package ca.uhn.fhir.rest.client.impl;

/*
 * #%L
 * HAPI FHIR - Client Framework
 * %%
 * Copyright (C) 2014 - 2018 University Health Network
 * %%
 * 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 static org.apache.commons.lang3.StringUtils.isNotBlank;

import java.io.IOException;
import java.io.InputStream;
import java.io.Reader;
import java.io.StringReader;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.Set;

import ca.uhn.fhir.rest.api.CacheControlDirective;
import ca.uhn.fhir.util.XmlDetectionUtil;
import org.apache.commons.io.IOUtils;
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.IBaseOperationOutcome;
import org.hl7.fhir.instance.model.api.IBaseResource;
import org.hl7.fhir.instance.model.api.IIdType;
import org.hl7.fhir.instance.model.api.IPrimitiveType;

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.RuntimeResourceDefinition;
import ca.uhn.fhir.parser.DataFormatException;
import ca.uhn.fhir.parser.IParser;
import ca.uhn.fhir.rest.api.Constants;
import ca.uhn.fhir.rest.api.EncodingEnum;
import ca.uhn.fhir.rest.api.SummaryEnum;
import ca.uhn.fhir.rest.client.api.IClientInterceptor;
import ca.uhn.fhir.rest.client.api.IHttpClient;
import ca.uhn.fhir.rest.client.api.IHttpRequest;
import ca.uhn.fhir.rest.client.api.IHttpResponse;
import ca.uhn.fhir.rest.client.api.IRestfulClient;
import ca.uhn.fhir.rest.client.api.IRestfulClientFactory;
import ca.uhn.fhir.rest.client.api.ServerValidationModeEnum;
import ca.uhn.fhir.rest.client.exceptions.FhirClientConnectionException;
import ca.uhn.fhir.rest.client.exceptions.InvalidResponseException;
import ca.uhn.fhir.rest.client.exceptions.NonFhirResponseException;
import ca.uhn.fhir.rest.client.method.HttpGetClientInvocation;
import ca.uhn.fhir.rest.client.method.IClientResponseHandler;
import ca.uhn.fhir.rest.client.method.IClientResponseHandlerHandlesBinary;
import ca.uhn.fhir.rest.client.method.MethodUtil;
import ca.uhn.fhir.rest.server.exceptions.BaseServerResponseException;
import ca.uhn.fhir.util.OperationOutcomeUtil;
import ca.uhn.fhir.util.XmlUtil;

public abstract class BaseClient implements IRestfulClient {

        /**
         * This property is used by unit tests - do not rely on it in production code
         * as it may change at any time. If you want to capture responses in a reliable
         * way in your own code, just use client interceptors
         */
        public static final String HAPI_CLIENT_KEEPRESPONSES = "hapi.client.keepresponses";

        private static final org.slf4j.Logger ourLog = org.slf4j.LoggerFactory.getLogger(BaseClient.class);

        private final IHttpClient myClient;
        private boolean myDontValidateConformance;
        private EncodingEnum myEncoding = null; // default unspecified (will be XML)
        private final RestfulClientFactory myFactory;
        private List<IClientInterceptor> myInterceptors = new ArrayList<IClientInterceptor>();
        private boolean myKeepResponses = false;
        private IHttpResponse myLastResponse;
        private String myLastResponseBody;
        private Boolean myPrettyPrint = false;
        private SummaryEnum mySummary;
        private final String myUrlBase;

        BaseClient(IHttpClient theClient, String theUrlBase, RestfulClientFactory theFactory) {
                super();
                myClient = theClient;
                myUrlBase = theUrlBase;
                myFactory = theFactory;

                /*
                 * This property is used by unit tests - do not rely on it in production code
                 * as it may change at any time. If you want to capture responses in a reliable
                 * way in your own code, just use client interceptors
                 */
                if ("true".equals(System.getProperty(HAPI_CLIENT_KEEPRESPONSES))) {
                        setKeepResponses(true);
                }

                if (XmlDetectionUtil.isStaxPresent() == false) {
                        myEncoding = EncodingEnum.JSON;
                }

