contract Agreement is
    IAgreement,
    AccessControlled,
    AccessRoles
{

    ////////////////////////
    // Type declarations
    ////////////////////////

    /// @notice agreement with signature of the platform operator representative
    struct SignedAgreement {
        address contractLegalRepresentative;
        uint256 signedBlockTimestamp;
        string agreementUri;
    }

    ////////////////////////
    // Immutable state
    ////////////////////////

    IEthereumForkArbiter private ETHEREUM_FORK_ARBITER;

    ////////////////////////
    // Mutable state
    ////////////////////////

    // stores all amendments to the agreement, first amendment is the original
    SignedAgreement[] private _amendments;

    // stores block numbers of all addresses that signed the agreement (signatory => block number)
    mapping(address => uint256) private _signatories;

    ////////////////////////
    // Modifiers
    ////////////////////////

    /// @notice logs that agreement was accepted by platform user
    /// @dev intended to be added to functions that if used make 'accepter' origin to enter legally binding agreement
    modifier acceptAgreement(address accepter) {
        acceptAgreementInternal(accepter);
        _;
    }

    modifier onlyLegalRepresentative(address legalRepresentative) {
        require(mCanAmend(legalRepresentative));
        _;
    }

    ////////////////////////
    // Constructor
    ////////////////////////

    constructor(IAccessPolicy accessPolicy, IEthereumForkArbiter forkArbiter)
        AccessControlled(accessPolicy)
        internal
    {
        require(forkArbiter != IEthereumForkArbiter(0x0));
        ETHEREUM_FORK_ARBITER = forkArbiter;
    }

    ////////////////////////
    // Public functions
    ////////////////////////

    function amendAgreement(string agreementUri)
        public
        onlyLegalRepresentative(msg.sender)
    {
        SignedAgreement memory amendment = SignedAgreement({
            contractLegalRepresentative: msg.sender,
            signedBlockTimestamp: block.timestamp,
            agreementUri: agreementUri
        });
        _amendments.push(amendment);
        emit LogAgreementAmended(msg.sender, agreementUri);
    }

    function ethereumForkArbiter()
        public
        constant
        returns (IEthereumForkArbiter)
    {
        return ETHEREUM_FORK_ARBITER;
    }

    function currentAgreement()
        public
        constant
        returns
        (
            address contractLegalRepresentative,
            uint256 signedBlockTimestamp,
            string agreementUri,
            uint256 index
        )
    {
        require(_amendments.length > 0);
        uint256 last = _amendments.length - 1;
        SignedAgreement storage amendment = _amendments[last];
        return (
            amendment.contractLegalRepresentative,
            amendment.signedBlockTimestamp,
            amendment.agreementUri,
            last
        );
    }

    function pastAgreement(uint256 amendmentIndex)
        public
        constant
        returns
        (
            address contractLegalRepresentative,
            uint256 signedBlockTimestamp,
            string agreementUri,
            uint256 index
        )
    {
        SignedAgreement storage amendment = _amendments[amendmentIndex];
        return (
            amendment.contractLegalRepresentative,
            amendment.signedBlockTimestamp,
            amendment.agreementUri,
            amendmentIndex
        );
    }

    function agreementSignedAtBlock(address signatory)
        public
        constant
        returns (uint256 blockNo)
    {
        return _signatories[signatory];
    }

    function amendmentsCount()
        public
        constant
        returns (uint256)
    {
        return _amendments.length;
    }

    ////////////////////////
    // Internal functions
    ////////////////////////

    /// provides direct access to derived contract
    function acceptAgreementInternal(address accepter)
        internal
    {
        if(_signatories[accepter] == 0) {
            require(_amendments.length > 0);
            _signatories[accepter] = block.number;
            emit LogAgreementAccepted(accepter);
        }
    }

    //
    // MAgreement Internal interface (todo: extract)
    //

    /// default amend permission goes to ROLE_PLATFORM_OPERATOR_REPRESENTATIVE
    function mCanAmend(address legalRepresentative)
        internal
        returns (bool)
    {
        return accessPolicy().allowed(legalRepresentative, ROLE_PLATFORM_OPERATOR_REPRESENTATIVE, this, msg.sig);
    }
}
/**
 * @title legally binding smart contract
 * @dev read IAgreement for details
 **/
function acceptAgreementInternal(address accepter)
        internal
    {
        if(_signatories[accepter] == 0) {
            require(_amendments.length > 0);
            _signatories[accepter] = block.number;
            emit LogAgreementAccepted(accepter);
        }
    }
////////////////////////
/// provides direct access to derived contract