local MAX_BUNNIES = 100000

-- This is the maximum amount of elements (quads) per batch
-- NOTE: This value is defined in [rlgl] module and can be changed there
local MAX_BATCH_ELEMENTS = 8192

-- Create the Bunny class.
local Bunny = {}
Bunny.__index = Bunny

function Bunny:new(pos, spd, col)
  local bunny = {}
  setmetatable(bunny,Bunny)
  bunny.position = pos
  bunny.speed = spd
  bunny.color = col
  return bunny
end

function Bunny:update(texture)
  self.position.x = self.position.x + self.speed.x
  self.position.y = self.position.y + self.speed.y
  if ((self.position.x + texture.width/2) > rl.GetScreenWidth())
    or ((self.position.x + texture.width/2) < 0) then
    self.speed.x = self.speed.x * -1
  end
  if ((self.position.y + texture.height/2) > rl.GetScreenHeight())
    or ((self.position.y + texture.height/2 - 40) < 0) then
    self.speed.y = self.speed.y * -1
  end
end

-- Initialization
local screenWidth = 800
local screenHeight = 450

rl.SetConfigFlags(rl.FLAG_VSYNC_HINT)
rl.InitWindow(screenWidth, screenHeight, "raylib [textures] example - bunnymark")

-- Load bunny texture
local texBunny = rl.LoadTexture("resources/wabbit_alpha.png")

local bunnies = {}

-- Main game loop
while not rl.WindowShouldClose() do    -- Detect window close button or ESC key
  -- Update
  if rl.IsMouseButtonDown(rl.MOUSE_LEFT_BUTTON) then
    -- Create more bunnies
    for i = 1, 100 do
      if #bunnies < MAX_BUNNIES then
        local speed = rl.new("Vector2", rl.GetRandomValue(-250, 250) / 60, rl.GetRandomValue(-250, 250) / 60)
        local color = rl.new("Color", rl.GetRandomValue(50, 240), rl.GetRandomValue(80, 240), rl.GetRandomValue(100, 240), 255)
        table.insert(bunnies, Bunny:new(rl.GetMousePosition(), speed, color))
      end
    end
  end

  -- Update bunnies
  for i=1,#bunnies do
    bunnies[i]:update(texBunny)
  end

  -- Draw
  rl.BeginDrawing()

  rl.ClearBackground(rl.RAYWHITE)

  for i=1,#bunnies do
    -- NOTE: When internal batch buffer limit is reached (MAX_BATCH_ELEMENTS),
    -- a draw call is launched and buffer starts being filled again;
    -- before issuing a draw call, updated vertex data from internal CPU buffer is send to GPU...
    -- Process of sending data is costly and it could happen that GPU data has not been completely
    -- processed for drawing while new data is tried to be sent (updating current in-use buffers)
    -- it could generates a stall and consequently a frame drop, limiting the number of drawn bunnies
    rl.DrawTexture(texBunny, bunnies[i].position.x, bunnies[i].position.y, bunnies[i].color);
  end

  rl.DrawRectangle(0, 0, screenWidth, 40, rl.BLACK)
  rl.DrawText("bunnies: " .. #bunnies, 120, 10, 20, rl.GREEN)
  rl.DrawText("batched draw calls: " .. math.ceil(1 + #bunnies / MAX_BATCH_ELEMENTS), 320, 10, 20, rl.MAROON)

  rl.DrawFPS(10, 10)

  rl.EndDrawing()
end

-- De-Initialization
rl.UnloadTexture(texBunny)
rl.CloseWindow()