Cursor

/*
Copyright (c) 2013 James Ahlborn

Licensed 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 com.healthmarketscience.jackcess;

import java.io.IOException;
import java.io.UncheckedIOException;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import com.healthmarketscience.jackcess.util.ColumnMatcher;
import com.healthmarketscience.jackcess.util.ErrorHandler;
import com.healthmarketscience.jackcess.util.IterableBuilder;

/**
 * Manages iteration for a {@link Table}.  Different cursors provide different
 * methods of traversing a table.  Cursors should be fairly robust in the face
 * of table modification during traversal (although depending on how the table
 * is traversed, row updates may or may not be seen).  Multiple cursors may
 * traverse the same table simultaneously.
 * <p>
 * Basic cursors will generally iterate table data in the order it appears in
 * the database and searches will require scanning the entire table.
 * Additional features are available when utilizing an {@link Index} backed
 * {@link IndexCursor}.
 * <p>
 * The {@link CursorBuilder} provides a variety of static utility methods to
 * construct cursors with given characteristics or easily search for specific
 * values as well as friendly and flexible construction options.
 * <p>
 * A Cursor instance is not thread-safe (see {@link Database} for more
 * thread-safety details).
 *
 * @author James Ahlborn
 * @usage _general_class_
 */
public interface Cursor extends Iterable<Row>
{

  public Id getId();

  public Table getTable();

  /**
   * Gets the currently configured ErrorHandler (always non-{@code null}).
   * This will be used to handle all errors.
   */
  public ErrorHandler getErrorHandler();

  /**
   * Sets a new ErrorHandler.  If {@code null}, resets to using the
   * ErrorHandler configured at the Table level.
   */
  public void setErrorHandler(ErrorHandler newErrorHandler);

  /**
   * Returns the currently configured ColumnMatcher, always non-{@code null}.
   */
  public ColumnMatcher getColumnMatcher();

  /**
   * Sets a new ColumnMatcher.  If {@code null}, resets to using the default
   * matcher (default depends on Cursor type).
   */
  public void setColumnMatcher(ColumnMatcher columnMatcher);

  /**
   * Returns the current state of the cursor which can be restored at a future
   * point in time by a call to {@link #restoreSavepoint}.
   * <p>
   * Savepoints may be used across different cursor instances for the same
   * table, but they must have the same {@link Id}.
   */
  public Savepoint getSavepoint();

  /**
   * Moves the cursor to a savepoint previously returned from
   * {@link #getSavepoint}.
   * @throws IllegalArgumentException if the given savepoint does not have a
   *         cursorId equal to this cursor's id
   */
  public void restoreSavepoint(Savepoint savepoint)
    throws IOException;

  /**
   * Resets this cursor for forward traversal.  Calls {@link #beforeFirst}.
   */
  public void reset();

  /**
   * Resets this cursor for forward traversal (sets cursor to before the first
   * row).
   */
  public void beforeFirst();

  /**
   * Resets this cursor for reverse traversal (sets cursor to after the last
   * row).
   */
  public void afterLast();

  /**
   * Returns {@code true} if the cursor is currently positioned before the
   * first row, {@code false} otherwise.
   */
  public boolean isBeforeFirst() throws IOException;

  /**
   * Returns {@code true} if the cursor is currently positioned after the
   * last row, {@code false} otherwise.
   */
  public boolean isAfterLast() throws IOException;

  /**
   * Returns {@code true} if the row at which the cursor is currently
   * positioned is deleted, {@code false} otherwise (including invalid rows).
   */
  public boolean isCurrentRowDeleted() throws IOException;

  /**
   * Calls {@link #beforeFirst} on this cursor and returns a modifiable
   * Iterator which will iterate through all the rows of this table.  Use of
   * the Iterator follows the same restrictions as a call to
   * {@link #getNextRow}.
   * <p>
   * For more flexible iteration see {@link #newIterable}.
   * @throws UncheckedIOException if an IOException is thrown by one of the
   *         operations, the actual exception will be contained within
   */
  @Override
  public Iterator<Row> iterator();

  /**
   * @return a Stream using the default Iterator.
   */
  default public Stream<Row> stream() {
    return StreamSupport.stream(spliterator(), false);
  }