        }

        protected Map<String, List<String>> createExtraParams() {
                HashMap<String, List<String>> retVal = new LinkedHashMap<String, List<String>>();

                if (getEncoding() == EncodingEnum.XML) {
                        retVal.put(Constants.PARAM_FORMAT, Collections.singletonList("xml"));
                } else if (getEncoding() == EncodingEnum.JSON) {
                        retVal.put(Constants.PARAM_FORMAT, Collections.singletonList("json"));
                }

                if (isPrettyPrint()) {
                        retVal.put(Constants.PARAM_PRETTY, Collections.singletonList(Constants.PARAM_PRETTY_VALUE_TRUE));
                }

                return retVal;
        }

        @Override
        public <T extends IBaseResource> T fetchResourceFromUrl(Class<T> theResourceType, String theUrl) {
                BaseHttpClientInvocation clientInvocation = new HttpGetClientInvocation(getFhirContext(), theUrl);
                ResourceResponseHandler<T> binding = new ResourceResponseHandler<T>(theResourceType);
                return invokeClient(getFhirContext(), binding, clientInvocation, null, false, false, null, null, null);
        }

        void forceConformanceCheck() {
                myFactory.validateServerBase(myUrlBase, myClient, this);
        }

        @Override
        public EncodingEnum getEncoding() {
                return myEncoding;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public IHttpClient getHttpClient() {
                return myClient;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public List<IClientInterceptor> getInterceptors() {
                return Collections.unmodifiableList(myInterceptors);
        }

        /**
         * For now, this is a part of the internal API of HAPI - Use with caution as this method may change!
         */
        public IHttpResponse getLastResponse() {
                return myLastResponse;
        }

        /**
         * For now, this is a part of the internal API of HAPI - Use with caution as this method may change!
         */
        public String getLastResponseBody() {
                return myLastResponseBody;
        }

        /**
         * {@inheritDoc}
         */
        @Override
        public String getServerBase() {
                return myUrlBase;
        }

        public SummaryEnum getSummary() {
                return mySummary;
        }

        public String getUrlBase() {
                return myUrlBase;
        }

        <T> T invokeClient(FhirContext theContext, IClientResponseHandler<T> binding, BaseHttpClientInvocation clientInvocation) {
                return invokeClient(theContext, binding, clientInvocation, false);
        }

        <T> T invokeClient(FhirContext theContext, IClientResponseHandler<T> binding, BaseHttpClientInvocation clientInvocation, boolean theLogRequestAndResponse) {
                return invokeClient(theContext, binding, clientInvocation, null, null, theLogRequestAndResponse, null, null, null);
        }

        <T> T invokeClient(FhirContext theContext, IClientResponseHandler<T> binding, BaseHttpClientInvocation clientInvocation, EncodingEnum theEncoding, Boolean thePrettyPrint,
                                                         boolean theLogRequestAndResponse, SummaryEnum theSummaryMode, Set<String> theSubsetElements, CacheControlDirective theCacheControlDirective) {

                if (!myDontValidateConformance) {
                        myFactory.validateServerBaseIfConfiguredToDoSo(myUrlBase, myClient, this);
                }

                // TODO: handle non 2xx status codes by throwing the correct exception,
                // and ensure it's passed upwards
                IHttpRequest httpRequest = null;
                IHttpResponse response = null;
                try {
                        Map<String, List<String>> params = createExtraParams();

                        if (clientInvocation instanceof HttpGetClientInvocation) {
                                if (theEncoding == EncodingEnum.XML) {
                                        params.put(Constants.PARAM_FORMAT, Collections.singletonList("xml"));
                                } else if (theEncoding == EncodingEnum.JSON) {
                                        params.put(Constants.PARAM_FORMAT, Collections.singletonList("json"));
                                }
                        }

                        if (theSummaryMode != null) {
                                params.put(Constants.PARAM_SUMMARY, Collections.singletonList(theSummaryMode.getCode()));
                        } else if (mySummary != null) {
                                params.put(Constants.PARAM_SUMMARY, Collections.singletonList(mySummary.getCode()));
                        }

                        if (thePrettyPrint == Boolean.TRUE) {
                                params.put(Constants.PARAM_PRETTY, Collections.singletonList(Constants.PARAM_PRETTY_VALUE_TRUE));
                        }

                        if (theSubsetElements != null && theSubsetElements.isEmpty() == false) {
                                params.put(Constants.PARAM_ELEMENTS, Collections.singletonList(StringUtils.join(theSubsetElements, ',')));
                        }

                        EncodingEnum encoding = getEncoding();
                        if (theEncoding != null) {
                                encoding = theEncoding;
                        }

                        httpRequest = clientInvocation.asHttpRequest(myUrlBase, params, encoding, thePrettyPrint);

