contract MultiSigWallet {

    uint256 constant public MAX_OWNER_COUNT = 50;

    event Confirmation(address indexed sender, uint256 indexed transactionId);
    event Revocation(address indexed sender, uint256 indexed transactionId);
    event Submission(uint256 indexed transactionId);
    event Execution(uint256 indexed transactionId);
    event ExecutionFailure(uint256 indexed transactionId);
    event Deposit(address indexed sender, uint256 value);
    event OwnerAddition(address indexed owner);
    event OwnerRemoval(address indexed owner);
    event RequirementChange(uint256 required);

    mapping (uint256 => Transaction) public transactions;
    mapping (uint256 => mapping (address => bool)) public confirmations;
    mapping (address => bool) public isOwner;

    address[] public owners;
    uint256 public required;
    uint256 public transactionCount;

    struct Transaction {
        address destination;
        uint256 value;
        bytes data;
        bool executed;
    }

    modifier onlyWallet() {
        if (msg.sender != address(this))
            revert("ONLY_WALLET_ERROR");
        _;
    }

    modifier ownerDoesNotExist(address owner) {
        if (isOwner[owner])
            revert("OWNER_DOES_NOT_EXIST_ERROR");
        _;
    }

    modifier ownerExists(address owner) {
        if (!isOwner[owner])
            revert("OWNER_EXISTS_ERROR");
        _;
    }

    modifier transactionExists(uint256 transactionId) {
        if (transactions[transactionId].destination == 0)
            revert("TRANSACTION_EXISTS_ERROR");
        _;
    }

    modifier confirmed(uint256 transactionId, address owner) {
        if (!confirmations[transactionId][owner])
            revert("CONFIRMED_ERROR");
        _;
    }

    modifier notConfirmed(uint256 transactionId, address owner) {
        if (confirmations[transactionId][owner])
            revert("NOT_CONFIRMED_ERROR");
        _;
    }

    modifier notExecuted(uint256 transactionId) {
        if (transactions[transactionId].executed)
            revert("NOT_EXECUTED_ERROR");
        _;
    }

    modifier notNull(address _address) {
        if (_address == 0)
            revert("NOT_NULL_ERROR");
        _;
    }

    modifier validRequirement(uint256 ownerCount, uint256 _required) {
        if (ownerCount > MAX_OWNER_COUNT || _required > ownerCount || _required == 0 || ownerCount == 0)
            revert("VALID_REQUIREMENT_ERROR");
        _;
    }

    /** @dev Fallback function allows to deposit ether. */
    function() public payable {
        if (msg.value > 0) {
            emit Deposit(msg.sender, msg.value);
        }
    }

    /** @dev Contract constructor sets initial owners and required number of confirmations.
      * @param _owners List of initial owners.
      * @param _required Number of required confirmations.
      */
    constructor(address[] _owners, uint256 _required)
        public
        validRequirement(_owners.length, _required)
    {
        for (uint256 i = 0; i < _owners.length; i++) {
            if (isOwner[_owners[i]] || _owners[i] == 0) {
                revert("OWNER_ERROR");
            }

            isOwner[_owners[i]] = true;
        }

        owners = _owners;
        required = _required;
    }

    /** @dev Allows to add a new owner. Transaction has to be sent by wallet.
      * @param owner Address of new owner.
      */
    function addOwner(address owner)
        public
        onlyWallet
        ownerDoesNotExist(owner)
        notNull(owner)
        validRequirement(owners.length + 1, required)
    {
        isOwner[owner] = true;
        owners.push(owner);
        emit OwnerAddition(owner);
    }

    /** @dev Allows to remove an owner. Transaction has to be sent by wallet.
      * @param owner Address of owner.
      */
    function removeOwner(address owner)
        public
        onlyWallet
        ownerExists(owner)
    {
        isOwner[owner] = false;
        for (uint256 i = 0; i < owners.length - 1; i++) {
            if (owners[i] == owner) {
                owners[i] = owners[owners.length - 1];
                break;
            }
        }

        owners.length -= 1;

        if (required > owners.length) {
            changeRequirement(owners.length);
        }

        emit OwnerRemoval(owner);
    }

    /** @dev Allows to replace an owner with a new owner. Transaction has to be sent by wallet.
      * @param owner Address of owner to be replaced.
      * @param owner Address of new owner.
      */
    function replaceOwner(address owner, address newOwner)
        public
        onlyWallet
        ownerExists(owner)
        ownerDoesNotExist(newOwner)
    {
        for (uint256 i = 0; i < owners.length; i++) {
            if (owners[i] == owner) {
                owners[i] = newOwner;
                break;
            }
        }

        isOwner[owner] = false;
        isOwner[newOwner] = true;
        emit OwnerRemoval(owner);
        emit OwnerAddition(newOwner);
    }

    /** @dev Allows to change the number of required confirmations. Transaction has to be sent by wallet.
      * @param _required Number of required confirmations.
      */
    function changeRequirement(uint256 _required)
        public
        onlyWallet
        validRequirement(owners.length, _required)
    {
        required = _required;
        emit RequirementChange(_required);
    }

