#!/usr/bin/env python3
import random
import sys

import pyglet

# TODO: Don't hardcode keyboard input
keypad_keys = [
	pyglet.window.key._1, pyglet.window.key._2, pyglet.window.key._3, pyglet.window.key._4,
	pyglet.window.key.Q, pyglet.window.key.W, pyglet.window.key.E, pyglet.window.key.R,
	pyglet.window.key.A, pyglet.window.key.S, pyglet.window.key.D, pyglet.window.key.F,
	pyglet.window.key.Z, pyglet.window.key.X, pyglet.window.key.C, pyglet.window.key.V,
]
keypad_keys = list(zip(keypad_keys, [
	pyglet.window.key.NUM_7, pyglet.window.key.NUM_8, pyglet.window.key.NUM_9, pyglet.window.key.NUM_SUBTRACT,
	pyglet.window.key.NUM_4, pyglet.window.key.NUM_5, pyglet.window.key.NUM_6, pyglet.window.key.NUM_ADD,
	pyglet.window.key.NUM_1, pyglet.window.key.NUM_2, pyglet.window.key.NUM_3, pyglet.window.key.NUM_ENTER,
	pyglet.window.key.NUM_DIVIDE, pyglet.window.key.NUM_0, pyglet.window.key.NUM_MULTIPLY, pyglet.window.key.NUM_SEPARATOR,
]))
# OSCOM Nano keys are arranged like
# 123C
# 456D
# 789E
# A0BF
# according to http://hobbylabs.org/oscom_nano.htm
# However, at the moment the indices of the keys are
# 0123
# 4567
# 89ab
# cdef
# This rearranges them so that the index and the hex digit match
keypad_keys = [keypad_keys[i] for i in [0xd, 0, 1, 2, 4, 5, 6, 8, 9, 0xa, 0xc, 0xe, 3, 7, 0xb, 0xf]]

def key_pressed(symbol):
	global keys_pressed, keypress_arrived
	for i in range(16):
		if symbol in keypad_keys[i]:
			keys_pressed[i] = True
			keypress_arrived = True
			break

def key_released(symbol):
	global keys_pressed
	for i in range(16):
		if symbol in keypad_keys[i]:
			keys_pressed[i] = False
			break

def draw_screen():
	global display_screen
	to_draw = []
	for y in range(32):
		for x in range(64):
			if display_screen[y * 64 + x]:
				to_draw.append((x, y))

	screen_points = []
	for x, y in to_draw:
		# pyglet has 0,0 at bottom left, so reverse the y
		y = 31 - y

		# TODO: Don't hardcode pixel size
		# Lol, what is a winding order
		screen_points.append(x * 10)
		screen_points.append(y * 10)

		screen_points.append(x * 10 + 10)
		screen_points.append(y * 10)

		screen_points.append(x * 10 + 10)
		screen_points.append(y * 10 + 10)

		screen_points.append(x * 10)
		screen_points.append(y * 10 + 10)

	if len(screen_points) > 0:
		pyglet.graphics.draw(len(screen_points) // 2,
			pyglet.gl.GL_QUADS,
			('v2i', screen_points)
		)

def step():
	global data_registers, ip, stack, i_register
	global ram, font_start
	global screen
	global delay_timer, sound_timer
	global keys_pressed, waiting_for_keypress, keypress_arrived

	# Keep track of whether we did a draw or a jump, for the draw
	# sprint feature
	did_draw = False
	did_jump = False

	# Don't execute any code in a waitstate, as it'd only end up
	# busylooping
	if waiting_for_keypress and not keypress_arrived: return did_draw, did_jump

	high_byte = ram[ip]
	ip = (ip + 1) & 0xfff
	low_byte = ram[ip]
	ip = (ip + 1) & 0xfff

	#print(hex(high_byte), hex(low_byte), hex(ip), [hex(i) for i in data_registers], [hex(i) for i in stack], hex(i_register), delay_timer)#debg
	#input()#debg

	# Instruction info gotten from http://mattmik.com/files/chip8/mastering/chip8.html

	# 00E0 clearscreen
	if high_byte == 0x00 and low_byte == 0xE0:
		screen = [False] * 64 * 32

	# 00EE ret
	elif high_byte == 0x00 and low_byte == 0xEE:
		ip = stack.pop()
		did_jump = True

	# 0nnn call_machine
	elif high_byte >> 4 == 0:
		# Our own non-standard debug
		if high_byte & 0xf == 0x1:
			print(low_byte & 0xf, data_registers[low_byte & 0xf])
		else:
			print("%03x: Can't call machine language!" % (ip - 2))
			sys.exit(1)

