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/*
 * Copyright (c)  2016, 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 io.siddhi.extension.execution.math;

import io.siddhi.annotation.Example;
import io.siddhi.annotation.Extension;
import io.siddhi.annotation.Parameter;
import io.siddhi.annotation.ParameterOverload;
import io.siddhi.annotation.ReturnAttribute;
import io.siddhi.annotation.util.DataType;
import io.siddhi.core.config.SiddhiQueryContext;
import io.siddhi.core.executor.ExpressionExecutor;
import io.siddhi.core.executor.function.FunctionExecutor;
import io.siddhi.core.util.config.ConfigReader;
import io.siddhi.core.util.snapshot.state.State;
import io.siddhi.core.util.snapshot.state.StateFactory;
import io.siddhi.query.api.definition.Attribute;
import io.siddhi.query.api.exception.SiddhiAppValidationException;

import static io.siddhi.extension.execution.math.util.MathUtil.convertToDouble;

/**
 * to_radians(a)
 * Converts a from degrees to radians.
 * 1 degrees = Pi / 180 = 0.005555556Pi = 0.0174532925 rad
 * Accept Type(s) :DOUBLE/INT/FLOAT/LONG
 * Return Type(s): DOUBLE
 */
@Extension(
        name = "toRadians",
        namespace = "math",
        description = "This function converts the value given in degrees to radians. It wraps the `java.lang.Math" +
                ".toRadians()` function.",
        parameters = {
                @Parameter(
                        name = "p1",
                        description = "The input value in degrees that should be converted to radians.",
                        type = {DataType.INT, DataType.LONG, DataType.FLOAT, DataType.DOUBLE},
                        dynamic = true)
        },
        parameterOverloads = {
                @ParameterOverload(parameterNames = {"p1"})
        },
        returnAttributes = @ReturnAttribute(
                description = "The value in radians after converting the input from degrees." ,
                type = {DataType.DOUBLE}),
        examples = @Example(
                syntax = "define stream InValueStream (inValue double); \n" +
                        "from InValueStream \n" +
                        "select math:toRadians(inValue) as radiansValue \n" +
                        "insert into OutMediationStream;",
                description = "This function converts the input, from degrees to radians and " +
                        "directs the result to 'OutMediationStream' output stream. For example, " +
                        "toRadians(6d) returns 0.10471975511965977.")
)
public class ToRadiansFunctionExtension extends FunctionExecutor {
    @Override
    protected StateFactory init(ExpressionExecutor[] expressionExecutors, ConfigReader configReader,
                                SiddhiQueryContext siddhiQueryContext) {
        if (attributeExpressionExecutors.length != 1) {
            throw new SiddhiAppValidationException("Invalid no of arguments passed to math:to_radians() function, " +
                    "required 1, but found " + attributeExpressionExecutors.length);
        }
        Attribute.Type attributeType = attributeExpressionExecutors[0].getReturnType();
        if (!((attributeType == Attribute.Type.DOUBLE)
                || (attributeType == Attribute.Type.INT)
                || (attributeType == Attribute.Type.FLOAT)
                || (attributeType == Attribute.Type.LONG))) {
            throw new SiddhiAppValidationException("Invalid parameter type found for the argument of " +
                    "math:to_radians() function, required " + Attribute.Type.INT + " or " + Attribute.Type.LONG +
                    " or " + Attribute.Type.FLOAT + " or " + Attribute.Type.DOUBLE +
                    ", but found " + attributeType.toString());
        }
        return null;
    }

    @Override
    protected Object execute(Object[] data, State state) {
        return null;    // This method won't get called. Hence, unimplemented.
    }

    @Override
    protected Object execute(Object data, State state) {
        if (data != null) {
            return Math.toRadians(convertToDouble(data));
        }
        return null;
    }

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

}