/*
 * 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.shardingsphere.database.connector.mysql.metadata.data.loader;

import com.google.common.base.Strings;
import org.apache.shardingsphere.database.connector.core.GlobalDataSourceRegistry;
import org.apache.shardingsphere.database.connector.core.metadata.data.loader.DialectMetaDataLoader;
import org.apache.shardingsphere.database.connector.core.metadata.data.loader.MetaDataLoaderMaterial;
import org.apache.shardingsphere.database.connector.core.metadata.data.model.ColumnMetaData;
import org.apache.shardingsphere.database.connector.core.metadata.data.model.ConstraintMetaData;
import org.apache.shardingsphere.database.connector.core.metadata.data.model.IndexMetaData;
import org.apache.shardingsphere.database.connector.core.metadata.data.model.SchemaMetaData;
import org.apache.shardingsphere.database.connector.core.metadata.data.model.TableMetaData;
import org.apache.shardingsphere.database.connector.core.metadata.database.datatype.DataTypeRegistry;
import org.apache.shardingsphere.database.connector.core.metadata.database.enums.TableType;

import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Types;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.Map;
import java.util.Map.Entry;
import java.util.stream.Collectors;

/**
 * Meta data loader for MySQL.
 */
public final class MySQLMetaDataLoader implements DialectMetaDataLoader {
    
    private static final String ORDER_BY_ORDINAL_POSITION = " ORDER BY ORDINAL_POSITION";
    
    private static final String TABLE_META_DATA_NO_ORDER =
            "SELECT TABLE_NAME, COLUMN_NAME, DATA_TYPE, COLUMN_KEY, EXTRA, COLLATION_NAME, ORDINAL_POSITION, COLUMN_TYPE, IS_NULLABLE FROM information_schema.columns WHERE TABLE_SCHEMA=?";
    
    private static final String TABLE_META_DATA_SQL = TABLE_META_DATA_NO_ORDER + ORDER_BY_ORDINAL_POSITION;
    
    private static final String TABLE_META_DATA_SQL_IN_TABLES = TABLE_META_DATA_NO_ORDER + " AND TABLE_NAME IN (%s)" + ORDER_BY_ORDINAL_POSITION;
    
    private static final String INDEX_META_DATA_SQL = "SELECT TABLE_NAME, INDEX_NAME, NON_UNIQUE, COLUMN_NAME FROM information_schema.statistics "
            + "WHERE TABLE_SCHEMA=? and TABLE_NAME IN (%s) ORDER BY NON_UNIQUE, INDEX_NAME, SEQ_IN_INDEX";
    
    private static final String CONSTRAINT_META_DATA_SQL = "SELECT CONSTRAINT_NAME, TABLE_NAME, REFERENCED_TABLE_NAME FROM information_schema.KEY_COLUMN_USAGE "
            + "WHERE TABLE_NAME IN (%s) AND REFERENCED_TABLE_SCHEMA IS NOT NULL";
    
    private static final String VIEW_META_DATA_SQL = "SELECT TABLE_NAME FROM information_schema.VIEWS WHERE TABLE_SCHEMA=? AND TABLE_NAME IN (%s)";
    
    @Override
    public Collection<SchemaMetaData> load(final MetaDataLoaderMaterial material) throws SQLException {
        Collection<TableMetaData> tableMetaDataList = new LinkedList<>();
        Map<String, Collection<ColumnMetaData>> columnMetaDataMap = loadColumnMetaDataMap(material.getDataSource(), material.getActualTableNames());
        Collection<String> viewNames = columnMetaDataMap.isEmpty() ? Collections.emptySet() : loadViewNames(material.getDataSource(), columnMetaDataMap.keySet());
        Map<String, Collection<IndexMetaData>> indexMetaDataMap = columnMetaDataMap.isEmpty() ? Collections.emptyMap() : loadIndexMetaData(material.getDataSource(), columnMetaDataMap.keySet());
        Map<String, Collection<ConstraintMetaData>> constraintMetaDataMap =
                columnMetaDataMap.isEmpty() ? Collections.emptyMap() : loadConstraintMetaDataMap(material.getDataSource(), columnMetaDataMap.keySet());
        for (Entry<String, Collection<ColumnMetaData>> entry : columnMetaDataMap.entrySet()) {
            Collection<IndexMetaData> indexMetaDataList = indexMetaDataMap.getOrDefault(entry.getKey(), Collections.emptyList());
            Collection<ConstraintMetaData> constraintMetaDataList = constraintMetaDataMap.getOrDefault(entry.getKey(), Collections.emptyList());
            tableMetaDataList.add(
                    new TableMetaData(entry.getKey(), entry.getValue(), indexMetaDataList, constraintMetaDataList, viewNames.contains(entry.getKey()) ? TableType.VIEW : TableType.TABLE));
        }
        return Collections.singletonList(new SchemaMetaData(material.getDefaultSchemaName(), tableMetaDataList));
    }
    
