1 files changed, 215 insertions, 0 deletions
diff --git a/engine/overworld/missable_objects.asm b/engine/overworld/missable_objects.asm
new file mode 100644
index 00000000..8587c0f7
--- /dev/null
+++ b/engine/overworld/missable_objects.asm
@@ -0,0 +1,215 @@
+MarkTownVisitedAndLoadMissableObjects:
+	ld a, [wCurMap]
+	cp ROUTE_1
+	jr nc, .notInTown
+	ld c, a
+	ld b, FLAG_SET
+	ld hl, wTownVisitedFlag   ; mark town as visited (for flying)
+	predef FlagActionPredef
+.notInTown
+	ld hl, MapHSPointers
+	ld a, [wCurMap]
+	ld b, $0
+	ld c, a
+	add hl, bc
+	add hl, bc
+	ld a, [hli]                ; load missable objects pointer in hl
+	ld h, [hl]
+	; fall through
+
+LoadMissableObjects:
+	ld l, a
+	push hl
+	ld de, MapHS00             ; calculate difference between out pointer and the base pointer
+	ld a, l
+	sub e
+	jr nc, .asm_f13c
+	dec h
+.asm_f13c
+	ld l, a
+	ld a, h
+	sub d
+	ld h, a
+	ld a, h
+	ld [H_DIVIDEND], a
+	ld a, l
+	ld [H_DIVIDEND+1], a
+	xor a
+	ld [H_DIVIDEND+2], a
+	ld [H_DIVIDEND+3], a
+	ld a, $3
+	ld [H_DIVISOR], a
+	ld b, $2
+	call Divide                ; divide difference by 3, resulting in the global offset (number of missable items before ours)
+	ld a, [wCurMap]
+	ld b, a
+	ld a, [H_DIVIDEND+3]
+	ld c, a                    ; store global offset in c
+	ld de, wMissableObjectList
+	pop hl
+.writeMissableObjectsListLoop
+	ld a, [hli]
+	cp $ff
+	jr z, .done     ; end of list
+	cp b
+	jr nz, .done    ; not for current map anymore
+	ld a, [hli]
+	inc hl
+	ld [de], a                 ; write (map-local) sprite ID
+	inc de
+	ld a, c
+	inc c
+	ld [de], a                 ; write (global) missable object index
+	inc de
+	jr .writeMissableObjectsListLoop
+.done
+	ld a, $ff
+	ld [de], a                 ; write sentinel
+	ret
+
+InitializeMissableObjectsFlags:
+	ld hl, wMissableObjectFlags
+	ld bc, wMissableObjectFlagsEnd - wMissableObjectFlags
+	xor a
+	call FillMemory ; clear missable objects flags
+	ld hl, MapHS00
+	xor a
+	ld [wMissableObjectCounter], a
+.missableObjectsLoop
+	ld a, [hli]
+	cp $ff          ; end of list
+	ret z
+	push hl
+	inc hl
+	ld a, [hl]
+	cp Hide
+	jr nz, .skip
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectCounter]
+	ld c, a
+	ld b, FLAG_SET
+	call MissableObjectFlagAction ; set flag if Item is hidden
+.skip
+	ld hl, wMissableObjectCounter
+	inc [hl]
+	pop hl
+	inc hl
+	inc hl
+	jr .missableObjectsLoop
+
+; tests if current sprite is a missable object that is hidden/has been removed
+IsObjectHidden:
+	ld a, [H_CURRENTSPRITEOFFSET]
+	swap a
+	ld b, a
+	ld hl, wMissableObjectList
+.loop
+	ld a, [hli]
+	cp $ff
+	jr z, .notHidden ; not missable -> not hidden
+	cp b
+	ld a, [hli]
+	jr nz, .loop
+	ld c, a
+	ld b, FLAG_TEST
+	ld hl, wMissableObjectFlags
+	call MissableObjectFlagAction
+	ld a, c
+	and a
+	jr nz, .hidden
+.notHidden
+	xor a
+.hidden
+	ld [$ffe5], a
+	ret
+
+; adds missable object (items, leg. pokemon, etc.) to the map
+; [wMissableObjectIndex]: index of the missable object to be added (global index)
+ShowObject:
+ShowObject2:
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectIndex]
+	ld c, a
+	ld b, FLAG_RESET
+	call MissableObjectFlagAction   ; reset "removed" flag
+	jp UpdateSprites
+
+; removes missable object (items, leg. pokemon, etc.) from the map
+; [wMissableObjectIndex]: index of the missable object to be removed (global index)
+HideObject:
+	ld hl, wMissableObjectFlags
+	ld a, [wMissableObjectIndex]
+	ld c, a
+	ld b, FLAG_SET
+	call MissableObjectFlagAction   ; set "removed" flag
+	jp UpdateSprites
+
+MissableObjectFlagAction:
+; identical to FlagAction
+
+	push hl
+	push de
+	push bc
+
+	; bit
+	ld a, c
+	ld d, a
+	and 7
+	ld e, a
+
+	; byte
+	ld a, d
+	srl a
+	srl a
+	srl a
+	add l
+	ld l, a
+	jr nc, .ok
+	inc h
+.ok
+
+	; d = 1 << e (bitmask)
+	inc e
+	ld d, 1
+.shift
+	dec e
+	jr z, .shifted
+	sla d
+	jr .shift
+.shifted
+
+	ld a, b
+	and a
+	jr z, .reset
+	cp 2
+	jr z, .read
+
+.set
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	or b
+	ld [hl], a
+	jr .done
+
+.reset
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	xor $ff
+	and b
+	ld [hl], a
+	jr .done
+
+.read
+	ld a, [hl]
+	ld b, a
+	ld a, d
+	and b
+
+.done
+	pop bc
+	pop de
+	pop hl
+	ld c, a
+	ret