--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/libmlk-rpg/rpg/battle-entity-state-moving.c	Fri Oct 01 20:30:00 2021 +0200
@@ -0,0 +1,111 @@
+/*
+ * battle-entity-state-moving.c -- the entity is moving
+ *
+ * Copyright (c) 2020-2021 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <math.h>
+#include <stdlib.h>
+
+#include <core/alloc.h>
+#include <core/panic.h>
+
+#include "battle-entity.h"
+#include "battle-entity-state.h"
+#include "character.h"
+#include "walksprite.h"
+
+#define SPEED 800
+#define SEC   1000
+#define WALK  40
+
+struct position {
+	struct battle_entity_state state;
+	struct walksprite ws;
+
+	/* Destination. */
+	int x;
+	int y;
+};
+
+static inline unsigned int
+orientation(const struct position *pos, const struct battle_entity *et)
+{
+	/* TODO: support diagonal. */
+	/* See: walksprite definitions. */
+	return pos->x < et->x ? 6 : 2;
+}
+
+static int
+update(struct battle_entity_state *st, struct battle_entity *et, unsigned int ticks)
+{
+	struct position *pos = st->data;
+	int step_x, step_y, delta_x, delta_y;
+
+	delta_x = pos->x < et->x ? -1 : +1;
+	delta_y = pos->y < et->y ? -1 : +1;
+	step_x = fmin(SPEED * ticks / SEC, abs(et->x - pos->x));
+	step_y = fmin(SPEED * ticks / SEC, abs(et->y - pos->y));
+
+	et->x += delta_x * step_x;
+	et->y += delta_y * step_y;
+
+	if (et->x != pos->x || et->y != pos->y)
+		walksprite_update(&pos->ws, ticks);
+	else
+		walksprite_reset(&pos->ws);
+
+	return et->x == pos->x && et->y == pos->y;
+}
+
+static void
+draw(const struct battle_entity_state *st, const struct battle_entity *et)
+{
+	/* TODO: compute orientation. */
+	struct position *pos = st->data;
+
+	walksprite_draw(&pos->ws, orientation(pos, et), et->x, et->y);
+}
+
+static void
+finish(struct battle_entity_state *st, struct battle_entity *et)
+{
+	(void)et;
+
+	free(st->data);
+}
+
+void
+battle_entity_state_moving(struct battle_entity *et, int destx, int desty)
+{
+	assert(et);
+
+	struct position *pos;
+
+	if (!(pos = alloc_new0(sizeof (*pos))))
+		panic();
+
+	walksprite_init(&pos->ws, et->ch->sprites[CHARACTER_SPRITE_NORMAL], 40);
+	pos->x = destx;
+	pos->y = desty;
+
+	pos->state.data = pos;
+	pos->state.update = update;
+	pos->state.draw = draw;
+	pos->state.finish = finish;
+
+	battle_entity_switch(et, &pos->state);
+}