1 files changed, 105 insertions, 0 deletions
diff --git a/src/valid_moves.c b/src/valid_moves.c
new file mode 100644
index 0000000..bcbbd46
--- /dev/null
+++ b/src/valid_moves.c
@@ -0,0 +1,105 @@
+#include <stdbool.h>
+
+#include "othello.h"
+
+bool is_valid_move(const player_color board[8][8],
+                   const player_color current_player, const struct move move) {
+  // The move must be a positive position
+  if (move.row < 0 || move.col < 0) {
+    return false;
+  }
+  // The move must be an empty spot to be valid
+  if (board[move.row][move.col] != EMPTY) {
+    return false;
+  }
+
+  const player_color other_color = current_player == WHITE ? BLACK : WHITE;
+
+  bool is_valid_up = false;
+  bool is_valid_down = false;
+  bool is_valid_left = false;
+  bool is_valid_right = false;
+
+  if (!is_valid_up && !is_valid_down && !is_valid_left && !is_valid_right) {
+    // Check if valid up
+    bool would_flip_oppenent = false;
+    bool has_other_end = false;
+    for (int i = move.row - 1; i > 0 && !has_other_end; i--) {
+      if (board[i][move.col] == current_player) {
+        has_other_end = true;
+      } else if (board[i][move.col] == other_color) {
+        would_flip_oppenent = true;
+      } else {
+        // We have reached an empty tile
+        break;
+      }
+    }
+    is_valid_up = has_other_end && would_flip_oppenent;
+  }
+
+  if (!is_valid_up && !is_valid_down && !is_valid_left && !is_valid_right) {
+    // Check if valid down
+    bool would_flip_oppenent = false;
+    bool has_other_end = false;
+    for (int i = move.row + 1; i < 8 && !has_other_end; i++) {
+      if (board[i][move.col] == current_player) {
+        has_other_end = true;
+      } else if (board[i][move.col] == other_color) {
+        would_flip_oppenent = true;
+      } else {
+        // We have reached an empty tile
+        break;
+      }
+    }
+    is_valid_down = has_other_end && would_flip_oppenent;
+  }
+
+  if (!is_valid_up && !is_valid_down && !is_valid_left && !is_valid_right) {
+    // Check if valid left
+    bool would_flip_oppenent = false;
+    bool has_other_end = false;
+    for (int i = move.col - 1; i > 0 && !has_other_end; i--) {
+      if (board[move.row][i] == current_player) {
+        has_other_end = true;
+      } else if (board[move.row][i] == other_color) {
+        would_flip_oppenent = true;
+      } else {
+        // We have reached an empty tile
+        break;
+      }
+    }
+    is_valid_left = has_other_end && would_flip_oppenent;
+  }
+
+  if (!is_valid_up && !is_valid_down && !is_valid_left && !is_valid_right) {
+    // Check if valid right
+    bool would_flip_oppenent = false;
+    bool has_other_end = false;
+    for (int i = move.col + 1; i < 8 && !has_other_end; i++) {
+      if (board[move.row][i] == current_player) {
+        has_other_end = true;
+      } else if (board[move.row][i] == other_color) {
+        would_flip_oppenent = true;
+      } else {
+        // We have reached an empty tile
+        break;
+      }
+    }
+    is_valid_right = has_other_end && would_flip_oppenent;
+  }
+
+  return is_valid_up || is_valid_down || is_valid_left || is_valid_right;
+}
+
+bool has_valid_moves(const player_color board[8][8],
+                     const player_color current_player) {
+  bool result = false;
+  struct move move;
+  for (move.row = 0; move.row < 8 && !result; move.row++) {
+    for (move.col = 0; move.col < 8 && !result; move.col++) {
+      result = is_valid_move(board, current_player, move);
+    }
+  }
+
+  return result;
+}