                        if (theCacheControlDirective != null) {
                                StringBuilder b = new StringBuilder();
                                addToCacheControlHeader(b, Constants.CACHE_CONTROL_NO_CACHE, theCacheControlDirective.isNoCache());
                                addToCacheControlHeader(b, Constants.CACHE_CONTROL_NO_STORE, theCacheControlDirective.isNoStore());
                                if (theCacheControlDirective.getMaxResults() != null) {
                                        addToCacheControlHeader(b, Constants.CACHE_CONTROL_MAX_RESULTS+"="+ Integer.toString(theCacheControlDirective.getMaxResults().intValue()), true);
                                }
                                if (b.length() > 0) {
                                        httpRequest.addHeader(Constants.HEADER_CACHE_CONTROL, b.toString());
                                }
                        }

                        if (theLogRequestAndResponse) {
                                ourLog.info("Client invoking: {}", httpRequest);
                                String body = httpRequest.getRequestBodyFromStream();
                                if (body != null) {
                                        ourLog.info("Client request body: {}", body);
                                }
                        }

                        for (IClientInterceptor nextInterceptor : myInterceptors) {
                                nextInterceptor.interceptRequest(httpRequest);
                        }

                        response = httpRequest.execute();

                        for (IClientInterceptor nextInterceptor : myInterceptors) {
                                nextInterceptor.interceptResponse(response);
                        }

                        String mimeType;
                        if (Constants.STATUS_HTTP_204_NO_CONTENT == response.getStatus()) {
                                mimeType = null;
                        } else {
                                mimeType = response.getMimeType();
                        }

                        Map<String, List<String>> headers = response.getAllHeaders();

                        if (response.getStatus() < 200 || response.getStatus() > 299) {
                                String body = null;
                                Reader reader = null;
                                try {
                                        reader = response.createReader();
                                        body = IOUtils.toString(reader);
                                } catch (Exception e) {
                                        ourLog.debug("Failed to read input stream", e);
                                } finally {
                                        IOUtils.closeQuietly(reader);
                                }

                                String message = "HTTP " + response.getStatus() + " " + response.getStatusInfo();
                                IBaseOperationOutcome oo = null;
                                if (Constants.CT_TEXT.equals(mimeType)) {
                                        message = message + ": " + body;
                                } else {
                                        EncodingEnum enc = EncodingEnum.forContentType(mimeType);
                                        if (enc != null) {
                                                IParser p = enc.newParser(theContext);
                                                try {
                                                        // TODO: handle if something other than OO comes back
                                                        oo = (IBaseOperationOutcome) p.parseResource(body);
                                                        String details = OperationOutcomeUtil.getFirstIssueDetails(getFhirContext(), oo);
                                                        if (isNotBlank(details)) {
                                                                message = message + ": " + details;
                                                        }
                                                } catch (Exception e) {
                                                        ourLog.debug("Failed to process OperationOutcome response");
                                                }
                                        }
                                }

                                keepResponseAndLogIt(theLogRequestAndResponse, response, body);

                                BaseServerResponseException exception = BaseServerResponseException.newInstance(response.getStatus(), message);
                                exception.setOperationOutcome(oo);

                                if (body != null) {
                                        exception.setResponseBody(body);
                                }

                                throw exception;
                        }
                        if (binding instanceof IClientResponseHandlerHandlesBinary) {
                                IClientResponseHandlerHandlesBinary<T> handlesBinary = (IClientResponseHandlerHandlesBinary<T>) binding;
                                if (handlesBinary.isBinary()) {
                                        InputStream reader = response.readEntity();
                                        try {
                                                return handlesBinary.invokeClient(mimeType, reader, response.getStatus(), headers);
                                        } finally {
                                                IOUtils.closeQuietly(reader);
                                        }
                                }
                        }

                        Reader reader = response.createReader();

                        if (ourLog.isTraceEnabled() || myKeepResponses || theLogRequestAndResponse) {
                                String responseString = IOUtils.toString(reader);
                                keepResponseAndLogIt(theLogRequestAndResponse, response, responseString);
                                reader = new StringReader(responseString);
                        }

                        try {
                                return binding.invokeClient(mimeType, reader, response.getStatus(), headers);
                        } finally {
                                IOUtils.closeQuietly(reader);
                        }