	# 1nnn jmp nnn
	elif high_byte >> 4 == 1:
		ip = ((high_byte & 0xf) << 8) | low_byte
		did_jump = True

	# 2nnn call nnn
	elif high_byte >> 4 == 2:
		stack.append(ip)
		ip = ((high_byte & 0xf) << 8) | low_byte
		did_jump = True

	# 3xnn skipeq vx, nn
	elif high_byte >> 4 == 3:
		if data_registers[high_byte & 0xf] == low_byte:
			ip = (ip + 2) & 0xfff

	# 4xnn skipneq vx, nn
	elif high_byte >> 4 == 4:
		if data_registers[high_byte & 0xf] != low_byte:
			ip = (ip + 2) & 0xfff

	# 5xy0 skipeq vx, vy
	elif high_byte >> 4 == 5 and low_byte & 0xf == 0:
		if data_registers[high_byte & 0xf] == data_registers[low_byte >> 4]:
			ip = (ip + 2) & 0xfff

	# 6xnn mov vx, nn
	elif high_byte >> 4 == 6:
		data_registers[high_byte & 0xf] = low_byte

	# 7xnn add vx, nn (no flags)
	elif high_byte >> 4 == 7:
		old_value = data_registers[high_byte & 0xf]
		data_registers[high_byte & 0xf] = (old_value + low_byte) & 0xff

	# 8xy0 mov vx, vy
	elif high_byte >> 4 == 8 and low_byte & 0xf == 0:
		data_registers[high_byte & 0xf] = data_registers[low_byte >> 4]

	# 8xy1 or vx, vy
	elif high_byte >> 4 == 8 and low_byte & 0xf == 1:
		old_value = data_registers[high_byte & 0xf]
		result = old_value | data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = result

	# 8xy2 and vx, vy
	elif high_byte >> 4 == 8 and low_byte & 0xf == 2:
		old_value = data_registers[high_byte & 0xf]
		result = old_value & data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = result

	# 8xy3 xor vx, vy
	elif high_byte >> 4 == 8 and low_byte & 0xf == 3:
		old_value = data_registers[high_byte & 0xf]
		result = old_value ^ data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = result

	# 8xy4 add vx, vy (carry flag)
	elif high_byte >> 4 == 8 and low_byte & 0xf == 4:
		old_value = data_registers[high_byte & 0xf]
		result = old_value + data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = result & 0xff
		if result > 255:
			data_registers[0xf] = 1
		else:
			data_registers[0xf] = 0

	# 8xy5 sub vx, vy (carry flag)
	elif high_byte >> 4 == 8 and low_byte & 0xf == 5:
		old_value = data_registers[high_byte & 0xf]
		result = old_value - data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = result & 0xff
		if result < 0:
			data_registers[0xf] = 0
		else:
			data_registers[0xf] = 1

	# 8xy6 shr vx, vy, 1 (LSB to VF)
	elif high_byte >> 4 == 8 and low_byte & 0xf == 6:
		other_value = data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = other_value >> 1
		data_registers[0xf] = other_value & 0x1

	# 8xy7 sub vx, vy, vx (carry flag)
	elif high_byte >> 4 == 8 and low_byte & 0xf == 7:
		old_value = data_registers[high_byte & 0xf]
		result = data_registers[low_byte >> 4] - old_value
		data_registers[high_byte & 0xf] = result & 0xff
		if result < 0:
			data_registers[0xf] = 0
		else:
			data_registers[0xf] = 1

	# 8xyE shl vx, vy, 1 (MSB to VF)
	elif high_byte >> 4 == 8 and low_byte & 0xf == 0xE:
		other_value = data_registers[low_byte >> 4]
		data_registers[high_byte & 0xf] = (other_value << 1) & 0xff
		data_registers[0xf] = other_value >> 7

	# 9xy0 skipneq vx, vy
	elif high_byte >> 4 == 9 and low_byte & 0xf == 0:
		if data_registers[high_byte & 0xf] != data_registers[low_byte >> 4]:
			ip = (ip + 2) & 0xfff

