package ca.uhn.fhir.context;

/*
 * #%L
 * HAPI FHIR - Core Library
 * %%
 * 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 ca.uhn.fhir.model.api.IFhirVersion;
import ca.uhn.fhir.rest.server.exceptions.InternalErrorException;

public enum FhirVersionEnum {

        /*
         * ***********************
         * Don't auto-sort this type!!!
         *
         * Or more accurately, entries should be sorted from OLDEST FHIR release
         * to NEWEST FHIR release instead of alphabetically
         * ***********************
         */

        DSTU2("ca.uhn.fhir.model.dstu2.FhirDstu2", null, false, new Version("1.0.2")),

        DSTU2_HL7ORG("org.hl7.fhir.instance.FhirDstu2Hl7Org", DSTU2, true, new Version("1.0.2")),

        DSTU2_1("org.hl7.fhir.dstu2016may.hapi.ctx.FhirDstu2_1", null, true, new Version("1.4.0")),

        DSTU3("org.hl7.fhir.dstu3.hapi.ctx.FhirDstu3", null, true, new Dstu3Version()),

        R4("org.hl7.fhir.r4.hapi.ctx.FhirR4", null, true, new R4Version()),;

        private final FhirVersionEnum myEquivalent;
        private final boolean myIsRi;
        private final String myVersionClass;
        private volatile Boolean myPresentOnClasspath;
        private volatile IFhirVersion myVersionImplementation;
        private String myFhirVersionString;

        FhirVersionEnum(String theVersionClass, FhirVersionEnum theEquivalent, boolean theIsRi, IVersionProvider theVersionExtractor) {
                myVersionClass = theVersionClass;
                myEquivalent = theEquivalent;
                myFhirVersionString = theVersionExtractor.provideVersion();
                myIsRi = theIsRi;
        }

        public String getFhirVersionString() {
                return myFhirVersionString;
        }

        public IFhirVersion getVersionImplementation() {
                if (!isPresentOnClasspath()) {
                        throw new IllegalStateException("Version " + name() + " is not present on classpath");
                }
                if (myVersionImplementation == null) {
                        try {
                                myVersionImplementation = (IFhirVersion) Class.forName(myVersionClass).newInstance();
                        } catch (Exception e) {
                                throw new InternalErrorException("Failed to instantiate FHIR version " + name(), e);
                        }
                }
                return myVersionImplementation;
        }

        public boolean isEqualOrNewerThan(FhirVersionEnum theVersion) {
                return ordinal() >= theVersion.ordinal();
        }

        public boolean isEquivalentTo(FhirVersionEnum theVersion) {
                if (this.equals(theVersion)) {
                        return true;
                }
                if (myEquivalent != null) {
                        return myEquivalent.equals(theVersion);
                }
                return false;
        }

        public boolean isNewerThan(FhirVersionEnum theVersion) {
                return !isEquivalentTo(theVersion) && ordinal() > theVersion.ordinal();
        }

        public boolean isOlderThan(FhirVersionEnum theVersion) {
                return !isEquivalentTo(theVersion) && ordinal() < theVersion.ordinal();
        }

        /**
         * Returns true if the given version is present on the classpath
         */
        public boolean isPresentOnClasspath() {
                Boolean retVal = myPresentOnClasspath;
                if (retVal == null) {
                        try {
                                Class.forName(myVersionClass);
                                retVal = true;
                        } catch (Exception e) {
                                retVal = false;
                        }
                        myPresentOnClasspath = retVal;
                }
                return retVal;
        }

        /**
         * Is this version using the HL7.org RI structures?
         */
        public boolean isRi() {
                return myIsRi;
        }

        public FhirContext newContext() {
                switch (this) {
                        case DSTU2:
                                return FhirContext.forDstu2();
                        case DSTU2_HL7ORG:
                                return FhirContext.forDstu2Hl7Org();
                        case DSTU2_1:
                                return FhirContext.forDstu2_1();
                        case DSTU3:
                                return FhirContext.forDstu3();
                        case R4:
                                return FhirContext.forR4();
                }
                throw new IllegalStateException("Unknown version: " + this); // should not happen
        }

        /**
         * Returns the {@link FhirVersionEnum} which corresponds to a specific version of
         * FHIR. Partial version strings (e.g. "3.0") are acceptable.
         *
         * @return Returns null if no version exists matching the given string
         */
        public static FhirVersionEnum forVersionString(String theVersionString) {
                for (FhirVersionEnum next : values()) {
                        if (next.getFhirVersionString().startsWith(theVersionString)) {
                                return next;
                        }
                }
                return null;
        }

        private interface IVersionProvider {
                String provideVersion();
        }

        private static class Version implements IVersionProvider {

                private String myVersion;

                public Version(String theVersion) {
                        super();
                        myVersion = theVersion;
                }

                @Override
                public String provideVersion() {
                        return myVersion;
                }

        }

        /**
         * This class attempts to read the FHIR version from the actual model
         * classes in order to supply an accurate version string even over time
         */
        private static class Dstu3Version implements IVersionProvider {

                private String myVersion;

                Dstu3Version() {
                        try {
                                Class<?> c = Class.forName("org.hl7.fhir.dstu3.model.Constants");
                                myVersion = (String) c.getDeclaredField("VERSION").get(null);
                        } catch (Exception e) {
                                myVersion = "3.0.1";
                        }
                }

                @Override
                public String provideVersion() {
                        return myVersion;
                }

        }

        private static class R4Version implements IVersionProvider {

                private String myVersion;

                R4Version() {
                        try {
                                Class<?> c = Class.forName("org.hl7.fhir.r4.model.Constants");
                                myVersion = (String) c.getDeclaredField("VERSION").get(null);
                        } catch (Exception e) {
                                myVersion = "4.0.0";
                        }
                }

                @Override
                public String provideVersion() {
                        return myVersion;
                }

        }

}