# JdbcRequester.java

    /*
     * Copyright (C) 2000 - 2024 Silverpeas
     *
     * This program is free software: you can redistribute it and/or modify
     * it under the terms of the GNU Affero General Public License as
     * published by the Free Software Foundation, either version 3 of the
     * License, or (at your option) any later version.
     *
     * As a special exception to the terms and conditions of version 3.0 of
     * the GPL, you may redistribute this Program in connection with Free/Libre
     * Open Source Software ("FLOSS") applications as described in Silverpeas's
     * FLOSS exception.  You should have received a copy of the text describing
     * the FLOSS exception, and it is also available here:
     * "https://www.silverpeas.org/legal/floss_exception.html"
     *
     * This program is distributed in the hope that it will be useful,
     * but WITHOUT ANY WARRANTY; without even the implied warranty of
     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     * GNU Affero General Public License for more details.
     *
     * You should have received a copy of the GNU Affero General Public License
     * along with this program.  If not, see <https://www.gnu.org/licenses/>.
     */

    package org.silverpeas.components.mydb.model;

    import org.silverpeas.components.mydb.model.predicates.AbstractColumnValuePredicate;
    import org.silverpeas.components.mydb.service.MyDBException;
    import org.silverpeas.components.mydb.service.MyDBRuntimeException;
    import org.silverpeas.core.admin.PaginationPage;
    import org.silverpeas.core.persistence.Transaction;
    import org.silverpeas.core.persistence.TransactionRuntimeException;
    import org.silverpeas.core.persistence.jdbc.sql.JdbcSqlQuery;
    import org.silverpeas.core.util.SilverpeasList;
    import org.silverpeas.kernel.util.StringUtil;
    import org.silverpeas.kernel.logging.SilverLogger;

    import javax.annotation.Nonnull;
    import java.sql.Connection;
    import java.sql.DatabaseMetaData;
    import java.sql.ResultSet;
    import java.sql.ResultSetMetaData;
    import java.sql.SQLException;
    import java.util.ArrayList;
    import java.util.LinkedHashMap;
    import java.util.List;
    import java.util.Map;
    import java.util.Objects;

    import static org.silverpeas.kernel.util.StringUtil.isDefined;

    /**
     * A requester of a remote enterprise data source by using the yet configured
     * {@link MyDBConnectionInfo} instance. If
     * no {@link MyDBConnectionInfo} instance is
     * available, then no connection is established and no request can be done.
     * @author mmoquillon
     */
    class JdbcRequester {

      private final MyDBConnectionInfo currentConnectionInfo;

      /**
       * Constructs a new JDBC requester with the specified {@link MyDBConnectionInfo} instance.
       * @param dsInfo a {@link MyDBConnectionInfo} instance.
       */
      JdbcRequester(final MyDBConnectionInfo dsInfo) {
        this.currentConnectionInfo = dsInfo;
      }

      /**
       * Is there is a data source set with this requester? A data source is set when there is a
       * {@link MyDBConnectionInfo} instance defined for the component instance to which this
       * requester is related.
       * @return true if there is a {@link MyDBConnectionInfo} instance set with this requester.
       * False otherwise.
       */
      private boolean isDataSourceDefined() {
        return currentConnectionInfo.isDefined();
      }

      /**
       * Gets all the tables in the data source (only public tables and views are fetched). If an error
       * occurs while requesting the data source, a {@link MyDBRuntimeException} is thrown.
       * @return a list of table names.
       */
      List<String> getTableNames() {
        try (Connection connection = currentConnectionInfo.openConnection()) {
          return getTableNames(connection);
        } catch (SQLException | MyDBException e) {
          throw new MyDBRuntimeException(e);
        }
      }

