3 files changed, 91 insertions, 1 deletions

diff --git a/src/libsok/sok-ctx.c b/src/libsok/sok-ctx.c
index d514fe3..26c6239 100644
--- a/src/libsok/sok-ctx.c
+++ b/src/libsok/sok-ctx.c
@@ -201,6 +201,73 @@ sok_ctx_count_goals_left(
   return r;
 }
 
+/* 
+ * static bool
+ * sok_ctx_has_corner_boxes(
+ *   const sok_ctx_t * const ctx
+ * ) {
+ *   for (size_t i = 0; i < ctx->level.num_boxes; i++) {
+ *     // right
+ *     const bool r = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x + 1,
+ *       .y = ctx->boxes[i].y, 
+ *     });
+ *                
+ *     // top-right
+ *     const bool tr = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x + 1,
+ *       .y = ctx->boxes[i].y - 1, 
+ *     });
+ * 
+ *     // top
+ *     const bool t = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x,
+ *       .y = ctx->boxes[i].y - 1, 
+ *     });
+ * 
+ *     // top-left
+ *     const bool tl = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x - 1,
+ *       .y = ctx->boxes[i].y - 1, 
+ *     });
+ * 
+ *     // left
+ *     const bool l = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x - 1,
+ *       .y = ctx->boxes[i].y, 
+ *     });
+ *                
+ *     // bottom-left
+ *     const bool bl = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x - 1,
+ *       .y = ctx->boxes[i].y + 1, 
+ *     });
+ * 
+ *     // bottom
+ *     const bool b = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x,
+ *       .y = ctx->boxes[i].y + 1, 
+ *     });
+ * 
+ *     const bool br = ctx_is_wall(ctx, (sok_pos_t) { 
+ *       .x = ctx->boxes[i].x + 1,
+ *       .y = ctx->boxes[i].y + 1, 
+ *     });
+ * 
+ *     if (
+ *       (r && tr && t) || // top-right
+ *       (t && tl && l) || // top-left
+ *       (l && bl && b) || // bottom-left
+ *       (b && br && r)    // bottom-right
+ *     ) {
+ *       // return
+ *       return true;
+ *     }
+ *   }
+ * 
+ *   return false;
+ * }
+ */ 
 
 void
 sok_ctx_init(sok_ctx_t * const ctx, void *user_data) {
@@ -232,8 +299,9 @@ sok_ctx_set_level(
   ctx->home = ctx->level.home;
   memcpy(ctx->boxes, ctx->level.boxes, ctx->level.num_boxes * sizeof(sok_pos_t));
 
-  // count number of goals left
+  // count number of goals left and check whether there are
   ctx->num_goals_left = sok_ctx_count_goals_left(ctx);
+  // ctx->is_lost = sok_ctx_is_lost(ctx);
 
   // return success
   return true;
@@ -322,6 +390,7 @@ sok_ctx_move_box(
     // update box and goal count
     ctx->boxes[box_ofs] = new_pos;
     ctx->num_goals_left = sok_ctx_count_goals_left(ctx);
+    // ctx->is_lost = sok_ctx_has_corner_boxes(ctx);
 
     // return success
     return true;
@@ -338,6 +407,15 @@ sok_ctx_is_done(
   return ctx->num_goals_left == 0;
 }
 
+/* 
+ * bool
+ * sok_ctx_is_lost(
+ *   const sok_ctx_t * const ctx
+ * ) {
+ *   return ctx->is_lost;
+ * }
+ */ 
+
 bool
 sok_ctx_move(
   sok_ctx_t * const ctx,
diff --git a/src/libsok/sok-solve.c b/src/libsok/sok-solve.c
index 225ce9b..34a8320 100644
--- a/src/libsok/sok-solve.c
+++ b/src/libsok/sok-solve.c
@@ -31,6 +31,14 @@ sok_solve_step(
     return false;
   }
 
+/* 
+ *   // make sure level is solvable
+ *   if (sok_ctx_is_lost(ctx)) {
+ *     // return failure
+ *     return false;
+ *   }
+ */ 
+
   for (size_t dir = 0; dir < SOK_DIR_LAST; dir++) {
     if (!sok_ctx_move(ctx, dir)) {
       continue;
diff --git a/src/libsok/sok.h b/src/libsok/sok.h
index a633d12..4fbae72 100644
--- a/src/libsok/sok.h
+++ b/src/libsok/sok.h
@@ -122,6 +122,9 @@ typedef struct {
   // number of open goals
   size_t num_goals_left;
 
+  // are there boxes in corners?
+  // _Bool is_lost;
+
   // player position
   sok_pos_t home;
 
@@ -137,6 +140,7 @@ void sok_ctx_init(sok_ctx_t * const ctx, void *user_data);
 _Bool sok_ctx_set_level(sok_ctx_t * const ctx, const char * const level);
 
 _Bool sok_ctx_is_done(const sok_ctx_t * const);
+// _Bool sok_ctx_is_lost(const sok_ctx_t * const);
 
 _Bool sok_ctx_move(sok_ctx_t * const, const sok_dir_t);
 _Bool sok_ctx_undo(sok_ctx_t * const);