/*
 * Copyright 2004-2019 H2 Group. Multiple-Licensed under the MPL 2.0,
 * and the EPL 1.0 (http://h2database.com/html/license.html).
 * Initial Developer: H2 Group
 */
package org.h2.index;

import java.util.ArrayList;

import org.h2.api.ErrorCode;
import org.h2.command.dml.AllColumnsForPlan;
import org.h2.engine.Constants;
import org.h2.engine.Session;
import org.h2.message.DbException;
import org.h2.result.Row;
import org.h2.result.SearchRow;
import org.h2.result.SortOrder;
import org.h2.table.Column;
import org.h2.table.IndexColumn;
import org.h2.table.PageStoreTable;
import org.h2.table.TableFilter;
import org.h2.util.Utils;

The scan index is not really an 'index' in the strict sense, because it can
not be used for direct lookup. It can only be used to iterate over all rows
of a table. Each regular table has one such object, even if no primary key or
indexes are defined.
/**
 * The scan index is not really an 'index' in the strict sense, because it can
 * not be used for direct lookup. It can only be used to iterate over all rows
 * of a table. Each regular table has one such object, even if no primary key or
 * indexes are defined.
 */
public class ScanIndex extends BaseIndex {
    private long firstFree = -1;
    private ArrayList<Row> rows = Utils.newSmallArrayList();
    private final PageStoreTable tableData;
    private long rowCount;

    public ScanIndex(PageStoreTable table, int id, IndexColumn[] columns,
            IndexType indexType) {
        super(table, id, table.getName() + "_DATA", columns, indexType);
        tableData = table;
    }

    @Override
    public void remove(Session session) {
        truncate(session);
    }

    @Override
    public void truncate(Session session) {
        rows = Utils.newSmallArrayList();
        firstFree = -1;
        if (tableData.getContainsLargeObject() && tableData.isPersistData()) {
            database.getLobStorage().removeAllForTable(table.getId());
        }
        tableData.setRowCount(0);
        rowCount = 0;
    }

    @Override
    public String getCreateSQL() {
        return null;
    }

    @Override
    public void close(Session session) {
        // nothing to do
    }

    @Override
    public Row getRow(Session session, long key) {
        return rows.get((int) key);
    }

    @Override
    public void add(Session session, Row row) {
        // in-memory
        if (firstFree == -1) {
            int key = rows.size();
            row.setKey(key);
            rows.add(row);
        } else {
            long key = firstFree;
            Row free = rows.get((int) key);
            firstFree = free.getKey();
            row.setKey(key);
            rows.set((int) key, row);
        }
        row.setDeleted(false);
        rowCount++;
    }

    @Override
    public void remove(Session session, Row row) {
        // in-memory
        if (rowCount == 1) {
            rows = Utils.newSmallArrayList();
            firstFree = -1;
        } else {
            Row free = session.createRow(null, 1);
            free.setKey(firstFree);
            long key = row.getKey();
            if (rows.size() <= key) {
                throw DbException.get(ErrorCode.ROW_NOT_FOUND_WHEN_DELETING_1,
                        rows.size() + ": " + key);
            }
            rows.set((int) key, free);
            firstFree = key;
        }
        rowCount--;
    }

    @Override
    public Cursor find(Session session, SearchRow first, SearchRow last) {
        return new ScanCursor(this);
    }

    @Override
    public double getCost(Session session, int[] masks,
            TableFilter[] filters, int filter, SortOrder sortOrder,
            AllColumnsForPlan allColumnsSet) {
        return tableData.getRowCountApproximation() + Constants.COST_ROW_OFFSET;
    }

    @Override
    public long getRowCount(Session session) {
        return rowCount;
    }

    
Get the next row that is stored after this row.
Params:
row – the current row or null to start the scan
Returns:
the next row or null if there are no more rows/**
     * Get the next row that is stored after this row.
     *
     * @param row the current row or null to start the scan
     * @return the next row or null if there are no more rows
     */
    Row getNextRow(Row row) {
        long key;
        if (row == null) {
            key = -1;
        } else {
            key = row.getKey();
        }
        while (true) {
            key++;
            if (key >= rows.size()) {
                return null;
            }
            row = rows.get((int) key);
            if (!row.isEmpty()) {
                return row;
            }
        }
    }

    @Override
    public int getColumnIndex(Column col) {
        // the scan index cannot use any columns
        return -1;
    }

    @Override
    public boolean isFirstColumn(Column column) {
        return false;
    }

    @Override
    public void checkRename() {
        throw DbException.getUnsupportedException("SCAN");
    }

    @Override
    public boolean needRebuild() {
        return false;
    }

    @Override
    public boolean canGetFirstOrLast() {
        return false;
    }

    @Override
    public Cursor findFirstOrLast(Session session, boolean first) {
        throw DbException.getUnsupportedException("SCAN");
    }

    @Override
    public long getRowCountApproximation() {
        return rowCount;
    }

    @Override
    public long getDiskSpaceUsed() {
        return 0;
    }

    @Override
    public String getPlanSQL() {
        return table.getSQL(new StringBuilder(), false).append(".tableScan").toString();
    }

}