      /**
       * Performs the specified database operations within the same connection with the data source and
       * within a same transaction. If no data source is defined, then a {@link MyDBRuntimeException}
       * is thrown. If the database * operations throw an exception, then a
       * {@link MyDBRuntimeException} is thrown.
       * @param operations the operation to execute on the database.
       */
      <T> T perform(final DbOperation<T> operations) {
        Objects.requireNonNull(operations);
        if (!isDataSourceDefined()) {
          throw new MyDBRuntimeException("No data source defined!");
        }
        try {
          return Transaction.performInOne(() -> {
            try (Connection connection = currentConnectionInfo.openConnection()) {
              return operations.execute(this, connection);
            }
          });
        } catch (TransactionRuntimeException e) {
          throw new MyDBRuntimeException(e);
        }
      }

      private List<String> getTableNames(final Connection connection) throws SQLException {
        Objects.requireNonNull(connection);
        final List<String> tableNames = new ArrayList<>();
        DatabaseMetaData dbMetaData = connection.getMetaData();
        ResultSet tables = dbMetaData.getTables(null, null, null, new String[]{"TABLE", "VIEW"});
        while (tables.next()) {
          String table = tables.getString("TABLE_NAME");
          if (isAuthorizedTable(connection, table)) {
            tableNames.add(table);
          }
        }
        return tableNames;
      }

      private boolean isAuthorizedTable(final Connection connection, String tableName) {
        try {
          JdbcSqlQuery.countAll().from(tableName).executeWith(connection);
          return true;
        } catch (SQLException e) {
          return false;
        }
      }

      /**
       * Gets the definition of all the columns of the specified database table and passes them to the
       * specified {@link ColumnConsumer} function.
       * @param connection a connection to the database.
       * @param tableName the name of the table from which the columns have to be get.
       * @param consumer the consumer of the column definitions.
       * @throws SQLException if an error occurs while requesting the database.
       */
      void loadColumns(final Connection connection, final String tableName,
          final ColumnConsumer consumer) throws SQLException {
        Objects.requireNonNull(connection);
        final DatabaseMetaData dbMetaData = connection.getMetaData();
        final List<String> columnPks = getPrimaryKeys(connection, tableName, dbMetaData);
        final Map<String, ForeignKeyDescriptor> columnFks =
            getForeignKeys(connection, tableName, dbMetaData);
        final ResultSet columns = dbMetaData.getColumns(connection.getCatalog(), null, tableName, null);
        while (columns.next()) {
          final String name = columns.getString("COLUMN_NAME");
          final int type = columns.getInt("DATA_TYPE");
          final int size = columns.getInt("COLUMN_SIZE");
          final boolean isAutoIncremented =
              StringUtil.getBooleanValue(columns.getString("IS_AUTOINCREMENT"));
          final boolean isNullable = StringUtil.getBooleanValue(columns.getString("IS_NULLABLE"));
          final boolean isPrimaryKey = columnPks.contains(name);
          final DefaultValue defaultValue = getDefaultValue(columns);
          consumer.accept(new ColumnDescriptor().withName(name)
              .withType(type)
              .withSize(size)
              .withPrimaryKey(isPrimaryKey)
              .withForeignKey(columnFks.get(name))
              .withNullable(isNullable)
              .withAutoIncrement(isAutoIncremented)
              .withDefaultValue(defaultValue));
        }
      }

      private Map<String, ForeignKeyDescriptor> getForeignKeys(final Connection connection,
          final String tableName, final DatabaseMetaData dbMetaData) throws SQLException {
        final Map<String, ForeignKeyDescriptor> columnFks = new LinkedHashMap<>(4);
        final ResultSet foreignKeys =
            dbMetaData.getImportedKeys(connection.getCatalog(), connection.getSchema(), tableName);
        while (foreignKeys.next()) {
          final String fkName = foreignKeys.getString("FK_NAME");
          final String columnName = foreignKeys.getString("FKCOLUMN_NAME");
          final String targetTableName = foreignKeys.getString("PKTABLE_NAME");
          final String targetColumnName = foreignKeys.getString("PKCOLUMN_NAME");
          columnFks.put(columnName,
              new ForeignKeyDescriptor(fkName, targetTableName, targetColumnName));
        }
        return columnFks;
      }

      private List<String> getPrimaryKeys(final Connection connection, final String tableName,
          final DatabaseMetaData dbMetaData) throws SQLException {
        final List<String> columnPks = new ArrayList<>(2);
        final ResultSet primaryKeys =
            dbMetaData.getPrimaryKeys(connection.getCatalog(), connection.getSchema(), tableName);
        while (primaryKeys.next()) {
          final String pk = primaryKeys.getString("COLUMN_NAME");
          columnPks.add(pk);
        }
        return columnPks;
      }

