/*-
 * #%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.BaseRuntimeChildDefinition;
import ca.uhn.fhir.context.BaseRuntimeElementCompositeDefinition;
import ca.uhn.fhir.context.BaseRuntimeElementDefinition;
import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.context.FhirVersionEnum;
import ca.uhn.fhir.context.RuntimeResourceDefinition;
import ca.uhn.fhir.context.RuntimeSearchParam;
import ca.uhn.fhir.i18n.Msg;
import jakarta.annotation.Nonnull;
import jakarta.annotation.Nullable;
import org.apache.commons.collections4.CollectionUtils;
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.IBaseResource;
import org.hl7.fhir.instance.model.api.IPrimitiveType;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;

import static org.apache.commons.lang3.StringUtils.isBlank;

public class SearchParameterUtil {

        public static List<String> getBaseAsStrings(FhirContext theContext, IBaseResource theResource) {
                Validate.notNull(theContext, "theContext must not be null");
                Validate.notNull(theResource, "theResource must not be null");
                RuntimeResourceDefinition def = theContext.getResourceDefinition(theResource);

                BaseRuntimeChildDefinition base = def.getChildByName("base");
                List<IBase> baseValues = base.getAccessor().getValues(theResource);
                List<String> retVal = new ArrayList<>();
                for (IBase next : baseValues) {
                        IPrimitiveType<?> nextPrimitive = (IPrimitiveType<?>) next;
                        retVal.add(nextPrimitive.getValueAsString());
                }

                return retVal;
        }

        /**
         * Given the resource type, fetch its patient-based search parameter name
         * 1. Attempt to find one called 'patient'
         * 2. If that fails, find one called 'subject'
         * 3. If that fails, find one by Patient Compartment.
         * 3.1 If that returns exactly 1 result then return it
         * 3.2 If that doesn't return exactly 1 result and is R4, fall to 3.3, otherwise, 3.5
         * 3.3 If that returns >1 result, throw an error
         * 3.4 If that returns 1 result, return it
         * 3.5 Find the search parameters by patient compartment using the R4 FHIR path, and return it if there is 1 result,
         * otherwise, fall to 3.3
         */
        public static Optional<RuntimeSearchParam> getOnlyPatientSearchParamForResourceType(
                        FhirContext theFhirContext, String theResourceType) {
                RuntimeSearchParam myPatientSearchParam = null;
                RuntimeResourceDefinition runtimeResourceDefinition = theFhirContext.getResourceDefinition(theResourceType);
                myPatientSearchParam = runtimeResourceDefinition.getSearchParam("patient");
                if (myPatientSearchParam == null) {
                        myPatientSearchParam = runtimeResourceDefinition.getSearchParam("subject");
                        if (myPatientSearchParam == null) {
                                final List<RuntimeSearchParam> searchParamsForCurrentVersion =
                                                runtimeResourceDefinition.getSearchParamsForCompartmentName("Patient");
                                final List<RuntimeSearchParam> searchParamsToUse;
                                // We want to handle a narrow code path in which attempting to process SearchParameters for a non-R4
                                // resource would have failed, and instead make another attempt to process them with the R4-equivalent
                                // FHIR path.
                                if (FhirVersionEnum.R4 == theFhirContext.getVersion().getVersion()
                                                || searchParamsForCurrentVersion.size() == 1) {
                                        searchParamsToUse = searchParamsForCurrentVersion;
                                } else {
                                        searchParamsToUse =
                                                        checkR4PatientCompartmentForMatchingSearchParam(runtimeResourceDefinition, theResourceType);
                                }
                                myPatientSearchParam =
                                                validateSearchParamsAndReturnOnlyOne(runtimeResourceDefinition, searchParamsToUse);
                        }
                }
                return Optional.of(myPatientSearchParam);
        }

        @Nonnull
        private static List<RuntimeSearchParam> checkR4PatientCompartmentForMatchingSearchParam(
                        RuntimeResourceDefinition theRuntimeResourceDefinition, String theResourceType) {
                final RuntimeSearchParam patientSearchParamForR4 =
                                FhirContext.forR4Cached().getResourceDefinition(theResourceType).getSearchParam("patient");

                return Optional.ofNullable(patientSearchParamForR4)
                                .map(patientSearchParamForR4NonNull ->
                                                theRuntimeResourceDefinition.getSearchParamsForCompartmentName("Patient").stream()
                                                                .filter(searchParam -> searchParam.getPath() != null)
                                                                .filter(searchParam ->
                                                                                searchParam.getPath().equals(patientSearchParamForR4NonNull.getPath()))
                                                                .collect(Collectors.toList()))
                                .orElse(Collections.emptyList());
        }

