extends Node

const BGM_NUM := 70
const BGM_LOOKUP := 0x043B97
const INST_NUM := 35
const INST_BRR_LOOKUP := 0x043C6F
const INST_LOOP := 0x043CD8
const INST_SR := 0x043D1E
const INST_ADSR := 0x043D64
const SFX_NUM := 8
const SFX_BRR_SPC_TABLE := 0x041F4F + 2 # (first two bytes are the length of 0x0020 = 32 bytes = 4*8)
const SFX_BRR_START := 0x041E3F + 2  # First two bytes are the length of the block, 0x010E = 270 bytes = 16 BRR packets = 480 samples
const SFX_ADSR := 0x041F71
const SFX_SR := 0x041F83
var bgm_tracks = []
var instrument_samples = []
var sfx_samples = []

func read_rom_address(rom: File) -> int:
	# Read a 3-byte little-endian address and wrap the bank to ROM space
	return rom.get_16() + ((rom.get_8() & 0x3F) << 16)

const MAX_15B = 1 << 15
const MAX_16B = 1 << 16
func unsigned16_to_signed(unsigned):
	return (unsigned + MAX_15B) % MAX_16B - MAX_15B

func get_reference_pitch_samplerate(tuning1: int, tuning2: int = 0) -> int:
	# This is non-trivial and subject to change
	var pitch_scale = tuning1/256.0 + tuning2/65536.0
	if tuning1 < 0x80:
		pitch_scale += 1.0
	return int(pitch_scale * 36000)
	# return (unsigned16_to_signed(pitch) + 0x8000) * 32000/4096

func process_sample(mantissa: int, exponent: int) -> int:
	# For filter arithmetic the samples need to be in signed form.
	# Sign-extend
	if mantissa >= 8:
		mantissa |= 0xFFF0
	if exponent > 12:
		exponent = 12
	var unsigned = (mantissa << exponent) & 0xFFFF
	return unsigned16_to_signed(unsigned)

func decode_brr(data: PoolByteArray):
	# Decodes a single 9byte BRR packet
	var exponent := data[0] >> 4
	var filter_designation := (data[0] >> 2) & 0x03
	var loop := bool(data[0] & 0x02)
	var end := bool(data[0] & 0x01)
	var samples := []
	for i in range(1, 9):
		var b := data[i]
		samples.append(process_sample(b >> 4, exponent))
		samples.append(process_sample(b & 0x0F, exponent))
	return [samples, loop, end, filter_designation]


func clamp_short(i: int):
	return min(max(i, -0x8000), 0x7FFF)

func make_sample(rom: File, size: int, sample_rate: int) -> AudioStreamSample:
	var audio := AudioStreamSample.new()
	audio.mix_rate = sample_rate
	audio.stereo = false
	audio.set_format(AudioStreamSample.FORMAT_16_BITS)

	if (size % 9) != 0:
		print_debug('Oh no! An instrument sample has an invalid size of %d! at $%06X' % [size, rom.get_position()-2])
		return audio

	var samples = [0, 0]  # Two zero samples for filter purposes, strip them from the actual output
	for pkt in (size / 9):
		var data = decode_brr(rom.get_buffer(9))
		samples.append_array(data[0])
		#var loop = data[1]
		var end = data[2]
		var filter = data[3]
		match filter:
			1:
				for i in range(samples.size()-8, samples.size()):
					samples[i] = clamp_short(samples[i] + (samples[i-1]*15)/16)
			2:
				for i in range(samples.size()-8, samples.size()):
					samples[i] = clamp_short(samples[i] + (samples[i-1]*61)/32 - (samples[i-2]*15)/16)
			3:
				for i in range(samples.size()-8, samples.size()):
					samples[i] = clamp_short(samples[i] + (samples[i-1]*115)/64 - (samples[i-2]*13)/16)
		if end:
			# print('End flag on packet')
			break
	var audio_data = PoolByteArray()
	for i in range(2, samples.size()):
		var b = samples[i]
		audio_data.append(b & 0xFF)
		audio_data.append(b >> 8)
	audio.data = audio_data
	return audio

func get_inst_sample_data(rom: File, id: int) -> AudioStreamSample:
	rom.seek(INST_SR + (id*2))
	var tuning1 := rom.get_8()
	var tuning2 := rom.get_8()
	var sample_rate := get_reference_pitch_samplerate(tuning1)

	rom.seek(INST_LOOP + (id*2))
	var loop_start_packet := rom.get_16()/9  # Note that Instrument $1F Steel Guitar has a length of $088B but a loop point of $088D which is 243.22... packets. Luckily it doesn't matter.