	# Annn mov i, nnn
	elif high_byte >> 4 == 0xA:
		i_register = ((high_byte & 0xf) << 8) | low_byte

	# Bnnn jmp nnn + v0
	elif high_byte >> 4 == 0xB:
		ip = ((high_byte & 0xf) << 8) | low_byte
		ip = (ip + data_registers[0]) & 0xfff
		did_jump = True

	# Cxnn maskedrandom vx, nn
	elif high_byte >> 4 == 0xC:
		result = random.randint(0, 255)
		data_registers[high_byte & 0xf] = result & low_byte

	# Dxyn draw vx, vy, n
	elif high_byte >> 4 == 0xD:
		# OSCOM Nano manual (page 38) says "<The screen behaves as
		# if the top was connected to the bottom and the sides to
		# each other>", but I can't find any info on how to do this
		# wrapping on the generally used sources.
		#
		# https://github.com/AfBu/haxe-chip-8-emulator looks like
		# it wraps the pixels to the next row down, but as it
		# doesn't seem to handle drawing out the bottom of the
		# screen at all, unsure how intentional this is.
		#
		# https://github.com/dmatlack/chip8 wraps the pixels on the
		# other side of the same line.
		#
		# The game "Blitz" seems to require draws off the bottom of
		# the screen to not result in anything. Therefore, as I
		# have yet to find any games that break with it, I'm just
		# skipping pixels that fall outside the screen.

		did_draw = True

		x_start = data_registers[high_byte & 0xf]
		y_start = data_registers[low_byte >> 4]

		any_unset = False
		# Sprite will be 8 pixels wide and n tall
		for dy in range(low_byte & 0xf):
			# Load this line's graphics
			line = ram[(i_register + dy) & 0xfff]

			y = y_start + dy
			# Screen is 32 lines tall
			if y >= 32:
				continue

			for dx in range(8):
				x = x_start + dx
				# Screen is 64 columns wide
				if x >= 64:
					continue

				# Pixels are stored MSB-left
				pixel = (line >> (7 - dx)) & 1

				screen_index = y * 64 + x

				if pixel:
					# Check if we are unsetting a pixel
					if screen[screen_index]:
						any_unset = True
					# XOR the pixel
					screen[screen_index] = not screen[screen_index]

		if any_unset:
			data_registers[0xf] = 1
		else:
			data_registers[0xf] = 0

	# Ex9E skipkey vx
	elif high_byte >> 4 == 0xE and low_byte == 0x9E:
		if keys_pressed[data_registers[high_byte & 0xf]]:
			ip = (ip + 2) & 0xfff

	# ExA1 skipnkey vx
	elif high_byte >> 4 == 0xE and low_byte == 0xA1:
		if not keys_pressed[data_registers[high_byte & 0xf]]:
			ip = (ip + 2) & 0xfff

	# Fx07 getdelay vx
	elif high_byte >> 4 == 0xF and low_byte == 0x07:
		data_registers[high_byte & 0xf] = delay_timer

	# Fx0A getkey vx
	elif high_byte >> 4 == 0xF and low_byte == 0x0A:
		if not waiting_for_keypress:
			# Wait for a key to be pressed and then re-execute
			# this instruction
			waiting_for_keypress = True
			keypress_arrived = False
			ip = (ip - 2) & 0xfff

		if keypress_arrived:
			# A key was pressed
			for i in range(16):
				if keys_pressed[i]:
					# Set vx to first key we found
					any_pressed = True
					data_registers[high_byte & 0xf] = i
					break

			waiting_for_keypress = False

	# Fx15 setdelay vx
	elif high_byte >> 4 == 0xF and low_byte == 0x15:
		delay_timer = data_registers[high_byte & 0xf]

	# Fx18 setsound vx
	elif high_byte >> 4 == 0xF and low_byte == 0x18:
		sound_timer = data_registers[high_byte & 0xf]

	# Fx1E add i, vx
	elif high_byte >> 4 == 0xF and low_byte == 0x1E:
		i_register = (i_register + data_registers[high_byte & 0xf]) & 0xfff

	# Fx29 mov i, digit(vx)
	elif high_byte >> 4 == 0xF and low_byte == 0x29:
		value = data_registers[high_byte & 0xf]
		if 0 <= value <= 0xf:
			# Each digit is 5 lines tall = 5 bytes long
			i_register = font_start + value * 5

		else:
			print('%03x: Bad font character' % (ip-2))
			sys.exit(1)