        /**
         * Given the resource type, fetch all its patient-based search parameter name that's available
         */
        public static Set<String> getPatientSearchParamsForResourceType(
                        FhirContext theFhirContext, String theResourceType) {
                RuntimeResourceDefinition runtimeResourceDefinition = theFhirContext.getResourceDefinition(theResourceType);

                List<RuntimeSearchParam> searchParams =
                                new ArrayList<>(runtimeResourceDefinition.getSearchParamsForCompartmentName("Patient"));
                // add patient search parameter for resources that's not in the compartment
                RuntimeSearchParam myPatientSearchParam = runtimeResourceDefinition.getSearchParam("patient");
                if (myPatientSearchParam != null) {
                        searchParams.add(myPatientSearchParam);
                }
                RuntimeSearchParam mySubjectSearchParam = runtimeResourceDefinition.getSearchParam("subject");
                if (mySubjectSearchParam != null) {
                        searchParams.add(mySubjectSearchParam);
                }
                if (CollectionUtils.isEmpty(searchParams)) {
                        String errorMessage = String.format(
                                        "Resource type [%s] is not eligible for this type of export, as it contains no Patient compartment, and no `patient` or `subject` search parameter",
                                        runtimeResourceDefinition.getId());
                        throw new IllegalArgumentException(Msg.code(2222) + errorMessage);
                }
                // deduplicate list of searchParams and get their names
                return searchParams.stream().map(RuntimeSearchParam::getName).collect(Collectors.toSet());
        }

        /**
         * Search the resource definition for a compartment named 'patient' and return its related Search Parameter.
         */
        public static RuntimeSearchParam getOnlyPatientCompartmentRuntimeSearchParam(
                        FhirContext theFhirContext, String theResourceType) {
                RuntimeResourceDefinition resourceDefinition = theFhirContext.getResourceDefinition(theResourceType);
                return getOnlyPatientCompartmentRuntimeSearchParam(resourceDefinition);
        }

        public static RuntimeSearchParam getOnlyPatientCompartmentRuntimeSearchParam(
                        RuntimeResourceDefinition runtimeResourceDefinition) {
                return validateSearchParamsAndReturnOnlyOne(
                                runtimeResourceDefinition, runtimeResourceDefinition.getSearchParamsForCompartmentName("Patient"));
        }

        public static RuntimeSearchParam getOnlyPatientCompartmentRuntimeSearchParam(
                        RuntimeResourceDefinition runtimeResourceDefinition, List<RuntimeSearchParam> theSearchParams) {
                return validateSearchParamsAndReturnOnlyOne(runtimeResourceDefinition, theSearchParams);
        }

        @Nonnull
        private static RuntimeSearchParam validateSearchParamsAndReturnOnlyOne(
                        RuntimeResourceDefinition theRuntimeResourceDefinition, List<RuntimeSearchParam> theSearchParams) {
                final RuntimeSearchParam patientSearchParam;
                if (CollectionUtils.isEmpty(theSearchParams)) {
                        String errorMessage = String.format(
                                        "Resource type [%s] for ID [%s] and version: [%s] is not eligible for this type of export, as it contains no Patient compartment, and no `patient` or `subject` search parameter",
                                        theRuntimeResourceDefinition.getName(),
                                        theRuntimeResourceDefinition.getId(),
                                        theRuntimeResourceDefinition.getStructureVersion());
                        throw new IllegalArgumentException(Msg.code(1774) + errorMessage);
                } else if (theSearchParams.size() == 1) {
                        patientSearchParam = theSearchParams.get(0);
                } else {
                        String errorMessage = String.format(
                                        "Resource type [%s] for ID [%s] and version: [%s] has more than one Search Param which references a patient compartment. We are unable to disambiguate which patient search parameter we should be searching by.",
                                        theRuntimeResourceDefinition.getName(),
                                        theRuntimeResourceDefinition.getId(),
                                        theRuntimeResourceDefinition.getStructureVersion());
                        throw new IllegalArgumentException(Msg.code(1775) + errorMessage);
                }
                return patientSearchParam;
        }

