contract ACL is IACL, TimeHelpers, AragonApp, ACLHelpers {
    /* Hardcoded constants to save gas
    bytes32 public constant CREATE_PERMISSIONS_ROLE = keccak256("CREATE_PERMISSIONS_ROLE");
    */
    bytes32 public constant CREATE_PERMISSIONS_ROLE = 0x0b719b33c83b8e5d300c521cb8b54ae9bd933996a14bef8c2f4e0285d2d2400a;

    enum Op { NONE, EQ, NEQ, GT, LT, GTE, LTE, RET, NOT, AND, OR, XOR, IF_ELSE } // op types

    struct Param {
        uint8 id;
        uint8 op;
        uint240 value; // even though value is an uint240 it can store addresses
        // in the case of 32 byte hashes losing 2 bytes precision isn't a huge deal
        // op and id take less than 1 byte each so it can be kept in 1 sstore
    }

    uint8 internal constant BLOCK_NUMBER_PARAM_ID = 200;
    uint8 internal constant TIMESTAMP_PARAM_ID    = 201;
    // 202 is unused
    uint8 internal constant ORACLE_PARAM_ID       = 203;
    uint8 internal constant LOGIC_OP_PARAM_ID     = 204;
    uint8 internal constant PARAM_VALUE_PARAM_ID  = 205;
    // TODO: Add execution times param type?

    /* Hardcoded constant to save gas
    bytes32 public constant EMPTY_PARAM_HASH = keccak256(uint256(0));
    */
    bytes32 public constant EMPTY_PARAM_HASH = 0x290decd9548b62a8d60345a988386fc84ba6bc95484008f6362f93160ef3e563;
    bytes32 public constant NO_PERMISSION = bytes32(0);
    address public constant ANY_ENTITY = address(-1);
    address public constant BURN_ENTITY = address(1); // address(0) is already used as "no permission manager"

    uint256 internal constant ORACLE_CHECK_GAS = 30000;

    string private constant ERROR_AUTH_INIT_KERNEL = "ACL_AUTH_INIT_KERNEL";
    string private constant ERROR_AUTH_NO_MANAGER = "ACL_AUTH_NO_MANAGER";
    string private constant ERROR_EXISTENT_MANAGER = "ACL_EXISTENT_MANAGER";

    // Whether someone has a permission
    mapping (bytes32 => bytes32) internal permissions; // permissions hash => params hash
    mapping (bytes32 => Param[]) internal permissionParams; // params hash => params

    // Who is the manager of a permission
    mapping (bytes32 => address) internal permissionManager;

    event SetPermission(address indexed entity, address indexed app, bytes32 indexed role, bool allowed);
    event SetPermissionParams(address indexed entity, address indexed app, bytes32 indexed role, bytes32 paramsHash);
    event ChangePermissionManager(address indexed app, bytes32 indexed role, address indexed manager);

    modifier onlyPermissionManager(address _app, bytes32 _role) {
        require(msg.sender == getPermissionManager(_app, _role), ERROR_AUTH_NO_MANAGER);
        _;
    }

    modifier noPermissionManager(address _app, bytes32 _role) {
        // only allow permission creation (or re-creation) when there is no manager
        require(getPermissionManager(_app, _role) == address(0), ERROR_EXISTENT_MANAGER);
        _;
    }

    /**
    * @dev Initialize can only be called once. It saves the block number in which it was initialized.
    * @notice Initialize an ACL instance and set `_permissionsCreator` as the entity that can create other permissions
    * @param _permissionsCreator Entity that will be given permission over createPermission
    */
    function initialize(address _permissionsCreator) public onlyInit {
        initialized();
        require(msg.sender == address(kernel()), ERROR_AUTH_INIT_KERNEL);

        _createPermission(_permissionsCreator, this, CREATE_PERMISSIONS_ROLE, _permissionsCreator);
    }

    /**
    * @dev Creates a permission that wasn't previously set and managed.
    *      If a created permission is removed it is possible to reset it with createPermission.
    *      This is the **ONLY** way to create permissions and set managers to permissions that don't
    *      have a manager.
    *      In terms of the ACL being initialized, this function implicitly protects all the other
    *      state-changing external functions, as they all require the sender to be a manager.
    * @notice Create a new permission granting `_entity` the ability to perform actions requiring `_role` on `_app`, setting `_manager` as the permission's manager
    * @param _entity Address of the whitelisted entity that will be able to perform the role
    * @param _app Address of the app in which the role will be allowed (requires app to depend on kernel for ACL)
    * @param _role Identifier for the group of actions in app given access to perform
    * @param _manager Address of the entity that will be able to grant and revoke the permission further.
    */
    function createPermission(address _entity, address _app, bytes32 _role, address _manager)
        external
        auth(CREATE_PERMISSIONS_ROLE)
        noPermissionManager(_app, _role)
    {
        _createPermission(_entity, _app, _role, _manager);
    }

