local ctx = {t = 0, currentPronoun = '', lastPeriod = -1}

function lovr.load()
  lovr.graphics.setBackgroundColor(0.0, 0.0, 0.0, 0.0)
  -- must seed rng etc
  math.randomseed(os.time())
end

local PRONOUNCES = {
  'he/him',
  'she/her',
  'they/them',
  'it/its',
  'fae/faer',
}

function lovr.update(dt) -- runs every frame
  ctx.t = ctx.t + dt
  
  -- calculate which 30-second period we're in
  local currentPeriod = math.floor(ctx.t / 30)
  
  -- if we've entered a new period, select a new random pronoun
  if currentPeriod > ctx.lastPeriod then
    ctx.currentPronoun = PRONOUNCES[math.random(#PRONOUNCES)]
    ctx.lastPeriod = currentPeriod
  end
end

function textOpacity(controllerPosition)
  local headsetPose = mat4(lovr.headset.getPose('head'))
  local headsetPosition = vec3(headsetPose:getPosition())
  local textPosition = vec3(controllerPosition:getPosition())
  
  -- Get the forward direction of the text plane (negative z-axis after transformations)
  local rawControllerPosition = {controllerPosition:unpack(true)}
  local textForward = vec3(
    -rawControllerPosition[9],  -- -m[3][1]
    -rawControllerPosition[10], -- -m[3][2]
    -rawControllerPosition[11]  -- -m[3][3]
  ):normalize()

  -- Calculate direction from text to headset
  local toHeadset = vec3(
    headsetPosition.x - textPosition.x,
    headsetPosition.y - textPosition.y,
    headsetPosition.z - textPosition.z
  ):normalize()
  
  -- Calculate dot product between text forward and direction to headset
  local dotProduct = textForward:dot(toHeadset)

  if dotProduct >= -0.5 then
    return 0
  end
  return 0.5 * ((-dotProduct) - 0.5) / 0.5
end


function lovr.draw(pass)
  pass:setColor(1, 0.3, 0.3, 0.5)
  local controllerPosition = mat4(lovr.headset.getPose('hand/right'))
  -- put it 5cm above hand
  controllerPosition:translate(0.05, 0, 0)
  -- put it some cm separate from my normal watch
  controllerPosition:translate(0, 0.05, 0)
  -- rotate such that it faces the hmd
  controllerPosition:rotate(math.pi/2, 0, 1, 0)
  controllerPosition:rotate(math.pi/2, 0, 0, 1)
  controllerPosition:rotate(math.pi/6, 0, 0, 1)
  -- scale down so its not the size of the hand
  controllerPosition = controllerPosition:scale(0.1, 0.1, 0.1)
  -- prevent z fighting with plane
  controllerPosition:translate(0,0,0.0001)
  -- scale down text
  controllerPosition = controllerPosition:scale(0.3, 0.3, 0.3)
  local textOpacity = textOpacity(controllerPosition)
  pass:setColor(1, 0.5, 0.5, textOpacity)
  pass:text(ctx.currentPronoun, controllerPosition)
end