package ca.cdr.api.fhir.interceptor;

import ca.cdr.api.fhirgw.json.GatewayTargetJson;
import ca.cdr.api.fhirgw.model.OperationRequest;
import ca.cdr.api.fhirgw.model.OperationResponse;
import ca.cdr.api.fhirgw.model.ReadRequest;
import ca.cdr.api.fhirgw.model.SearchPageRequest;
import ca.cdr.api.fhirgw.model.SearchRequest;
import ca.cdr.api.fhirgw.model.SearchResponse;
import ca.cdr.api.fhirgw.model.SearchResultsAccumulator;
import ca.uhn.fhir.interceptor.api.IPointcut;
import ca.uhn.fhir.rest.server.servlet.ServletRequestDetails;
import org.apache.commons.lang3.ArrayUtils;

import javax.annotation.Nonnull;
import java.security.KeyStore;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;

/**
 * Value for {@link CdrHook#value()}
 * <p>
 * Hook pointcuts are divided into several broad categories:
 * <ul>
 * <li>FHIRGW_xxx: Hooks on the FHIR Gateway module</li>
 * </ul>
 * </p>
 */
public enum CdrPointcut implements IPointcut {

        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway is about to invoke a FHIR <b>read</b> or <b>vread</b> operation against an individual
         * target server. This hook is called once for each target that will be called, so if a single client read is being
         * multicasted against two target servers, this hook will be invoked twice.
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.ReadRequest} - The read that is about to be invoked. The hook method can modify this request, and modifications will affect the operation that is actually performed against the target server.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails} - A bean containing details about the request that
         * is about to be processed.
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         */
        FHIRGW_READ_TARGET_PREINVOKE(void.class,
                ReadRequest.class,
                GatewayTargetJson.class,
                ServletRequestDetails.class
        ),

        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway is about to invoke a FHIR <b>operation</b> operation against an individual
         * target server.
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.OperationRequest} - The read that is about to be invoked. The hook method can modify this request, and modifications will affect the operation that is actually performed against the target server.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails} - A bean containing details about the request that
         * is about to be processed.
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         */
        FHIRGW_OPERATION_TARGET_PREINVOKE(void.class,
                OperationRequest.class,
                GatewayTargetJson.class,
                ServletRequestDetails.class
        ),


        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway has finished invoking a FHIR <b>extended operation</b> operation against an individual
         * target server. This hook is called once for each target that has been called, so if a single client operation is being
         * multicasted against two target servers, this hook will be invoked twice.
         * <p>
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchResultsAccumulator} - The accumulator being used to collect the search results so far. This may be empty in the case of operations
         * which do not return search results. Some operations, such as <b>$everything</b>, will return search results, but others such as <b>$</b>
         * Hook methods may use this object to inspect results received by other endpoints when searching in serial mode, and can
         * modify the results as needed. Note that the {@link #FHIRGW_SEARCH_TARGET_POSTINVOKE} pointcut is invoked once for each gateway
         * target, <b>before</b> the search results are added to the accumulator. Results from the current target are found in the
         * {@link SearchResponse} object, and will be moved from that object into the accumulator after this pointcut is complete.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.OperationResponse} - This object contains the Operation Response from the individual Gateway Target that was called. Interceptors may modify this object in any way they want. This may be null if the operation returns a Bundle (check the SearchResultsAccumulator instead).
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         *
         **/
        FHIRGW_OPERATION_TARGET_POSTINVOKE(void.class,
                OperationRequest.class,
                SearchResultsAccumulator.class,
                OperationResponse.class,
                GatewayTargetJson.class,
                ServletRequestDetails.class
        ),

        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway is about to invoke a FHIR <b>search</b> operation against an individual
         * target server. This hook is called once for each target that will be called, so if a single client search is being
         * multicasted against two target servers, this hook will be invoked twice.
         * <p>
         * This hook can be contrasted with {@link #FHIRGW_SEARCH_PAGE_TARGET_PREINVOKE}:
         * <ul>
         *    <li>{@link #FHIRGW_SEARCH_TARGET_PREINVOKE} is called before the initial search is performed (which should return search results as well as paging links)</li>
         *    <li>{@link #FHIRGW_SEARCH_PAGE_TARGET_PREINVOKE} is called before the subsequent pages of results are fetched</li>
         * </ul>
         * </p>
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchRequest} - The search that is about to be invoked. The hook method can modify this request, and modifications will affect the operation that is actually performed against the target server.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchResultsAccumulator} - The accumulator being used to collect the search results so far. Hook methods may use this object to inspect results recieved by other endpoints when searching in serial mode, and can modify the results as needed.
         * </li>
         * <li>
         * {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails} - A bean containing details about the request that
         * is about to be processed.
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         */
        FHIRGW_SEARCH_TARGET_PREINVOKE(void.class,
                SearchRequest.class,
                GatewayTargetJson.class,
                SearchResultsAccumulator.class,
                ServletRequestDetails.class
                ),