  /**
   * Convenience method for constructing a new IterableBuilder for this
   * cursor.  An IterableBuilder provides a variety of options for more
   * flexible iteration.
   */
  public IterableBuilder newIterable();

  /**
   * Delete the current row.
   * <p>
   * Note, re-deleting an already deleted row is allowed (it does nothing).
   * @throws IllegalStateException if the current row is not valid (at
   *         beginning or end of table)
   */
  public void deleteCurrentRow() throws IOException;

  /**
   * Update the current row.
   * @return the given row values if long enough, otherwise a new array,
   *         updated with the current row values
   * @throws IllegalStateException if the current row is not valid (at
   *         beginning or end of table), or deleted.
   */
  public Object[] updateCurrentRow(Object... row) throws IOException;

  /**
   * Update the current row.
   * @return the given row, updated with the current row values
   * @throws IllegalStateException if the current row is not valid (at
   *         beginning or end of table), or deleted.
   */
  public <M extends Map<String,Object>> M updateCurrentRowFromMap(M row)
    throws IOException;

  /**
   * Moves to the next row in the table and returns it.
   * @return The next row in this table (Column name -&gt; Column value), or
   *         {@code null} if no next row is found
   */
  public Row getNextRow() throws IOException;

  /**
   * Moves to the next row in the table and returns it.
   * @param columnNames Only column names in this collection will be returned
   * @return The next row in this table (Column name -&gt; Column value), or
   *         {@code null} if no next row is found
   */
  public Row getNextRow(Collection<String> columnNames)
    throws IOException;

  /**
   * Moves to the previous row in the table and returns it.
   * @return The previous row in this table (Column name -&gt; Column value), or
   *         {@code null} if no previous row is found
   */
  public Row getPreviousRow() throws IOException;

  /**
   * Moves to the previous row in the table and returns it.
   * @param columnNames Only column names in this collection will be returned
   * @return The previous row in this table (Column name -&gt; Column value), or
   *         {@code null} if no previous row is found
   */
  public Row getPreviousRow(Collection<String> columnNames)
    throws IOException;

  /**
   * Moves to the next row as defined by this cursor.
   * @return {@code true} if a valid next row was found, {@code false}
   *         otherwise
   */
  public boolean moveToNextRow() throws IOException;

  /**
   * Moves to the previous row as defined by this cursor.
   * @return {@code true} if a valid previous row was found, {@code false}
   *         otherwise
   */
  public boolean moveToPreviousRow() throws IOException;

  /**
   * Moves to the row with the given rowId.  If the row is not found (or an
   * exception is thrown), the cursor is restored to its previous state.
   *
   * @return {@code true} if a valid row was found with the given id,
   *         {@code false} if no row was found
   */
  public boolean findRow(RowId rowId) throws IOException;

  /**
   * Moves to the first row (as defined by the cursor) where the given column
   * has the given value.  This may be more efficient on some cursors than
   * others.  If a match is not found (or an exception is thrown), the cursor
   * is restored to its previous state.
   * <p>
   * Warning, this method <i>always</i> starts searching from the beginning of
   * the Table (you cannot use it to find successive matches).
   *
   * @param columnPattern column from the table for this cursor which is being
   *                      matched by the valuePattern
   * @param valuePattern value which is equal to the corresponding value in
   *                     the matched row.  If this object is an instance of
   *                     {@link java.util.function.Predicate}, it will be
   *                     applied to the potential row value instead
   *                     (overriding any configured ColumnMatcher)
   * @return {@code true} if a valid row was found with the given value,
   *         {@code false} if no row was found
   */
  public boolean findFirstRow(Column columnPattern, Object valuePattern)
    throws IOException;

  /**
   * Moves to the next row (as defined by the cursor) where the given column
   * has the given value.  This may be more efficient on some cursors than
   * others.  If a match is not found (or an exception is thrown), the cursor
   * is restored to its previous state.
   *
   * @param columnPattern column from the table for this cursor which is being
   *                      matched by the valuePattern
   * @param valuePattern value which is equal to the corresponding value in
   *                     the matched row.  If this object is an instance of
   *                     {@link java.util.function.Predicate}, it will be
   *                     applied to the potential row value instead
   *                     (overriding any configured ColumnMatcher)
   * @return {@code true} if a valid row was found with the given value,
   *         {@code false} if no row was found
   */
  public boolean findNextRow(Column columnPattern, Object valuePattern)
    throws IOException;

