local SCREEN_WIDTH          = 384
local SCREEN_HEIGHT         = 224
local AXIS_COLOUR           = 0xFFFFFFFF
local MINI_AXIS_COLOUR      = 0xFFFF00FF
local AXIS_SIZE             = 25
local MINI_AXIS_SIZE        = 2
local HITBOX_VULNERABILITY  = 0
local HITBOX_ATTACK         = 1
local HITBOX_PUSH           = 2
local HITBOX_VULNERABILITY_COLOUR = 0x0000FF40
local HITBOX_ATTACK_COLOUR  = 0xFF000040
local HITBOX_PUSH_COLOUR    = 0x00FF0040

local address = {
	player1          = 0x00FF8400,
	player2          = 0x00FF8800,
	left_screen_edge = 0x00FF8026,
	top_screen_edge  = 0x00FF8028,
}
local globals = {
	left_screen_edge = 0,
	top_screen_edge  = 0,
}
local player1   = {}
local player2   = {}


function update_globals()
	globals.left_screen_edge = memory.readword(address.left_screen_edge)
	globals.top_screen_edge  = memory.readword(address.top_screen_edge)
end


function hitbox_load(obj, i, type, facing_dir, offset_x, offset_y, addr)
	local hval    = memory.readwordsigned(addr + 0)
	local vval    = memory.readwordsigned(addr + 2)
	local hrad    = memory.readwordsigned(addr + 4)
	local vrad    = memory.readwordsigned(addr + 6)

	if facing_dir == 1 then
		hval  = -hval
	end

	local left   = offset_x + hval - hrad
	local top    = offset_y + vval - vrad
	local right  = offset_x + hval + hrad
	local bottom = offset_y + vval + vrad

	if type == HITBOX_VULNERABILITY then
		obj[HITBOX_VULNERABILITY][i] = {
			left   = left,
			right  = right,
			bottom = bottom,
			top    = top,
			hval   = offset_x+hval,
			vval   = offset_y+vval,
			type   = type
		}
	else
		obj[type] = {
			left   = left,
			right  = right,
			bottom = bottom,
			top    = top,
			hval   = offset_x+hval,
			vval   = offset_y+vval,
			type   = type
		}
	end
end


function update_game_object(obj, base)
	obj.facing_dir   = memory.readbyte(base + 0xB)
	obj.pos_x        = memory.readword(base + 0x10)
	obj.pos_y        = memory.readword(base + 0x14)
	obj.opponent_dir = memory.readbyte(base + 0x5D)

	-- Load the vulnerability hitboxes
	obj[HITBOX_VULNERABILITY] = {}
	for i = 0, 2 do
		local v_hb_addr_table = memory.readdword(base + 0x80 + (i*4))
		local v_hb_curr_id    = memory.readbyte(base + 0x94 + i)
		hitbox_load(obj, i, HITBOX_VULNERABILITY, obj.facing_dir, obj.pos_x, obj.pos_y, v_hb_addr_table+(v_hb_curr_id*8))
	end

	-- Load the attack hitbox
	local a_hb_addr_table = memory.readdword(base + 0x8c)
	local animation_ptr   = memory.readdword(base + 0x1C)
	local a_hb_curr_id    = memory.readbyte(animation_ptr + 0x0A)
	hitbox_load(obj, 0, HITBOX_ATTACK, obj.facing_dir, obj.pos_x, obj.pos_y, a_hb_addr_table+(a_hb_curr_id*0x20))

	-- Load the push hitbox
	local p_hb_addr_table = memory.readdword(base + 0x90)
	local p_hb_curr_id    = memory.readbyte(base + 0x97)
	hitbox_load(obj, 0, HITBOX_PUSH, obj.facing_dir, obj.pos_x, obj.pos_y, p_hb_addr_table+(p_hb_curr_id*8))
end


function game_x_to_mame(x)
	return (x - globals.left_screen_edge)
end


function game_y_to_mame(y)
	-- Why subtract 17? No idea, the game driver does the same thing.
	return (SCREEN_HEIGHT - (y - 17) + globals.top_screen_edge)
end


function draw_hitbox(hb)
	local left   = game_x_to_mame(hb.left)
	local bottom = game_y_to_mame(hb.bottom)
	local right  = game_x_to_mame(hb.right)
	local top    = game_y_to_mame(hb.top)
	local hval   = game_x_to_mame(hb.hval)
	local vval   = game_y_to_mame(hb.vval)

	if hb.type == HITBOX_VULNERABILITY then
		colour = HITBOX_VULNERABILITY_COLOUR
	elseif hb.type == HITBOX_ATTACK then
		colour = HITBOX_ATTACK_COLOUR
	elseif hb.type == HITBOX_PUSH then
		colour = HITBOX_PUSH_COLOUR
	end

	gui.drawline(hval, vval-MINI_AXIS_SIZE, hval, vval+MINI_AXIS_SIZE, MINI_AXIS_COLOUR)
	gui.drawline(hval-MINI_AXIS_SIZE, vval, hval+MINI_AXIS_SIZE, vval, MINI_AXIS_COLOUR)
	gui.box(left, top, right, bottom, colour)
end


function draw_game_object(obj)
	local x = game_x_to_mame(obj.pos_x)
	local y = game_y_to_mame(obj.pos_y)

	for i = 0, 2 do
		draw_hitbox(obj[HITBOX_VULNERABILITY][i])
	end
	draw_hitbox(obj[HITBOX_ATTACK])
	draw_hitbox(obj[HITBOX_PUSH])

	gui.drawline(x, y-AXIS_SIZE, x, y+AXIS_SIZE, AXIS_COLOUR)
	gui.drawline(x-AXIS_SIZE, y, x+AXIS_SIZE, y, AXIS_COLOUR)
end


function render_vsav_hitboxes()
	update_globals()

	update_game_object(player1, address.player1)
	draw_game_object(player1)
	update_game_object(player2, address.player2)
	draw_game_object(player2)
end


gui.register( function()
	render_vsav_hitboxes()
end)