/*
 * Copyright (c) 1998, 2021 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0 which is available at
 * http://www.eclipse.org/legal/epl-2.0,
 * or the Eclipse Distribution License v. 1.0 which is available at
 * http://www.eclipse.org/org/documents/edl-v10.php.
 *
 * SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 */

// Contributors:
//     Oracle - initial API and implementation from Oracle TopLink
package org.eclipse.persistence.tools.history;

import java.util.*;

import org.eclipse.persistence.history.*;
import org.eclipse.persistence.internal.databaseaccess.DatasourcePlatform;
import org.eclipse.persistence.internal.helper.*;
import org.eclipse.persistence.internal.history.*;
import org.eclipse.persistence.mappings.*;
import org.eclipse.persistence.descriptors.ClassDescriptor;
import org.eclipse.persistence.sessions.*;
import org.eclipse.persistence.queries.*;
import org.eclipse.persistence.sessions.broker.*;
import org.eclipse.persistence.tools.schemaframework.*;
import org.eclipse.persistence.sessions.server.*;

/**
 * <b>Purpose:</b>One stop shopping for all your history needs.
 *
 * @author Stephen McRitchie
 * @since Oracle 10g AS
 */
public class HistoryFacade {

    private static Map<Session, Long> timeOffsetsMap = new IdentityHashMap<>();

    protected HistoryFacade() {
    }

    protected static void buildHistoricalTableDefinition(HistoryPolicy policy,
                                                         String name,
                                                         TableDefinition def,
                                                         TableCreator creator) {

        if (def == null) {
            return;
        }

        TableDefinition histDef = (TableDefinition)def.clone();
        histDef.setName(name);
        FieldDefinition fieldDef = new FieldDefinition();
        fieldDef.setName(policy.getStartFieldName());
        fieldDef.setType(ClassConstants.TIMESTAMP);
        fieldDef.setSize(6);
        histDef.addField(fieldDef);
        fieldDef = new FieldDefinition();
        fieldDef.setName(policy.getEndFieldName());
        fieldDef.setType(ClassConstants.TIMESTAMP);
        fieldDef.setSize(6);
        histDef.addField(fieldDef);
        histDef.setForeignKeys(new Vector<>());

        for (FieldDefinition fieldDef2 : histDef.getFields()) {
            // For now foreign key constraints are not supported, because shallow inserts are not...
            fieldDef2.setForeignKeyFieldName(null);
            if (fieldDef2.getName().equals("ROW_START") &&
                (!histDef.getPrimaryKeyFieldNames().isEmpty())) {
                fieldDef2.setIsPrimaryKey(true);
            }
            if (fieldDef2.getName().equals("VERSION") &&
                (!histDef.getPrimaryKeyFieldNames().isEmpty())) {
                fieldDef2.setIsPrimaryKey(true);
            }
        }
        creator.addTableDefinition(histDef);
    }

    public static long currentDatabaseTimeMillis(org.eclipse.persistence.sessions.Session session) {
        return currentDatabaseTimeMillis(session, null);
    }

    /**
     * PUBLIC:
     */
    public static long currentDatabaseTimeMillis(org.eclipse.persistence.sessions.Session session,
                                   Class domainClass) {
        Session rootSession = session;
        while (rootSession.isUnitOfWork() || rootSession.isClientSession() ||
               rootSession instanceof HistoricalSession ||
               rootSession.isSessionBroker()) {
            if (rootSession.isUnitOfWork()) {
                rootSession = ((UnitOfWork)rootSession).getParent();
            } else if (rootSession.isClientSession()) {
                rootSession = ((ClientSession)rootSession).getParent();
            } else if (rootSession instanceof HistoricalSession) {
                rootSession = ((HistoricalSession)rootSession).getParent();
            } else {
                SessionBroker broker = (SessionBroker)rootSession;
                rootSession = broker.getSessionForClass(domainClass);
                if (rootSession == broker) {
                    break;
                }
            }
        }
        if (timeOffsetsMap.containsKey(rootSession)) {
            Long offset = timeOffsetsMap.get(rootSession);
            return System.currentTimeMillis() + offset;
        } else {
            DatabaseQuery query =
                rootSession.getPlatform().getTimestampQuery();
            long startTime = System.currentTimeMillis();
            java.sql.Timestamp databaseTime =
                (java.sql.Timestamp)rootSession.executeQuery(query);
            long endTime = System.currentTimeMillis();
            long jvmTime = (endTime - startTime) / 2 + startTime;
            long offset = databaseTime.getTime() - jvmTime;
            timeOffsetsMap.put(rootSession, offset);
            return jvmTime + offset;
        }
    }

    /**
     * PUBLIC:
     * Generates a mirroring historical schema given a
     * conventional schema and a session with HistoryPolicies set on
     * the descriptors.
     */
    public static void generateHistoricalTableDefinitions(TableCreator creator, Session session) {

