A snake game

package snake

import "core:fmt"
import rl "vendor:raylib"

WIN_HEIGHT :: 450
WIN_WIDTH :: 800
SNAKE_MAXLENGTH :: 100
SNAKE_STEP :: 20
GAME_TITLE :: "Snake game"

Vec2i :: struct {
  x, y: i32,
}

// Define a struct to handle the snake's state
Snake :: struct {
  head:   Vec2i,
  body:   [SNAKE_MAXLENGTH]Vec2i,
  length: int,
}

// Initialize the snake with a starting position and length
snake_init :: proc() -> Snake {
  return Snake{head = Vec2i{0, 0}, length = 1}
}

// Update snake position and handle wrapping around the screen
snake_update_position :: proc(snake: ^Snake) {
  prev_head := snake.head

  if rl.IsKeyDown(.RIGHT) {
    snake.head.x += SNAKE_STEP
    if snake.head.x >= WIN_WIDTH {
      snake.head.x = 0
    }
  } else if rl.IsKeyDown(.LEFT) {
    snake.head.x -= SNAKE_STEP
    if snake.head.x < 0 {
      snake.head.x = WIN_WIDTH - SNAKE_STEP
    }
  } else if rl.IsKeyDown(.UP) {
    snake.head.y -= SNAKE_STEP
    if snake.head.y < 0 {
      snake.head.y = WIN_HEIGHT - SNAKE_STEP
    }
  } else if rl.IsKeyDown(.DOWN) {
    snake.head.y += SNAKE_STEP
    if snake.head.y >= WIN_HEIGHT {
      snake.head.y = 0
    }
  }

  // Move body segments, keeping length within SNAKE_MAXLENGTH
  for i := snake.length - 1; i > 0; i -= 1 {
    snake.body[i] = snake.body[i - 1]
  }
  snake.body[0] = prev_head

  if snake.length < SNAKE_MAXLENGTH {
    snake.length += 1
  }
}

// Render the snake on the screen
snake_draw :: proc(snake: ^Snake) {
  for i in 0 ..< snake.length {
    pos := snake.body[i]
    color: rl.Color
    if i == 0 {
      color = rl.GREEN // Head color
    } else {
      color = rl.BLUE // Body color
    }
    rl.DrawRectangle(pos.x, pos.y, SNAKE_STEP, SNAKE_STEP, color)
  }
  rl.DrawRectangle(snake.head.x, snake.head.y, SNAKE_STEP, SNAKE_STEP, rl.GREEN)
}


main :: proc() {
  rl.InitWindow(WIN_WIDTH, WIN_HEIGHT, GAME_TITLE)
  defer rl.CloseWindow()
  rl.SetTargetFPS(60)

  snake := snake_init()

  for !rl.WindowShouldClose() {
    snake_update_position(&snake)

    rl.BeginDrawing()
    defer rl.EndDrawing()
    rl.ClearBackground(rl.BLACK)

    snake_draw(&snake)
  }
}