require("utils")

local Snake = R("snake.snake")
local window = R("snake.window")

local empty_block = "  "
local snake_block = "██"
local food_block = "🍎"
local initial_vel = 300       -- ms
local vel_decrease_rate = 0.9 -- reduce velocity in 20% on each size increase

local function make_empty_board(height, width)
  local board = {}

  for _ = 1, height do
    local line = {}
    for _ = 1, width do
      table.insert(line, empty_block)
    end
    table.insert(board, line)
  end

  return board
end

-- initial state
local GameState = {}

function GameState:new(width, height)
  local instance = {}
  setmetatable(instance, self)
  self.__index = self

  self:init(width, height)

  return instance
end

function GameState:init(width, hight)
  self.velocity = initial_vel -- ms
  self.status = "running"     -- 'idle' | 'running' | 'game-over'
  self.snake = Snake:new()
  self.board_width = width
  self.board_height = hight
  self.food = nil
end

function GameState:update()
  self.snake:move()

  if
      self.snake:board_colision_check(self.board_height, self.board_width)
      or self.snake:snake_colision_check()
  then
    self.status = "game-over"
  end

  -- generate food
  -- random - https://www.codecademy.com/resources/docs/lua/mathematical-library/random
  math.randomseed(vim.loop.now())

  while not self.food do
    local pos = {
      x = math.random(1, self.board_width),
      y = math.random(1, self.board_height),
    }

    if not self.snake:is_over_position(pos) then
      self.food = pos
    end
  end

  -- check food collision
  if self.snake:is_over_position(self.food) then
    self.food = nil
    self.velocity = self.velocity * vel_decrease_rate
    self.snake:grow()
  end
end

function GameState:view()
  local board = make_empty_board(self.board_height, self.board_width)

  if self.status == "game-over" then
    -- print game over screen
    local view = {
      "",
      "Game Over 🐍❌",
      "",
      "Hit <C-r>  to restart",
      "",
    }
    window.write_lines(view)
    return
  end

  -- print snake
  for _, pos in ipairs(self.snake.queue) do
    board[pos.y][pos.x] = snake_block
  end

  -- print food
  if self.food then
    board[self.food.y][self.food.x] = food_block
  end

  -- make view
  local view = {}
  for _, line in ipairs(board) do
    table.insert(view, table.concat(line, ""))
  end

  -- scoreboard
  local score = string.format(
    "Size: %d\tFrameRate: %.2f FPS",
    self.snake.size,
    1000 / self.velocity
  )
  table.insert(view, 1, score)

  window.write_lines(view)
end

local Game = {
  state = GameState:new(),
}

function Game:new()
  local instance = {}
  setmetatable(instance, self)
  self.__index = self

  self.width = 80
  self.height = 40

  self.state = GameState:new(self.width, self.height)

  return instance
end

function Game:start()
  -- make this window open again
  window.open({ height = self.height + 1, width = self.width * #empty_block })

  self.state:init(self.width, self.height)

  local function should_schedule()
    return not (
      self.state.status ~= "running" -- not if game over
      or self.state.velocity == 0    -- not if no velocity
    )
  end

  local function loop()
    self.state:update()

    self.state:view()
    -- schedule next call
    if should_schedule() then
      vim.defer_fn(loop, self.state.velocity)
    end
  end

  -- start loop
  vim.defer_fn(loop, 0)
end

function Game:setup()
  -- commands
  local function start()
    self:start()
  end

  local function quit()
    self.state.status = "idle"
    window.close()
  end

  vim.api.nvim_create_user_command(
    "Snake",
    start,
    { desc = "Start Snake game" }
  )

  -- keymap
  local opts = {
    noremap = true,
    silent = true,
    buffer = window.buf,
  }

  for key in pairs(Snake.direction_map) do
    local move = function()
      self.state.snake:change_dir(key)
    end

    vim.keymap.set({ "n" }, key, move, opts)
  end

  vim.keymap.set({ "n" }, "q", quit, opts)
  vim.keymap.set({ "n" }, "r", start, opts)
end

return {
  setup = function()
    local game = Game:new()
    game:setup()
  end,
}