/*-
 * #%L
 * HAPI FHIR - Core Library
 * %%
 * Copyright (C) 2014 - 2025 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%
 */
package ca.uhn.fhir.util;

import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.i18n.Msg;
import jakarta.annotation.Nonnull;
import org.apache.commons.lang3.StringUtils;
import org.apache.commons.lang3.Validate;
import org.hl7.fhir.instance.model.api.IBase;
import org.hl7.fhir.instance.model.api.IBaseDatatype;
import org.hl7.fhir.instance.model.api.IBaseExtension;
import org.hl7.fhir.instance.model.api.IBaseHasExtensions;
import org.hl7.fhir.instance.model.api.IPrimitiveType;

import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.function.Predicate;
import java.util.stream.Collectors;

/**
 * Utility for modifying with extensions in a FHIR version-independent approach.
 */
public class ExtensionUtil {

        /**
         * Non instantiable
         */
        private ExtensionUtil() {
                // nothing
        }

        /**
         * Returns an extension with the specified URL creating one if it doesn't exist.
         *
         * @param theBase Base resource to get extension from
         * @param theUrl  URL for the extension
         * @return Returns a extension with the specified URL.
         * @throws IllegalArgumentException IllegalArgumentException is thrown in case resource doesn't support extensions
         */
        public static IBaseExtension<?, ?> getOrCreateExtension(IBase theBase, String theUrl) {
                IBaseHasExtensions baseHasExtensions = validateExtensionSupport(theBase);
                IBaseExtension<?, ?> extension = getExtensionByUrl(baseHasExtensions, theUrl);
                if (extension == null) {
                        extension = baseHasExtensions.addExtension();
                        extension.setUrl(theUrl);
                }
                return extension;
        }

        /**
         * Returns an new empty extension.
         *
         * @param theBase Base resource to add the extension to
         * @return Returns a new extension
         * @throws IllegalArgumentException IllegalArgumentException is thrown in case resource doesn't support extensions
         */
        public static IBaseExtension<?, ?> addExtension(IBase theBase) {
                return addExtension(theBase, null);
        }

        /**
         * Returns an extension with the specified URL
         *
         * @param theBase Base resource to add the extension to
         * @param theUrl  URL for the extension
         * @return Returns a new extension with the specified URL.
         * @throws IllegalArgumentException IllegalArgumentException is thrown in case resource doesn't support extensions
         */
        public static IBaseExtension<?, ?> addExtension(IBase theBase, String theUrl) {
                IBaseHasExtensions baseHasExtensions = validateExtensionSupport(theBase);
                IBaseExtension<?, ?> extension = baseHasExtensions.addExtension();
                if (theUrl != null) {
                        extension.setUrl(theUrl);
                }
                return extension;
        }

        /**
         * Adds an extension with the specified value
         *
         * @param theBase        The resource to update extension on
         * @param theUrl         Extension URL
         * @param theValueType   Type of the value to set in the extension
         * @param theValue       Extension value
         * @param theFhirContext The context containing FHIR resource definitions
         */
        public static void addExtension(
                        FhirContext theFhirContext, IBase theBase, String theUrl, String theValueType, Object theValue) {
                IBaseExtension<?, ?> ext = addExtension(theBase, theUrl);
                setExtension(theFhirContext, ext, theValueType, theValue);
        }

        private static IBaseHasExtensions validateExtensionSupport(IBase theBase) {
                if (!(theBase instanceof IBaseHasExtensions)) {
                        throw new IllegalArgumentException(
                                        Msg.code(1747) + String.format("Expected instance that supports extensions, but got %s", theBase));
                }
                return (IBaseHasExtensions) theBase;
        }

        /**
         * Checks if the specified instance has an extension with the specified URL
         *
         * @param theBase         The base resource to check extensions on
         * @param theExtensionUrl URL of the extension
         * @return Returns true if extension is exists and false otherwise
         */
        public static boolean hasExtension(IBase theBase, String theExtensionUrl) {
                IBaseHasExtensions baseHasExtensions;
                try {
                        baseHasExtensions = validateExtensionSupport(theBase);
                } catch (Exception e) {
                        return false;
                }

                return getExtensionByUrl(baseHasExtensions, theExtensionUrl) != null;
        }

        /**
         * Checks if the specified instance has an extension with the specified URL
         *
         * @param theBase         The base resource to check extensions on
         * @param theExtensionUrl URL of the extension
         * @return Returns true if extension is exists and false otherwise
         */
        public static boolean hasExtension(IBase theBase, String theExtensionUrl, String theExtensionValue) {
                if (!hasExtension(theBase, theExtensionUrl)) {
                        return false;
                }
                IBaseDatatype value = getExtensionByUrl(theBase, theExtensionUrl).getValue();
                if (value == null) {
                        return theExtensionValue == null;
                }
                return value.toString().equals(theExtensionValue);
        }

