;

	  
      // extensions

      new_depth = full_new_depth(depth,move,board,single_reply,node_type==NodePV, height);

      if (depth == 1 && opt_value == ValueInf && new_depth < depth) opt_value = eval(board,alpha,beta, false, in_check);

      // futility pruning

	  if (UseFutility && depth <= 2 && node_type != NodePV) {
		  
         if (!in_check && new_depth < depth && !move_is_tactical(move,board) && !move_is_dangerous(move,board)) {

            ASSERT(!move_is_check(move,board));

            // optimistic evaluation

	    if (depth==2){
	    	FutilityMargin = FutilityMargin2;
	    }
	    else{
		FutilityMargin = FutilityMargin1;
	    }


            if (opt_value == +ValueInf) {
			if (!quick_futility)  {
				opt_value = eval(board,alpha,beta, false, in_check);
			} else {
				opt_value = board->piece_material[White] - board->piece_material[Black];
				if (COLOUR_IS_BLACK(board->turn)){ 
					opt_value = -opt_value;
				}
			}
			ASSERT(opt_value<+ValueInf);
            }

            value = opt_value + FutilityMargin;

            // pruning

            if (value <= alpha) {

               if (value > best_value) {
                  best_value = value;
                  PV_CLEAR(pv);
               }

               continue;
            }
         }
      } 

	 // history pruning
      reduced = false;

      if (UseHistory && depth >= HistoryDepth && node_type != NodePV) {
         if (!in_check && played_nb >= HistoryMoveNb && new_depth < depth) {
            ASSERT(best_value!=ValueNone);
            ASSERT(played_nb>0);
            ASSERT(sort->pos>0&&move==LIST_MOVE(sort->list,sort->pos-1));
            value = sort->value; // history score
            if (value < HistoryValue) {
               ASSERT(value>=0&&value<16384);
               ASSERT(move!=trans_move);
               ASSERT(!move_is_tactical(move,board));
               ASSERT(!move_is_check(move,board));
               new_depth--;
               reduced = true;
            }
         }
      }   

      // rebel reduction

      if (use_rebel_reduction && !in_check && !reduced && depth > 2 && new_depth < depth && node_type != NodePV && !move_is_tactical(move,board) && !move_is_dangerous(move,board)) { 

	switch (depth) {
		case 3: margin = 500; break;
		case 4: margin = 600; break;
		case 5: margin = 700; break;
		case 6: margin = 800; break;
		case 7: margin = 900; break;
		case 8: margin = 1000; break;
		default: margin = 1600; break;
	}

        // optimistic evaluation
        if (opt_value == +ValueInf) {
	    opt_value = board->piece_material[White] - board->piece_material[Black];
		if (COLOUR_IS_BLACK(board->turn)){ 
			opt_value = -opt_value;
		}
               ASSERT(opt_value<+ValueInf);
        }

        value = opt_value + margin;

	if (alpha > value) { 
		new_depth --; 
		reduced = true;
		//rebel_reduction = true;
	}

      }


	  SearchStack[height].reduced = reduced;

      // recursive search

	  move_do(board,move,undo);

      if (node_type != NodePV || best_value == ValueNone) { // first move
		 value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NODE_OPP(node_type));
      } else { // other moves
		 value = -full_search(board,-alpha-1,-alpha,new_depth,height+1,new_pv,NodeCut);
         if (value > alpha) { // && value < beta
			value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NodePV);
         }
      }

      // history-pruning re-search
	  if(research_on_beta) {
		if (reduced && value >= beta) {

	         ASSERT(node_type!=NodePV);

			 SearchStack[height].reduced = false;
			 new_depth++;
			 ASSERT(new_depth==depth-1);
		 
			 value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NODE_OPP(node_type));
		} 
	  } else {
		if (reduced && value > alpha) {

	         ASSERT(node_type!=NodePV);

			 SearchStack[height].reduced = false;
			 new_depth++;
			 ASSERT(new_depth==depth-1);
		 
			 value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NODE_OPP(node_type));
		} 
	  }

      move_undo(board,move,undo);

      played[played_nb++] = move;

      if (value > best_value) {
         best_value = value;
         pv_cat(pv,new_pv,move);
         if (value > alpha) {
            alpha = value;
            best_move = move;
			SearchStack[height].best_move = move;
            if (value >= beta){ 
				goto cut;
			}
         }
      }

      if (node_type == NodeCut) node_type = NodeAll;
   }

   // ALL node

   if (best_value == ValueNone) { // no legal move
      if (in_check) {
         ASSERT(board_is_mate(board));
         return VALUE_MATE(height);
      } else {
         ASSERT(board_is_stalemate(board));
         return ValueDraw;
      }
   }

cut:

