From f8afe2fed4cff27eaacbe4bc11393c0237bec11b Mon Sep 17 00:00:00 2001
From: eug-vs <eugene@eug-vs.xyz>
Date: Thu, 18 Aug 2022 04:40:05 +0300
Subject: feat: add board estimates and best moves

---
 src/main.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 77 insertions(+), 2 deletions(-)

diff --git a/src/main.c b/src/main.c
index eaded89..338952f 100644
--- a/src/main.c
+++ b/src/main.c
@@ -155,7 +155,7 @@ int validate_move(int move[2], int color, int* board) {
       }
 
       if (target_piece != EMPTY) break;
-      if ((piece & NO_COLOR) == PAWN || piece == KNIGHT || piece == KING) break;
+      if ((piece & NO_COLOR) == PAWN || (piece & NO_COLOR) == KNIGHT || piece == KING) break;
     }
     legal_move++;
   }
@@ -181,12 +181,85 @@ int apply_move(int move[2], int* board) {
   board[origin] = EMPTY;
 
   if (target_piece != EMPTY) {
-    printf("Captured %s\n", pieces[target_piece]);
+    // printf("Captured %s\n", pieces[target_piece]);
   }
 
   return board[destination];
 }
 
+int estimate_board(int* board, int color) {
+  int counter = 0;
+  for (int rank = 7; rank >= 0; rank--) {
+    for (int file = 0; file < 8; file++) {
+      int piece = board[rank * 16 + file];
+      if (piece != EMPTY) {
+        int sign = (piece % 2 == color) ? 1 : -1;
+        switch (piece & NO_COLOR) {
+          case KNIGHT:
+            counter += 3 * sign;
+            break;
+          case BISHOP:
+            counter += 3 * sign;
+            break;
+          case ROOK:
+            counter += 4 * sign;
+            break;
+          case QUEEN:
+            counter += 9 * sign;
+            break;
+          default:
+            counter += 1 * sign;
+            break;
+        }
+      }
+    }
+  }
+  return counter;
+}
+
+void find_best_move(int* board, int color) {
+  int fake_board[128];
+  int best_estimate = -10000;
+  int best_move[2];
+
+
+  for (int rank = 7; rank >= 0; rank--) {
+    for (int file = 0; file < 8; file++) {
+      int index = rank * 16 + file;
+      int piece = board[index];
+      if (piece != EMPTY && (piece % 2) == color) {
+        for (int rank_destination = 7; rank_destination >= 0; rank_destination--) {
+          for (int file_destination = 0; file_destination < 8; file_destination++) {
+            int index_destination = rank_destination * 16 + file_destination;
+            int move[2] = { index, index_destination };
+            if (validate_move(move, color, board) >= 0) {
+              // Generate fake board
+              for (int r = 7; r >= 0; r--) {
+                for (int f = 0; f < 8; f++) {
+                  fake_board[r * 16 + f] = board[r * 16 + f];
+                }
+              }
+
+              apply_move(move, fake_board);
+              int estimate = estimate_board(fake_board, color);
+              if (estimate > best_estimate) {
+                best_estimate = estimate;
+                best_move[0] = move[0];
+                best_move[1] = move[1];
+              }
+            }
+          }
+        }
+      }
+    }
+  }
+
+  char move_in_notation[] = "xy XY";
+  index_to_notation(best_move[0], move_in_notation);
+  index_to_notation(best_move[1], move_in_notation + 3);
+  printf("Best move for %i is %s with score %i\n", color, move_in_notation, best_estimate);
+}
+
 int main() {
   int board[128];
   parse_FEN(DEFAULT_FEN, board);
@@ -197,7 +270,9 @@ int main() {
   int color = 0;
 
   while (1) {
+    printf("Current board estimate is %i\n", estimate_board(board, color));
     printf("Enter a move for %s:\n", COLORS[color]);
+    find_best_move(board, color);
     input_move(move);
 
     int error = validate_move(move, color, board);
-- 
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