/**
 * 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.hadoop.hive.ql.metadata;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Map;
import java.util.List;
import java.util.TreeMap;

import org.apache.hadoop.hive.metastore.api.SQLForeignKey;

/**
 * ForeignKeyInfo is a metadata structure containing the foreign keys associated with a table.
 * The fields include the child database name, the child table name, mapping of the constraint
 * name to the foreign key columns associated with the key. The foreign key column structure 
 * contains the parent database name, parent table name, associated parent column name,
 * associated child column name and the position of the foreign key column in the key.
 * The position is one-based index.
 */
@SuppressWarnings("serial")
public class ForeignKeyInfo implements Serializable {

  public class ForeignKeyCol {
    public String parentTableName;
    public String parentDatabaseName;
    public String parentColName;
    public String childColName;
    public Integer position;

    public ForeignKeyCol(String parentTableName, String parentDatabaseName, String parentColName,
      String childColName, Integer position) {
      this.parentTableName = parentTableName;
      this.parentDatabaseName = parentDatabaseName;
      this.parentColName = parentColName;
      this.childColName = childColName;
      this.position = position;
    }
  }

  // Mapping from constraint name to list of foreign keys
  Map<String, List<ForeignKeyCol>> foreignKeys;
  String childTableName;
  String childDatabaseName;

  public ForeignKeyInfo() {}

  public ForeignKeyInfo(List<SQLForeignKey> fks, String childTableName, String childDatabaseName) {
    this.childTableName = childTableName;
    this.childDatabaseName = childDatabaseName;
    foreignKeys = new TreeMap<String, List<ForeignKeyCol>>();
    if (fks == null) {
      return;
    }
    for (SQLForeignKey fk : fks) {
      if (fk.getFktable_db().equalsIgnoreCase(childDatabaseName) &&
          fk.getFktable_name().equalsIgnoreCase(childTableName)) {
        ForeignKeyCol currCol = new ForeignKeyCol(fk.getPktable_name(), fk.getPktable_db(),
          fk.getPkcolumn_name(), fk.getFkcolumn_name(), fk.getKey_seq());
        String constraintName = fk.getFk_name();
        if (foreignKeys.containsKey(constraintName)) {
          foreignKeys.get(constraintName).add(currCol);
        } else {
          List<ForeignKeyCol> currList = new ArrayList<ForeignKeyCol>();
          currList.add(currCol);
          foreignKeys.put(constraintName, currList);
        }
      }
    }
  }

  public String getChildTableName() {
    return childTableName;
  }

  public String getChildDatabaseName() {
    return childDatabaseName;
  }

  public Map<String, List<ForeignKeyCol>> getForeignKeys() {
    return foreignKeys;
  }

  public void setChildTableName(String tableName) {
    this.childTableName = tableName;
  }

  public void setChildDatabaseName(String databaseName) {
    this.childDatabaseName = databaseName;
  }

  public void setForeignKeys(Map<String, List<ForeignKeyCol>> foreignKeys) {
    this.foreignKeys = foreignKeys;
  }

  @Override
  public String toString() {
    StringBuilder sb = new StringBuilder();
    sb.append("Foreign Keys for " + childDatabaseName+"."+childTableName+":");
    sb.append("[");
    if (foreignKeys != null && foreignKeys.size() > 0) {
      for (Map.Entry<String, List<ForeignKeyCol>> me : foreignKeys.entrySet()) {
        sb.append(" {Constraint Name: " + me.getKey() + ",");
        List<ForeignKeyCol> currCol = me.getValue();
        if (currCol != null && currCol.size() > 0) {
          for (ForeignKeyCol fkc : currCol) {
            sb.append (" (Parent Column Name: " + fkc.parentDatabaseName +
              "."+ fkc.parentTableName + "." + fkc.parentColName +
              ", Column Name: " + fkc.childColName + ", Key Sequence: " + fkc.position+ "),");
          }
          sb.setLength(sb.length()-1);
        }
        sb.append("},");
      }
      sb.setLength(sb.length()-1);
    }
    sb.append("]");
    return sb.toString();
  }
}