    /**
    * @dev Grants permission if allowed. This requires `msg.sender` to be the permission manager
    * @notice Grant `_entity` the ability to perform actions requiring `_role` on `_app`
    * @param _entity Address of the whitelisted entity that will be able to perform the role
    * @param _app Address of the app in which the role will be allowed (requires app to depend on kernel for ACL)
    * @param _role Identifier for the group of actions in app given access to perform
    */
    function grantPermission(address _entity, address _app, bytes32 _role)
        external
    {
        grantPermissionP(_entity, _app, _role, new uint256[](0));
    }

    /**
    * @dev Grants a permission with parameters if allowed. This requires `msg.sender` to be the permission manager
    * @notice Grant `_entity` the ability to perform actions requiring `_role` on `_app`
    * @param _entity Address of the whitelisted entity that will be able to perform the role
    * @param _app Address of the app in which the role will be allowed (requires app to depend on kernel for ACL)
    * @param _role Identifier for the group of actions in app given access to perform
    * @param _params Permission parameters
    */
    function grantPermissionP(address _entity, address _app, bytes32 _role, uint256[] _params)
        public
        onlyPermissionManager(_app, _role)
    {
        bytes32 paramsHash = _params.length > 0 ? _saveParams(_params) : EMPTY_PARAM_HASH;
        _setPermission(_entity, _app, _role, paramsHash);
    }

    /**
    * @dev Revokes permission if allowed. This requires `msg.sender` to be the the permission manager
    * @notice Revoke from `_entity` the ability to perform actions requiring `_role` on `_app`
    * @param _entity Address of the whitelisted entity to revoke access from
    * @param _app Address of the app in which the role will be revoked
    * @param _role Identifier for the group of actions in app being revoked
    */
    function revokePermission(address _entity, address _app, bytes32 _role)
        external
        onlyPermissionManager(_app, _role)
    {
        _setPermission(_entity, _app, _role, NO_PERMISSION);
    }

    /**
    * @notice Set `_newManager` as the manager of `_role` in `_app`
    * @param _newManager Address for the new manager
    * @param _app Address of the app in which the permission management is being transferred
    * @param _role Identifier for the group of actions being transferred
    */
    function setPermissionManager(address _newManager, address _app, bytes32 _role)
        external
        onlyPermissionManager(_app, _role)
    {
        _setPermissionManager(_newManager, _app, _role);
    }

    /**
    * @notice Remove the manager of `_role` in `_app`
    * @param _app Address of the app in which the permission is being unmanaged
    * @param _role Identifier for the group of actions being unmanaged
    */
    function removePermissionManager(address _app, bytes32 _role)
        external
        onlyPermissionManager(_app, _role)
    {
        _setPermissionManager(address(0), _app, _role);
    }

    /**
    * @notice Burn non-existent `_role` in `_app`, so no modification can be made to it (grant, revoke, permission manager)
    * @param _app Address of the app in which the permission is being burned
    * @param _role Identifier for the group of actions being burned
    */
    function createBurnedPermission(address _app, bytes32 _role)
        external
        auth(CREATE_PERMISSIONS_ROLE)
        noPermissionManager(_app, _role)
    {
        _setPermissionManager(BURN_ENTITY, _app, _role);
    }

    /**
    * @notice Burn `_role` in `_app`, so no modification can be made to it (grant, revoke, permission manager)
    * @param _app Address of the app in which the permission is being burned
    * @param _role Identifier for the group of actions being burned
    */
    function burnPermissionManager(address _app, bytes32 _role)
        external
        onlyPermissionManager(_app, _role)
    {
        _setPermissionManager(BURN_ENTITY, _app, _role);
    }

    /**
     * @notice Get parameters for permission array length
     * @param _entity Address of the whitelisted entity that will be able to perform the role
     * @param _app Address of the app
     * @param _role Identifier for a group of actions in app
     * @return Length of the array
     */
    function getPermissionParamsLength(address _entity, address _app, bytes32 _role) external view returns (uint) {
        return permissionParams[permissions[permissionHash(_entity, _app, _role)]].length;
    }

    /**
    * @notice Get parameter for permission
    * @param _entity Address of the whitelisted entity that will be able to perform the role
    * @param _app Address of the app
    * @param _role Identifier for a group of actions in app
    * @param _index Index of parameter in the array
    * @return Parameter (id, op, value)
    */
    function getPermissionParam(address _entity, address _app, bytes32 _role, uint _index)
        external
        view
        returns (uint8, uint8, uint240)
    {
        Param storage param = permissionParams[permissions[permissionHash(_entity, _app, _role)]][_index];
        return (param.id, param.op, param.value);
    }

