/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.
 */
package org.apache.sling.jcr.repoinit.impl;

import javax.jcr.InvalidItemStateException;
import javax.jcr.RepositoryException;
import javax.jcr.Session;

import java.io.StringReader;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.concurrent.atomic.AtomicBoolean;

import org.apache.sling.commons.metrics.MetricsService;
import org.apache.sling.jcr.api.SlingRepository;
import org.apache.sling.jcr.api.SlingRepositoryInitializer;
import org.apache.sling.jcr.repoinit.JcrRepoInitOpsProcessor;
import org.apache.sling.jcr.repoinit.impl.RetryableOperation.RetryableOperationResult;
import org.apache.sling.repoinit.parser.RepoInitParser;
import org.apache.sling.repoinit.parser.operations.Operation;
import org.osgi.framework.Constants;
import org.osgi.service.component.ComponentConstants;
import org.osgi.service.component.annotations.Activate;
import org.osgi.service.component.annotations.Component;
import org.osgi.service.component.annotations.ConfigurationPolicy;
import org.osgi.service.component.annotations.Reference;
import org.osgi.service.metatype.annotations.AttributeDefinition;
import org.osgi.service.metatype.annotations.Designate;
import org.osgi.service.metatype.annotations.ObjectClassDefinition;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * SlingRepositoryInitializer Factory that executes repoinit statements configured
 * through OSGi configurations. A configuration can contain URLs from which the
 * statements are read or inlined statements.
 */
@Designate(ocd = RepositoryInitializerFactory.Config.class, factory = true)
@Component(
        service = SlingRepositoryInitializer.class,
        configurationPolicy = ConfigurationPolicy.REQUIRE,
        configurationPid = "org.apache.sling.jcr.repoinit.RepositoryInitializer",
        property = {
            Constants.SERVICE_VENDOR + "=The Apache Software Foundation",
            // SlingRepositoryInitializers are executed in ascending
            // order of their service ranking
            Constants.SERVICE_RANKING + ":Integer=100"
        })
public class RepositoryInitializerFactory implements SlingRepositoryInitializer {

    @ObjectClassDefinition(
            name = "Apache Sling Repository Initializer Factory",
            description = "Initializes the JCR content repository using repoinit statements.")
    public @interface Config {

        @AttributeDefinition(
                name = "References",
                description =
                        "References to the source text that provides repoinit statements." + " format is a raw URL.")
        String[] references() default {};

        @AttributeDefinition(name = "Scripts", description = "Contents of a repo init script.")
        String[] scripts() default {};
    }

    private final Logger log = LoggerFactory.getLogger(getClass());

    private static final String METRIC_REPOINIT_FAILED = RepositoryInitializerFactory.class.getName() + ".failed";

    @Reference
    private RepoInitParser parser;

    @Reference
    private JcrRepoInitOpsProcessor processor;

    @Reference
    MetricsService metrics;

    private RepositoryInitializerFactory.Config config;

    // assume that repoinit succeeds ... and just this to true if it fails
    private AtomicBoolean aRepoInitStatementFailed = new AtomicBoolean(false);

    private String componentId;

    @Activate
    public void activate(final RepositoryInitializerFactory.Config config, Map<String, Object> properties) {
        this.config = config;
        this.componentId =
                properties.getOrDefault(ComponentConstants.COMPONENT_ID, "").toString();
        log.debug("Activated: {}", this);
        metrics.gauge(METRIC_REPOINIT_FAILED, this::failureStateAsMetric);
    }

    @Override
    public String toString() {
        return getClass().getSimpleName()
                + ", references=" + Arrays.toString(config.references())
                + ", scripts=" + (config.scripts() != null ? config.scripts().length : 0);
    }

    @Override
    public void processRepository(final SlingRepository repo) throws Exception {
        if ((config.references() != null && config.references().length > 0)
                || (config.scripts() != null && config.scripts().length > 0)) {