      /**
       * Requests the content of the specified table by applying the given predicate and uses the
       * specified converters to convert each row and each row's value to their corresponding business
       * object, ready to be handled by the caller.
       * @param <V> the type of the business objects representing the row's values.
       * @param <R> the type of the business objects representing the rows.
       * @param connection a connection to the database.
       * @param tableName the name of the table to request.
       * @param predicate a predicate to use to filter the table's content.
       * @param orderBy a order by directive already built (without the clause key words).
       * @param converters the converters to use to convert each row and each row's value to a business
       * object.
       * @param pagination a pagination in order to avoid bad performances.
       * @return a list of rows, matching the given predicate, in their business representation. If no
       * rows match the specified predicate or if the table is empty, an empty list is returned.
       * @throws SQLException if an error occurs while requesting the database.
       */
      <V, R> SilverpeasList<R> request(final Connection connection, final String tableName,
          final AbstractColumnValuePredicate predicate, final String orderBy, final DataConverters<V, R> converters,
          final PaginationPage pagination)
          throws SQLException {
        Objects.requireNonNull(connection);
        Objects.requireNonNull(tableName);
        Objects.requireNonNull(predicate);
        JdbcSqlQuery query = JdbcSqlQuery.select("*").from(tableName);
        query = isDefined(orderBy) ? predicate.apply(query).orderBy(orderBy) : predicate.apply(query);
        if (pagination != null) {
          query.withPagination(pagination.asCriterion());
        }
        return query.executeWith(connection, rs -> {
          try {
            final Map<String, V> row = new LinkedHashMap<>();
            ResultSetMetaData rsMetaData = rs.getMetaData();
            for (int i = 1; i <= rsMetaData.getColumnCount(); i++) {
              V value = converters.getValueConverter()
                  .convert(rs.getObject(i), rs.getMetaData().getColumnType(i));
              row.put(rsMetaData.getColumnName(i), value);
            }
            return converters.getRowConverter().convert(row);
          } catch (SQLException e) {
            throw new MyDBRuntimeException(e);
          }
        });
      }

      /**
       * Deletes all the rows in the specified table name that match the specified predicate. If no
       * criteria is given, then the table is emptied. If the table is already empty, nothing is done.
       * @param connection a connection to the database.
       * @param tableName the name of the table in which some of the rows have to be deleted.
       * @param criteria the criteria the rows to delete have to match.
       * @throws SQLException if an error occurs while deleting the rows in the specified table.
       */
      long delete(final Connection connection, final String tableName,
          final Map<String, Object> criteria) throws SQLException {
        final JdbcSqlQuery query = JdbcSqlQuery.deleteFrom(tableName);
        return applyCriteria(query, criteria).executeWith(connection);
      }

      /**
       * Updates the rows in the specified table that match the given criteria with the values defined
       * in the specified dictionary <code>values</code>.
       * @param connection a connection to the database.
       * @param tableName the name of the table in which the rows will be updated.
       * @param values the values with which the rows will be updated.
       * @param criteria the criteria the rows have to match.
       * @throws SQLException if an error occurs while updating the rows in the specified table.
       */
      long update(final Connection connection, final String tableName, final Map<String, Object> values,
          Map<String, Object> criteria) throws SQLException {
        final JdbcSqlQuery query = JdbcSqlQuery.update(tableName);
        values.forEach(query::withUpdateParam);
        return applyCriteria(query, criteria).executeWith(connection);
      }