	# Fx33 mov [i … i+2], bcd(vx)
	elif high_byte >> 4 == 0xF and low_byte == 0x33:
		value = data_registers[high_byte & 0xf]
		highdigit = value // 100
		middigit = value // 10 % 10
		lowdigit = value % 10
		ram[i_register] = highdigit
		ram[(i_register + 1) & 0xfff] = middigit
		ram[(i_register + 2) & 0xfff] = lowdigit

	# Fx55 mov [i … i+x], v0 … vx (updates i)
	elif high_byte >> 4 == 0xF and low_byte == 0x55:
		for register in range((high_byte & 0xf) + 1):
			ram[i_register] = data_registers[register]
			i_register = (i_register + 1) & 0xfff

	# Fx65 mov v0 … vx, [i … i+x] (updates i)
	elif high_byte >> 4 == 0xF and low_byte == 0x65:
		for register in range((high_byte & 0xf) + 1):
			data_registers[register] = ram[i_register]
			i_register = (i_register + 1) & 0xfff

	# Fallback
	else:
		print('%03x: Unrecognized!' % (ip-2))

	return did_draw, did_jump

def tick_timers():
	global delay_timer, sound_timer

	# Tick the delay timer down until it reaches 0
	if delay_timer > 0:
		# The timer should tick down at 60Hz
		delay_timer -= 1

	# Play a sound using pyglet if we have a non-zero sound timer
	# It will run asynchronously from the other parts, which means it
	# won't experience slowdown similarily to the delay timer
	# Unsure if this is good or bad
	if sound_timer > 0:
		# sound_timer is in the unit of 1/60th of a second, while
		# Square takes length in seconds
		pyglet.media.synthesis.Square(sound_timer/60).play()
		sound_timer = 0

def advance_interpreter(dt):
	global cpu_clock
	global screen, display_screen, screen_fps
	global cpu_cycles_to_go, frames_to_go
	# Each tic (60Hz) we need to run cpu_clock / 60Hz cycles and
	# draw screen_fps / 60 frames
	cpu_cycles_to_go += cpu_clock / 60
	frames_to_go += screen_fps / 60
	tick_timers()
	
	while cpu_cycles_to_go >= 1:
		did_draw, _ = step()
		cpu_cycles_to_go -= 1

		# If we did a draw, run upto two ticks' cycles to reach
		# the next draw. Chip-8 draws are often paired, an erase
		# and a draw. If we don't hit both in the same frame, it
		# will cause flicker.
		# Since this will put the number of cycles to go below zero
		# if we run out of our own cycles, on average we will run
		# the right number of cycles per tick
		# Also, to avoid pairing draw half of one pair and erase
		# half of another, the sprint is invalidated by a jump, a
		# call or a ret
		if did_draw:
			#sprint_run_out = True#debg
			for cycle in range(2*cpu_clock // 60):
				did_draw, did_jump = step()
				cpu_cycles_to_go -= 1

				# Exit as soon as we hit the other draw
				if did_draw:
					#sprint_run_out = False#debg
					#print('Sprint succeeded! %i' % cycle)#debg
					break

				if did_jump:
					#sprint_run_out = False#debg
					#print('Sprint failed! (jump) %i' % cycle)#debg
					break
			#if sprint_run_out: print('Sprint failed! (ran out)')#debg

	if frames_to_go >= 1:
		# Only draw the latest frame. This means FPS >60 won't work
		# but why would you ever want to run chip-8 faster than
		# that
		display_screen = screen[:]
		frames_to_go -= int(frames_to_go)

def initialize_ram():
	global ram, font_start
	ram = [0]*(1<<12)