            // loginAdministrative is ok here, definitely an admin operation
            @SuppressWarnings("deprecation")
            final Session s = repo.loginAdministrative(null);
            try {
                if (config.references() != null) {
                    final RepoinitTextProvider p = new RepoinitTextProvider();
                    for (final String reference : config.references()) {
                        if (reference == null || reference.trim().length() == 0) {
                            continue;
                        }
                        final String repoinitText = p.getRepoinitText("raw:" + reference);
                        final List<Operation> ops;
                        try (StringReader sr = new StringReader(repoinitText)) {
                            ops = parser.parse(sr);
                        }
                        String sourceReference =
                                String.format("Configuration PID %s, reference URL %s", componentId, reference);
                        String msg = String.format(
                                "Executing %s repoinit operations from \"%s\"", ops.size(), sourceReference);
                        log.info(msg);
                        applyOperations(s, ops, msg, sourceReference);
                    }
                }
                if (config.scripts() != null) {
                    int scriptIndex = 0;
                    for (final String script : config.scripts()) {
                        if (script == null || script.trim().length() == 0) {
                            continue;
                        }
                        final List<Operation> ops;
                        try (StringReader sr = new StringReader(script)) {
                            ops = parser.parse(sr);
                        }
                        String sourceReference =
                                String.format("Configuration PID %s, script[%d]", componentId, scriptIndex);
                        String msg = String.format(
                                "Executing %s repoinit operations from \"%s\"", ops.size(), sourceReference);
                        log.info(msg);
                        applyOperations(s, ops, msg, sourceReference);
                        scriptIndex++;
                    }
                }
            } finally {
                s.logout();
            }
        }
    }

    /**
     * Apply the operations within a session, support retries
     * @param session the JCR session to use
     * @param ops the list of operations
     * @param logMessage the messages to print when retry
     * @param reference the reference identifying the source of the repoinit script
     * @throws Exception if the application fails despite the retry
     */
    protected void applyOperations(Session session, List<Operation> ops, String logMessage, String reference)
            throws RepositoryException {

        RetryableOperation retry = new RetryableOperation.Builder()
                .withBackoffBaseMsec(1000)
                .withMaxRetries(3)
                .build();
        RetryableOperation.RetryableOperationResult result =
                applyOperationInternal(session, ops, logMessage, reference, retry);
        if (!result.isSuccessful()) {
            String msg = String.format(
                    "Applying repoinit operation failed despite retry; set loglevel to DEBUG to see all exceptions. "
                            + "Last exception message from \"%s\" was: %s",
                    result.getReference(), result.getFailureTrace().getMessage());
            aRepoInitStatementFailed.set(true);
            throw new RepositoryException(msg, result.getFailureTrace());
        }
    }

    /**
     * Perform the operations
     * @param session the session to use
     * @param ops the operations
     * @param logMessage logmessage which should be printed
     * @param reference the reference identifying the source of the repoinit script
     * @param retry the retry object
     * @return
     */
    protected RetryableOperationResult applyOperationInternal(
            Session session, List<Operation> ops, String logMessage, String reference, RetryableOperation retry) {
        return retry.apply(
                () -> {
                    try {
                        processor.apply(session, ops);
                        if (session.hasPendingChanges()) {
                            session.save();
                        }
                        return new RetryableOperation.RetryableOperationResult(true, false, reference, null);
                    } catch (InvalidItemStateException | RepoInitException ex) {
                        // a retry makes sense, because this exception might be caused by an concurrent operation
                        log.debug("(temporarily) failed to apply repoinit operations", ex);
                        try {
                            session.refresh(false); // discard all pending changes
                        } catch (RepositoryException e1) {
                            // ignore
                        }
                        return new RetryableOperation.RetryableOperationResult(false, true, reference, ex);
                    } catch (RepositoryException ex) {
                        // a permanent error, retry is not useful
                        try {
                            session.refresh(false); // discard all pending changes
                        } catch (RepositoryException e1) {
                            // ignore
                        }
                        return new RetryableOperation.RetryableOperationResult(false, false, reference, ex);
                    }
                },
                logMessage);
    }

    /**
     * return the state of the repoinit execution usable for a simple gauge metric
     * @return 1 if repoinit did not finish successfully, 0 otherwise
     */
    protected int failureStateAsMetric() {
        return aRepoInitStatementFailed.get() ? 1 : 0;
    }
}