Remove all code from main.asm (some labeled INCBINs, like out-of-context graphics, are still present)

engine/routines/ stores isolated out-of-context routines as individual files. It might be preferable later to append them to their related engine/ files in unique little SECTIONs, relying on the linkerscript to place them appropriately; or some other organization method. In the meantime, they're now easily findable apart from main.asm's other content.

engine/routines/switchpartymons.asm

@@ -0,0 +1,145 @@
+_SwitchPartyMons:
+	ld a, [wd0e3]
+	dec a
+	ld [Buffer3], a
+	ld b, a
+	ld a, [wMenuCursorY]
+	dec a
+	ld [Buffer2], a
+	cp b
+	jr z, .skip
+	call .SwapMonAndMail
+	ld a, [Buffer3]
+	call .ClearSprite
+	ld a, [Buffer2]
+	call .ClearSprite
+.skip
+	ret
+
+.ClearSprite: ; 50f34 (14:4f34)
+	push af
+	hlcoord 0, 1
+	ld bc, 2 * SCREEN_WIDTH
+	call AddNTimes
+	ld bc, 2 * SCREEN_WIDTH
+	ld a, " "
+	call ByteFill
+	pop af
+	ld hl, Sprites
+	ld bc, $10
+	call AddNTimes
+	ld de, $4
+	ld c, $4
+.gfx_loop
+	ld [hl], $a0
+	add hl, de
+	dec c
+	jr nz, .gfx_loop
+	ld de, SFX_SWITCH_POKEMON
+	call WaitPlaySFX
+	ret
+
+.SwapMonAndMail: ; 50f62 (14:4f62)
+	push hl
+	push de
+	push bc
+	ld bc, PartySpecies
+	ld a, [Buffer2]
+	ld l, a
+	ld h, $0
+	add hl, bc
+	ld d, h
+	ld e, l
+	ld a, [Buffer3]
+	ld l, a
+	ld h, $0
+	add hl, bc
+	ld a, [hl]
+	push af
+	ld a, [de]
+	ld [hl], a
+	pop af
+	ld [de], a
+	ld a, [Buffer2]
+	ld hl, PartyMon1Species
+	ld bc, PARTYMON_STRUCT_LENGTH
+	call AddNTimes
+	push hl
+	ld de, wd002
+	ld bc, PARTYMON_STRUCT_LENGTH
+	call CopyBytes
+	ld a, [Buffer3]
+	ld hl, PartyMon1
+	ld bc, PARTYMON_STRUCT_LENGTH
+	call AddNTimes
+	pop de
+	push hl
+	ld bc, PARTYMON_STRUCT_LENGTH
+	call CopyBytes
+	pop de
+	ld hl, wd002
+	ld bc, PARTYMON_STRUCT_LENGTH
+	call CopyBytes
+	ld a, [Buffer2]
+	ld hl, PartyMonOT
+	call SkipNames
+	push hl
+	call .CopyNameTowd002
+	ld a, [Buffer3]
+	ld hl, PartyMonOT
+	call SkipNames
+	pop de
+	push hl
+	call .CopyName
+	pop de
+	ld hl, wd002
+	call .CopyName
+	ld hl, PartyMonNicknames
+	ld a, [Buffer2]
+	call SkipNames
+	push hl
+	call .CopyNameTowd002
+	ld hl, PartyMonNicknames
+	ld a, [Buffer3]
+	call SkipNames
+	pop de
+	push hl
+	call .CopyName
+	pop de
+	ld hl, wd002
+	call .CopyName
+	ld hl, sPartyMail
+	ld a, [Buffer2]
+	ld bc, MAIL_STRUCT_LENGTH
+	call AddNTimes
+	push hl
+	ld de, wd002
+	ld bc, MAIL_STRUCT_LENGTH
+	ld a, BANK(sPartyMail)
+	call GetSRAMBank
+	call CopyBytes
+	ld hl, sPartyMail
+	ld a, [Buffer3]
+	ld bc, MAIL_STRUCT_LENGTH
+	call AddNTimes
+	pop de
+	push hl
+	ld bc, MAIL_STRUCT_LENGTH
+	call CopyBytes
+	pop de
+	ld hl, wd002
+	ld bc, MAIL_STRUCT_LENGTH
+	call CopyBytes
+	call CloseSRAM
+	pop bc
+	pop de
+	pop hl
+	ret
+
+.CopyNameTowd002: ; 51036 (14:5036)
+	ld de, wd002
+
+.CopyName: ; 51039 (14:5039)
+	ld bc, NAME_LENGTH
+	call CopyBytes
+	ret