# GetDevicesOfUserFunctionExecutor.java

    /*
     * Copyright (c) 2017, WSO2 Inc. (http://www.wso2.org) All Rights Reserved.
     *
     * WSO2 Inc. licenses this file to you under the Apache License,
     * Version 2.0 (the "License"); you may not use this file except
     * in compliance with the License.
     * You may obtain a copy of the License at
     *
     * http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing,
     * software distributed under the License is distributed on an
     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     * KIND, either express or implied. See the License for the
     * specific language governing permissions and limitations
     * under the License.
     */

    package org.wso2.extension.siddhi.device;

    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.json.JSONArray;
    import org.wso2.carbon.device.mgt.common.Device;
    import org.wso2.carbon.device.mgt.common.DeviceManagementException;
    import org.wso2.carbon.device.mgt.core.service.DeviceManagementProviderService;
    import org.wso2.extension.siddhi.device.utils.DeviceUtils;
    import org.wso2.siddhi.core.config.ExecutionPlanContext;
    import org.wso2.siddhi.core.exception.ExecutionPlanRuntimeException;
    import org.wso2.siddhi.core.executor.ExpressionExecutor;
    import org.wso2.siddhi.core.executor.function.FunctionExecutor;
    import org.wso2.siddhi.query.api.definition.Attribute;
    import org.wso2.siddhi.query.api.exception.ExecutionPlanValidationException;

    import java.util.List;

    /**
     * getDevicesOfUser(user , deviceType [, status])
     * Returns list of ids of devices belongs to a user
     * Accept Type(s): (STRING, STRING, STRING)
     * Return Type(s): (STRING)
     */
    public class GetDevicesOfUserFunctionExecutor extends FunctionExecutor {

        private static Log log = LogFactory.getLog(GetDevicesOfUserFunctionExecutor.class);
        private Attribute.Type returnType = Attribute.Type.STRING;

        @Override
        protected void init(ExpressionExecutor[] attributeExpressionExecutors,
                            ExecutionPlanContext executionPlanContext) {
            if (attributeExpressionExecutors.length != 2 && attributeExpressionExecutors.length != 3) {
                throw new ExecutionPlanValidationException(
                        "Invalid no of arguments passed to device:getDevicesOfUser() function, minimum 2, or 3 with " +
                        "optional. but found " + attributeExpressionExecutors.length);
            }
            if (attributeExpressionExecutors[0].getReturnType() != Attribute.Type.STRING) {
                throw new ExecutionPlanValidationException(
                        "Invalid parameter type found for the first argument (user) of device:getDevicesOfUser() " +
                        "function, required " + Attribute.Type.STRING + " as user, but found " +
                        attributeExpressionExecutors[0].getReturnType().toString());
            }
            if (attributeExpressionExecutors[1].getReturnType() != Attribute.Type.STRING) {
                throw new ExecutionPlanValidationException(
                        "Invalid parameter type found for the second argument (device type) of device:getDevicesOfUser() " +
                        "function, required " + Attribute.Type.STRING + " as device type, but found " +
                        attributeExpressionExecutors[1].getReturnType().toString());
            }
            if (attributeExpressionExecutors.length == 3
                && attributeExpressionExecutors[2].getReturnType() != Attribute.Type.STRING) {
                throw new ExecutionPlanValidationException(
                        "Invalid optional parameter type found for the third argument (status) of " +
                        "device:getDevicesOfUser() function, required " + Attribute.Type.STRING + " as status, but found " +
                        attributeExpressionExecutors[2].getReturnType().toString());
            }
        }

        @Override
        protected Object execute(Object[] data) {
            if (data[0] == null) {
                throw new ExecutionPlanRuntimeException("Invalid input given to device:getDevicesOfUser() function. " +
                                                        "First argument cannot be null");
            }
            if (data[1] == null) {
                throw new ExecutionPlanRuntimeException("Invalid input given to device:getDevicesOfUser() function. " +
                                                        "Second argument cannot be null");
            }
            if (data.length == 3 && data[2] == null) {
                throw new ExecutionPlanRuntimeException("Invalid input given to device:getDevicesOfUser() function. " +
                                                        "Third argument cannot be null");
            }
            String user = (String) data[0];
            String deviceType = (String) data[1];
            String status = null;
            if (data.length == 3) {
                status = (String) data[2];
            }

            JSONArray deviceIds = new JSONArray();
            try {
                DeviceManagementProviderService deviceManagementProviderService = DeviceUtils.getDeviceManagementProviderService();
                List<Device> devices = deviceManagementProviderService.getDevicesOfUser(user, deviceType, false);
                for (Device device : devices) {
                    if (status == null || status.equalsIgnoreCase(device.getEnrolmentInfo().getStatus().toString())) {
                        deviceIds.put(device.getDeviceIdentifier());
                    }
                }
            } catch (DeviceManagementException e) {
                log.error("Error occurred while getting " + deviceType + " devices of user " + user +
                          ", with status " + status, e);
            }
            return deviceIds.toString();
        }

        @Override
        protected Object execute(Object data) {
            return null;  //Since the getDevicesOfUser function takes in 2 or 3 parameters, this method does not get called. Hence,not implemented.
        }

        @Override
        public void start() {
            //Nothing to start
        }

        @Override
        public void stop() {
            //Nothing to stop
        }

        @Override
        public Attribute.Type getReturnType() {
            return returnType;
        }

        @Override
        public Object[] currentState() {
            return null;    //No need to maintain a state.
        }

        @Override
        public void restoreState(Object[] state) {
            //Since there's no need to maintain a state, nothing needs to be done here.
        }
    }