package org.hl7.fhir.dstu2016may.hapi.validation;

import java.io.StringReader;
import java.util.*;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;

import org.apache.commons.lang3.Validate;
import org.hl7.fhir.dstu2016may.model.OperationOutcome.IssueSeverity;
import org.hl7.fhir.dstu2016may.model.StructureDefinition;
import org.hl7.fhir.dstu2016may.validation.*;
import org.hl7.fhir.dstu2016may.validation.IResourceValidator.BestPracticeWarningLevel;
import org.hl7.fhir.utilities.validation.ValidationMessage;
import org.w3c.dom.*;
import org.xml.sax.InputSource;

import com.google.gson.*;

import ca.uhn.fhir.context.ConfigurationException;
import ca.uhn.fhir.context.FhirContext;
import ca.uhn.fhir.rest.api.EncodingEnum;
import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;
import ca.uhn.fhir.validation.IValidationContext;
import ca.uhn.fhir.validation.IValidatorModule;

public class FhirInstanceValidator extends BaseValidatorBridge implements IValidatorModule {

        private static final org.slf4j.Logger ourLog = org.slf4j.LoggerFactory.getLogger(FhirInstanceValidator.class);
        private BestPracticeWarningLevel myBestPracticeWarningLevel;
        private DocumentBuilderFactory myDocBuilderFactory;
        private StructureDefinition myStructureDefintion;
        private IValidationSupport myValidationSupport;

        /**
         * Constructor
         * 
         * Uses {@link DefaultProfileValidationSupport} for {@link IValidationSupport validation support}
         */
        public FhirInstanceValidator() {
                this(new DefaultProfileValidationSupport());
        }

        /**
         * Constructor which uses the given validation support
         * 
         * @param theValidationSupport
         *           The validation support
         */
        public FhirInstanceValidator(IValidationSupport theValidationSupport) {
                myDocBuilderFactory = DocumentBuilderFactory.newInstance();
                myDocBuilderFactory.setNamespaceAware(true);
                myValidationSupport = theValidationSupport;
        }

        private String determineResourceName(Document theDocument) {
                Element root = null;

                NodeList list = theDocument.getChildNodes();
                for (int i = 0; i < list.getLength(); i++) {
                        if (list.item(i) instanceof Element) {
                                root = (Element) list.item(i);
                                break;
                        }
                }
                root = theDocument.getDocumentElement();
                return root.getLocalName();
        }

        /**
         * Returns the "best practice" warning level (default is {@link BestPracticeWarningLevel#Hint}).
         * <p>
         * The FHIR Instance Validator has a number of checks for best practices in terms of FHIR usage. If this setting is
         * set to {@link BestPracticeWarningLevel#Error}, any resource data which does not meet these best practices will be
         * reported at the ERROR level. If this setting is set to {@link BestPracticeWarningLevel#Ignore}, best practice
         * guielines will be ignored.
         * </p>
         * 
         * @see {@link #setBestPracticeWarningLevel(BestPracticeWarningLevel)}
         */
        public BestPracticeWarningLevel getBestPracticeWarningLevel() {
                return myBestPracticeWarningLevel;
        }

        /**
         * Returns the {@link IValidationSupport validation support} in use by this validator. Default is an instance of
         * {@link DefaultProfileValidationSupport} if the no-arguments constructor for this object was used.
         */
        public IValidationSupport getValidationSupport() {
                return myValidationSupport;
        }

        /**
         * Sets the "best practice warning level". When validating, any deviations from best practices will be reported at
         * this level.
         * <p>
         * The FHIR Instance Validator has a number of checks for best practices in terms of FHIR usage. If this setting is
         * set to {@link BestPracticeWarningLevel#Error}, any resource data which does not meet these best practices will be
         * reported at the ERROR level. If this setting is set to {@link BestPracticeWarningLevel#Ignore}, best practice
         * guielines will be ignored.
         * </p>
         * 
         * @param theBestPracticeWarningLevel
         *           The level, must not be <code>null</code>
         */
        public void setBestPracticeWarningLevel(BestPracticeWarningLevel theBestPracticeWarningLevel) {
                Validate.notNull(theBestPracticeWarningLevel);
                myBestPracticeWarningLevel = theBestPracticeWarningLevel;
        }

        public void setStructureDefintion(StructureDefinition theStructureDefintion) {
                myStructureDefintion = theStructureDefintion;
        }