   ASSERT(value_is_ok(best_value));

   // move ordering

   if (best_move != MoveNone) {

      good_move(best_move,board,depth,height);

      if (best_value >= beta && !move_is_tactical(best_move,board)) {

		 ASSERT(played_nb>0&&played[played_nb-1]==best_move);

         for (i = 0; i < played_nb-1; i++) {
            move = played[i];
            ASSERT(move!=best_move);
            history_bad(move,board);
         }

         history_good(best_move,board);
      }
   }

   // transposition table

   if (depth >= TransDepth) {

      trans_move = best_move;
      trans_depth = depth;
      trans_min_value = (best_value > old_alpha) ? value_to_trans(best_value,height) : -ValueInf;
      trans_max_value = (best_value < beta)      ? value_to_trans(best_value,height) : +ValueInf;

      trans_store(Trans,board->key,trans_move,trans_depth,trans_min_value,trans_max_value);
   }

   return best_value;
}

// full_no_null()

static int full_no_null(board_t * board, int alpha, int beta, int depth, int height, mv_t pv[], int node_type, int trans_move, int * best_move) {

   int value, best_value;
   int move;
   int new_depth;
   attack_t attack[1];
   sort_t sort[1];
   undo_t undo[1];
   mv_t new_pv[HeightMax];

   ASSERT(board!=NULL);
   ASSERT(range_is_ok(alpha,beta));
   ASSERT(depth_is_ok(depth));
   ASSERT(height_is_ok(height));
   ASSERT(pv!=NULL);
   ASSERT(node_type==NodePV||node_type==NodeCut||node_type==NodeAll);
   ASSERT(trans_move==MoveNone||move_is_ok(trans_move));
   ASSERT(best_move!=NULL);

   ASSERT(board_is_legal(board));
   ASSERT(!board_is_check(board));
   ASSERT(depth>=1);

   // init

   SearchStack[height].best_move = MoveNone;
   SearchStack[height].move = MoveNone;
   SearchStack[height].threat_move = MoveNone;
   SearchStack[height].reduced = false;

   SearchCurrent->node_nb++;
   SearchInfo->check_nb--;
   PV_CLEAR(pv);

   if (height > SearchCurrent->max_depth) SearchCurrent->max_depth = height;

   if (SearchInfo->check_nb <= 0) {
      SearchInfo->check_nb += SearchInfo->check_inc;
      search_check();
   }

   attack_set(attack,board);
   ASSERT(!ATTACK_IN_CHECK(attack));

   *best_move = MoveNone;
   best_value = ValueNone;

   // move loop

   sort_init(sort,board,attack,depth,height,trans_move);

   while ((move=sort_next(sort)) != MoveNone) {

	  SearchStack[height].move = move;

      new_depth = full_new_depth(depth,move,board,false,false,height);

      move_do(board,move,undo);
      value = -full_search(board,-beta,-alpha,new_depth,height+1,new_pv,NODE_OPP(node_type));
      move_undo(board,move,undo);

      if (value > best_value) {
         best_value = value;
         pv_cat(pv,new_pv,move);
         if (value > alpha) {
            alpha = value;
            *best_move = move;
			SearchStack[height].best_move = move;
            if (value >= beta) goto cut;
         }
      }
   }

   // ALL node

   if (best_value == ValueNone) { // no legal move => stalemate
      ASSERT(board_is_stalemate(board));
      best_value = ValueDraw;
   }

cut:

   ASSERT(value_is_ok(best_value));

   return best_value;
}

// full_quiescence()

static int full_quiescence(board_t * board, int alpha, int beta, int depth, int height, mv_t pv[]) {

   bool in_check;
   int old_alpha;
   int value, best_value;
   int best_move;
   int move;
   int opt_value;
   attack_t attack[1];
   sort_t sort[1];
   undo_t undo[1];
   mv_t new_pv[HeightMax];
   int cd;

