solve: check for corners

3 files changed, 85 insertions, 95 deletions

diff --git a/src/core/sok-ctx.c b/src/core/sok-ctx.c
index e278af1..036bf66 100644
--- a/src/core/sok-ctx.c
+++ b/src/core/sok-ctx.c
@@ -183,6 +183,52 @@ pos_find(
   return len;
 }
 
+static bool
+tile_is_goal(
+  const sok_ctx_t * const ctx,
+  const sok_pos_t pos
+) {
+  const size_t num_goals = ctx->level.num_goals;
+  return pos_find(pos, ctx->level.goals, num_goals) < num_goals;
+}
+
+static bool
+tile_is_corner(
+  const sok_ctx_t * const ctx,
+  const sok_pos_t pos
+) {
+  // right
+  const bool r = ctx_is_wall(ctx, (sok_pos_t) {
+    .x = pos.x + 1,
+    .y = pos.y,
+  });
+
+  // top
+  const bool t = ctx_is_wall(ctx, (sok_pos_t) {
+    .x = pos.x,
+    .y = pos.y - 1,
+  });
+
+  // left
+  const bool l = ctx_is_wall(ctx, (sok_pos_t) {
+    .x = pos.x - 1,
+    .y = pos.y,
+  });
+
+  // bottom
+  const bool b = ctx_is_wall(ctx, (sok_pos_t) {
+    .x = pos.x,
+    .y = pos.y + 1,
+  });
+
+  return (
+    (t && r) || // top-right
+    (t && l) || // top-left
+    (b && l) || // bottom-left
+    (b && r)    // bottom-right
+  );
+}
+
 static size_t
 sok_ctx_count_goals_left(
   sok_ctx_t * const ctx
@@ -201,73 +247,29 @@ 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;
- * }
- */
+static bool
+sok_ctx_box_is_stuck(
+  const sok_ctx_t * const ctx,
+  const size_t i
+) {
+  return (
+    !tile_is_goal(ctx, ctx->boxes[i]) &&
+    tile_is_corner(ctx, ctx->boxes[i])
+  );
+}
+
+static bool
+sok_ctx_has_stuck_boxes(
+  const sok_ctx_t * const ctx
+) {
+  for (size_t i = 0; i < ctx->level.num_boxes; i++) {
+    if (sok_ctx_box_is_stuck(ctx, i)) {
+      return true;
+    }
+  }
+
+  return false;
+}
 
 void
 sok_ctx_init(sok_ctx_t * const ctx, void *user_data) {
@@ -301,7 +303,7 @@ sok_ctx_set_level(
 
   // 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);
+  ctx->is_lost = sok_ctx_has_stuck_boxes(ctx);
 
   // return success
   return true;
@@ -329,15 +331,6 @@ tile_is_box(
 }
 
 static bool
-tile_is_goal(
-  const sok_ctx_t * const ctx,
-  const sok_pos_t pos
-) {
-  const size_t num_goals = ctx->level.num_goals;
-  return pos_find(pos, ctx->level.goals, num_goals) < num_goals;
-}
-
-static bool
 sok_ctx_push_move(
   sok_ctx_t * const ctx,
   const sok_dir_t dir,
@@ -390,7 +383,7 @@ 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);
+    ctx->is_lost = sok_ctx_has_stuck_boxes(ctx);
 
     // return success
     return true;
@@ -407,14 +400,12 @@ 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_is_lost(
+  const sok_ctx_t * const ctx
+) {
+  return ctx->is_lost;
+}
 
 bool
 sok_ctx_move(
diff --git a/src/core/sok-solve.c b/src/core/sok-solve.c
index 45d227c..0d4e500 100644
--- a/src/core/sok-solve.c
+++ b/src/core/sok-solve.c
@@ -36,13 +36,12 @@ sok_solve_step(
     // return failure
     return false;
   }
-/* 
- *   // make sure level is solvable
- *   if (sok_ctx_is_lost(ctx)) {
- *     // return failure
- *     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)) {
diff --git a/src/core/sok.h b/src/core/sok.h
index 92fb4e7..d24d22b 100644
--- a/src/core/sok.h
+++ b/src/core/sok.h
@@ -132,7 +132,7 @@ typedef struct {
   size_t num_goals_left;
 
   // are there boxes in corners?
-  // _Bool is_lost;
+  _Bool is_lost;
 
   // player position
   sok_pos_t home;
@@ -149,7 +149,7 @@ 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_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);