1 files changed, 74 insertions, 0 deletions
diff --git a/engine/pokemon/correct_nick_errors.asm b/engine/pokemon/correct_nick_errors.asm
new file mode 100644
index 000000000..5d44846bf
--- /dev/null
+++ b/engine/pokemon/correct_nick_errors.asm
@@ -0,0 +1,74 @@
+CorrectNickErrors:: ; 669f
+; error-check monster nick before use
+; must be a peace offering to gamesharkers
+
+; input: de = nick location
+
+	push bc
+	push de
+	ld b, MON_NAME_LENGTH
+
+.checkchar
+; end of nick?
+	ld a, [de]
+	cp "@" ; terminator
+	jr z, .end
+
+; check if this char is a text command
+	ld hl, .textcommands
+	dec hl
+.loop
+; next entry
+	inc hl
+; reached end of commands table?
+	ld a, [hl]
+	cp -1
+	jr z, .done
+
+; is the current char between this value (inclusive)...
+	ld a, [de]
+	cp [hl]
+	inc hl
+	jr c, .loop
+; ...and this one?
+	cp [hl]
+	jr nc, .loop
+
+; replace it with a "?"
+	ld a, "?"
+	ld [de], a
+	jr .loop
+
+.done
+; next char
+	inc de
+; reached end of nick without finding a terminator?
+	dec b
+	jr nz, .checkchar
+
+; change nick to "?@"
+	pop de
+	push de
+	ld a, "?"
+	ld [de], a
+	inc de
+	ld a, "@"
+	ld [de], a
+.end
+; if the nick has any errors at this point it's out of our hands
+	pop de
+	pop bc
+	ret
+
+.textcommands ; 66cf
+; table defining which characters are actually text commands
+; format:
+	;      ≥           <
+	db TX_START,   TX_BOX    + 1
+	db "<PLAY_G>", "<JP_18>" + 1
+	db "<NI>",     "<NO>"    + 1
+	db "<ROUTE>",  "<GREEN>" + 1
+	db "<ENEMY>",  "<ENEMY>" + 1
+	db "<MOM>",    "<TM>"    + 1
+	db "<ROCKET>", "┘"       + 1
+	db -1 ; end