reverse rainbow when repeat

colcat.c

@@ -35,8 +35,24 @@ char help_text[] = "\nUsage: colcat [args] [--] [FILES] \n"
 
 /* Print the nth colour of the <rainbow_len> chars long rainbow */
 void print_next_colour(int current) {
+    static bool reverse = false;
+
+    if (current % rainbow_len == 0) {
+        reverse = !reverse;
+    }
+    if (current == 0) {
+        reverse = false;
+    }
+
+    int index = 0;
+    if (!reverse) {
+        index = (current % num_colours) / col_dist;
+    } else {
+        index = num_colours -1- (current % num_colours) / col_dist;
+    }
+
     if (current % col_dist == 0) {
-        struct colour c = colours[(current % num_colours) / col_dist];
+        struct colour c = colours[index];
         printf("\x1b[38;2;%d;%d;%dm", c.r, c.g, c.b);
     }
 }