   ASSERT(board!=NULL);
   ASSERT(range_is_ok(alpha,beta));
   ASSERT(depth_is_ok(depth));
   ASSERT(height_is_ok(height));
   ASSERT(pv!=NULL);

   ASSERT(board_is_legal(board));
   ASSERT(depth<=0);

   // init

   SearchStack[height].best_move = MoveNone;
   SearchStack[height].move = MoveNone;
   SearchStack[height].threat_move = MoveNone;
   SearchStack[height].reduced = false;

   SearchCurrent->node_nb++;
   SearchInfo->check_nb--;
   PV_CLEAR(pv);

   if (height > SearchCurrent->max_depth) SearchCurrent->max_depth = height;

   if (SearchInfo->check_nb <= 0) {
      SearchInfo->check_nb += SearchInfo->check_inc;
      search_check();
   }

   // draw?

   if (board_is_repetition(board)/* || recog_draw(board)*/) return ValueDraw;

   // mate-distance pruning


      // lower bound

      value = VALUE_MATE(height+2); // does not work if the current position is mate
      if (value > alpha && board_is_mate(board)) value = VALUE_MATE(height);

      if (value > alpha) {
         alpha = value;
         if (value >= beta) return value;
      }

      // upper bound

      value = -VALUE_MATE(height+1);

      if (value < beta) {
         beta = value;
         if (value <= alpha) return value;
      }
   

   // more init

   attack_set(attack,board);
   in_check = ATTACK_IN_CHECK(attack);

   if (in_check) {
      ASSERT(depth<0);
      depth++; // in-check extension
   }

   // height limit

   if (height >= HeightMax-1) return eval(board, alpha, beta, false, false);

   // more init

   old_alpha = alpha;
   best_value = ValueNone;
   best_move = MoveNone;

   /* if (UseDelta) */ opt_value = +ValueInf;

   if (!in_check) {

      // lone-king stalemate?

      if (simple_stalemate(board)) return ValueDraw;

      // stand pat

      value = eval(board, alpha, beta, true, in_check);

      ASSERT(value>best_value);
      best_value = value;
      if (value > alpha) {
         alpha = value;
         if (value >= beta) goto cut;
      }

      if (UseDelta) {
         opt_value = value + DeltaMargin;
         ASSERT(opt_value<+ValueInf);
      }
   }

   // move loop


   sort_init_qs(sort,board,attack, depth>=CheckDepth);

   while ((move=sort_next_qs(sort)) != MoveNone) {

	  SearchStack[height].move = move;

      // delta pruning

      if (UseDelta && beta == old_alpha+1) {

         if (!in_check && !move_is_check(move,board) && !capture_is_dangerous(move,board)) {

            ASSERT(move_is_tactical(move,board));

            // optimistic evaluation

            value = opt_value;

            int to = MOVE_TO(move);
            int capture = board->square[to];

            if (capture != Empty) {
               value += VALUE_PIECE(capture);
            } else if (MOVE_IS_EN_PASSANT(move)) {
               value += ValuePawn;
            }

            if (MOVE_IS_PROMOTE(move)) value += ValueQueen - ValuePawn;

            // pruning

            if (value <= alpha) {

               if (value > best_value) {
                  best_value = value;
                  PV_CLEAR(pv);
               }

               continue;
            }
         }
      }

      move_do(board,move,undo);
      value = -full_quiescence(board,-beta,-alpha,depth-1,height+1,new_pv);
      move_undo(board,move,undo);

      if (value > best_value) {
         best_value = value;
         pv_cat(pv,new_pv,move);
         if (value > alpha) {
            alpha = value;
            best_move = move;
			SearchStack[height].best_move = move;
            if (value >= beta) goto cut;
         }
      }
   }

   // ALL node

   if (best_value == ValueNone) { // no legal move
      ASSERT(board_is_mate(board));
      return VALUE_MATE(height);
   }

cut:

   ASSERT(value_is_ok(best_value));

   return best_value;
}

// full_new_depth()

static int full_new_depth(int depth, int move, board_t * board, bool single_reply, bool in_pv, int height) {

   int new_depth;

   ASSERT(depth_is_ok(depth));
   ASSERT(move_is_ok(move));
   ASSERT(board!=NULL);
   ASSERT(single_reply==true||single_reply==false);
   ASSERT(in_pv==true||in_pv==false);

