/ld27

-- monkey patches for zoetrope Sprite

-- displace on a specific axis

function Sprite:displaceDir(other, dir)

   if not self.solid or self == other or not other.solid then return end

   if STRICT then assert(other:instanceOf(Sprite), 'asked to displace a non-sprite') end

   if other.sprites then

      -- handle groups

      for _, spr in pairs(other.sprites) do

         self:displace(spr, dir)

      end

   else

      -- handle sprites

      local dim = util.dim(dir)

      local negMove = (other[dir] - self[dir]) + other[dim]

      local posMove = (self[dir] + self[dim]) - other[dir]

      -- TODO: re-add hinting?

      if negMove < posMove then

         chg = - negMove

      else

         chg = posMove

      end

   end

   other[dir] = other[dir] + chg

end

-- don't use zoetrope physics

function Sprite:update(elapsed)

   self:doPhysics('x', elapsed)

   self:doPhysics('y', elapsed)

   self:doPhysics('rotation', elapsed)

   if self.onUpdate then self:onUpdate(elapsed) end

end

-- directional physics

function Sprite:doPhysics(dir, elapsed)

   local vel = self.velocity

   local acc = self.acceleration

   local drag = self.drag

   local minVel = self.minVelocity

   local maxVel = self.maxVelocity

   -- check existence of properties

   if STRICT then

      assert(vel, 'active sprite has no velocity property')

      assert(acc, 'active sprite has no acceleration property')

      assert(drag, 'active sprite has no drag property')

      assert(minVel, 'active sprite has no minVelocity property')

      assert(maxVel, 'active sprite has no maxVelocity property')

      assert(dir=='x' or dir=='y' or dir=='rotation', 'direction should be x, y, or rotation')

   end

   vel.x = vel.x or 0

   vel.y = vel.y or 0

   vel.rotation = vel.rotation or 0

   -- physics

   if acc[dir] and acc[dir] ~= 0 then

      vel[dir] = vel[dir] + acc[dir] * elapsed

   else

      if drag[dir] then

         if vel[dir] > 0 then

            vel[dir] = vel[dir] - drag[dir] * elapsed

            if vel[dir] < 0 then vel[dir] = 0 end

         elseif vel[dir] < 0 then

            vel[dir] = vel[dir] + drag[dir] * elapsed

            if vel[dir] > 0 then vel[dir] = 0 end

         end

      end

   end

   if minVel[dir] and vel[dir] < minVel[dir] then vel[dir] = minVel[dir] end

   if maxVel[dir] and vel[dir] > maxVel[dir] then vel[dir] = maxVel[dir] end

   -- ugly hack for falling through floor on really slow frames

   if math.abs(vel[dir] * elapsed) > 16 then

      print('skip')

      return

   end

   if vel[dir] ~= 0 then self[dir] = self[dir] + vel[dir] * elapsed end

   if the.activeMaze and (dir == 'x' or dir == 'y') then -- doesn't make sense for rotation

      if self[dir] < 0 then self[dir] = 0 end

      local edge = the.activeMaze[util.dim(dir)] - the.player[util.dim(dir)]

      -- TODO: take map position into account

      if self[dir] > edge then self[dir] = edge end

   end

end