    /** @dev Allows an owner to submit and confirm a transaction.
      * @param destination Transaction target address.
      * @param value Transaction ether value.
      * @param data Transaction data payload.
      * @return Returns transaction ID.
      */
    function submitTransaction(address destination, uint256 value, bytes data)
        public
        returns (uint256 transactionId)
    {
        transactionId = addTransaction(destination, value, data);
        confirmTransaction(transactionId);
    }

    /** @dev Allows an owner to confirm a transaction.
      * @param transactionId Transaction ID.
      */
    function confirmTransaction(uint256 transactionId)
        public
        ownerExists(msg.sender)
        transactionExists(transactionId)
        notConfirmed(transactionId, msg.sender)
    {
        confirmations[transactionId][msg.sender] = true;
        emit Confirmation(msg.sender, transactionId);
        executeTransaction(transactionId);
    }

    /** @dev Allows an owner to revoke a confirmation for a transaction.
      * @param transactionId Transaction ID.
      */
    function revokeConfirmation(uint256 transactionId)
        public
        ownerExists(msg.sender)
        confirmed(transactionId, msg.sender)
        notExecuted(transactionId)
    {
        confirmations[transactionId][msg.sender] = false;
        emit Revocation(msg.sender, transactionId);
    }

    /** @dev Allows anyone to execute a confirmed transaction.
      * @param transactionId Transaction ID.
      */
    function executeTransaction(uint256 transactionId)
        public
        ownerExists(msg.sender)
        notExecuted(transactionId)
    {
        if (isConfirmed(transactionId)) {
            Transaction storage transaction = transactions[transactionId];
            transaction.executed = true;
            if (transaction.destination.call.value(transaction.value)(transaction.data))
                emit Execution(transactionId);
            else {
                emit ExecutionFailure(transactionId);
                transaction.executed = false;
            }
        }
    }

    /** @dev Returns the confirmation status of a transaction.
      * @param transactionId Transaction ID.
      * @return Confirmation status.
      */
    function isConfirmed(uint256 transactionId)
        public
        view
        returns (bool)
    {
        uint256 count = 0;
        for (uint256 i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                count += 1;
            }

            if (count >= required) {
                return true;
            }
        }
    }

    /* Internal functions */

    /** @dev Adds a new transaction to the transaction mapping, if transaction does not exist yet.
      * @param destination Transaction target address.
      * @param value Transaction ether value.
      * @param data Transaction data payload.
      * @return Returns transaction ID.
      */
    function addTransaction(address destination, uint256 value, bytes data)
        internal
        notNull(destination)
        returns (uint256 transactionId)
    {
        transactionId = transactionCount;
        transactions[transactionId] = Transaction({
            destination: destination,
            value: value,
            data: data,
            executed: false
        });
        transactionCount += 1;
        emit Submission(transactionId);
    }


    /* Web3 call functions */

    /** @dev Returns number of confirmations of a transaction.
      * @param transactionId Transaction ID.
      * @return Number of confirmations.
      */
    function getConfirmationCount(uint256 transactionId)
        public
        view
        returns (uint256 count)
    {
        for (uint256 i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                count += 1;
            }
        }
    }

    /** @dev Returns total number of transactions after filers are applied.
      * @param pending Include pending transactions.
      * @param executed Include executed transactions.
      * @return Total number of transactions after filters are applied.
      */
    function getTransactionCount(bool pending, bool executed)
        public
        view
        returns (uint256 count)
    {
        for (uint256 i = 0; i < transactionCount; i++) {
            if (pending && !transactions[i].executed || executed && transactions[i].executed) {
                count += 1;
            }
        }
    }

    /** @dev Returns list of owners.
      * @return List of owner addresses.
      */
    function getOwners() public view returns (address[]) {
        return owners;
    }

    /** @dev Returns array with owner addresses, which confirmed transaction.
      * @param transactionId Transaction ID.
      * @return Returns array of owner addresses.
      */
    function getConfirmations(uint256 transactionId)
        public
        view
        returns (address[] _confirmations)
    {
        address[] memory confirmationsTemp = new address[](owners.length);
        uint256 count = 0;
        uint256 i;

        for (i = 0; i < owners.length; i++) {
            if (confirmations[transactionId][owners[i]]) {
                confirmationsTemp[count] = owners[i];
                count += 1;
            }
        }

        _confirmations = new address[](count);

        for (i = 0; i < count; i++) {
            _confirmations[i] = confirmationsTemp[i];
        }
    }
}
/** @title Multisignature wallet - Allows multiple parties to agree on transactions before execution.
 * @author Stefan George - <stefan.george@consensys.net>
 */
function replaceOwner(address owner, address newOwner)
        public
        onlyWallet
        ownerExists(owner)
        ownerDoesNotExist(newOwner)
    {
        for (uint256 i = 0; i < owners.length; i++) {
            if (owners[i] == owner) {
                owners[i] = newOwner;
                break;
            }
        }

        isOwner[owner] = false;
        isOwner[newOwner] = true;
        emit OwnerRemoval(owner);
        emit OwnerAddition(newOwner);
    }
/** @dev Allows to replace an owner with a new owner. Transaction has to be sent by wallet.
 * @param owner Address of owner to be replaced.
 * @param owner Address of new owner.
 */