        /**
         * Gets the first extension with the specified URL
         *
         * @param theBase         The resource to get the extension for
         * @param theExtensionUrl URL of the extension to get. Must be non-null
         * @return Returns the first available extension with the specified URL, or null if such extension doesn't exist
         */
        public static IBaseExtension<?, ?> getExtensionByUrl(IBase theBase, String theExtensionUrl) {
                Predicate<IBaseExtension<?, ?>> filter;
                if (theExtensionUrl == null) {
                        filter = (e -> true);
                } else {
                        filter = (e -> theExtensionUrl.equals(e.getUrl()));
                }

                return getExtensionsMatchingPredicate(theBase, filter).stream()
                                .findFirst()
                                .orElse(null);
        }

        /**
         * Given a resource or other structure that can have direct extensions,
         * pulls out any extensions that have the given theExtensionUrl and a primitive value type,
         * and returns a list of the string version of the extension values.
         */
        public static List<String> getExtensionPrimitiveValues(IBase theBase, String theExtensionUrl) {
                if (theBase instanceof IBaseHasExtensions) {
                        return ((IBaseHasExtensions) theBase)
                                        .getExtension().stream()
                                                        .filter(t -> theExtensionUrl.equals(t.getUrl()))
                                                        .filter(t -> t.getValue() instanceof IPrimitiveType<?>)
                                                        .map(t -> (IPrimitiveType<?>) t.getValue())
                                                        .map(IPrimitiveType::getValueAsString)
                                                        .filter(StringUtils::isNotBlank)
                                                        .collect(Collectors.toList());
                }
                return Collections.emptyList();
        }

        /**
         * Gets all extensions that match the specified filter predicate
         *
         * @param theBase   The resource to get the extension for
         * @param theFilter Predicate to match the extension against
         * @return Returns all extension with the specified URL, or an empty list if such extensions do not exist
         */
        public static List<IBaseExtension<?, ?>> getExtensionsMatchingPredicate(
                        IBase theBase, Predicate<? super IBaseExtension<?, ?>> theFilter) {
                return validateExtensionSupport(theBase).getExtension().stream()
                                .filter(theFilter)
                                .collect(Collectors.toList());
        }

        /**
         * Removes all extensions.
         *
         * @param theBase The resource to clear the extension for
         * @return Returns all extension that were removed
         */
        public static List<IBaseExtension<?, ?>> clearAllExtensions(IBase theBase) {
                return clearExtensionsMatchingPredicate(theBase, (e -> true));
        }

        /**
         * Removes all extensions by URL.
         *
         * @param theBase The resource to clear the extension for
         * @param theUrl  The url to clear extensions for
         * @return Returns all extension that were removed
         */
        public static List<IBaseExtension<?, ?>> clearExtensionsByUrl(IBase theBase, String theUrl) {
                return clearExtensionsMatchingPredicate(theBase, (e -> theUrl.equals(e.getUrl())));
        }

        /**
         * Removes all extensions that match the specified predicate
         *
         * @param theBase   The base object to clear the extension for
         * @param theFilter Defines which extensions should be cleared
         * @return Returns all extension that were removed
         */
        private static List<IBaseExtension<?, ?>> clearExtensionsMatchingPredicate(
                        IBase theBase, Predicate<? super IBaseExtension<?, ?>> theFilter) {
                List<IBaseExtension<?, ?>> retVal = getExtensionsMatchingPredicate(theBase, theFilter);
                validateExtensionSupport(theBase).getExtension().removeIf(theFilter);
                return retVal;
        }

