pragma solidity 0.4.11;

contract AssetInterface {
    function _performTransferWithReference(address _to, uint _value, string _reference, address _sender) returns(bool);
    function _performTransferToICAPWithReference(bytes32 _icap, uint _value, string _reference, address _sender) returns(bool);
    function _performApprove(address _spender, uint _value, address _sender) returns(bool);    
    function _performTransferFromWithReference(address _from, address _to, uint _value, string _reference, address _sender) returns(bool);
    function _performTransferFromToICAPWithReference(address _from, bytes32 _icap, uint _value, string _reference, address _sender) returns(bool);
    function _performGeneric(bytes, address) payable returns(bytes32){
        revert();
    }
}

contract AssetProxy {
    function _forwardApprove(address _spender, uint _value, address _sender) returns(bool);
    function _forwardTransferFromWithReference(address _from, address _to, uint _value, string _reference, address _sender) returns(bool);
    function _forwardTransferFromToICAPWithReference(address _from, bytes32 _icap, uint _value, string _reference, address _sender) returns(bool);
    function balanceOf(address _owner) constant returns(uint);
}

/**
 * @title EToken2 Asset implementation contract.
 *
 * Basic asset implementation contract, without any additional logic.
 * Every other asset implementation contracts should derive from this one.
 * Receives calls from the proxy, and calls back immediatly without arguments modification.
 *
 * Note: all the non constant functions return false instead of throwing in case if state change
 * didn't happen yet.
 */
contract Asset is AssetInterface {
    // Assigned asset proxy contract, immutable.
    AssetProxy public proxy;

    /**
     * Only assigned proxy is allowed to call.
     */
    modifier onlyProxy() {
        if (proxy == msg.sender) {
            _;
        }
    }

    /**
     * Sets asset proxy address.
     *
     * Can be set only once.
     *
     * @param _proxy asset proxy contract address.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function init(AssetProxy _proxy) returns(bool) {
        if (address(proxy) != 0x0) {
            return false;
        }
        proxy = _proxy;
        return true;
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function _performTransferWithReference(address _to, uint _value, string _reference, address _sender) onlyProxy() returns(bool) {
        return _transferWithReference(_to, _value, _reference, _sender);
    }

    /**
     * Calls back without modifications.
     *
     * @return success.
     * @dev function is virtual, and meant to be overridden.
     */
    function _transferWithReference(address _to, uint _value, string _reference, address _sender) internal returns(bool) {
        return proxy._forwardTransferFromWithReference(_sender, _to, _value, _reference, _sender);
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function _performTransferToICAPWithReference(bytes32 _icap, uint _value, string _reference, address _sender) onlyProxy() returns(bool) {
        return _transferToICAPWithReference(_icap, _value, _reference, _sender);
    }

    /**
     * Calls back without modifications.
     *
     * @return success.
     * @dev function is virtual, and meant to be overridden.
     */
    function _transferToICAPWithReference(bytes32 _icap, uint _value, string _reference, address _sender) internal returns(bool) {
        return proxy._forwardTransferFromToICAPWithReference(_sender, _icap, _value, _reference, _sender);
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function _performTransferFromWithReference(address _from, address _to, uint _value, string _reference, address _sender) onlyProxy() returns(bool) {
        return _transferFromWithReference(_from, _to, _value, _reference, _sender);
    }

    /**
     * Calls back without modifications.
     *
     * @return success.
     * @dev function is virtual, and meant to be overridden.
     */
    function _transferFromWithReference(address _from, address _to, uint _value, string _reference, address _sender) internal returns(bool) {
        return proxy._forwardTransferFromWithReference(_from, _to, _value, _reference, _sender);
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function _performTransferFromToICAPWithReference(address _from, bytes32 _icap, uint _value, string _reference, address _sender) onlyProxy() returns(bool) {
        return _transferFromToICAPWithReference(_from, _icap, _value, _reference, _sender);
    }

    /**
     * Calls back without modifications.
     *
     * @return success.
     * @dev function is virtual, and meant to be overridden.
     */
    function _transferFromToICAPWithReference(address _from, bytes32 _icap, uint _value, string _reference, address _sender) internal returns(bool) {
        return proxy._forwardTransferFromToICAPWithReference(_from, _icap, _value, _reference, _sender);
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return success.
     * @dev function is final, and must not be overridden.
     */
    function _performApprove(address _spender, uint _value, address _sender) onlyProxy() returns(bool) {
        return _approve(_spender, _value, _sender);
    }

    /**
     * Calls back without modifications.
     *
     * @return success.
     * @dev function is virtual, and meant to be overridden.
     */
    function _approve(address _spender, uint _value, address _sender) internal returns(bool) {
        return proxy._forwardApprove(_spender, _value, _sender);
    }

    /**
     * Passes execution into virtual function.
     *
     * Can only be called by assigned asset proxy.
     *
     * @return bytes32 result.
     * @dev function is final, and must not be overridden.
     */
    function _performGeneric(bytes _data, address _sender) payable onlyProxy() returns(bytes32) {
        return _generic(_data, _sender);
    }

    modifier onlyMe() {
        if (this == msg.sender) {
            _;
        }
    }

    // Most probably the following should never be redefined in child contracts.
    address genericSender;
    function _generic(bytes _data, address _sender) internal returns(bytes32) {
        // Restrict reentrancy.
        if (genericSender != 0x0) {
            throw;
        }
        genericSender = _sender;
        bytes32 result = _callReturn(this, _data, msg.value);
        delete genericSender;
        return result;
    }

    function _callReturn(address _target, bytes _data, uint _value) internal returns(bytes32 result) {
        bool success;
        assembly {
            success := call(div(mul(gas, 63), 64), _target, _value, add(_data, 32), mload(_data), 0, 32)
            result := mload(0)
        }
        if (!success) {
            throw;
        }
    }

    // Decsendants should use _sender() instead of msg.sender to properly process proxied calls.
    function _sender() constant internal returns(address) {
        return this == msg.sender ? genericSender : msg.sender;
    }
}