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/*
========================================================================
SchemaCrawler
http://www.schemacrawler.com
Copyright (c) 2000-2020, Sualeh Fatehi .
All rights reserved.
------------------------------------------------------------------------

SchemaCrawler 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.

SchemaCrawler and the accompanying materials are made available under
the terms of the Eclipse Public License v1.0, GNU General Public License
v3 or GNU Lesser General Public License v3.

You may elect to redistribute this code under any of these licenses.

The Eclipse Public License is available at:
http://www.eclipse.org/legal/epl-v10.html

The GNU General Public License v3 and the GNU Lesser General Public
License v3 are available at:
http://www.gnu.org/licenses/

========================================================================
*/
package schemacrawler.analysis.associations;


import static java.util.Objects.requireNonNull;

import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;

import schemacrawler.schema.Column;
import schemacrawler.schema.Index;
import schemacrawler.schema.IndexColumn;
import schemacrawler.schema.PrimaryKey;
import schemacrawler.schema.Table;
import schemacrawler.schema.TableConstraintColumn;

final class TableCandidateKeys
  implements Iterable
{

  private final Table table;
  private final Set tableKeys;

  TableCandidateKeys(final Table table)
  {
    this.table = requireNonNull(table, "No table provided");
    tableKeys = new HashSet<>();
    listTableKeys(table);
  }

  @Override
  public Iterator iterator()
  {
    return tableKeys.iterator();
  }

  @Override
  public String toString()
  {
    return String.format("%s: %s", table, tableKeys);
  }

  private Set listTableKeys(final Table table)
  {
    final PrimaryKey primaryKey = table.getPrimaryKey();
    if (primaryKey != null
        && primaryKey
             .getColumns()
             .size() == 1)
    {
      addColumnFromPrimaryKey(table, primaryKey);
    }

    for (final Index index : table.getIndexes())
    {
      if (index != null
          && index.isUnique()
          && index
               .getColumns()
               .size() == 1)
      {
        addColumnFromIndex(table, index);
      }
    }

    return tableKeys;
  }

  private void addColumnFromIndex(final Table table, final Index index)
  {
    final IndexColumn indexColumn = index
      .getColumns()
      .get(0);
    table
      .lookupColumn(indexColumn.getName())
      .ifPresent(column -> tableKeys.add(column));
  }

  private void addColumnFromPrimaryKey(final Table table,
                                       final PrimaryKey primaryKey)
  {
    final TableConstraintColumn tableConstraintColumn = primaryKey
      .getColumns()
      .get(0);
    table
      .lookupColumn(tableConstraintColumn.getName())
      .ifPresent(column -> tableKeys.add(column));
  }

}