local Screen = require("screen")
local scrn, w, h, its
local noise

function _init()
  scrn = Screen:new("Envelope", 14, 3)
  scrn:autocolor()
  w,h = scrn:size()
  noise = audio.new()
  audio.samplelength(noise, 32)
  audio.sampleloop(noise, 0, audio.samplelength(noise))
  audio.play(0, noise)
  audio.play(3, noise)
  for x=0,audio.samplelength(noise)-1 do
    audio.samplevalue(noise, x, math.sin(x/audio.samplelength(noise)*math.pi*2)*127)
  end
end

function _step(t)
  scrn:step()
  if input.hotkey() == "q" then
    return sys.exit()
  end
  local mx,my,mb = input.mouse()
  mx = mx / 10
  my = math.min(math.max(-128, my - 180), 127)
  if mb > 0 then
    audio.samplevalue(noise, mx, my)
  end
  gfx.cls()
  gfx.fgcolor(1)
  lineto(650,180)
  lineto(-10,180)
  gfx.fgcolor(2)
  lineto(-5, 180+audio.samplevalue(noise, audio.samplelength(noise)-1))
  for x=0,audio.samplelength(noise)-1 do
    lineto(5+10*x, 180+audio.samplevalue(noise, x))
  end
  lineto(5+10*audio.samplelength(noise), 180+audio.samplevalue(noise, 0))
end

local _x, _y = -8,-8
function lineto(x,y)
  gfx.line(_x,_y, x,y)
  _x,_y = x,y
end