    private Collection<String> loadViewNames(final DataSource dataSource, final Collection<String> tableNames) throws SQLException {
        Collection<String> result = new LinkedList<>();
        try (
                Connection connection = dataSource.getConnection();
                PreparedStatement preparedStatement = connection.prepareStatement(getViewMetaDataSQL(tableNames))) {
            String databaseName = "".equals(connection.getCatalog()) ? GlobalDataSourceRegistry.getInstance().getCachedDatabaseTables().get(tableNames.iterator().next()) : connection.getCatalog();
            preparedStatement.setString(1, databaseName);
            try (ResultSet resultSet = preparedStatement.executeQuery()) {
                while (resultSet.next()) {
                    result.add(resultSet.getString(1));
                }
            }
        }
        return result;
    }
    
    private String getViewMetaDataSQL(final Collection<String> tableNames) {
        return String.format(VIEW_META_DATA_SQL, tableNames.stream().map(each -> String.format("'%s'", each)).collect(Collectors.joining(",")));
    }
    
    private Map<String, Collection<ConstraintMetaData>> loadConstraintMetaDataMap(final DataSource dataSource, final Collection<String> tables) throws SQLException {
        Map<String, Collection<ConstraintMetaData>> result = new LinkedHashMap<>(tables.size(), 1F);
        try (
                Connection connection = dataSource.getConnection();
                PreparedStatement preparedStatement = connection.prepareStatement(getConstraintMetaDataSQL(tables))) {
            try (ResultSet resultSet = preparedStatement.executeQuery()) {
                while (resultSet.next()) {
                    String constraintName = resultSet.getString("CONSTRAINT_NAME");
                    String tableName = resultSet.getString("TABLE_NAME");
                    String referencedTableName = resultSet.getString("REFERENCED_TABLE_NAME");
                    if (!result.containsKey(tableName)) {
                        result.put(tableName, new LinkedList<>());
                    }
                    result.get(tableName).add(new ConstraintMetaData(constraintName, referencedTableName));
                }
            }
        }
        return result;
    }
    
    private String getConstraintMetaDataSQL(final Collection<String> tableNames) {
        return String.format(CONSTRAINT_META_DATA_SQL, tableNames.stream().map(each -> String.format("'%s'", each)).collect(Collectors.joining(",")));
    }
    
    private Map<String, Collection<ColumnMetaData>> loadColumnMetaDataMap(final DataSource dataSource, final Collection<String> tables) throws SQLException {
        Map<String, Collection<ColumnMetaData>> result = new HashMap<>(tables.size(), 1F);
        try (
                Connection connection = dataSource.getConnection();
                PreparedStatement preparedStatement = connection.prepareStatement(getTableMetaDataSQL(tables))) {
            String databaseName = "".equals(connection.getCatalog()) ? GlobalDataSourceRegistry.getInstance().getCachedDatabaseTables().get(tables.iterator().next()) : connection.getCatalog();
            preparedStatement.setString(1, databaseName);
            try (ResultSet resultSet = preparedStatement.executeQuery()) {
                while (resultSet.next()) {
                    String tableName = resultSet.getString("TABLE_NAME");
                    ColumnMetaData columnMetaData = loadColumnMetaData(resultSet);
                    if (!result.containsKey(tableName)) {
                        result.put(tableName, new LinkedList<>());
                    }
                    result.get(tableName).add(columnMetaData);
                }
            }
        }
        return result;
    }
    