                } catch (DataFormatException e) {
                        String msg;
                        if (httpRequest != null) {
                                msg = getFhirContext().getLocalizer().getMessage(BaseClient.class, "failedToParseResponse", httpRequest.getHttpVerbName(), httpRequest.getUri(), e.toString());
                        } else {
                                msg = getFhirContext().getLocalizer().getMessage(BaseClient.class, "failedToParseResponse", "UNKNOWN", "UNKNOWN", e.toString());
                        }
                        throw new FhirClientConnectionException(msg, e);
                } catch (IllegalStateException e) {
                        throw new FhirClientConnectionException(e);
                } catch (IOException e) {
                        String msg;
                        msg = getFhirContext().getLocalizer().getMessage(BaseClient.class, "failedToParseResponse", httpRequest.getHttpVerbName(), httpRequest.getUri(), e.toString());
                        throw new FhirClientConnectionException(msg, e);
                } catch (RuntimeException e) {
                        throw e;
                } catch (Exception e) {
                        throw new FhirClientConnectionException(e);
                } finally {
                        if (response != null) {
                                response.close();
                        }
                }
        }

        private void addToCacheControlHeader(StringBuilder theBuilder, String theDirective, boolean theActive) {
                if (theActive) {
                        if (theBuilder.length() > 0) {
                                theBuilder.append(", ");
                        }
                        theBuilder.append(theDirective);
                }
        }

        /**
         * For now, this is a part of the internal API of HAPI - Use with caution as this method may change!
         */
        public boolean isKeepResponses() {
                return myKeepResponses;
        }

        /**
         * Returns the pretty print flag, which is a request to the server for it to return "pretty printed" responses. Note
         * that this is currently a non-standard flag (_pretty) which is supported only by HAPI based servers (and any other
         * servers which might implement it).
         */
        public boolean isPrettyPrint() {
                return Boolean.TRUE.equals(myPrettyPrint);
        }

        private void keepResponseAndLogIt(boolean theLogRequestAndResponse, IHttpResponse response, String responseString) {
                if (myKeepResponses) {
                        myLastResponse = response;
                        myLastResponseBody = responseString;
                }
                if (theLogRequestAndResponse) {
                        String message = "HTTP " + response.getStatus() + " " + response.getStatusInfo();
                        if (StringUtils.isNotBlank(responseString)) {
                                ourLog.info("Client response: {}\n{}", message, responseString);
                        } else {
                                ourLog.info("Client response: {}", message, responseString);
                        }
                } else {
                        ourLog.trace("FHIR response:\n{}\n{}", response, responseString);
                }
        }

        @Override
        public void registerInterceptor(IClientInterceptor theInterceptor) {
                Validate.notNull(theInterceptor, "Interceptor can not be null");
                myInterceptors.add(theInterceptor);
        }

        /**
         * This method is an internal part of the HAPI API and may change, use with caution. If you want to disable the
         * loading of conformance statements, use
         * {@link IRestfulClientFactory#setServerValidationModeEnum(ServerValidationModeEnum)}
         */
        public void setDontValidateConformance(boolean theDontValidateConformance) {
                myDontValidateConformance = theDontValidateConformance;
        }

        /**
         * Sets the encoding that will be used on requests. Default is <code>null</code>, which means the client will not
         * explicitly request an encoding. (This is perfectly acceptable behaviour according to the FHIR specification. In
         * this case, the server will choose which encoding to return, and the client can handle either XML or JSON)
         */
        @Override
        public void setEncoding(EncodingEnum theEncoding) {
                myEncoding = theEncoding;
                // return this;
        }

        /**
         * For now, this is a part of the internal API of HAPI - Use with caution as this method may change!
         */
        public void setKeepResponses(boolean theKeepResponses) {
                myKeepResponses = theKeepResponses;
        }

        /**
         * Sets the pretty print flag, which is a request to the server for it to return "pretty printed" responses. Note
         * that this is currently a non-standard flag (_pretty) which is supported only by HAPI based servers (and any other
         * servers which might implement it).
         */
        @Override
        public void setPrettyPrint(Boolean thePrettyPrint) {
                myPrettyPrint = thePrettyPrint;
                // return this;
        }

        @Override
        public void setSummary(SummaryEnum theSummary) {
                mySummary = theSummary;
        }

