From df800f05416aa11bd04501b6dd771307d05dc8b7 Mon Sep 17 00:00:00 2001
From: Santo Cariotti <santo@dcariotti.me>
Date: Mon, 20 Jun 2022 14:53:17 +0200
Subject: Add exercises

---
 Year_3/Blockchain/TicTacToe.sol | 153 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 153 insertions(+)
 create mode 100644 Year_3/Blockchain/TicTacToe.sol

(limited to 'Year_3/Blockchain/TicTacToe.sol')

diff --git a/Year_3/Blockchain/TicTacToe.sol b/Year_3/Blockchain/TicTacToe.sol
new file mode 100644
index 0000000..582e10d
--- /dev/null
+++ b/Year_3/Blockchain/TicTacToe.sol
@@ -0,0 +1,153 @@
+// SPDX-License-Identifier: None
+
+pragma solidity ^0.8.0;
+
+contract TicTacToe {
+    enum Player { X, O }
+    struct PlayerInfo {
+        address payable id;
+        Player p_type;
+    }
+    enum Cell { X, O, NONE }
+    enum GameStatus { TURN_X, TURN_O, WAIT, END }
+
+    mapping(address => PlayerInfo) players;
+    address[2] playerIds;
+    Cell[3][3] cells;
+    Player turn;
+    GameStatus status = GameStatus.WAIT;
+    uint immutable minFee;
+    uint fee;
+    uint8 moves = 9;
+
+    event Movement(address sender, Player player, Cell[3][3] cells);
+    event EndGame(address winner, uint amount);
+
+    constructor(address payable firstPlayer, address payable secondPlayer, uint _minFee) {
+        require(firstPlayer != address(0) && secondPlayer != address(0), "You must define both address");
+        require(firstPlayer != secondPlayer, "Players must be different");
+
+        players[firstPlayer] = PlayerInfo({
+            id: firstPlayer,
+            p_type: Player.X
+        });
+        playerIds[0] = firstPlayer;
+        players[secondPlayer] = PlayerInfo({
+            id: secondPlayer,
+            p_type: Player.O
+        });
+        playerIds[1] = secondPlayer;
+        minFee = _minFee;
+        turn = Player(getRandomTurn());
+
+        for (uint8 i = 0; i < 3; ++i)
+            for (uint8 j = 0; j < 3; ++j)
+                cells[i][j] = Cell.NONE;
+    }
+
+    function play(uint x, uint y) public payable {
+        require(status != GameStatus.END, "Game is over");
+        require(players[msg.sender].id != address(0), "You're not one of the players");
+        require(players[msg.sender].p_type == turn, "It's not your turn");
+        require(msg.value >= minFee, "Value is less than the min fee");
+
+        fee += msg.value;
+
+        if (cells[y][x] != Cell.NONE) {
+            revert("Can't use this cell");
+        }
+
+        cells[y][x] = (turn == Player.X ? Cell.X : Cell.O);
+        turn = Player(1 - uint(turn));
+        moves--;
+        checkGame();
+    }
+
+    function getBoard() public view returns (Cell[3][3] memory) {
+        return cells;
+    }
+
+    /*
+    -------------
+    |   |   |   |
+    |---|---|---|
+    |   |   |   |
+    |---|---|---|
+    |   |   |   |
+    -------------
+    */
+
+    function checkGame() internal {
+        // It's useless to check when moves > 4
+        if (moves > 4) return;
+
+        bool result = false;
+        PlayerInfo memory winner;
+
+        if (moves == 0) {
+            emit EndGame(address(this), fee);
+            status = GameStatus.END;
+        }
+
+        // Diagonal wins
+        if (
+            (cells[0][0] == cells[1][1] && cells[0][0] == cells[2][2]) ||
+            (cells[0][2] == cells[1][1] && cells[0][2] == cells[2][0])
+        ) {
+            address addr = address(0);
+            if (cells[0][0] != Cell.NONE) {
+                addr = playerIds[uint256(cells[0][0])];
+                winner = players[addr];
+                assert(uint(winner.p_type) == uint(cells[0][0]));
+                result = true;
+            } else if (cells[0][2] != Cell.NONE) {
+                addr = playerIds[uint256(cells[0][2])];
+                winner = players[addr];
+                assert(uint(winner.p_type) == uint(cells[0][2]));
+                result = true;
+            }
+        }
+
+        if (!result) {
+            for (uint8 i = 0; i < 3; i+=3) {
+                for (uint8 j = 0; j < 3; j+=3) {
+                    if (cells[i][j] == Cell.NONE) continue;
+
+                    address addr = playerIds[uint256(cells[i][j])];
+
+                    if (
+                        (cells[i][j] == cells[i+1][j] && cells[i][j] == cells[i+2][j]) ||
+                        (cells[i][j] == cells[i][j+1] && cells[i][j+1] == cells[i][j+2])
+                    ) {
+                        result = true; 
+                    }
+
+                    if (result) {
+                        winner = players[addr];
+                        assert(uint(winner.p_type) == uint(cells[i][j]));
+                        break;
+                    }
+
+               }
+
+                if (result) break;
+            }
+        }
+
+        if (result && winner.id != address(0)) {
+            assert(fee == address(this).balance);
+            winner.id.transfer(fee);
+            status = GameStatus.END;
+            emit EndGame(winner.id, fee);
+            fee = 0;
+        }
+    }
+
+    function getRandomTurn() internal view returns (uint8) {
+        return uint8(
+            uint256(
+                keccak256(abi.encode(block.timestamp, block.difficulty))
+            ) % 2
+        );
+    }
+}
-- 
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