        /**
         * Gets all extensions with the specified URL
         *
         * @param theBase         The resource to get the extension for
         * @param theExtensionUrl URL of the extension to get. Must be non-null
         * @return Returns all extension with the specified URL, or an empty list if such extensions do not exist
         */
        public static List<IBaseExtension<?, ?>> getExtensionsByUrl(IBaseHasExtensions theBase, String theExtensionUrl) {
                Predicate<IBaseExtension<?, ?>> urlEqualityPredicate = e -> theExtensionUrl.equals(e.getUrl());
                return getExtensionsMatchingPredicate(theBase, urlEqualityPredicate);
        }

        /**
         * Sets value of the extension as a string
         *
         * @param theExtension   The extension to set the value on
         * @param theValue       The value to set
         * @param theFhirContext The context containing FHIR resource definitions
         */
        public static void setExtension(FhirContext theFhirContext, IBaseExtension<?, ?> theExtension, String theValue) {
                setExtension(theFhirContext, theExtension, "string", theValue);
        }

        /**
         * Sets value of the extension
         *
         * @param theExtension     The extension to set the value on
         * @param theExtensionType Element type of the extension
         * @param theValue         The value to set
         * @param theFhirContext   The context containing FHIR resource definitions
         */
        public static void setExtension(
                        FhirContext theFhirContext, IBaseExtension<?, ?> theExtension, String theExtensionType, Object theValue) {
                theExtension.setValue(TerserUtil.newElement(theFhirContext, theExtensionType, theValue));
        }

        /**
         * Sets or replaces existing extension with the specified value as a string
         *
         * @param theBase        The resource to update extension on
         * @param theUrl         Extension URL
         * @param theValue       Extension value
         * @param theFhirContext The context containing FHIR resource definitions
         */
        public static void setExtensionAsString(FhirContext theFhirContext, IBase theBase, String theUrl, String theValue) {
                IBaseExtension<?, ?> ext = getOrCreateExtension(theBase, theUrl);
                setExtension(theFhirContext, ext, theValue);
        }

        /**
         * Sets or replaces existing extension with the specified value
         *
         * @param theBase        The resource to update extension on
         * @param theUrl         Extension URL
         * @param theValueType   Type of the value to set in the extension
         * @param theValue       Extension value
         * @param theFhirContext The context containing FHIR resource definitions
         */
        public static void setExtension(
                        FhirContext theFhirContext, IBase theBase, String theUrl, String theValueType, Object theValue) {
                IBaseExtension<?, ?> ext = getOrCreateExtension(theBase, theUrl);
                setExtension(theFhirContext, ext, theValueType, theValue);
        }

        /**
         * Compares two extensions, returns true if they have the same value and url
         *
         * @param theLeftExtension  : Extension to be evaluated #1
         * @param theRightExtension : Extension to be evaluated #2
         * @return Result of the comparison
         */
        public static boolean equals(IBaseExtension<?, ?> theLeftExtension, IBaseExtension<?, ?> theRightExtension) {
                return TerserUtil.equals(theLeftExtension, theRightExtension);
        }

        /**
         * Given an extension, looks for the first child extension with the given URL of {@literal theChildExtensionUrl}
         * and a primitive datatype value, and returns the String version of that value. E.g. if the
         * value is a FHIR boolean, it would return the string "true" or "false. If the extension
         * has no value, or the value is not a primitive datatype, or the URL is not found, the method
         * will return {@literal null}.
         *
         * @param theExtension The parent extension. Must not be null.
         * @param theChildExtensionUrl The child extension URL. Must not be null or blank.
         * @since 6.6.0
         */
        public static <D, T extends IBaseExtension<T, D>> String extractChildPrimitiveExtensionValue(
                        @Nonnull IBaseExtension<T, D> theExtension, @Nonnull String theChildExtensionUrl) {
                Validate.notNull(theExtension, "theExtension must not be null");
                Validate.notBlank(theChildExtensionUrl, "theChildExtensionUrl must not be null or blank");

                Optional<T> codeExtension = theExtension.getExtension().stream()
                                .filter(t -> theChildExtensionUrl.equals(t.getUrl()))
                                .findFirst();
                String retVal = null;
                if (codeExtension.isPresent() && codeExtension.get().getValue() instanceof IPrimitiveType) {
                        IPrimitiveType<?> codeValue =
                                        (IPrimitiveType<?>) codeExtension.get().getValue();
                        retVal = codeValue.getValueAsString();
                }
                return retVal;
        }
}