    private ColumnMetaData loadColumnMetaData(final ResultSet resultSet) throws SQLException {
        String columnName = resultSet.getString("COLUMN_NAME");
        String dataType = resultSet.getString("DATA_TYPE");
        boolean primaryKey = "PRI".equalsIgnoreCase(resultSet.getString("COLUMN_KEY"));
        String extra = resultSet.getString("EXTRA");
        boolean generated = "auto_increment".equals(extra);
        String collationName = resultSet.getString("COLLATION_NAME");
        boolean caseSensitive = null != collationName && !collationName.endsWith("_ci");
        boolean visible = !"INVISIBLE".equalsIgnoreCase(extra);
        boolean unsigned = resultSet.getString("COLUMN_TYPE").toUpperCase().contains("UNSIGNED");
        boolean nullable = "YES".equals(resultSet.getString("IS_NULLABLE"));
        return new ColumnMetaData(columnName, DataTypeRegistry.getDataType(getDatabaseType(), dataType).orElse(Types.OTHER), primaryKey, generated, caseSensitive, visible, unsigned, nullable);
    }
    
    private String getTableMetaDataSQL(final Collection<String> tables) {
        return tables.isEmpty() ? TABLE_META_DATA_SQL : String.format(TABLE_META_DATA_SQL_IN_TABLES, tables.stream().map(each -> String.format("'%s'", each)).collect(Collectors.joining(",")));
    }
    
    private Map<String, Collection<IndexMetaData>> loadIndexMetaData(final DataSource dataSource, final Collection<String> tableNames) throws SQLException {
        Map<String, Map<String, IndexMetaData>> tableToIndex = new HashMap<>(tableNames.size(), 1F);
        try (
                Connection connection = dataSource.getConnection();
                PreparedStatement preparedStatement = connection.prepareStatement(getIndexMetaDataSQL(tableNames))) {
            String databaseName = "".equals(connection.getCatalog()) ? GlobalDataSourceRegistry.getInstance().getCachedDatabaseTables().get(tableNames.iterator().next()) : connection.getCatalog();
            preparedStatement.setString(1, databaseName);
            try (ResultSet resultSet = preparedStatement.executeQuery()) {
                while (resultSet.next()) {
                    String indexName = resultSet.getString("INDEX_NAME");
                    String tableName = resultSet.getString("TABLE_NAME");
                    if (!tableToIndex.containsKey(tableName)) {
                        tableToIndex.put(tableName, new HashMap<>());
                    }
                    Map<String, IndexMetaData> indexMap = tableToIndex.get(tableName);
                    String columnName = resultSet.getString("COLUMN_NAME");
                    if (Strings.isNullOrEmpty(columnName)) {
                        continue;
                    }
                    if (indexMap.containsKey(indexName)) {
                        indexMap.get(indexName).getColumns().add(columnName);
                    } else {
                        IndexMetaData indexMetaData = new IndexMetaData(indexName, new LinkedList<>(Collections.singleton(columnName)));
                        indexMetaData.setUnique("0".equals(resultSet.getString("NON_UNIQUE")));
                        indexMap.put(indexName, indexMetaData);
                    }
                }
            }
        }
        Map<String, Collection<IndexMetaData>> result = new HashMap<>(tableToIndex.size(), 1F);
        for (Entry<String, Map<String, IndexMetaData>> entry : tableToIndex.entrySet()) {
            result.put(entry.getKey(), entry.getValue().values());
        }
        return result;
    }
    
    private String getIndexMetaDataSQL(final Collection<String> tableNames) {
        return String.format(INDEX_META_DATA_SQL, tableNames.stream().map(each -> String.format("'%s'", each)).collect(Collectors.joining(",")));
    }
    
    @Override
    public String getDatabaseType() {
        return "MySQL";
    }
}