	# Font data is from http://mattmik.com/files/chip8/mastering/chip8.html
	# and http://devernay.free.fr/hacks/chip8/C8TECH10.HTM#2.4
	font = [
		0xf0, 0x90, 0x90, 0x90, 0xf0, # 0
		0x20, 0x60, 0x20, 0x20, 0x70, # 1
		0xf0, 0x10, 0xf0, 0x80, 0xf0, # 2
		0xf0, 0x10, 0xf0, 0x10, 0xf0, # 3
		0x90, 0x90, 0xf0, 0x10, 0x10, # 4
		0xf0, 0x80, 0xf0, 0x10, 0xf0, # 5
		0xf0, 0x80, 0xf0, 0x90, 0xf0, # 6
		0xf0, 0x10, 0x20, 0x40, 0x40, # 7
		0xf0, 0x90, 0xf0, 0x90, 0xf0, # 8
		0xf0, 0x90, 0xf0, 0x10, 0xf0, # 9
		0xf0, 0x90, 0xf0, 0x90, 0x90, # A
		0xe0, 0x90, 0xe0, 0x90, 0xe0, # B
		0xf0, 0x80, 0x80, 0x80, 0xf0, # C
		0xe0, 0x90, 0x90, 0x90, 0xe0, # D
		0xf0, 0x80, 0xf0, 0x80, 0xf0, # E
		0xf0, 0x80, 0xf0, 0x80, 0x80, # F
	]
	# Unsure where the font should go. Both http://www.multigesture.net/articles/how-to-write-an-emulator-chip-8-interpreter/
	# and http://stevelosh.com/blog/2016/12/chip8-graphics/?m=1#fonts
	# say it goes at 0x50, but most resources don't have its location
	# specified and I have run into implementations that have it at
	# start of memory (http://craigthomas.ca/blog/2017/10/15/writing-a-chip-8-emulator-built-in-font-set-part-4/)
	# and even a resource stating it's at high memory (http://www.multigesture.net/wp-content/uploads/mirror/goldroad/chip8.shtml)
	# The location honestly shouldn't matter, but I'm putting it at
	# 0x50
	font_start = 0x50
	ram[font_start:font_start + len(font)] = font

	test_program = [
		## Arithmetic test
		#0x65, 0x42, # 0x42 → v5 | v5: 42
		#0x82, 0x50, # v5 → v2 | v2: 42, v5: 42
		#0x72, 0x69, # v2 + 0x69 → v2 | v2: ab, v5: 42
		#0x85, 0x24, # v5 + v2 → v5 | v2: ab, v5: ed, vf: 00
		#0x85, 0x24, # v5 + v2 → v5 | v2: ab, v5: 98, vf: 01

		#0x85, 0x25, # v5 - v2 → v5 | v2: ab, v5: ed, vf: 00
		#0x82, 0x57, # v5 - v2 → v2 | v2: 42, v5: ed, vf: 01

		#0x63, 0x01, # 0x01 → v3 | v2: 42, v3: 01, v5: ed, vf: 01
		#0x85, 0x22, # v5 & v2 → v5 | v2: 42, v3: 01, v5: 40, vf: 01
		#0x83, 0x51, # v3 | v5 → v3 | v2: 42, v3: 41, v5: 40, vf: 01
		#0x82, 0x33, # v2 ^ v3 → v2 | v2: 3, v3: 41, v5: 40, vf: 01

		#0x82, 0x56, # v5 >> 1 → v2 | v2: 20, v3: 41, v5: 40, vf: 00
		#0x85, 0x36, # v3 >> 1 → v5 | v2: 20, v3: 41, v5: 20, vf: 01

		#0x64, 0x70, # 0x70 → v4 | v2: 20, v3: 41, v4: 70, v5: 20, vf: 01
		#0x84, 0x4E, # v4 << 1 → v4 | v2: 20, v3: 41, v4: e0, v5: 20, vf: 00
		#0x84, 0x4E, # v4 << 1 → v4 | v2: 20, v3: 41, v4: c0, v5: 20, vf: 01

		## RNG test
		#0xC0, 0xff, # RNG → v0
		#0xC0, 0xff, # RNG → v0
		#0xC0, 0xff, # RNG → v0
		#0xC0, 0xff, # RNG → v0
		#0xC0, 0x06, # RNG & 0x00001110 → v0
		#0xC0, 0x06, # RNG & 0x00001110 → v0
		#0xC0, 0x06, # RNG & 0x00001110 → v0
		#0xC0, 0x06, # RNG & 0x00001110 → v0

		## Flow control test
		#0x60, 0x00, # mov v0, 0
		#0x22, 0x06, # call 0x206
		#0x12, 0x02, # jmp 0x202
		#0x70, 0x01, # add v0, 1
		#0x00, 0xee, # ret