        public static List<RuntimeSearchParam> getAllPatientCompartmentRuntimeSearchParamsForResourceType(
                        FhirContext theFhirContext, String theResourceType) {
                RuntimeResourceDefinition runtimeResourceDefinition = theFhirContext.getResourceDefinition(theResourceType);
                return getAllPatientCompartmentRuntimeSearchParams(runtimeResourceDefinition);
        }

        public static List<RuntimeSearchParam> getAllPatientCompartmenRuntimeSearchParams(FhirContext theFhirContext) {
                return theFhirContext.getResourceTypes().stream()
                                .flatMap(type ->
                                                getAllPatientCompartmentRuntimeSearchParamsForResourceType(theFhirContext, type).stream())
                                .collect(Collectors.toList());
        }

        public static Set<String> getAllResourceTypesThatAreInPatientCompartment(FhirContext theFhirContext) {
                return theFhirContext.getResourceTypes().stream()
                                .filter(type -> CollectionUtils.isNotEmpty(
                                                getAllPatientCompartmentRuntimeSearchParamsForResourceType(theFhirContext, type)))
                                .collect(Collectors.toSet());
        }

        private static List<RuntimeSearchParam> getAllPatientCompartmentRuntimeSearchParams(
                        RuntimeResourceDefinition theRuntimeResourceDefinition) {
                List<RuntimeSearchParam> patient = theRuntimeResourceDefinition.getSearchParamsForCompartmentName("Patient");
                return patient;
        }

        /**
         * Return true if any search parameter in the resource can point at a patient, false otherwise
         */
        public static boolean isResourceTypeInPatientCompartment(FhirContext theFhirContext, String theResourceType) {
                RuntimeResourceDefinition runtimeResourceDefinition = theFhirContext.getResourceDefinition(theResourceType);
                return CollectionUtils.isNotEmpty(getAllPatientCompartmentRuntimeSearchParams(runtimeResourceDefinition));
        }

        @Nullable
        public static String getCode(FhirContext theContext, IBaseResource theResource) {
                return getStringChild(theContext, theResource, "code");
        }

        @Nullable
        public static String getURL(FhirContext theContext, IBaseResource theResource) {
                return getStringChild(theContext, theResource, "url");
        }

        @Nullable
        public static String getExpression(FhirContext theFhirContext, IBaseResource theResource) {
                return getStringChild(theFhirContext, theResource, "expression");
        }

        private static String getStringChild(FhirContext theFhirContext, IBaseResource theResource, String theChildName) {
                Validate.notNull(theFhirContext, "theContext must not be null");
                Validate.notNull(theResource, "theResource must not be null");
                RuntimeResourceDefinition def = theFhirContext.getResourceDefinition(theResource);

                BaseRuntimeChildDefinition base = def.getChildByName(theChildName);
                return base.getAccessor()
                                .getFirstValueOrNull(theResource)
                                .map(t -> ((IPrimitiveType<?>) t))
                                .map(t -> t.getValueAsString())
                                .orElse(null);
        }

        public static String stripModifier(String theSearchParam) {
                String retval;
                int colonIndex = theSearchParam.indexOf(":");
                if (colonIndex == -1) {
                        retval = theSearchParam;
                } else {
                        retval = theSearchParam.substring(0, colonIndex);
                }
                return retval;
        }

        /**
         * Many SearchParameters combine a series of potential expressions into a single concatenated
         * expression. For example, in FHIR R5 the "encounter" search parameter has an expression like:
         * <code>AuditEvent.encounter | CarePlan.encounter | ChargeItem.encounter | ......</code>.
         * This method takes such a FHIRPath expression and splits it into a series of separate
         * expressions. To achieve this, we iteratively splits a string on any <code> or </code> or <code>|</code> that
         * is <b>not</b> contained inside a set of parentheses. e.g.
         * <p>
         * "Patient.select(a or b)" -->  ["Patient.select(a or b)"]
         * "Patient.select(a or b) or Patient.select(c or d )" --> ["Patient.select(a or b)", "Patient.select(c or d)"]
         * "Patient.select(a|b) or Patient.select(c or d )" --> ["Patient.select(a|b)", "Patient.select(c or d)"]
         * "Patient.select(b) | Patient.select(c)" -->  ["Patient.select(b)", "Patient.select(c)"]
         *
         * @param thePaths The FHIRPath expression to split
         * @return The split strings
         */
        public static String[] splitSearchParameterExpressions(String thePaths) {
                if (!StringUtils.containsAny(thePaths, " or ", " |")) {
                        return new String[] {thePaths};
                }
                List<String> topLevelOrExpressions = splitOutOfParensToken(thePaths, " or ");
                return topLevelOrExpressions.stream()
                                .flatMap(s -> splitOutOfParensToken(s, " |").stream())
                                .toArray(String[]::new);
        }