      /**
       * Inserts into the specified table a new row with the specified values.
       * @param connection a connection to the database.
       * @param tableName the name of the table into which the row will be inserted.
       * @param values the values of the row to insert as a map of column names to column values.
       */
      void insert(final Connection connection, final String tableName, final Map<String, Object> values)
          throws SQLException {
        final JdbcSqlQuery query = JdbcSqlQuery.insertInto(tableName);
        values.forEach(query::withInsertParam);
        query.executeWith(connection);
      }

      private JdbcSqlQuery applyCriteria(final JdbcSqlQuery query, final Map<String, Object> criteria) {
        final StringBuilder clauses = new StringBuilder(criteria.size());
        final List<Object> values = new ArrayList<>(criteria.size());
        final String conjunction = " and ";
        criteria.forEach((key, value) -> {
          if (value == null) {
            clauses.append(key).append(" is null").append(conjunction);
          } else {
            clauses.append(key).append(" = ?").append(conjunction);
            values.add(value);
          }
        });
        clauses.setLength(clauses.length() - conjunction.length());
        return query.where(clauses.toString(), values);
      }

      private DefaultValue getDefaultValue(final ResultSet resultSet)
          throws SQLException {
        String defaultValue = resultSet.getString("COLUMN_DEF");
        return new DefaultValue(defaultValue);
      }

      /**
       * A provider of converters of data. They convert database data to their corresponding business
       * data.
       * @param <V> the business type representing a column's value in a given row of a database table.
       * @param <R> the business type representing a given row of a database table.
       */
      static class DataConverters<V, R> {
        private final ValueConverter<V> valueConverter;
        private final RowConverter<V, R> rowConverter;

        DataConverters(final ValueConverter<V> valueConverter, final RowConverter<V, R> rowConverter) {
          this.valueConverter = valueConverter;
          this.rowConverter = rowConverter;
        }

        /**
         * Converter of a database table row's value to a business object representing that value.
         * @return a {@link ValueConverter} instance.
         */
        ValueConverter<V> getValueConverter() {
          return valueConverter;
        }

        /**
         * Converter of a database table row to a business object representing that row.
         * @return a {@link RowConverter} instance.
         */
        RowConverter<V, R> getRowConverter() {
          return rowConverter;
        }
      }

      /**
       * Descriptor of a foreign key. It should be mapped to a column in a given table for which it
       * references another column of another table.
       */
      static class ForeignKeyDescriptor {
        private final String name;
        private final String targetTableName;
        private final String targetColumnName;

        private ForeignKeyDescriptor(final String name, final String targetTableName,
            final String targetColumnName) {
          this.name = name;
          this.targetTableName = targetTableName;
          this.targetColumnName = targetColumnName;
        }

        /**
         * Gets the name of the foreign key. Useful to retrieve the columns that made up a composite
         * foreign keys.
         * @return the name of the foreign key.
         */
        String getName() {
          return name;
        }

        /**
         * Gets the name of the table targeted by this key.
         * @return the name of the targeted table.
         */
        String getTargetTableName() {
          return targetTableName;
        }

        /**
         * Gets the name of the column in the targeted table that is targeted by this key.
         * @return the name of the targeted column.
         */
        String getTargetColumnName() {
          return targetColumnName;
        }
      }

      class DefaultValue {
        private final String pattern;

        public DefaultValue(final String valuePattern) {
          this.pattern = valuePattern;
        }

        public boolean isDefined() {
          return pattern != null;
        }

        public String get() {
          String value = null;
          if (isDefined()) {
            try (Connection connection = currentConnectionInfo.openConnection()) {
              value = computeSQLFunction(connection, pattern);
            } catch (MyDBException | SQLException e) {
              throw new MyDBRuntimeException(e);
            }
            int index = value.indexOf("::");
            if (index != -1) {
              value = parseDefaultValue(value, index);
            }
          }
          return value;
        }

        @Nonnull
        private String parseDefaultValue(String defaultValue, final int valueLength) {
          defaultValue = defaultValue.substring(0, valueLength);
          if (defaultValue.startsWith("'") && defaultValue.endsWith("'")) {
            defaultValue = defaultValue.substring(1, defaultValue.length() - 1);
          }
          return defaultValue;
        }