   ASSERT(depth>0);

   new_depth = depth - 1;
   
   if (SearchCurrent->max_extensions > height){
		if ((single_reply)
			|| (in_pv && MOVE_TO(move) == board->cap_sq // recapture
				&& (see_move(move,board) > 0 || ABS(VALUE_PIECE(board->square[MOVE_TO(move)])-VALUE_PIECE(board->square[MOVE_FROM(move)])) <= 250 ))
			|| (in_pv && PIECE_IS_PAWN(MOVE_PIECE(move,board))
				  && PAWN_RANK(MOVE_TO(move),board->turn) == Rank7
				  /* && see_move(move,board) >= 0 */) 
			|| move_is_check(move,board)) {
			new_depth++;
		}
   }

   ASSERT(new_depth>=0&&new_depth<=depth);

   return new_depth;
}

// do_null()

static bool do_null(const board_t * board) {

   ASSERT(board!=NULL);

   // use null move if the side-to-move has at least one piece

   return board->piece_size[board->turn] >= 2; // king + one piece
}

// do_ver()

static bool do_ver(const board_t * board) {

   ASSERT(board!=NULL);

   // use verification if the side-to-move has at most one piece

   return board->piece_size[board->turn] <= 3; // king + one piece was 2
}

// pv_fill()

static void pv_fill(const mv_t pv[], board_t * board) {

   int move;
   int trans_move, trans_depth, trans_min_value, trans_max_value;
   undo_t undo[1];

   ASSERT(pv!=NULL);
   ASSERT(board!=NULL);


   move = *pv;

   if (move != MoveNone && move != MoveNull) {

      move_do(board,move,undo);
      pv_fill(pv+1,board);
      move_undo(board,move,undo);

      trans_move = move;
      trans_depth = -127; // HACK
      trans_min_value = -ValueInf;
      trans_max_value = +ValueInf;

      trans_store(Trans,board->key,trans_move,trans_depth,trans_min_value,trans_max_value);
   }
}

// move_is_dangerous()

static bool move_is_dangerous(int move, const board_t * board) {

   int piece;

   ASSERT(move_is_ok(move));
   ASSERT(board!=NULL);

   ASSERT(!move_is_tactical(move,board));

   piece = MOVE_PIECE(move,board);

   if (PIECE_IS_PAWN(piece)
    && PAWN_RANK(MOVE_TO(move),board->turn) >= Rank7) {
      return true;
   }

   return false;
}

// capture_is_dangerous()

static bool capture_is_dangerous(int move, const board_t * board) {

   int piece, capture;

   ASSERT(move_is_ok(move));
   ASSERT(board!=NULL);

   ASSERT(move_is_tactical(move,board));

   piece = MOVE_PIECE(move,board);

   if (PIECE_IS_PAWN(piece)
    && PAWN_RANK(MOVE_TO(move),board->turn) >= Rank7) {
      return true;
   }

   capture = move_capture(move,board);

   if (PIECE_IS_QUEEN(capture)) return true;

   if (PIECE_IS_PAWN(capture)
    && PAWN_RANK(MOVE_TO(move),board->turn) <= Rank2) {
      return true;
   }

   return false;
}

// simple_stalemate()

static bool simple_stalemate(const board_t * board) {

   int me, opp;
   int king;
   int opp_flag;
   int from, to;
   int capture;
   const inc_t * inc_ptr;
   int inc;

   ASSERT(board!=NULL);

   ASSERT(board_is_legal(board));
   ASSERT(!board_is_check(board));

   // lone king?

   me = board->turn;
   if (board->piece_size[me] != 1 || board->pawn_size[me] != 0) return false; // no

   // king in a corner?

   king = KING_POS(board,me);
   if (king != A1 && king != H1 && king != A8 && king != H8) return false; // no

   // init

   opp = COLOUR_OPP(me);
   opp_flag = COLOUR_FLAG(opp);

   // king can move?

   from = king;

   for (inc_ptr = KingInc; (inc=*inc_ptr) != IncNone; inc_ptr++) {
      to = from + inc;
      capture = board->square[to];
      if (capture == Empty || FLAG_IS(capture,opp_flag)) {
         if (!is_attacked(board,to,opp)) return false; // legal king move
      }
   }

   // no legal move

   ASSERT(board_is_stalemate((board_t*)board));

   return true;
}

// end of search_full.cpp

