+
+#include <stdio.h>
+#include <assert.h>
+
+#include "puzzles.h"
+
+struct midend_data {
+ char *seed;
+ int nstates, statesize, statepos;
+ game_params *params;
+ game_state **states;
+};
+
+#define ensure(me) do { \
+ if ((me)->nstates >= (me)->statesize) { \
+ (me)->statesize = (me)->nstates + 128; \
+ (me)->states = sresize((me)->states, (me)->statesize, game_state *); \
+ } \
+} while (0)
+
+midend_data *midend_new(void)
+{
+ midend_data *me = snew(midend_data);
+
+ me->nstates = me->statesize = me->statepos = 0;
+ me->states = NULL;
+ me->params = default_params();
+ me->seed = NULL;
+
+ return me;
+}
+
+void midend_free(midend_data *me)
+{
+ sfree(me->states);
+ sfree(me->seed);
+ free_params(me->params);
+ sfree(me);
+}
+
+void midend_size(midend_data *me, int *x, int *y)
+{
+ game_size(me->params, x, y);
+}
+
+void midend_set_params(midend_data *me, game_params *params)
+{
+ free_params(me->params);
+ me->params = params;
+}
+
+void midend_new_game(midend_data *me, char *seed)
+{
+ while (me->nstates > 0)
+ free_game(me->states[--me->nstates]);
+
+ assert(me->nstates == 0);
+
+ sfree(me->seed);
+ if (seed)
+ me->seed = dupstr(seed);
+ else
+ me->seed = new_game_seed(me->params);
+
+ ensure(me);
+ me->states[me->nstates++] = new_game(me->params, me->seed);
+ me->statepos = 1;
+}
+
+void midend_restart_game(midend_data *me)
+{
+ while (me->nstates > 1)
+ free_game(me->states[--me->nstates]);
+ me->statepos = me->nstates;
+}
+
+void midend_undo(midend_data *me)
+{
+ if (me->statepos > 1)
+ me->statepos--;
+}
+
+void midend_redo(midend_data *me)
+{
+ if (me->statepos < me->nstates)
+ me->statepos++;
+}
+
+int midend_process_key(midend_data *me, int x, int y, int button)
+{
+ game_state *s;
+
+ if (button == 'n' || button == 'N' || button == '\x0E') {
+ midend_new_game(me, NULL);
+ return 1;
+ } else if (button == 'r' || button == 'R') {
+ midend_restart_game(me);
+ return 1;
+ } else if (button == 'u' || button == 'u' ||
+ button == '\x1A' || button == '\x1F') {
+ midend_undo(me);
+ return 1;
+ } else if (button == '\x12') {
+ midend_redo(me);
+ return 1;
+ } else if (button == 'q' || button == 'Q' || button == '\x11') {
+ return 0;
+ }
+
+ s = make_move(me->states[me->statepos-1], x, y, button);
+
+ if (s) {
+ while (me->nstates > me->statepos)
+ free_game(me->states[--me->nstates]);
+ ensure(me);
+ me->states[me->nstates] = s;
+ me->statepos = ++me->nstates;
+ }
+
+ return 1;
+}