Added move pawn code

assignment1-18/chessboard.c

@@ -1,5 +1,10 @@
+// vim: set ts=4 sw=4 et tw=80:
+
 #include <stdio.h>
 #include "./chessboard.h"
+#include <string.h>
+#include <stdbool.h>
+#include <stdlib.h>
 
 void init_chessboard(struct chessboard * cb) {
     int i;
@@ -60,9 +65,89 @@ void print_chessboard(struct chessboard * cb) {
 
 }
 
+void cb_move(struct chessboard* cb, int from_row, int from_col, int to_row,
+             int to_col) {
+    cb->position[to_row][to_col] = cb->position[from_row][from_col];
+    cb->position[from_row][from_col] = EMPTY;
+}
+
+bool is_empty(struct chessboard* cb, int row, int col) {
+    return cb->position[row][col] == EMPTY;
+}
+
+inline enum player player(struct chessboard* cb, int row, int col) {
+     return cb->position[row][col] < 7 ? WHITE : BLACK;
+}
+
+enum mstatus move_pawn(struct chessboard* cb, enum player p, int from_row,
+                       int from_col, int to_row, int to_col) {
+    // two forward if in the starting position, no capture is valid
+    if (((p == WHITE && from_row == 1 && to_row == 3 &&
+          is_empty(cb, 2, from_col)) ||
+         (p == BLACK && from_row == 7 && to_row == 5 &&
+          is_empty(cb, 6, from_col))) &&
+        from_col == to_col &&
+        is_empty(cb, to_row, to_col)) {
+        cb_move(cb, from_row, from_col, to_row, to_col);
+        return VALID;
+    // one forward, no capture is valid
+    } else if (((p == WHITE && to_row - from_row == 1) ||
+                (p == BLACK && from_row - to_row == 1)) &&
+               from_col == to_col &&
+               is_empty(cb, to_row, to_col)) {
+        cb_move(cb, from_row, from_col, to_row, to_col);
+        return VALID;
+    // one forward, one left or right, with capture, is valid
+    } else if (to_row = from_row + (p == WHITE ? 1 : -1) &&
+               abs(from_col - to_col) == 1 &&
+               !is_empty(cb, to_row, to_col) &&
+               player(cb, to_row, to_col) != p) {
+        cb_move(cb, from_row, from_col, to_row, to_col);
+        return VALID;
+    } else {
+        return INVALID;
+    }
+}
+
 enum mstatus move(
         struct chessboard * cb, enum player p,
         const char * from, const char * to)
 {
-    
+    // if you are giving us garbage, we behave like Rome's municipal services
+    if (strlen(from) != 2 || strlen(to) != 2 || from[0] < 'a' || from[0] > 'h'
+            || to[0] < 'a' || to[0] > 'h' || from[1] < '1' ||  from[1] > '8'
+            || to[1] < '1' || to[1] > '8') {
+        return INVALID;
     }
+
+    int from_row = from[0] - 'a', to_row = to[0] - 'a';
+    int from_col = from[1] - '1', to_col = to[0] - '1';
+
+    // if you are moving thin air, EH VOLEVIH
+    if (cb->position[from_row][from_col] == EMPTY) {
+        return INVALID;
+    }
+
+    // if you are moving someone else's pieces, "thou shall not steal"
+    if (cb->position[from_row][from_col] / 7 != p) {
+        return INVALID;
+    }
+
+    // if you are trying to suicide (capture your piecies), sorry but assisted
+    // suicide is not legal in italy
+    if (cb->position[to_row][to_col] != EMPTY &&
+            cb->position[from_row][from_col] / 7 ==
+            cb->position[to_row][to_col] / 7) {
+        return INVALID;
+    }
+
+    // try to understand which piece we are moving
+    switch (cb->position[from_row][from_col]) {
+    case WHITE_PAWN:
+    case BLACK_PAWN:
+        return move_pawn(cb, p, from_row, from_col, to_row, to_col);
+    default:
+        return INVALID;
+    }
+}
+