    /**
    * @dev Get manager for permission
    * @param _app Address of the app
    * @param _role Identifier for a group of actions in app
    * @return address of the manager for the permission
    */
    function getPermissionManager(address _app, bytes32 _role) public view returns (address) {
        return permissionManager[roleHash(_app, _role)];
    }

    /**
    * @dev Function called by apps to check ACL on kernel or to check permission statu
    * @param _who Sender of the original call
    * @param _where Address of the app
    * @param _where Identifier for a group of actions in app
    * @param _how Permission parameters
    * @return boolean indicating whether the ACL allows the role or not
    */
    function hasPermission(address _who, address _where, bytes32 _what, bytes memory _how) public view returns (bool) {
        // Force cast the bytes array into a uint256[], by overwriting its length
        // Note that the uint256[] doesn't need to be initialized as we immediately overwrite it
        // with _how and a new length, and _how becomes invalid from this point forward
        uint256[] memory how;
        uint256 intsLength = _how.length / 32;
        assembly {
            how := _how
            mstore(how, intsLength)
        }

        return hasPermission(_who, _where, _what, how);
    }

    function hasPermission(address _who, address _where, bytes32 _what, uint256[] memory _how) public view returns (bool) {
        bytes32 whoParams = permissions[permissionHash(_who, _where, _what)];
        if (whoParams != NO_PERMISSION && evalParams(whoParams, _who, _where, _what, _how)) {
            return true;
        }

        bytes32 anyParams = permissions[permissionHash(ANY_ENTITY, _where, _what)];
        if (anyParams != NO_PERMISSION && evalParams(anyParams, ANY_ENTITY, _where, _what, _how)) {
            return true;
        }

        return false;
    }

    function hasPermission(address _who, address _where, bytes32 _what) public view returns (bool) {
        uint256[] memory empty = new uint256[](0);
        return hasPermission(_who, _where, _what, empty);
    }

    function evalParams(
        bytes32 _paramsHash,
        address _who,
        address _where,
        bytes32 _what,
        uint256[] _how
    ) public view returns (bool)
    {
        if (_paramsHash == EMPTY_PARAM_HASH) {
            return true;
        }

        return _evalParam(_paramsHash, 0, _who, _where, _what, _how);
    }

    /**
    * @dev Internal createPermission for access inside the kernel (on instantiation)
    */
    function _createPermission(address _entity, address _app, bytes32 _role, address _manager) internal {
        _setPermission(_entity, _app, _role, EMPTY_PARAM_HASH);
        _setPermissionManager(_manager, _app, _role);
    }

    /**
    * @dev Internal function called to actually save the permission
    */
    function _setPermission(address _entity, address _app, bytes32 _role, bytes32 _paramsHash) internal {
        permissions[permissionHash(_entity, _app, _role)] = _paramsHash;
        bool entityHasPermission = _paramsHash != NO_PERMISSION;
        bool permissionHasParams = entityHasPermission && _paramsHash != EMPTY_PARAM_HASH;

        emit SetPermission(_entity, _app, _role, entityHasPermission);
        if (permissionHasParams) {
            emit SetPermissionParams(_entity, _app, _role, _paramsHash);
        }
    }

    function _saveParams(uint256[] _encodedParams) internal returns (bytes32) {
        bytes32 paramHash = keccak256(abi.encodePacked(_encodedParams));
        Param[] storage params = permissionParams[paramHash];

        if (params.length == 0) { // params not saved before
            for (uint256 i = 0; i < _encodedParams.length; i++) {
                uint256 encodedParam = _encodedParams[i];
                Param memory param = Param(decodeParamId(encodedParam), decodeParamOp(encodedParam), uint240(encodedParam));
                params.push(param);
            }
        }

        return paramHash;
    }

    function _evalParam(
        bytes32 _paramsHash,
        uint32 _paramId,
        address _who,
        address _where,
        bytes32 _what,
        uint256[] _how
    ) internal view returns (bool)
    {
        if (_paramId >= permissionParams[_paramsHash].length) {
            return false; // out of bounds
        }

        Param memory param = permissionParams[_paramsHash][_paramId];

        if (param.id == LOGIC_OP_PARAM_ID) {
            return _evalLogic(param, _paramsHash, _who, _where, _what, _how);
        }

        uint256 value;
        uint256 comparedTo = uint256(param.value);