        private static List<String> splitOutOfParensToken(String thePath, String theToken) {
                int tokenLength = theToken.length();
                int index = thePath.indexOf(theToken);
                int rightIndex = 0;
                List<String> retVal = new ArrayList<>();
                while (index > -1) {
                        String left = thePath.substring(rightIndex, index);
                        if (allParensHaveBeenClosed(left)) {
                                retVal.add(left.trim());
                                rightIndex = index + tokenLength;
                        }
                        index = thePath.indexOf(theToken, index + tokenLength);
                }
                String pathTrimmed = thePath.substring(rightIndex).trim();
                if (!pathTrimmed.isEmpty()) {
                        retVal.add(pathTrimmed);
                }
                return retVal;
        }

        private static boolean allParensHaveBeenClosed(String thePaths) {
                int open = StringUtils.countMatches(thePaths, "(");
                int close = StringUtils.countMatches(thePaths, ")");
                return open == close;
        }

        /**
         * Given a FHIRPath expression which presumably addresses a FHIR reference or
         * canonical reference element (i.e. a FHIRPath expression used in a "reference"
         * SearchParameter), tries to determine whether the path could potentially resolve
         * to a canonical reference.
         * <p>
         * Just because a SearchParameter is a Reference SP, doesn't necessarily mean that it
         * can reference a canonical. So first we try to rule out the SP based on the path it
         * contains. This matters because a SearchParameter of type Reference can point to
         * a canonical element (in which case we need to _include any canonical targets). Or it
         * can point to a Reference element (in which case we only need to _include actual
         * references by ID).
         * </p>
         * <p>
         * This isn't perfect because there's really no definitive and comprehensive
         * way of determining the datatype that a SearchParameter or a FHIRPath point to. But
         * we do our best if the path is simple enough to just manually check the type it
         * points to, or if it ends in an explicit type declaration.
         * </p>
         * <p>
         * Because it is not possible to deterministically determine the datatype for a
         * FHIRPath expression in all cases, this method is cautious: it will return
         * {@literal true} if it isn't sure.
         * </p>
         *
         * @return Returns {@literal true} if the path could return a {@literal canonical} or {@literal CanonicalReference}, or returns {@literal false} if the path could only return a {@literal Reference}.
         */
        public static boolean referencePathCouldPotentiallyReferenceCanonicalElement(
                        FhirContext theContext, String theResourceType, String thePath, boolean theReverse) {

                // If this path explicitly wants a reference and not a canonical, we can ignore it since we're
                // only looking for canonicals here
                if (thePath.endsWith(".ofType(Reference)")) {
                        return false;
                }

                BaseRuntimeElementCompositeDefinition<?> currentDef = theContext.getResourceDefinition(theResourceType);

                String remainingPath = thePath;
                boolean firstSegment = true;
                while (remainingPath != null) {

                        int dotIdx = remainingPath.indexOf(".");
                        String currentSegment;
                        if (dotIdx == -1) {
                                currentSegment = remainingPath;
                                remainingPath = null;
                        } else {
                                currentSegment = remainingPath.substring(0, dotIdx);
                                remainingPath = remainingPath.substring(dotIdx + 1);
                        }

                        if (isBlank(currentSegment)) {
                                return true;
                        }

                        if (firstSegment) {
                                firstSegment = false;
                                if (Character.isUpperCase(currentSegment.charAt(0))) {
                                        // This is just the resource name
                                        if (!theReverse && !theResourceType.equals(currentSegment)) {
                                                return false;
                                        }
                                        continue;
                                }
                        }

                        BaseRuntimeChildDefinition child = currentDef.getChildByName(currentSegment);
                        if (child == null) {
                                return true;
                        }
                        BaseRuntimeElementDefinition<?> def = child.getChildByName(currentSegment);
                        if (def == null) {
                                return true;
                        }
                        if (def.getName().equals("Reference")) {
                                return false;
                        }
                        if (!(def instanceof BaseRuntimeElementCompositeDefinition)) {
                                return true;
                        }

                        currentDef = (BaseRuntimeElementCompositeDefinition<?>) def;
                }

                return true;
        }
}