        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway is about to invoke a FHIR <b>search</b> paging operation against an individual
         * target server. This hook is called once for each target that will be called, so if a single client search is being
         * multicasted against two target servers, this hook will be invoked twice.
         * <p>
         * This hook can be contrasted with {@link #FHIRGW_SEARCH_TARGET_PREINVOKE}:
         * <ul>
         *    <li>{@link #FHIRGW_SEARCH_TARGET_PREINVOKE} is called before the initial search is performed (which should return search results as well as paging links)</li>
         *    <li>{@link #FHIRGW_SEARCH_PAGE_TARGET_PREINVOKE} is called before the subsequent pages of results are fetched</li>
         * </ul>
         * </p>
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchPageRequest} - The search that is about to be invoked. The hook method can modify this request, and modifications will affect the operation that is actually performed against the target server.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchResultsAccumulator} - The accumulator being used to collect the search results so far. Hook methods may use this object to inspect results received by other endpoints when searching in serial mode, and can modify the results as needed.
         * </li>
         * <li>
         * {@link ca.uhn.fhir.rest.server.servlet.ServletRequestDetails} - A bean containing details about the request that
         * is about to be processed.
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         */
        FHIRGW_SEARCH_PAGE_TARGET_PREINVOKE(void.class,
                SearchPageRequest.class,
                GatewayTargetJson.class,
                SearchResultsAccumulator.class,
                ServletRequestDetails.class
        ),

        /**
         * <b>FHIR Gateway Hook:</b>
         * This hook is called when the FHIR Gateway has finished invoking a FHIR <b>search</b> operation against an individual
         * target server. This hook is called once for each target that has been called, so if a single client search is being
         * multicasted against two target servers, this hook will be invoked twice.
         * <p>
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@link ca.cdr.api.fhirgw.json.GatewayTargetJson} - The gateway target server definition. Hook methods should not modify this object, and any changes will be ignored.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchResultsAccumulator} - The accumulator being used to collect the search results so far.
         * Hook methods may use this object to inspect results received by other endpoints when searching in serial mode, and can
         * modify the results as needed. Note that the {@link #FHIRGW_SEARCH_TARGET_POSTINVOKE} pointcut is invoked once for each gateway
         * target, <b>before</b> the search results are added to the accumulator. Results from the current target are found in the
         * {@link SearchResponse} object, and will be moved from that object into the accumulator after this pointcut is complete.
         * </li>
         * <li>
         * {@link ca.cdr.api.fhirgw.model.SearchResponse} - This object contains the search results from the individual Gateway Target that was called. Interceptors may modify this object in any way they want.
         * </li>
         * </ul>
         * </p>
         * Hook methods must return <code>void</code>.
         */
        FHIRGW_SEARCH_TARGET_POSTINVOKE(void.class,
                GatewayTargetJson.class,
                SearchResultsAccumulator.class,
                SearchResponse.class,
                ServletRequestDetails.class
        ),

        /**
         * <b>Endpoint Hook:</b>
         * The pointcut provides the capability to supply a provisioned KeyStore file for TLS base encryption.
         * Note that pointcut {@link #SERVER_CONFIGURATION_KEYSTORE} is invoked only if the endpoint listener
         * is said to required TLS encryption for incoming connections through environment property <b>tls.enabled</b>
         * <p>
         * <p>
         * Hooks may accept the following parameters:
         * <ul>
         * <li>
         * {@java.lang.String} - The keystore password
         * </li>
         * </ul>
         *
         * </p>
         * Hook methods must return <code>KeyStore</code>.
         */
        SERVER_CONFIGURATION_KEYSTORE(KeyStore.class,
                String.class),
        ;

        private final List<String> myParameterTypes;
        private final Class<?> myReturnType;
        private final ExceptionHandlingSpec myExceptionHandlingSpec;

        CdrPointcut(@Nonnull Class<?> theReturnType, @Nonnull ExceptionHandlingSpec theExceptionHandlingSpec, String... theParameterTypes) {
                myReturnType = theReturnType;
                myExceptionHandlingSpec = theExceptionHandlingSpec;
                myParameterTypes = Collections.unmodifiableList(Arrays.asList(theParameterTypes));
        }

        CdrPointcut(@Nonnull Class<?> theReturnType, String... theParameterTypes) {
                this(theReturnType, new ExceptionHandlingSpec(), theParameterTypes);
        }

        CdrPointcut(@Nonnull Class<?> theReturnType, Class<?>... theParameterTypes) {
                this(theReturnType, new ExceptionHandlingSpec(), toNames(theParameterTypes));
        }

        CdrPointcut(@Nonnull Class<?> theReturnType) {
                this(theReturnType, new ExceptionHandlingSpec(), ArrayUtils.EMPTY_STRING_ARRAY);
        }

        private static String[] toNames(Class<?>[] theParameterTypes) {
                return Arrays.stream(theParameterTypes).map(t -> t.getName()).collect(Collectors.toList()).toArray(new String[0]);
        }

        private static Class<?> toReturnTypeClass(String theReturnType) {
                try {
                        return Class.forName(theReturnType);
                } catch (ClassNotFoundException theE) {
                        return UnknownType.class;
                }
        }

        @Override
        public boolean isShouldLogAndSwallowException(@Nonnull Throwable theException) {
                for (Class<? extends Throwable> next : myExceptionHandlingSpec.myTypesToLogAndSwallow) {
                        if (next.isAssignableFrom(theException.getClass())) {
                                return true;
                        }
                }
                return false;
        }

        @Override
        @Nonnull
        public Class<?> getReturnType() {
                return myReturnType;
        }

        @Override
        @Nonnull
        public List<String> getParameterTypes() {
                return myParameterTypes;
        }

        private static class UnknownType {
        }

        private static class ExceptionHandlingSpec {

                private final Set<Class<? extends Throwable>> myTypesToLogAndSwallow = new HashSet<>();

                ExceptionHandlingSpec addLogAndSwallow(@Nonnull Class<? extends Throwable> theType) {
                        myTypesToLogAndSwallow.add(theType);
                        return this;
                }

        }

}