Build a simple betting contract that rewards correct guesses of outcomes. This contract utilizes aspects of game theory; you may want to use a paper and pen to make a note of possible game states that may arise.

• There can only be one contract owner
• Bets to the contract will be comprised of both: an amount of Ether bet and the gambler's expected outcome
• The contract owner must define all possible outcomes from the start
• The contract owner must be able to assign an oracle; the oracle cannot be a gambler or later place a bet
• The contract owner cannot be a gambler
• Each gambler can only bet once
• If all gamblers bet on the same outcome, reimburse all gamblers their funds
• If no gamblers bet on the correct outcome, the oracle wins the sum of the funds
• The oracle may choose the correct outcome only after all gamblers have placed their bets
• You may add as many auxiliary functions as you want, they are not necessary however

There are at least two aspects of this scheme that leave it open to malicious attack. Can you find them?

• Start with two gamblers
• Start with one oracle
• Start with any amount of outcomes
• Add events (bet made, betting closed, etc.)
• The contract must be able to pass all tests

1. The contract is deployed, owner and outcomes are set (e.g. [1, 2, 3, 4])
2. Owner chooses their oracle
3. User at address A makes a bet of 50 wei on outcome 1, becomes gamblerA
4. User at address B makes a bet of 210 wei on outcome 2, becomes gamblerB
5. User at address A makes a bet on outcome 3, is not allowed to do so (each gambler can only bet once)
6. User at address G tries to make a bet, is not allowed to do so (only two gamblers in the vanilla contract)
7. Oracle decided on the correct outcome, chooses outcome 2
8. Winnings are dispersed, the game is over and gamblerA and gamblerB are removed from the game
9. User at address B withdraws the winnings they earned (260 wei) when they gambled on outcome 2

• (HARD) There can be multiple gamblers
  • The winners receive a propotional share of the total funds at stake if they all bet on the correct outcome
• (HARD) Each gambler can place multiple bets
• (HARD) Set up a multi-payout system where more than one outcome yields rewards
• There can be multiple oracles
  • Need an odd number of oracles to break ties
• The creater of the contract receives a fixed percentage of the winnings
• Cap the number of bets that can be made
• Cap the amount of time that passes after bet placement