        @Override
        public void unregisterInterceptor(IClientInterceptor theInterceptor) {
                Validate.notNull(theInterceptor, "Interceptor can not be null");
                myInterceptors.remove(theInterceptor);
        }

        static ArrayList<Class<? extends IBaseResource>> toTypeList(Class<? extends IBaseResource> thePreferResponseType) {
                ArrayList<Class<? extends IBaseResource>> preferResponseTypes = null;
                if (thePreferResponseType != null) {
                        preferResponseTypes = new ArrayList<Class<? extends IBaseResource>>(1);
                        preferResponseTypes.add(thePreferResponseType);
                }
                return preferResponseTypes;
        }

        protected final class ResourceResponseHandler<T extends IBaseResource> implements IClientResponseHandler<T> {

                private boolean myAllowHtmlResponse;
                private IIdType myId;
                private List<Class<? extends IBaseResource>> myPreferResponseTypes;
                private Class<T> myReturnType;

                public ResourceResponseHandler() {
                        this(null);
                }

                public ResourceResponseHandler(Class<T> theReturnType) {
                        this(theReturnType, null, null);
                }

                public ResourceResponseHandler(Class<T> theReturnType, Class<? extends IBaseResource> thePreferResponseType, IIdType theId) {
                        this(theReturnType, thePreferResponseType, theId, false);
                }

                public ResourceResponseHandler(Class<T> theReturnType, Class<? extends IBaseResource> thePreferResponseType, IIdType theId, boolean theAllowHtmlResponse) {
                        this(theReturnType, toTypeList(thePreferResponseType), theId, theAllowHtmlResponse);
                }

                public ResourceResponseHandler(Class<T> theClass, List<Class<? extends IBaseResource>> thePreferResponseTypes) {
                        this(theClass, thePreferResponseTypes, null, false);
                }

                public ResourceResponseHandler(Class<T> theReturnType, List<Class<? extends IBaseResource>> thePreferResponseTypes, IIdType theId, boolean theAllowHtmlResponse) {
                        myReturnType = theReturnType;
                        myId = theId;
                        myPreferResponseTypes = thePreferResponseTypes;
                        myAllowHtmlResponse = theAllowHtmlResponse;
                }

                @Override
                public T invokeClient(String theResponseMimeType, Reader theResponseReader, int theResponseStatusCode, Map<String, List<String>> theHeaders) throws BaseServerResponseException {
                        EncodingEnum respType = EncodingEnum.forContentType(theResponseMimeType);
                        if (respType == null) {
                                if (myAllowHtmlResponse && theResponseMimeType.toLowerCase().contains(Constants.CT_HTML) && myReturnType != null) {
                                        return readHtmlResponse(theResponseReader);
                                }
                                throw NonFhirResponseException.newInstance(theResponseStatusCode, theResponseMimeType, theResponseReader);
                        }
                        IParser parser = respType.newParser(getFhirContext());
                        parser.setServerBaseUrl(getUrlBase());
                        if (myPreferResponseTypes != null) {
                                parser.setPreferTypes(myPreferResponseTypes);
                        }
                        T retVal = parser.parseResource(myReturnType, theResponseReader);

                        MethodUtil.parseClientRequestResourceHeaders(myId, theHeaders, retVal);

                        return retVal;
                }

                @SuppressWarnings("unchecked")
                private T readHtmlResponse(Reader theResponseReader) {
                        RuntimeResourceDefinition resDef = getFhirContext().getResourceDefinition(myReturnType);
                        IBaseResource instance = resDef.newInstance();
                        BaseRuntimeChildDefinition textChild = resDef.getChildByName("text");
                        BaseRuntimeElementCompositeDefinition<?> textElement = (BaseRuntimeElementCompositeDefinition<?>) textChild.getChildByName("text");
                        IBase textInstance = textElement.newInstance();
                        textChild.getMutator().addValue(instance, textInstance);

                        BaseRuntimeChildDefinition divChild = textElement.getChildByName("div");
                        BaseRuntimeElementDefinition<?> divElement = divChild.getChildByName("div");
                        IPrimitiveType<?> divInstance = (IPrimitiveType<?>) divElement.newInstance();
                        try {
                                divInstance.setValueAsString(IOUtils.toString(theResponseReader));
                        } catch (Exception e) {
                                throw new InvalidResponseException(400, "Failed to process HTML response from server: " + e.getMessage(), e);
                        }
                        divChild.getMutator().addValue(textInstance, divInstance);
                        return (T) instance;
                }

                public void setPreferResponseTypes(List<Class<? extends IBaseResource>> thePreferResponseTypes) {
                        myPreferResponseTypes = thePreferResponseTypes;
                }
        }

}