        // First add all table definitions to a hashtable.
        Map<String, TableDefinition> tableDefinitions = new HashMap<>(creator.getTableDefinitions().size());
        for (TableDefinition def : creator.getTableDefinitions()) {
            tableDefinitions.put(def.getFullName(), def);
        }
        Set<String> generatedTables = new HashSet<>();
        for (ClassDescriptor descriptor : session.getDescriptors().values()) {
            HistoryPolicy policy = descriptor.getHistoryPolicy();
            if (policy != null) {
                List<String> names = policy.getHistoryTableNames();
                for (int i = 0; i < descriptor.getTableNames().size(); i++) {
                    String name = (String)descriptor.getTableNames().get(i);
                    String histName = names.get(i);
                    if (!generatedTables.contains(histName)) {
                        generatedTables.add(histName);
                        TableDefinition def = tableDefinitions.get(name);
                        buildHistoricalTableDefinition(policy, histName, def, creator);
                    }
                }
            }
            for (DatabaseMapping mapping : descriptor.getMappings()) {
                if (mapping.isManyToManyMapping()) {
                    ManyToManyMapping m2mMapping = (ManyToManyMapping)mapping;
                    policy = m2mMapping.getHistoryPolicy();
                    if (policy != null) {
                        String name = m2mMapping.getRelationTableName();
                        String histName = policy.getHistoryTableNames().get(0);
                        if (!generatedTables.contains(histName)) {
                            generatedTables.add(histName);
                            TableDefinition def = tableDefinitions.get(name);
                            buildHistoricalTableDefinition(policy, histName, def, creator);
                        }
                    }
                } else if (mapping.isDirectCollectionMapping()) {
                    DirectCollectionMapping dcMapping = (DirectCollectionMapping)mapping;
                    policy = dcMapping.getHistoryPolicy();
                    if (policy != null) {
                        String name = dcMapping.getReferenceTableName();
                        String histName = policy.getHistoryTableNames().get(0);
                        if (!generatedTables.contains(histName)) {
                            generatedTables.add(histName);
                            TableDefinition def = tableDefinitions.get(name);
                            buildHistoricalTableDefinition(policy, histName, def, creator);
                        }
                    }
                }
            }
        }
    }

    /**
     * PUBLIC:
     * Generates HistoryPolicies for a given object model.  The policies
     * are of the recommended form, with START/END, and the history table name
     * being the current table name with a _HIST suffix.  Hence Employee would
     * become Employee_Hist.
     */
    public static void generateHistoryPolicies(Iterator<ClassDescriptor> descriptors, DatasourcePlatform platform) {
        HistoryPolicy basePolicy = new HistoryPolicy();
        basePolicy.addStartFieldName("ROW_START");
        basePolicy.addEndFieldName("ROW_END");

        HistoryPolicy policy = null;

        while (descriptors.hasNext()) {
            ClassDescriptor descriptor = descriptors.next();
            policy = (HistoryPolicy)basePolicy.clone();
            List<DatabaseTable> tables = descriptor.getTables();
            int size = tables.size();
            if (size == 0) {
                continue;
            }
            for (int i = 0; i < size; i++) {
                DatabaseTable table = tables.get(i);
                String name = table.getQualifiedNameDelimited(platform);
                String historicalName;
                if(table.shouldUseDelimiters()) {
                    historicalName = name.substring(0, name.length() - 1) + "_HIST" + Helper.getDefaultEndDatabaseDelimiter();
                } else {
                    historicalName = name + "_HIST";
                }
                policy.addHistoryTableName(name, historicalName);
            }
            descriptor.setHistoryPolicy(policy);

            for (Enumeration<DatabaseMapping> mappings = descriptor.getMappings().elements();
                 mappings.hasMoreElements(); ) {
                DatabaseMapping mapping =
                        mappings.nextElement();
                if (mapping instanceof ManyToManyMapping) {
                    ManyToManyMapping m2mMapping = (ManyToManyMapping)mapping;
                    policy = (HistoryPolicy)basePolicy.clone();
                    policy.addHistoryTableName(m2mMapping.getRelationTableName() +
                                               "_HIST");
                    m2mMapping.setHistoryPolicy(policy);
                } else if (mapping instanceof DirectCollectionMapping) {
                    DirectCollectionMapping dcMapping =
                        (DirectCollectionMapping)mapping;
                    policy = (HistoryPolicy)basePolicy.clone();
                    policy.addHistoryTableName(dcMapping.getReferenceTableName() +
                                               "_HIST");
                    dcMapping.setHistoryPolicy(policy);
                }
            }
        }
    }

    public static void generateHistoryPolicies(org.eclipse.persistence.sessions.Project project) {
        generateHistoryPolicies(project.getDescriptors().values().iterator(), project.getDatasourceLogin().getPlatform());
    }

    public static void generateHistoryPolicies(org.eclipse.persistence.sessions.Session session) {
        generateHistoryPolicies(session.getDescriptors().values().iterator(), session.getPlatform());
    }
}