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package org.drools.compiler.rule.builder.util;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.util.HashMap;
import java.util.Map;
import java.util.function.Supplier;

import org.kie.api.runtime.rule.AccumulateFunction;
import org.kie.internal.builder.conf.AccumulateFunctionOption;
import org.kie.internal.utils.ChainedProperties;

import static org.drools.util.ClassUtils.convertFromPrimitiveType;

public class AccumulateUtil {

    public static String getFunctionName(Supplier> exprClassSupplier, String functionName) {
        if (functionName.equals("sum")) {
            final Class exprClass = exprClassSupplier.get();
            if (exprClass == int.class || exprClass == Integer.class) {
                functionName = "sumI";
            } else if (exprClass == long.class || exprClass == Long.class) {
                functionName = "sumL";
            } else if (exprClass == BigInteger.class) {
                functionName = "sumBI";
            } else if (exprClass == BigDecimal.class) {
                functionName = "sumBD";
            }
        } else if (functionName.equals("average")) {
            final Class exprClass = exprClassSupplier.get();
            if (exprClass == BigDecimal.class) {
                functionName = "averageBD";
            }
        } else if (functionName.equals("max")) {
            final Class exprClass = convertFromPrimitiveType( exprClassSupplier.get() );
            if (exprClass == Integer.class) {
                functionName = "maxI";
            } else if (exprClass == Long.class) {
                functionName = "maxL";
            } else if (Number.class.isAssignableFrom( exprClass )) {
                functionName = "maxN";
            }
        } else if (functionName.equals("min")) {
            final Class exprClass = convertFromPrimitiveType( exprClassSupplier.get() );
            if (exprClass == Integer.class) {
                functionName = "minI";
            } else if (exprClass == Long.class) {
                functionName = "minL";
            } else if (Number.class.isAssignableFrom( exprClass )) {
                functionName = "minN";
            }
        }
        return functionName;
    }

    @SuppressWarnings("unchecked")
    public static AccumulateFunction loadAccumulateFunction(ClassLoader classLoader, String identifier,
                                                            String className) {
        try {
            Class clazz = (Class) classLoader.loadClass(className);
            return clazz.newInstance();
        } catch (ClassNotFoundException e) {
            throw new RuntimeException("Error loading accumulate function for identifier " + identifier + ". Class " + className + " not found",
                                       e);
        } catch (InstantiationException e) {
            throw new RuntimeException("Error loading accumulate function for identifier " + identifier + ". Instantiation failed for class " + className,
                                       e);
        } catch (IllegalAccessException e) {
            throw new RuntimeException("Error loading accumulate function for identifier " + identifier + ". Illegal access to class " + className,
                                       e);
        }
    }

    public static Map buildAccumulateFunctionsMap(ChainedProperties chainedProperties, ClassLoader typesClassLoader) {
        Map accumulateFunctions = new HashMap<>();
        Map temp = new HashMap<>();
        chainedProperties.mapStartsWith(temp,
                                        AccumulateFunctionOption.PROPERTY_NAME,
                                        true);
        int index = AccumulateFunctionOption.PROPERTY_NAME.length();
        for (Map.Entry entry : temp.entrySet()) {
            String identifier = entry.getKey().trim().substring(index);
            accumulateFunctions.put(identifier,
                                    AccumulateUtil.loadAccumulateFunction(typesClassLoader, identifier,
                                                                          entry.getValue()));
        }
        return accumulateFunctions;
    }
}