1 files changed, 95 insertions, 14 deletions
diff --git a/lib/coordinate.c b/lib/coordinate.c
index 2dc0215..7518a78 100644
--- a/lib/coordinate.c
+++ b/lib/coordinate.c
@@ -3,29 +3,110 @@
 
 #include "coordinate.h"
 
-static int _valid_coord(char col, char row) {
+/*
+ * Returns 0 if the coordinate is between a1 and h8.
+ */
+int coord_is_valid(char *s) {
+    if (strnlen(s, 3) != 2)
+        return 1;
+
+    char col = tolower(s[0]);
+    char row = tolower(s[1]);
+
     if (col >= 'a' && col <= 'h' && row >= '1' && row <= '8')
         return 0;
 
-    return 1;
+    return 2;
 }
 
-int coord_init(Coord* c, char col, char row) {
-    char lower_col = tolower(col);
-    char lower_row = tolower(row);
+/*
+ * Does not check if s is a valid string representing. If input is
+ * untrusted, use coord_is_valid(char*) to check it.
+ */
+Coord coord_init(char* s) {
+    Coord c;
+    char col = tolower(s[0]);
+    char row = tolower(s[1]);
 
-    if (! _valid_coord(lower_col, lower_row))
-        return 1;
+    c.col = col;
+    c.row = row;
+
+    return c;
+}
+
+/*
+ * Returns 0 if c is the null coordinate
+ */
+int coord_is_null(Coord c) {
+    return (c.col == 0 && c.row == 0);
+}
 
-    c->row = row;
-    c->col = col;
+/*
+ * Returns the null coordinate
+ */
+Coord coord_null() {
+    Coord c;
 
-    return 0;        
+    c.col = 0;
+    c.row = 0;
+
+    return c;
 }
 
-int coord_init_from_str(Coord* c, char* s) {
-    if (strlen(s) != 2)
-        return 1;
+/*
+ * Set Coord row
+ */
+Coord coord_set_row(Coord c, char row) {
+    c.row = row;
+
+    return c;
+}
+
+/*
+ * Set Coord column
+ */
+Coord coord_set_col(Coord c, char col) {
+    c.col = col;
+
+    return c;
+}
+
+/*
+ * Returns the next coordinate. Useful for traversing the board forwards.
+ */
+Coord coord_next(Coord c) {
+    if (coord_is_null(c))
+        c = coord_init("a8");
+    else
+        if (c.col == 'h')
+            if (c.row == '1')
+                c = coord_null();
+            else {
+                c.row -= 1;
+                c.col = 'a';
+            }
+        else
+            c.col += 1;
+
+    return c;
+}
+
+/*
+ * Returns the previous coordinate. Useful for traversing the board backwards.
+ */
+Coord coord_prev(Coord c) {
+    if (coord_is_null(c))
+        c = coord_init("h1");
+    else
+        if (c.col == 'a')
+            if (c.row == '8')
+                c = coord_null();
+            else {
+                c.row += 1;
+                c.col = 'h';
+            }
+        else
+            c.col -= 1;
 
-    return coord_init(c, s[0], s[1]);
+    return c;
 }