import term, math
from types import Vector

## This is a pocketlang implementation of:
## https://www.youtube.com/watch?v=xGmXxpIj6vs&t=279s&ab_channel=ChrisDeLeonofHomeTeamGameDev

## x, y velocity of snake.
vx = 0; vy = 0

## position (at the middle).
px = 0; py = 0

## tile size.
tx = 0; ty = 0

## apple position.
ax = 15; ay = 15

## tail, trail
trail = []
tail = 15

## score
score = 0

def init()
  size = term.getsize()
  tx = size.x
  ty = size.y
  
  px = tx / 2; py = ty / 2
end

def frame()
  px += vx
  py += vy
  if px < 0 then px = tx - 1 end
  if px > tx - 1 then px = 0 end
  if py < 0 then py = ty - 1 end
  if py > ty - 1 then py = 0 end
  
  term.clear()
  term.write('press Q to quit | score = $score')
  
  for i in trail
    term.setposition(i.x, i.y)
    term.start_bg(0, 0xff, 0)
    term.write(' ')
    term.end_bg()
    
    if i.x == px and i.y == py
      tail = 5
    end
  end
  
  term.setposition(ax, ay)
  term.start_bg(0xff, 0, 0)
  term.write(' ')
  term.end_bg()
  
  trail.append(Vector(px, py))
  while trail.length > tail
    trail.pop(0)
  end
  
  if px == ax and py == ay
    tail += 1
    score += 1
    ax = math.rand() % tx
    ay = math.rand() % ty
  end
  term.flush()
end

def handle(event)
  if event.type == term.EVENT_KEY_DOWN
    if event.keycode == term.KEY_Q
      term.stop()
    end
    
    ## The "Switch Statement" alternative.
    {
      term.KEY_LEFT: fn
        vx = -1; vy = 0
      end,
      
      term.KEY_UP: fn
        vx = 0; vy = -1
      end,
      
      term.KEY_DOWN: fn
        vx = 0; vy = 1
      end,
      
      term.KEY_RIGHT: fn
        vx = 1; vy = 0
      end,
      
      term.KEY_T: fn
        math.sin(12)
      end,

    }.get(event.keycode, fn end)()
  
  end
end


def main()
  config = term.Config()
  config.capture_events = true
  config.hide_cursor = true
  config.new_buffer = true
  config.fps = 20
  config.init_fn = init
  config.event_fn = handle
  config.frame_fn = frame
  term.run(config)
end


main()