package main

import (
  "os"
  "log"
  "github.com/gdamore/tcell/v2"
  "github.com/gdamore/tcell/v2/encoding"
)


type Game struct {
  screen tcell.Screen
  level []string
  player_x int
  player_y int
}

func (game *Game) Render() {
  var comb []rune
  game.screen.Clear()

  for y, line := range game.level {
    for x, cell := range line {
      game.screen.SetContent(x, y, cell, comb, tcell.StyleDefault)
    }
  }

  game.screen.SetContent(game.player_x, game.player_y, '@', comb, tcell.StyleDefault)

  game.screen.Show()
}

func (game *Game) Exit() {
    game.screen.Fini()
    os.Exit(0)
}

func (game *Game) Occupied(x int, y int) bool {
  return game.level[y][x] != '.'
}

func (game *Game) MovePlayer(x_delta int, y_delta int) {
  if !game.Occupied(game.player_x + x_delta, game.player_y + y_delta) {
    game.player_x += x_delta
    game.player_y += y_delta
  }
}

func (game *Game) HandleKeys(ev *tcell.EventKey) {
  switch ev.Key() {
  case tcell.KeyEscape:
    game.Exit()
  case tcell.KeyUp:
    game.MovePlayer(0, -1)
  case tcell.KeyDown:
    game.MovePlayer(0, 1)
  case tcell.KeyRight:
    game.MovePlayer(1, 0)
  case tcell.KeyLeft:
    game.MovePlayer(-1, 0)
  }

  switch ev.Rune() {
  case 'q':
    game.Exit()
  }
}

func (game *Game) HandleEvents() {
  switch ev := game.screen.PollEvent().(type) {
  case *tcell.EventResize:
    game.screen.Sync()
  case *tcell.EventKey:
    game.HandleKeys(ev)
  }
}

func MakeGame() (*Game) {
  var game Game
  var err error

  encoding.Register()

  game.screen, err = tcell.NewScreen()
  if err != nil { log.Fatal(err) }

  err = game.screen.Init()
  if err != nil { log.Fatal(err) }

  game.player_x = 1
  game.player_y = 1

  return &game
}

// This program just prints "Hello, World!".  Press ESC to exit.
func main() {
  game := MakeGame()

  game.level = []string{
    "###########################",
    "#...#.....................#",
    "#.###.#########.#########.#",
    "#.....#.......#...#.....#.#",
    "#######.#####.#####.###.#.#",
    "#.....#.#.......#...#...#.#",
    "#.###.#.#.....#.#.#.#.###.#",
    "#...#.#.#.....#.#.#.#.....#",
    "###.#.#.#.....#.#.#.#######",
    "#...#...#.....#...#.......#",
    "###########################",
  }

  game.Render()

  for {
    game.HandleEvents()
    game.Render()
  }
}