local scroll_x = 0
local scroll_y = 0

memory.usememorydomain("M68K BUS")

function draw_trig(base)
    if base ~= 0xFFFFFF then
        if memory.read_u16_be(base) <= 0x8000 then
            local posx = memory.read_u16_be(base+2)
            local posy = memory.read_u16_be(base+4)
            local posxa = bit.band(posx,0xFFE0)
            if posx ~= posxa then
                --posx()
            end
            local posya = bit.band(posy,0xFFE0)
            local x1 = bit.band(posxa+scroll_x-0x180,0xFFFF)+320/2
            if x1 >= 0x8000 then
                x1 = -(0x10000-x1)
            end
            local x2 = x1+0x1F
            local x3 = bit.band(posxa+scroll_x+0x40,0xFFFF)+320/2
            if x3 >= 0x8000 then
                x3 = -(0x10000-x3)
            end
            local x4 = x3+0x1F
            local y1 = bit.band(posya-scroll_y-0x120,0xFFFF)+224/2
            if posy ~= posya then
                y1 = y1+0x20
            end
            if y1 >= 0x8000 then
                y1 = -(0x10000-y1)
            end
            local y2 = y1+0x160+0x1F
            if posy ~= posya then
                y2 = y2-0x20
            end
            gui.drawBox(x1,y1,x2,y2,0xffff0000)
            gui.drawBox(x3,y1,x4,y2,0xff000000)
        end
        draw_trig(memory.read_u16_be(base+6)+0xFF0000)
        draw_trig(memory.read_u16_be(base+8)+0xFF0000)
    end
end

function draw_yet(base)
    if base ~= 0xFFFFFF then
        if memory.read_u16_be(base) <= 0x8000 then
            local posx = memory.read_u16_be(base+2)
            local posy = memory.read_u16_be(base+4)
            local posxa = bit.band(posx,0xFFE0)
            local posya = bit.band(posy,0xFFF0)
            if posx ~= posxa then
                posx()
            end
            if posy ~= posya then
                posx()
            end
            local x1 = bit.band(posxa+scroll_x-0x180,0xFFFF)+320/2
            if x1 >= 0x8000 then
                x1 = -(0x10000-x1)
            end
            local x2 = x1+0x180+0x40+0x1F
            local y1 = bit.band(posy-scroll_y+0x40,0xFFFF)+224/2
            if y1 >= 0x8000 then
                y1 = -(0x10000-y1)
            end
            local y2 = y1+0xF
            local y3 = bit.band(posy-scroll_y-0x120,0xFFFF)+224/2
            if y3 >= 0x8000 then
                y3 = -(0x10000-y3)
            end
            local y4 = y3+0xF
            gui.drawBox(x1,y1,x2,y2,0xffff0000)
            gui.drawBox(x1,y3,x2,y4,0xff000000)
        end
        draw_yet(memory.read_u16_be(base+10)+0xFF0000)
        draw_yet(memory.read_u16_be(base+12)+0xFF0000)
    end
end

function draw_enemy(base)
    local x = memory.read_u16_be(base+8)
    local y = memory.read_u16_be(base+12)
    local x1 = x-1
    local x2 = x+1
    local y1 = y-1
    local y2 = y+1
    if memory.read_u16_be(base+0x14) >= 0 then
        local bbox = memory.read_u32_be(base+0x38)
        x1 = x+memory.read_u16_be(bbox+0)
        x2 = x1+memory.read_u16_be(bbox+2)-1
        y1 = y+memory.read_u16_be(bbox+4)
        y2 = y1+memory.read_u16_be(bbox+6)-1
    end
    gui.drawBox(x1-bit.band(-scroll_x,0xFFFF), y1-scroll_y, x2-bit.band(-scroll_x,0xFFFF)+2, y2-scroll_y+2,0xff000000)
end

function draw_enemies()
    local base = memory.read_u16_be(0xFF3662)+0xFF0000
    while base ~= 0xFFFFFF do
        draw_enemy(base)
        base = memory.read_u16_be(base+2)+0xFF0000
    end
end

function draw_bullet(base)
    local x = memory.read_u16_be(base+0x1C)
    local y = memory.read_u16_be(base+0x20)
    local x1 = x
    local x2 = x+12
    local y1 = y
    local y2 = y+12
    gui.drawBox(x1-bit.band(-scroll_x,0xFFFF), y1-scroll_y, x2-bit.band(-scroll_x,0xFFFF)+2, y2-scroll_y+2,0xff000000)
end

function draw_bullets()
    local base = memory.read_u16_be(0xFF3BDA)+0xFF0000
    while base ~= 0xFFFFFF do
        draw_bullet(base)
        base = memory.read_u16_be(base+2)+0xFF0000
    end
end

function draw_aero()
    local state = memory.read_u16_be(0xFF3688)
    local dir = memory.read_u16_be(0xFF368A)
    local x = memory.read_u16_be(0xFF0176)
    local y = memory.read_u16_be(0xFF017A)
    local x1 = x-12
    local x2 = x
    local y1 = y
    local y2 = y+12
    if state == 2 or state == 3 then
        x1 = x-16-dir
        x2 = x1+32
        y1 = y+0x18
        y2 = y1+16
    end
    if state == 1 then
        x1 = x-16-dir
        x2 = x1+32
        y1 = y+4
        y2 = y1+16
    end
    gui.drawBox(x1-bit.band(-scroll_x,0xFFFF), y1-scroll_y, x2-bit.band(-scroll_x,0xFFFF)+2, y2-scroll_y+2,0xffffff00)
end

event.onframeend(function ()
    gui.drawBox(320/2-1,224/2-1,320/2+1,224/2+1,0xff000000)
    scroll_x = memory.read_u16_be(0xFFD114)
    scroll_y = memory.read_u16_be(0xFFD074)
    draw_trig(memory.read_u16_be(0xFFCB02)+0xFF0000)
    draw_yet(memory.read_u16_be(0xFFCB04)+0xFF0000)
    draw_enemies()
    draw_bullets()
    draw_aero()
end)