INCLUDE "charmap.asm"

; bit 0-1: sram bank
; bit 2: bootstrap or execute
; bit 3: specify bootstrap mail buffer scratch dest
; bit 4: base16 or hex encoding. base16 assumes little endian, hex encoding assumes big endian
; if upper 7 bits are %1110001 (- or /), execute directly. bit 4 corresponds to jump encoding

wBoxNames EQU $d8bf
OpenSRAM EQU $30e1
CloseSRAM EQU $30f1
jp_de EQU $30fd
CopyBytes EQU $311a
wOverworldMap EQU $c700
_ComposeMailMessage EQU $6242
wJumptableIndex EQU $ce63

SECTION "Bootstrap", ROM0

callw: MACRO
	if _NARG == 1
		call \1 + $d6f3
	else
		call \1, \2 + $d6f3
	endc
ENDM

Bootstrap::
	ld a, [wJumptableIndex]
	push af
	callw _Bootstrap
	pop af
	ld [wJumptableIndex], a
	ret

_Bootstrap:
	ld hl, wBoxNames
	ld a, [hli]
	ld b, a
	callw DecodeCharPairPointer
	ld h, d
	ld l, e ; hl = bootstrap dest or execute src
	ld a, b
	and "-"
	cp "-"
	jr nz, .notDirectExecute
	jp hl
.notDirectExecute
	bit 2, b
	jr z, .bootstrap
	ld a, b
	and $3
	call OpenSRAM
	ld a, [hli]
	ld b, a
	ld a, [hli]
	ld c, a
	ld a, [hli]
	ld e, a
	ld a, [hli]
	ld d, a
	push de ; execute dest
	call CopyBytes
	call jp_de + 1 ; skip push de as de is already pushed
	jr .closeSRAM
.bootstrap
	push bc ; save flags for later
	push de ; save dest for later
	bit 3, b
	ld de, wOverworldMap + $55 ; mail buffer dest
	ld hl, wBoxNames + 9
	callw nz, DecodeCharPairPointer
	push de ; save mail buffer dest for later
.getBootstrapCharsLoop
	ld hl, _ComposeMailMessage
	ld a, $4
	rst $08
	dec de
	ld a, [de]
	inc de
	cp "!"
	jr nz, .getBootstrapCharsLoop
	pop hl ; mail buffer
	pop de ; dest
	pop af ; save a byte here as b goes into a
	and $3 ; bank
	call OpenSRAM
	callw CharPairDecode
	ld [de], a
	inc de
	callw CharPairDecode
	ld [de], a
	inc de
	push de ; save count dest for later
	inc de
	inc de
	ld bc, 0
.bootstrapCopyLoop
	callw CharPairDecode
	ld [de], a
	inc de
	inc bc
	ld a, [hl]
	cp "!"
	jr nz, .bootstrapCopyLoop
	pop hl
	ld a, b
	ld [hli], a
	ld [hl], c
.closeSRAM
	jp CloseSRAM

DecodeCharPairPointer:
	callw CharPairDecode
	ld d, a
	callw CharPairDecode
	ld e, a
	ret

CharPairDecode:
	push bc
	ld a, [wBoxNames]
	bit 4, a
	jr nz, .HexDecode
; fallthrough

.Base16Decode:
	callw ReadAndFilterChar
	add a
	add a
	add a
	add a
	ld b, a
	callw ReadAndFilterChar
	and $f
	jr .orPopAndReturn

.HexDecode:
	callw HexDecodeChar
	add a
	add a
	add a
	add a
	ld b, a
	callw HexDecodeChar
.orPopAndReturn
	or b
	pop bc
	ret

HexDecodeChar:
; saves 1 byte
	callw ReadAndFilterChar
	sub "0"
	ret nc
	add ("0" - "A" + $0a)
	ret

ReadAndFilterChar:
	ld a, [hli]
	cp $4e
	ret nz
	ld a, [hli]
	ret