/*******************************************************************************
 * Copyright (c) 2009, 2017 IBM Corporation and others.
 * 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.
 * 
 * SPDX-License-Identifier: EPL-2.0
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *     Zend Technologies
 *******************************************************************************/
package org.eclipse.dltk.internal.core.index.sql.h2;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URL;
import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.HashSet;
import java.util.Set;

import org.eclipse.core.runtime.FileLocator;
import org.eclipse.core.runtime.Path;
import org.eclipse.core.runtime.Platform;
import org.eclipse.core.runtime.preferences.IEclipsePreferences;
import org.eclipse.core.runtime.preferences.InstanceScope;
import org.eclipse.dltk.core.index.sql.h2.H2Index;
import org.eclipse.dltk.core.index.sql.h2.H2IndexPreferences;
import org.eclipse.osgi.util.NLS;
import org.osgi.service.prefs.BackingStoreException;

/**
 * Utilities for initializing model schema
 * 
 * @author michael
 * 
 */
public class Schema {

	public static final String VERSION = "0.8.1"; //$NON-NLS-1$

	/** Contains already created tables names */
	private static final Set<String> TABLES_CACHE = new HashSet<>();

	/**
	 * Creates the database schema using given connection.
	 * 
	 * @param connection
	 *            Database connection
	 * @throws SQLException
	 */
	public void initialize(Connection connection) throws SQLException {
		try {
			try (Statement statement = connection.createStatement()) {
				statement.executeUpdate(readSqlFile("resources/basic.sql")); //$NON-NLS-1$
			}

			// Store new schema version:
			storeSchemaVersion(VERSION);

		} catch (SQLException e) {
			H2Index.error("An exception was thrown while initializing schema", //$NON-NLS-1$
					e);
			throw e;
		}
	}

	/**
	 * Generate table name according to element type and language nature
	 * 
	 * @param elementType
	 *            Element type
	 * @param natureId
	 *            Language nature
	 * @param isReference
	 *            Whether the element is reference or declaration
	 * @return
	 */
	public String getTableName(int elementType, String natureId,
			boolean isReference) {
		StringBuilder tableName = new StringBuilder();
		if (isReference) {
			tableName.append("R_"); //$NON-NLS-1$
		} else {
			tableName.append("D_"); //$NON-NLS-1$
		}
		tableName.append(natureId.toUpperCase().replace('.', '_')).append('_')
				.append(elementType);
		return tableName.toString();
	}

	/**
	 * Creates elements table
	 * 
	 * @param connection
	 *            Database connection
	 * @param tableName
	 *            Table name
	 * @param isReference
	 *            Whether to create table for element references or element
	 *            declarations
	 * @throws SQLException
	 */
	public void createTable(Connection connection, String tableName,
			boolean isReference) throws SQLException {

		synchronized (TABLES_CACHE) {
			if (TABLES_CACHE.add(tableName)) {

				String query = isReference
						? readSqlFile("resources/element_ref.sql") //$NON-NLS-1$
						: readSqlFile("resources/element_decl.sql"); //$NON-NLS-1$
				query = NLS.bind(query, tableName);

				try {
					try (Statement statement = connection.createStatement()) {
						statement.executeUpdate(query);
					}
				} catch (SQLException e) {
					H2Index.error(
							"An exception was thrown while creating elements table", //$NON-NLS-1$
							e);
					throw e;
				}
			}
		}
	}

	/**
	 * Checks whether the schema version is compatible with the stored one.
	 */
	public boolean isCompatible() {
		String storedVersion = getStoredSchemaVersion();
		if (storedVersion != null && VERSION.equals(storedVersion)) {
			return true;
		}
		return false;
	}

	private String getStoredSchemaVersion() {
		return Platform.getPreferencesService().getString(H2Index.PLUGIN_ID,
				H2IndexPreferences.SCHEMA_VERSION, null, null);
	}

	private void storeSchemaVersion(String newVersion) {
		IEclipsePreferences node = InstanceScope.INSTANCE
				.getNode(H2Index.PLUGIN_ID);
		node.put(H2IndexPreferences.SCHEMA_VERSION, newVersion);
		try {
			node.flush();
		} catch (BackingStoreException e) {
		}
	}

	static String readSqlFile(String sqlFile) {
		try {
			URL url = FileLocator.find(H2Index.getDefault().getBundle(),
					new Path(sqlFile), null);
			URL resolved = FileLocator.resolve(url);

			StringBuilder buf = new StringBuilder();
			try (BufferedReader r = new BufferedReader(
					new InputStreamReader(resolved.openStream()))) {
				String line;
				while ((line = r.readLine()) != null) {
					buf.append(line).append('\n');
				}
			}
			return buf.toString();
		} catch (IOException e) {
			H2Index.error("An exception is thrown while reading file: " //$NON-NLS-1$
					+ sqlFile, e);
		}
		return null;
	}
}