5 files changed, 54 insertions, 17 deletions

diff --git a/src/core/sok-solve.c b/src/core/sok-solve.c
index 34a8320..45d227c 100644
--- a/src/core/sok-solve.c
+++ b/src/core/sok-solve.c
@@ -7,7 +7,8 @@ static bool
 sok_solve_step(
   sok_ctx_t * const ctx,
   sok_cache_t * const cache,
-  void (*on_error)(const char * const)
+  const sok_solve_cbs_t * const cbs,
+  void * const user_data
 ) {
   // check for success
   if (sok_ctx_is_done(ctx)) {
@@ -22,15 +23,19 @@ sok_solve_step(
 
   // add to cache
   if (!sok_cache_add(cache, ctx)) {
-    if (on_error) {
+    if (cbs && cbs->on_error) {
       // log error
-      on_error("sok_cache_add() failed");
+      cbs->on_error("sok_cache_add() failed", user_data);
     }
 
     // return failure
     return false;
   }
 
+  if (cbs && cbs->on_step && !cbs->on_step(ctx, user_data)) {
+    // return failure
+    return false;
+  }
 /* 
  *   // make sure level is solvable
  *   if (sok_ctx_is_lost(ctx)) {
@@ -45,16 +50,16 @@ sok_solve_step(
     }
 
     // recurse, check for success
-    if (sok_solve_step(ctx, cache, on_error)) {
+    if (sok_solve_step(ctx, cache, cbs, user_data)) {
       // return success
       return true;
     }
 
     // undo move
     if (!sok_ctx_undo(ctx)) {
-      if (on_error) {
+      if (cbs && cbs->on_error) {
         // log error
-        on_error("sok_ctx_undo() failed");
+        cbs->on_error("sok_ctx_undo() failed", user_data);
       }
 
       // return failure
@@ -66,20 +71,25 @@ sok_solve_step(
   return false;
 }
 
-bool 
+bool
 sok_solve(
   sok_ctx_t * const ctx,
-  void (*on_error)(const char * const)
+  const sok_solve_cbs_t * const cbs,
+  void *user_data
 ) {
   // init cache
   sok_cache_t cache;
   if (!sok_cache_init(&cache, SOK_CACHE_DEFAULT_CAPACITY)) {
-    on_error("sok_cache_init() failed");
+    if (cbs && cbs->on_error) {
+      cbs->on_error("sok_cache_init() failed", user_data);
+    }
+
+    // return failure
     return false;
   }
 
   // solve
-  const bool r = sok_solve_step(ctx, &cache, on_error);
+  const bool r = sok_solve_step(ctx, &cache, cbs, user_data);
 
   // finalize cache
   sok_cache_fini(&cache);
diff --git a/src/core/sok.h b/src/core/sok.h
index 1503b5f..92fb4e7 100644
--- a/src/core/sok.h
+++ b/src/core/sok.h
@@ -245,9 +245,15 @@ _Bool sok_cache_add(sok_cache_t * const, const sok_ctx_t * const);
 /* solve */
 /*********/
 
+typedef struct {
+  _Bool (*on_step)(const sok_ctx_t *, void *);
+  void (*on_error)(const char * const, void *);
+} sok_solve_cbs_t;
+
 _Bool sok_solve(
   sok_ctx_t * const,
-  void (*on_error)(const char * const)
+  const sok_solve_cbs_t * const,
+  void * const
 );
 
 #ifdef __cplusplus
diff --git a/src/sdl/main.c b/src/sdl/main.c
index 46f30c3..c3a9abe 100644
--- a/src/sdl/main.c
+++ b/src/sdl/main.c
@@ -60,11 +60,18 @@ load_font(
 
 static void
 solve_on_error(
-  const char * const err
+  const char * const err,
+  void *user_data
 ) {
+  UNUSED(user_data);
   die("Error solving level: %s", err);
 }
 
+static const sok_solve_cbs_t
+SOLVE_CBS = {
+  .on_error = solve_on_error,
+};
+
 static void
 set_level(
   draw_ctx_t * const draw_ctx,
@@ -233,7 +240,7 @@ int main(int argc, char *argv[]) {
           // get current number of moves
           const size_t old_num_moves = ctx.num_moves;
 
-          if (sok_solve(&ctx, solve_on_error)) {
+          if (sok_solve(&ctx, &SOLVE_CBS, NULL)) {
             // found solution, print it
             log_moves(&ctx, old_num_moves);
           } else {
diff --git a/src/solve/main.c b/src/solve/main.c
index 140cfc5..b8b966f 100644
--- a/src/solve/main.c
+++ b/src/solve/main.c
@@ -7,11 +7,18 @@
 
 static void
 solve_on_error(
-  const char * const err
+  const char * const err,
+  void *user_data
 ) {
+  UNUSED(user_data);
   die("Error solving level: %s", err);
 }
 
+static const sok_solve_cbs_t
+SOLVE_CBS = {
+  .on_error = solve_on_error,
+};
+
 int main(int argc, char *argv[]) {
   // init context
   sok_ctx_t ctx;
@@ -30,7 +37,7 @@ int main(int argc, char *argv[]) {
     }
 
     // solve level
-    if (!sok_solve(&ctx, solve_on_error)) {
+    if (!sok_solve(&ctx, &SOLVE_CBS, NULL)) {
       die("Couldn't solve level: %d", (int) level_num);
     }
   }
diff --git a/src/text/main.c b/src/text/main.c
index 204da0f..6b7513c 100644
--- a/src/text/main.c
+++ b/src/text/main.c
@@ -10,11 +10,18 @@
 
 static void
 solve_on_error(
-  const char * const err
+  const char * const err,
+  void *data
 ) {
+  UNUSED(data);
   die("Error solving level: %s", err);
 }
 
+static const sok_solve_cbs_t
+SOLVE_CBS = {
+  .on_error = solve_on_error,
+};
+
 static void
 draw_moves(
   const sok_ctx_t * const ctx,
@@ -104,7 +111,7 @@ int main(int argc, char *argv[]) {
         // get current number of moves
         const size_t old_num_moves = ctx.num_moves;
 
-        if (sok_solve(&ctx, solve_on_error)) {
+        if (sok_solve(&ctx, &SOLVE_CBS, NULL)) {
           // found solution, print it
           draw_moves(&ctx, old_num_moves);
         } else {