  /**
   * Moves to the first row (as defined by the cursor) where the given columns
   * have the given values.  This may be more efficient on some cursors than
   * others.  If a match is not found (or an exception is thrown), the cursor
   * is restored to its previous state.
   * <p>
   * Warning, this method <i>always</i> starts searching from the beginning of
   * the Table (you cannot use it to find successive matches).
   *
   * @param rowPattern column names and values which must be equal to the
   *                   corresponding values in the matched row.  If a value is
   *                   an instance of {@link java.util.function.Predicate}, it
   *                   will be applied to the potential row value instead
   *                   (overriding any configured ColumnMatcher)
   * @return {@code true} if a valid row was found with the given values,
   *         {@code false} if no row was found
   */
  public boolean findFirstRow(Map<String,?> rowPattern) throws IOException;

  /**
   * Moves to the next row (as defined by the cursor) where the given columns
   * have the given values.  This may be more efficient on some cursors than
   * others.  If a match is not found (or an exception is thrown), the cursor
   * is restored to its previous state.
   *
   * @param rowPattern column names and values which must be equal to the
   *                   corresponding values in the matched row.  If a value is
   *                   an instance of {@link java.util.function.Predicate}, it
   *                   will be applied to the potential row value instead
   *                   (overriding any configured ColumnMatcher)
   * @return {@code true} if a valid row was found with the given values,
   *         {@code false} if no row was found
   */
  public boolean findNextRow(Map<String,?> rowPattern) throws IOException;

  /**
   * Returns {@code true} if the current row matches the given pattern.
   * @param columnPattern column from the table for this cursor which is being
   *                      matched by the valuePattern
   * @param valuePattern value which is equal to the corresponding value in
   *                     the matched row.  If this object is an instance of
   *                     {@link java.util.function.Predicate}, it will be
   *                     applied to the potential row value instead
   *                     (overriding any configured ColumnMatcher)
   */
  public boolean currentRowMatches(Column columnPattern, Object valuePattern)
    throws IOException;

  /**
   * Returns {@code true} if the current row matches the given pattern.
   * @param rowPattern column names and values which must be equal to the
   *                   corresponding values in the matched row.  If a value is
   *                   an instance of {@link java.util.function.Predicate}, it
   *                   will be applied to the potential row value instead
   *                   (overriding any configured ColumnMatcher)
   */
  public boolean currentRowMatches(Map<String,?> rowPattern) throws IOException;

  /**
   * Moves forward as many rows as possible up to the given number of rows.
   * @return the number of rows moved.
   */
  public int moveNextRows(int numRows) throws IOException;

  /**
   * Moves backward as many rows as possible up to the given number of rows.
   * @return the number of rows moved.
   */
  public int movePreviousRows(int numRows) throws IOException;

  /**
   * Returns the current row in this cursor (Column name -&gt; Column value).
   */
  public Row getCurrentRow() throws IOException;

  /**
   * Returns the current row in this cursor (Column name -&gt; Column value).
   * @param columnNames Only column names in this collection will be returned
   */
  public Row getCurrentRow(Collection<String> columnNames)
    throws IOException;

  /**
   * Returns the given column from the current row.
   */
  public Object getCurrentRowValue(Column column) throws IOException;

  /**
   * Updates a single value in the current row.
   * @throws IllegalStateException if the current row is not valid (at
   *         beginning or end of table), or deleted.
   */
  public void setCurrentRowValue(Column column, Object value)
    throws IOException;

  /**
   * Identifier for a cursor.  Will be equal to any other cursor of the same
   * type for the same table.  Primarily used to check the validity of a
   * Savepoint.
   */
  public interface Id
  {
  }

  /**
   * Value object which maintains the current position of the cursor.
   */
  public interface Position
  {
    /**
     * Returns the unique RowId of the position of the cursor.
     */
    public RowId getRowId();
  }

  /**
   * Value object which represents a complete save state of the cursor.
   * Savepoints are created by calling {@link Cursor#getSavepoint} and used by
   * calling {@link Cursor#restoreSavepoint} to return the the cursor state at
   * the time the Savepoint was created.
   */
  public interface Savepoint
  {
    public Id getCursorId();

    public Position getCurrentPosition();
  }

}