        /**
         * Sets the {@link IValidationSupport validation support} in use by this validator. Default is an instance of
         * {@link DefaultProfileValidationSupport} if the no-arguments constructor for this object was used.
         */
        public void setValidationSupport(IValidationSupport theValidationSupport) {
                myValidationSupport = theValidationSupport;
        }

        protected List<ValidationMessage> validate(final FhirContext theCtx, String theInput, EncodingEnum theEncoding) {
                HapiWorkerContext workerContext = new HapiWorkerContext(theCtx, myValidationSupport);

                InstanceValidator v;
                try {
                        v = new InstanceValidator(workerContext);
                } catch (Exception e) {
                        throw new ConfigurationException(e);
                }

                v.setBestPracticeWarningLevel(myBestPracticeWarningLevel);
                v.setAnyExtensionsAllowed(true);
                v.setResourceIdRule(IResourceValidator.IdStatus.OPTIONAL);

                List<ValidationMessage> messages = new ArrayList<ValidationMessage>();

                if (theEncoding == EncodingEnum.XML) {
                        Document document;
                        try {
                                DocumentBuilder builder = myDocBuilderFactory.newDocumentBuilder();
                                InputSource src = new InputSource(new StringReader(theInput));
                                document = builder.parse(src);
                        } catch (Exception e2) {
                                ourLog.error("Failure to parse XML input", e2);
                                ValidationMessage m = new ValidationMessage();
                                m.setLevel(ValidationMessage.IssueSeverity.FATAL);
                                m.setMessage("Failed to parse input, it does not appear to be valid XML:" + e2.getMessage());
                                return Collections.singletonList(m);
                        }

                        String resourceName = determineResourceName(document);
                        StructureDefinition profile = findStructureDefinitionForResourceName(theCtx, resourceName);
                        if (profile != null) {
                                try {
                                        v.validate(messages, document, profile);
                                } catch (Exception e) {
                                        throw new InternalErrorException("Unexpected failure while validating resource", e);
                                }
                        }
                } else if (theEncoding == EncodingEnum.JSON) {
                        Gson gson = new GsonBuilder().create();
                        JsonObject json = gson.fromJson(theInput, JsonObject.class);

                        String resourceName = json.get("resourceType").getAsString();
                        StructureDefinition profile = findStructureDefinitionForResourceName(theCtx, resourceName);
                        if (profile != null) {
                                try {
                                        v.validate(messages, json, profile);
                                } catch (Exception e) {
                                        throw new InternalErrorException("Unexpected failure while validating resource", e);
                                }
                        }
                } else {
                        throw new IllegalArgumentException("Unknown encoding: " + theEncoding);
                }

                for (int i = 0; i < messages.size(); i++) {
                        ValidationMessage next = messages.get(i);
                        if ("Binding has no source, so can't be checked".equals(next.getMessage())) {
                                messages.remove(i);
                                i--;
                        }
                }
                return messages;
        }

        private StructureDefinition findStructureDefinitionForResourceName(final FhirContext theCtx, String resourceName) {
                String sdName = "http://hl7.org/fhir/StructureDefinition/" + resourceName;
                StructureDefinition profile = myStructureDefintion != null ? myStructureDefintion : myValidationSupport.fetchStructureDefinition(theCtx, sdName);
                return profile;
        }

        @Override
        protected List<ValidationMessage> validate(IValidationContext<?> theCtx) {
                return validate(theCtx.getFhirContext(), theCtx.getResourceAsString(), theCtx.getResourceAsStringEncoding());
        }


}