Dice rolling game smart contract skeleton

Dice.sol

pragma solidity ^0.5.0;

import "https://github.com/OpenZeppelin/openzeppelin-contracts/blob/v2.5.0/contracts/token/ERC20/IERC20.sol";

contract Dice {

	IERC20 public nativeGameToken;
	mapping(address => UserBet) private userBets;

	struct UserBet {
		IERC20 betToken;
		uint8 betValue;
		uint256 amount;
		bool isBetPlaced;
	}

	/**
	 * Initializes the contract with an address of an ERC-20 token
	 */
	constructor(IERC20 _nativeGameToken) public{
		// TODO: Complete this
		// [OPTIONAL] Ensure that _nativeGameToken is valid
        	// Store _nativeGameToken to contracts Storage
	}

	/**
	 * Allows a user to place a bet on a dice value using a specific ERC-20 token amount.
	 * Returns the amount that was bet.
	 */
	function placeBet(IERC20 betToken, uint256 amount, uint8 betValue) external returns(uint256) {
		// TODO: Complete this
		// Ensure that User has not placed a bet already
		// Ensure that thet betValue is between 1-6

		// Create a new user bet for the sender

		// Return the amount of the bet
	}

	/**
	 * Returns whether the caller has already placed a bet.
	 */
	function isBetPlaced() public view returns(bool){
		// TODO: Complete this
		// Return True if bet from sender was placed, False otherwise
	}

	/**
	 * Rolls the dice and transfers the funds to the winner appropriately.
	 * Returns a pair of values:
	 *	(a) A boolean that indicates if the caller has won, 
	 *	(b) The roll of the dice.
	 */
	function rollDice() external returns(bool, uint8) {
		// TODO: Complete this
		// Ensure that sender has already placed a bet
	    	// Ensure that contract is able to send at least 6*betAmount Tokens on behalf of the user
	    	// Ensure that contract can send at least bet amount of Tokens on behalf of the sender

		// Toggle isBetPlaced for the sender's bet to False

		// Roll the dice 

		// Check if sender has won.

		// If won send tokens bet amount*6 from owner to ender 
		// Otherwise send bet amount of tokens from sender to owner
		// Return if the sender has won or not and the roll of the dice
	}

	/**
	 * Generates a NOT cryptographically secure pseudo random number in the range of 1-6 (inclussive)
	 */
	function random() private view returns (uint8) {
		// WARNING!
		// This random generator is not secure!
		// This is only for the sake of the exercise!
		uint256 blockValue = uint256(blockhash(block.number-1 + block.timestamp));
		return uint8(blockValue % 5) + 1;
	}
    
}