	var lookup_offset := INST_BRR_LOOKUP + (id*3)
	rom.seek(lookup_offset)
	var brr_offset := read_rom_address(rom)
	rom.seek(brr_offset)
	var size := rom.get_16()
	var num_samples := (size/9)*16
	var audio := make_sample(rom, size, sample_rate)
	audio.loop_mode = AudioStreamSample.LOOP_FORWARD
	audio.loop_begin = loop_start_packet * 16  # Each 9byte packet is 16 samples
	audio.loop_end = num_samples-1
	print_debug('Loaded instrument #%02X with lookup offset $%06X, BRR data offset $%06X, length $%04X (%f packets, %d samples) and loop point %d samples' % [id, lookup_offset, brr_offset, size, size/9.0, num_samples, audio.loop_begin])
	return audio

func load_sfx_samples_data(rom: File):
	var sample_rates = []
	rom.seek(SFX_SR)
	for i in SFX_NUM:
		var tuning1 := rom.get_8()
		var tuning2 := rom.get_8()
		sample_rates.append(get_reference_pitch_samplerate(tuning1))
	var brr_spc_addrs = []
	var brr_spc_loop_addrs = []
	rom.seek(SFX_BRR_SPC_TABLE)
	for i in SFX_NUM:
		brr_spc_addrs.append(rom.get_16())
		brr_spc_loop_addrs.append(rom.get_16())
	var brr_spc_start = brr_spc_addrs[0]
	for i in SFX_NUM:
		brr_spc_addrs[i] += SFX_BRR_START - brr_spc_start
	for i in SFX_NUM:
		rom.seek(brr_spc_addrs[i])
		# print('Loading sfx sample #%X with BRR data offset $%06X' % [i, rom.get_position()])
		sfx_samples.append(make_sample(rom, 900, sample_rates[i]))  # Use 900 as a limit, it won't be hit, parser stops after End packet anyway
		# print('size of %d samples' % sfx_samples[i].data.size())


# Called when the node enters the scene tree for the first time.
func load_samples(rom: File):
	load_sfx_samples_data(rom)
	for i in INST_NUM:
		instrument_samples.append(get_inst_sample_data(rom, i))





func get_song_data(rom: File, id: int):
	var lookup_offset := BGM_LOOKUP + (id*3)
	rom.seek(lookup_offset)
	var offset := read_rom_address(rom)
	var bank := offset & 0xFF0000
	rom.seek(offset)
	var _block_size := rom.get_16()  # Unused since we pull the individual tracks
	var track_ptrs = []
	for i in 10:
		var a := bank + rom.get_16()
		if a < offset:
			a += 0x010000  # Bank shift
		track_ptrs.append(a)

	if track_ptrs[0] != track_ptrs[1]:
		print('Master is not channel 1, interesting', track_ptrs)
	var tracks = []
	for i in range(1, track_ptrs.size()-1):
		var length = track_ptrs[i+1] - track_ptrs[i]
		tracks.append(rom.get_buffer(length))
	return tracks

func load_bgms(rom: File):
	for i in BGM_NUM:
		bgm_tracks.append(get_song_data(rom, i))






var player := AudioStreamPlayer.new()  # Make one for each channel, later
func play_sample(id: int):
	print('Playing sample #%02X' % id)
	player.stream = instrument_samples[id]
	player.play()

func play_sfx(id: int):
	print('Playing sample #%02X' % id)
	player.stream = sfx_samples[id]
	player.play()

func parse_rom(rom: File):
	load_samples(rom)
	load_bgms(rom)

func _ready() -> void:
	add_child(player)

# Called every frame. 'delta' is the elapsed time since the previous frame.
#func _process(delta: float) -> void:
#	pass