		## Skip test
		#0x61, 0xf0, # mov v1, 0xf0
		#0x62, 0xf1, # mov v2, 0xf1
		#0x83, 0x10, # mov v3, v1
		#0x31, 0xf0, # skipeq v3, 0xf0
		#0x00, 0x00, # ill
		#0x31, 0x00, # skipeq v3, 0
		#0x6e, 0x01, # mov ve, 1
		#0x51, 0x30, # skipeq v1, v3
		#0x00, 0x00, # ill
		#0x42, 0xf0, # skipneq v2, 0xf0
		#0x00, 0x00, # ill
		#0x91, 0x20, # skipneq v1, v2
		#0x00, 0x00, # ill
		#0x6d, 0x01, # mov vd, 1

		## Timer test
		#0xF0, 0x07, # getdelay v0
		#0x40, 0x00, # skipneq v0, 0
		#0x22, 0x08, # call 0x208
		#0x12, 0x00, # jmp 0x200
		#0x60, 0xff, # mov v0, 0xff
		#0xf0, 0x15, # setdelay v0
		#0x00, 0xee, # ret

		## Input wait test
		#0xf1, 0x0a, # getkey v1

		## Input skip test
		#0x61, 0x00, # mov v1, 0
		#0x62, 0x0a, # mov v2, 0xa
		#0x63, 0x0b, # mov v3, 0xb
		#0xe2, 0xa1, # skipnkey v2
		#0x71, 0x01, # add v1, 1
		#0xe3, 0x9e, # skipkey v3
		#0x12, 0x06, # jmp 0x206

		## Input wait test the second
		#0xa1, 0x23, # mov i, 0x123
		#0xf0, 0x0a, # getkey v0
		#0xf0, 0x1e, # add i, v0
		#0x12, 0x02, # jmp 0x202

		## Drawing program / drawing test
		## From the OSCOM Nano manual
		#0x6a, 0x01, # mov va, 1
		#0x60, 0x10, # mov v0, 0x10
		#0x61, 0x20, # mov v1, 0x20
		#0xa2, 0x50, # mov i, 0x250

		#0xf2, 0x0a, # getkey v2

		#0x42, 0x01, # skipneq v2, 1
		#0x22, 0x2e, # call 0x22e

		#0x42, 0x02, # skipneq v2, 2
		#0x80, 0xa5, # sub v0, va

		#0x42, 0x03, # skipneq v2, 3
		#0x22, 0x34, # call 0x234

		#0x42, 0x04, # skipneq v2, 4
		#0x81, 0xa5, # sub v1, va

		#0x42, 0x06, # skipneq v2, 6
		#0x81, 0xa4, # add v1, va

		#0x42, 0x07, # skipneq v2, 7
		#0x22, 0x3a, # call 0x23a

		#0x42, 0x08, # skipneq v2, 8
		#0x80, 0xa4, # add v0, va

		#0x42, 0x09, # skipneq v2, 9
		#0x22, 0x40, # call 0x240

		#0xD1, 0x01, # draw v0, v1, 1

		#0x12, 0x08, # jmp 0x208

		## 22e
		#0x81, 0xa5, # sub v1, va
		#0x80, 0xa5, # sub v0, va
		#0x00, 0xee, # ret

		## 234
		#0x80, 0xa5, # sub v0, va
		#0x81, 0xa4, # add v1, va
		#0x00, 0xee, # ret

		## 23a
		#0x80, 0xa4, # add v0, va
		#0x81, 0xa5, # sub v1, va
		#0x00, 0xee, # ret

		## 240
		#0x80, 0xa4, # add v0, va
		#0x81, 0xa4, # add v1, va
		#0x00, 0xee, # ret

		## This was missing from the original
		## Actually, never mind, it was just separately
		## 246
		#0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
		## 250
		#0x80,

		## Font test
		#0x60, 0x0a, # mov v0, 0x0a
		#0xf1, 0x0a, # getkey v1
		#0x00, 0xe0, # clearscreen
		#0xf1, 0x29, # mov i, digit(v1)
		#0xd0, 0x05, # draw v0, v0, 5
		#0x12, 0x02, # jmp 0x202

		## Base converter
		## From the OSCOM Nano manual
		## Modified to run several times and display input
		#0x6a, 0x00, # mov va, 0
		#0x6b, 0x00, # mov vb, 0

