// SPDX-License-Identifier: MIT
pragma solidity 0.8.30;

/// @notice No-stakes, two-wallet tic-tac-toe. Each move is publicly verifiable.
contract TactyraBoard {
    struct Game { address x; address o; uint8[9] cells; uint8 turn; uint8 status; uint8 winner; uint8 moves; }
    // status: 1 invited, 2 active, 3 finished, 4 cancelled; winner: 0 draw/none, 1 X, 2 O.
    uint256 public gameCount;
    mapping(uint256 => Game) private games;
    event Invited(uint256 indexed id, address indexed x, address indexed o);
    event Accepted(uint256 indexed id);
    event Moved(uint256 indexed id, address indexed account, uint8 cell, uint8 mark, uint8 winner, uint8 status);
    event Cancelled(uint256 indexed id);
    event Resigned(uint256 indexed id, address indexed account, uint8 winner);
    error InvalidOpponent(); error WrongState(); error NotParticipant(); error NotYourTurn(); error InvalidCell(); error Occupied();
    function getGame(uint256 id) external view returns (Game memory) { return games[id]; }
    function create(address opponent) external returns (uint256 id) {
        if (opponent == address(0) || opponent == msg.sender) revert InvalidOpponent();
        id = ++gameCount;
        Game storage g = games[id]; g.x = msg.sender; g.o = opponent; g.turn = 1; g.status = 1;
        emit Invited(id, msg.sender, opponent);
    }
    function accept(uint256 id) external {
        Game storage g = games[id];
        if (g.status != 1) revert WrongState();
        if (msg.sender != g.o) revert NotParticipant();
        g.status = 2; emit Accepted(id);
    }
    function cancel(uint256 id) external {
        Game storage g = games[id];
        if (g.status != 1) revert WrongState();
        if (msg.sender != g.x) revert NotParticipant();
        g.status = 4; emit Cancelled(id);
    }
    function move(uint256 id, uint8 cell) external {
        Game storage g = games[id];
        if (g.status != 2) revert WrongState();
        uint8 mark = msg.sender == g.x ? 1 : msg.sender == g.o ? 2 : 0;
        if (mark == 0) revert NotParticipant();
        if (g.turn != mark) revert NotYourTurn();
        if (cell > 8) revert InvalidCell();
        if (g.cells[cell] != 0) revert Occupied();
        g.cells[cell] = mark; ++g.moves;
        if (_won(g.cells, mark)) { g.winner = mark; g.status = 3; }
        else if (g.moves == 9) { g.status = 3; }
        else { g.turn = mark == 1 ? 2 : 1; }
        emit Moved(id, msg.sender, cell, mark, g.winner, g.status);
    }
    function resign(uint256 id) external {
        Game storage g = games[id];
        if (g.status != 2) revert WrongState();
        if (msg.sender != g.x && msg.sender != g.o) revert NotParticipant();
        g.winner = msg.sender == g.x ? 2 : 1; g.status = 3;
        emit Resigned(id, msg.sender, g.winner);
    }
    function _won(uint8[9] storage b, uint8 m) private view returns (bool) {
        for (uint8 i; i < 3; ++i) {
            if (b[i*3] == m && b[i*3+1] == m && b[i*3+2] == m) return true;
            if (b[i] == m && b[i+3] == m && b[i+6] == m) return true;
        }
        return (b[0] == m && b[4] == m && b[8] == m) || (b[2] == m && b[4] == m && b[6] == m);
    }
}