package ca.uhn.fhir.util;

/*-
 * #%L
 * HAPI FHIR - Core Library
 * %%
 * Copyright (C) 2014 - 2022 Smile CDR, Inc.
 * %%
 * Licensed 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.
 * #L%
 */

import ca.uhn.fhir.context.FhirContext;
import org.apache.commons.lang3.StringUtils;
import org.hl7.fhir.instance.model.api.IBase;

import java.lang.reflect.Method;
import java.util.Arrays;
import java.util.List;
import java.util.stream.Collectors;

/**
 * Helper class for handling updates of the instances that support property modification via <code>setProperty</code>
 * and <code>getProperty</code> methods.
 */
public class PropertyModifyingHelper {

        public static final String GET_PROPERTY_METHOD_NAME = "getProperty";
        public static final String SET_PROPERTY_METHOD_NAME = "setProperty";
        public static final String DEFAULT_DELIMITER = ", ";

        private IBase myBase;

        private String myDelimiter = DEFAULT_DELIMITER;

        private FhirContext myFhirContext;

        /**
         * Creates a new instance initializing the dependencies.
         *
         * @param theFhirContext FHIR context holding the resource definitions
         * @param theBase        The base class to set properties on
         */
        public PropertyModifyingHelper(FhirContext theFhirContext, IBase theBase) {
                if (findGetPropertyMethod(theBase) == null) {
                        throw new IllegalArgumentException("Specified base instance does not support property retrieval.");
                }
                myBase = theBase;
                myFhirContext = theFhirContext;
        }

        /**
         * Gets the method with the specified name and parameter types.
         *
         * @param theObject       Non-null instance to get the method from
         * @param theMethodName   Name of the method to get
         * @param theParamClasses Parameters types that method parameters should be assignable as
         * @return Returns the method with the given name and parameters or null if it can't be found
         */
        protected Method getMethod(Object theObject, String theMethodName, Class... theParamClasses) {
                for (Method m : theObject.getClass().getDeclaredMethods()) {
                        if (m.getName().equals(theMethodName)) {
                                if (theParamClasses.length == 0) {
                                        return m;
                                }
                                if (m.getParameterCount() != theParamClasses.length) {
                                        continue;
                                }
                                for (int i = 0; i < theParamClasses.length; i++) {
                                        if (!m.getParameterTypes()[i].isAssignableFrom(theParamClasses[i])) {
                                                continue;
                                        }
                                }
                                return m;
                        }
                }
                return null;
        }

        /**
         * Gets all non-blank fields as a single string joined with the delimiter provided by {@link #getDelimiter()}
         *
         * @param theFiledNames Field names to retrieve values for
         * @return Returns all specified non-blank fileds as a single string.
         */
        public String getFields(String... theFiledNames) {
                return Arrays.stream(theFiledNames)
                        .map(this::get)
                        .filter(s -> !StringUtils.isBlank(s))
                        .collect(Collectors.joining(getDelimiter()));
        }

        /**
         * Gets property with the specified name from the provided base class.
         *
         * @param thePropertyName Name of the property to get
         * @return Returns property value converted to string. In case of multiple values, they are joined with the
         * specified delimiter.
         */
        public String get(String thePropertyName) {
                return getMultiple(thePropertyName)
                        .stream()
                        .collect(Collectors.joining(getDelimiter()));
        }

        /**
         * Sets property or adds to a collection of properties with the specified name from the provided base class.
         *
         * @param thePropertyName Name of the property to set or add element to in case property is a collection
         */
        public void set(String thePropertyName, String theValue) {
                if (theValue == null || theValue.isEmpty()) {
                        return;
                }

                try {
                        IBase value = myFhirContext.getElementDefinition("string").newInstance(theValue);
                        Method setPropertyMethod = findSetPropertyMethod(myBase, int.class, String.class, value.getClass());
                        int hashCode = thePropertyName.hashCode();
                        setPropertyMethod.invoke(myBase, hashCode, thePropertyName, value);
                } catch (Exception e) {
                        throw new IllegalStateException(String.format("Unable to set property %s on %s", thePropertyName, myBase), e);
                }
        }

        /**
         * Gets property values with the specified name from the provided base class.
         *
         * @param thePropertyName Name of the property to get
         * @return Returns property values converted to string.
         */
        public List<String> getMultiple(String thePropertyName) {
                Method getPropertyMethod = findGetPropertyMethod(myBase);
                Object[] values;
                try {
                        values = (Object[]) getPropertyMethod.invoke(myBase, thePropertyName.hashCode(), thePropertyName, true);
                } catch (Exception e) {
                        throw new IllegalStateException(String.format("Instance %s does not supply property %s", myBase, thePropertyName), e);
                }

                return Arrays.stream(values)
                        .map(String::valueOf)
                        .filter(s -> !StringUtils.isEmpty(s))
                        .collect(Collectors.toList());
        }

        private Method findGetPropertyMethod(IBase theAddress) {
                return getMethod(theAddress, GET_PROPERTY_METHOD_NAME);
        }

        private Method findSetPropertyMethod(IBase theAddress, Class... theParamClasses) {
                return getMethod(theAddress, SET_PROPERTY_METHOD_NAME, theParamClasses);
        }

        /**
         * Gets the delimiter used when concatenating multiple field values
         *
         * @return Returns the delimiter
         */
        public String getDelimiter() {
                return myDelimiter;
        }

        /**
         * Sets the delimiter used when concatenating multiple field values
         *
         * @param theDelimiter The delimiter to set
         */
        public void setDelimiter(String theDelimiter) {
                this.myDelimiter = theDelimiter;
        }

        /**
         * Gets the base instance that this helper operates on
         *
         * @return Returns the base instance
         */
        public IBase getBase() {
                return myBase;
        }
}