        @Nonnull
        private String computeSQLFunction(final Connection connection, final String function) {
          try {
            return JdbcSqlQuery.select(function)
                .executeUniqueWith(connection, r -> r.getString(1));
          } catch (SQLException e) {
            // not a function or cannot be computed by the database
            SilverLogger.getLogger(this).silent(e);
            return function;
          }
        }
      }

      /**
       * A descriptor of a column in a database table.
       */
      class ColumnDescriptor {
        private String name;
        private int type;
        private int size;
        private boolean primaryKey;
        private ForeignKeyDescriptor foreignKey;
        private boolean nullable;
        private boolean autoIncrementable;
        private DefaultValue defaultValue;

        private ColumnDescriptor() {
        }

        /**
         * Gets the name of the column.
         * @return the unique name of the column in the table.
         */
        String getName() {
          return name;
        }

        private ColumnDescriptor withName(final String name) {
          this.name = name;
          return this;
        }

        /**
         * Gets the SQL type code of this column.
         * @return the code of the SQL type of the values that column accepts.
         * @see java.sql.Types
         */
        int getType() {
          return type;
        }

        private ColumnDescriptor withType(final int type) {
          this.type = type;
          return this;
        }

        /**
         * Gets the size of the column SQL type.
         * @return the size of the column type.
         */
        int getSize() {
          return size;
        }

        private ColumnDescriptor withSize(final int size) {
          this.size = size;
          return this;
        }

        /**
         * Is this column a primary key?
         * @return true if the values of this column are primary keys. False otherwise.
         */
        boolean isPrimaryKey() {
          return primaryKey;
        }

        private ColumnDescriptor withPrimaryKey(final boolean primaryKey) {
          this.primaryKey = primaryKey;
          return this;
        }

        /**
         * Is this column can be nullable.
         * @return true if this column can be valued with null, false otherwise.
         */
        boolean isNullable() {
          return nullable;
        }

        private ColumnDescriptor withNullable(final boolean nullable) {
          this.nullable = nullable;
          return this;
        }

        /**
         * Is the valuation of this column can be incrementable?
         * @return true of the valuation of this column is taken in charge by the database. False
         * otherwise.
         */
        boolean isAutoIncrementable() {
          return autoIncrementable;
        }

        private ColumnDescriptor withAutoIncrement(final boolean isAutoIncrement) {
          this.autoIncrementable = isAutoIncrement;
          return this;
        }

        /**
         * Gets the default value of this column if any.
         * @return the default value set with this column, null if no such a default value was set.
         */
        DefaultValue getDefaultValue() {
          return defaultValue;
        }

        private ColumnDescriptor withDefaultValue(final DefaultValue defaultValue) {
          this.defaultValue = defaultValue;
          return this;
        }

        /**
         * Gets a descriptor of the foreign key that is mapped with this column.
         * @return a foreign key descriptor or null if this column isn't a foreign key.
         */
        ForeignKeyDescriptor getForeignKey() {
          return this.foreignKey;
        }

        private ColumnDescriptor withForeignKey(final ForeignKeyDescriptor foreignKey) {
          this.foreignKey = foreignKey;
          return this;
        }
      }

      /**
       * An operation on the behalf of the database.
       * @param <T> the type of the result.
       */
      @FunctionalInterface
      interface DbOperation<T> {
        T execute(final JdbcRequester requester, final Connection connection) throws SQLException;
      }

      /**
       * A consumer of a database column description.
       */
      @FunctionalInterface
      interface ColumnConsumer {
        void accept(final ColumnDescriptor column);
      }

      /**
       * A converter of the database row to a business object.
       * @param <V> the type of the business value in a row.
       * @param <R> the type of the business row.
       */
      @FunctionalInterface
      interface RowConverter<V, R> {
        R convert(final Map<String, V> row);
      }

      /**
       * A converter of a value in a column to a business object.
       * @param <V> the type of the business value.
       */
      @FunctionalInterface
      interface ValueConverter<V> {
        V convert(final Object value, final int valueType);
      }
    }