local screen_width, screen_height = 960, 540
love.window.setMode(screen_width, screen_height)
local game_time = os.time()
love.math.setRandomSeed(game_time)
game_time = 0 -- TEMP ?

-- local core
-- local generate_system
-- generate_system = function(object)
-- end
-- core = generate_system()

local star = {
  x = 0, y = 0, orbital_radius = 0, body_radius = 100^0.5,
  children = {
    {
      orbital_radius = 100, body_radius = 6^0.5,
      children = {
        {
          orbital_radius = 10, body_radius = 1.5^0.5,
        }
      }
    },
    {
      orbital_radius = 50, body_radius = 3^0.5,
    },
    {
      orbital_radius = 200, body_radius = 12^0.5,
      children = {
        {
          orbital_radius = 25, body_radius = 3^0.5,
          children = {
            {
              orbital_radius = 5, body_radius = 1^0.5,
            }
          }
        }
      }
    }
  }
}
local set_offsets
set_offsets = function(object)
  object.rotation_offset = math.pi * 2 * love.math.random()
  if object.children then
    for i = 1, #object.children do
      set_offsets(object.children[i])
    end
  end
end
set_offsets(star)

-- max size star
star = {
  x = 0, y = 0, orbital_radius = 0, body_radius = 100^0.5, rotation_offset = 0,
  children = {
    {
      orbital_radius = 950 / 2, body_radius = 10^0.5, rotation_offset = 0,
    },
    {
      orbital_radius = 530 / 2, body_radius = 10^0.5, rotation_offset = math.pi / 2,
    },
    {
      orbital_radius = 30 / 2, body_radius = 1^0.5, rotation_offset = 0,
    }
  }
}

-- min size star
star = {
  x = 0, y = 0, orbital_radius = 0, body_radius = 10^0.5, rotation_offset = 0,
  children = {
    {
      orbital_radius = 950 / 2, body_radius = 2^0.5, rotation_offset = 0,
    },
    {
      orbital_radius = 530 / 2, body_radius = 2^0.5, rotation_offset = math.pi / 2,
    },
    {
      orbital_radius = 30 / 2, body_radius = 0.1^0.5, rotation_offset = 0,
    }
  }
}

local generate_bodies
generate_bodies = function(parent)
  local object
  if parent then
    object = {
      rotation_offset = math.pi * 2 * love.math.random(),
      body_radius = love.math.random() * math.sqrt(parent.body_radius / 2) + parent.body_radius * 0.05,
    }
    object.orbital_radius = object.body_radius * 1.1 + parent.body_radius * 1.05 + love.math.random() * parent.body_radius^2.5
  else
    object = {
      x = 0, y = 0, orbital_radius = 0, rotation_offset = 0, body_radius = math.sqrt(love.math.random() * 200 + 20),
    }
  end
  object.children = {}

  local potential_child_count = math.floor(object.body_radius)
  if love.math.random() > 0.5 then return object end
  if potential_child_count >= 1 then
    for i = 1, potential_child_count do
      local child_object = generate_bodies(object)
      if child_object then
        table.insert(object.children, child_object)
      end
    end
  end

  return object
end
star = generate_bodies()

function love.update(dt)
  game_time = game_time + dt

  local update_object_position
  update_object_position = function(object, parent_x, parent_y, parent_mass)
    local temporary_speed_up = 1
    local argument = game_time / object.orbital_radius^1.337 * temporary_speed_up * parent_mass + object.rotation_offset
    if (argument == math.huge) or (argument ~= argument) then
      argument = 0
    end
    object.x, object.y = parent_x + object.orbital_radius * math.cos(argument), parent_y + object.orbital_radius * math.sin(argument)
    if object.children then
      for i = 1, #object.children do
        update_object_position(object.children[i], object.x, object.y, object.body_radius^2)
      end
    end
  end
  update_object_position(star, 0, 0, 0)
end

function love.draw()
  love.graphics.setColor(1, 1, 1, 1)
  love.graphics.translate(screen_width / 2, screen_height / 2)

  local draw_object
  draw_object = function(object, parent_x, parent_y)
    love.graphics.circle("fill", object.x, object.y, math.max(object.body_radius, 0.8))
    love.graphics.circle("line", parent_x, parent_y, object.orbital_radius) -- orbital path
    if object.children then
      for i = 1, #object.children do
        draw_object(object.children[i], object.x, object.y)
      end
    end
  end
  draw_object(star, 0, 0)
end

function love.keypressed(key)
  if key == "escape" then
    love.event.quit()
  elseif key == "r" then
    star = generate_bodies()
  end
end