		#0xf0, 0x0a, # getkey v0
		#0x82, 0x00, # mov v2, v0
		#0x00, 0xe0, # clearscreen
		#0xf0, 0x29, # mov i, digit(v0)
		#0xda, 0xb5, # draw va, vb, 5
		#0x7a, 0x06, # add va, 6

		#0xf1, 0x0a, # getkey v1
		#0xf1, 0x29, # mov i, digit(v1)
		#0xda, 0xb5, # draw va, vb, 5
		#0x7b, 0x07, # add vb, 7
		#0x6a, 0x00, # mov va, 0

		#0x63, 0x00, # mov v3, 0
		## 21c
		#0x80, 0x24, # add v0, v2
		#0x73, 0x01, # add v3, 1
		#0x33, 0x0f, # skipeq v3, 0xf
		#0x12, 0x1c, # jmp 0x21c
		#0x80, 0x14, # add v0, v1

		#0xA2, 0x50, # mov i, 0x250
		#0xf0, 0x33, # mov [i … i+2], bcd(v0)
		#0xf2, 0x65, # mov v0 … v2, [i … i+2]

		#0xf0, 0x29, # mov i, digit(v0)
		#0xda, 0xb5, # draw va, vb, 5
		#0x7a, 0x06, # add va, 6
		#0xf1, 0x29, # mov i, digit(v1)
		#0xda, 0xb5, # draw va, vb, 5
		#0x7a, 0x06, # add va, 6
		#0xf2, 0x29, # mov i, digit(v2)
		#0xda, 0xb5, # draw va, vb, 5
		#0x12, 0x00, # jmp 0x200

	]
	#ram[0x200:len(test_program) + 0x200] = test_program

def initialize_screen():
	global screen, display_screen, screen_fps
	screen = [False] * 64 * 32
	display_screen = screen[:]
	# TODO: Support changing FPS
	screen_fps = 60

def initialize_timers():
	global delay_timer, sound_timer
	delay_timer = 0
	sound_timer = 0

def initialize_keyboard():
	global keys_pressed, waiting_for_keypress, keypress_arrived
	keys_pressed = [False]*16
	waiting_for_keypress = False
	keypress_arrived = False

def initialize_cpu(clockspeed):
	global cpu_clock, data_registers, ip, stack, i_register
	data_registers = [0] * 16

	# According to the OSCOM Nano manual the program is loaded here
	ip = 0x200

	# It doesn't seem to be specified where this is stored, so put it
	# in its own "address space"
	stack = []

	i_register = 0

	cpu_clock = clockspeed

def load_program(f):
	global ram
	# ram is an array of numbers, not a bytestring
	program = [i for i in f.read()]
	# Load at 0x200
	ram[0x200: 0x200 + len(program)] = program

def main():
	global window
	global cpu_cycles_to_go, frames_to_go

	if len(sys.argv) == 2:
		program_path = sys.argv[1]
		# Run the interpreter at 500Hz by default
		# This was picked from https://github.com/AfBu/haxe-CHIP-8-emulator/wiki/(Super)CHIP-8-Secrets
		cpu_clock = 500
	elif len(sys.argv) == 3:
		program_path = sys.argv[1]
		cpu_clock = int(sys.argv[2])
	else:
		print(f'Usage: {sys.argv[0]} program [cpu-speed]', file=sys.stderr)
		sys.exit(1)

	# TODO: Don't hardcode the size
	window = pyglet.window.Window(640, 320, resizable = True)

	# Don't use pulse driver, as it is really buggy and can crash the
	# python process
	pyglet.options['audio'] = ('openal', 'directsound', 'silent')

	# Hook up our screen drawing routine
	@window.event
	def on_draw():
		# Clear the screen
		window.clear()
		# Draw things
		draw_screen()

	# Handle keyboard input
	@window.event
	def on_key_press(symbol, modifiers):
		key_pressed(symbol)
	@window.event
	def on_key_release(symbol, modifiers):
		key_released(symbol)

	initialize_ram()
	initialize_screen()
	initialize_timers()
	initialize_keyboard()
	initialize_cpu(cpu_clock)

	# TODO: Deal with missing file gracefully
	with open(program_path, 'rb') as f:
		load_program(f)

	cpu_cycles_to_go = 0
	frames_to_go = 0
	# Start the emulation
	pyglet.clock.schedule_interval(advance_interpreter, 1/60)

	pyglet.app.run()

if __name__ == '__main__':
	main()