        // get value
        if (param.id == ORACLE_PARAM_ID) {
            value = checkOracle(IACLOracle(param.value), _who, _where, _what, _how) ? 1 : 0;
            comparedTo = 1;
        } else if (param.id == BLOCK_NUMBER_PARAM_ID) {
            value = getBlockNumber();
        } else if (param.id == TIMESTAMP_PARAM_ID) {
            value = getTimestamp();
        } else if (param.id == PARAM_VALUE_PARAM_ID) {
            value = uint256(param.value);
        } else {
            if (param.id >= _how.length) {
                return false;
            }
            value = uint256(uint240(_how[param.id])); // force lost precision
        }

        if (Op(param.op) == Op.RET) {
            return uint256(value) > 0;
        }

        return compare(value, Op(param.op), comparedTo);
    }

    function _evalLogic(Param _param, bytes32 _paramsHash, address _who, address _where, bytes32 _what, uint256[] _how)
        internal
        view
        returns (bool)
    {
        if (Op(_param.op) == Op.IF_ELSE) {
            uint32 conditionParam;
            uint32 successParam;
            uint32 failureParam;

            (conditionParam, successParam, failureParam) = decodeParamsList(uint256(_param.value));
            bool result = _evalParam(_paramsHash, conditionParam, _who, _where, _what, _how);

            return _evalParam(_paramsHash, result ? successParam : failureParam, _who, _where, _what, _how);
        }

        uint32 param1;
        uint32 param2;

        (param1, param2,) = decodeParamsList(uint256(_param.value));
        bool r1 = _evalParam(_paramsHash, param1, _who, _where, _what, _how);

        if (Op(_param.op) == Op.NOT) {
            return !r1;
        }

        if (r1 && Op(_param.op) == Op.OR) {
            return true;
        }

        if (!r1 && Op(_param.op) == Op.AND) {
            return false;
        }

        bool r2 = _evalParam(_paramsHash, param2, _who, _where, _what, _how);

        if (Op(_param.op) == Op.XOR) {
            return r1 != r2;
        }

        return r2; // both or and and depend on result of r2 after checks
    }

    function compare(uint256 _a, Op _op, uint256 _b) internal pure returns (bool) {
        if (_op == Op.EQ)  return _a == _b;                              // solium-disable-line lbrace
        if (_op == Op.NEQ) return _a != _b;                              // solium-disable-line lbrace
        if (_op == Op.GT)  return _a > _b;                               // solium-disable-line lbrace
        if (_op == Op.LT)  return _a < _b;                               // solium-disable-line lbrace
        if (_op == Op.GTE) return _a >= _b;                              // solium-disable-line lbrace
        if (_op == Op.LTE) return _a <= _b;                              // solium-disable-line lbrace
        return false;
    }

    function checkOracle(IACLOracle _oracleAddr, address _who, address _where, bytes32 _what, uint256[] _how) internal view returns (bool) {
        bytes4 sig = _oracleAddr.canPerform.selector;

        // a raw call is required so we can return false if the call reverts, rather than reverting
        bytes memory checkCalldata = abi.encodeWithSelector(sig, _who, _where, _what, _how);
        uint256 oracleCheckGas = ORACLE_CHECK_GAS;

        bool ok;
        assembly {
            ok := staticcall(oracleCheckGas, _oracleAddr, add(checkCalldata, 0x20), mload(checkCalldata), 0, 0)
        }

        if (!ok) {
            return false;
        }

        uint256 size;
        assembly { size := returndatasize }
        if (size != 32) {
            return false;
        }

        bool result;
        assembly {
            let ptr := mload(0x40)       // get next free memory ptr
            returndatacopy(ptr, 0, size) // copy return from above `staticcall`
            result := mload(ptr)         // read data at ptr and set it to result
            mstore(ptr, 0)               // set pointer memory to 0 so it still is the next free ptr
        }

        return result;
    }

    /**
    * @dev Internal function that sets management
    */
    function _setPermissionManager(address _newManager, address _app, bytes32 _role) internal {
        permissionManager[roleHash(_app, _role)] = _newManager;
        emit ChangePermissionManager(_app, _role, _newManager);
    }

    function roleHash(address _where, bytes32 _what) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("ROLE", _where, _what));
    }

    function permissionHash(address _who, address _where, bytes32 _what) internal pure returns (bytes32) {
        return keccak256(abi.encodePacked("PERMISSION", _who, _where, _what));
    }
}
// Allow public initialize() to be first
function removePermissionManager(address _app, bytes32 _role)
        external
        onlyPermissionManager(_app, _role)
    {
        _setPermissionManager(address(0), _app, _role);
    }
/**
 * @notice Remove the manager of `_role` in `_app`
 * @param _app Address of the app in which the permission is being unmanaged
 * @param _role Identifier for the group of actions being unmanaged
 */