Implemented status reduction potion support

* New script command `needed_status_point` added.
* The items are not yet implemented.

doc/script_commands.txt

@@ -4294,6 +4294,14 @@ This command will force a stat recalculation for the attached player.
 
 ---------------------------------------
 
+*needed_status_point(<type>,<val>{,<char id>});
+
+Returns the number of stat points needed to change the specified stat <type> by <val>.
+If <val> is negative, returns the number of stat points that would be needed to
+raise the specified stat from (current value - <val>) to current value.
+
+---------------------------------------
+
 *get_revision()
 
 This command will return the SVN revision number that the server is currently

npc/other/CashShop_Functions.txt

@@ -304,3 +304,23 @@ function	script	F_Snowball	{
 	}
 	end;
 }
+
+// Status reduction potion
+//============================================================
+// - Permanently reduces base stat <type> by 1.
+// - Returns status points equals to points needed to raise
+//   that stat to original value.
+// - Doesn't work if base status <type> is already 1.
+// * callfunc("F_CashReduceStat",<type>{,<itemid>});
+function	script	F_CashReduceStat	{
+	.@type = getarg(0);
+	.@itemid = getarg(1, 0);
+
+	if(readparam(.@type) < 2) return;
+
+	if(.@itemid)
+		delitem .@itemid,1;
+	StatusPoint += needed_status_point(.@type, -1);
+	statusup2 .@type,-1;
+	return;
+}

src/map/script.c

@@ -21661,6 +21661,22 @@ BUILDIN_FUNC(setrandomoption) {
 	return SCRIPT_CMD_FAILURE;
 }
 
+/// Returns the number of stat points needed to change the specified stat by val.
+/// If val is negative, returns the number of stat points that would be needed to
+/// raise the specified stat from (current value - val) to current value.
+/// *needed_status_point(<type>,<val>{,<char id>});
+/// @author [secretdataz]
+BUILDIN_FUNC(needed_status_point) {
+	struct map_session_data *sd;
+	int type, val;
+	if (!script_charid2sd(4, sd))
+		return SCRIPT_CMD_FAILURE;
+	type = script_getnum(st, 2);
+	val = script_getnum(st, 3);
+
+	script_pushint(st, pc_need_status_point(sd, type, val));
+	return SCRIPT_CMD_SUCCESS;
+}
 #include "../custom/script.inc"
 
 // declarations that were supposed to be exported from npc_chat.c
@@ -22243,6 +22259,7 @@ struct script_function buildin_func[] = {
 	BUILDIN_DEF(getrandomoptinfo, "i"),
 	BUILDIN_DEF(getequiprandomoption, "iii?"),
 	BUILDIN_DEF(setrandomoption,"iiiii?"),
+	BUILDIN_DEF(needed_status_point,"ii?"),
 
 #include "../custom/script_def.inc"