package liquibase.sqlgenerator.core;

 import liquibase.database.Database;

 import liquibase.database.core.MySQLDatabase;

 import liquibase.exception.DatabaseException;

 import liquibase.exception.UnexpectedLiquibaseException;

 import liquibase.exception.ValidationErrors;

 import liquibase.sql.Sql;

 import liquibase.sql.UnparsedSql;

 import liquibase.sqlgenerator.SqlGenerator;

 import liquibase.sqlgenerator.SqlGeneratorChain;

 import liquibase.statement.core.FindForeignKeyConstraintsStatement;

 public class FindForeignKeyConstraintsGeneratorMySQL extends AbstractSqlGenerator<FindForeignKeyConstraintsStatement> {

     @Override

     public int getPriority() {

         return PRIORITY_DATABASE;

     }

     @Override

     public boolean supports(FindForeignKeyConstraintsStatement statement, Database database) {

         return database instanceof MySQLDatabase;

     }

     public ValidationErrors validate(FindForeignKeyConstraintsStatement findForeignKeyConstraintsStatement,

             Database database, SqlGeneratorChain sqlGeneratorChain) {

         ValidationErrors validationErrors = new ValidationErrors();

         validationErrors.checkRequiredField("baseTableName", findForeignKeyConstraintsStatement.getBaseTableName());

         return validationErrors;

     }

     public Sql[] generateSql(FindForeignKeyConstraintsStatement statement, Database database,

             SqlGeneratorChain sqlGeneratorChain) {

         StringBuilder sb = new StringBuilder();

         sb.append("SELECT ");

         sb.append("RC.TABLE_NAME as ").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_BASE_TABLE_NAME)

                 .append(", ");

         sb.append("KCU.COLUMN_NAME as ")

                 .append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_BASE_TABLE_COLUMN_NAME).append(", ");

         sb.append("RC.REFERENCED_TABLE_NAME ")

                 .append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_FOREIGN_TABLE_NAME).append(", ");

         sb.append("KCU.REFERENCED_COLUMN_NAME as ")

                 .append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_FOREIGN_COLUMN_NAME).append(", ");

         sb.append("RC.CONSTRAINT_NAME as ").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_CONSTRAINT_NAME)

                 .append(" ");

         sb.append("FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS RC,");

         sb.append("     INFORMATION_SCHEMA.KEY_COLUMN_USAGE KCU ");

         sb.append("WHERE RC.TABLE_NAME = KCU.TABLE_NAME ");

         sb.append("AND RC.CONSTRAINT_SCHEMA = KCU.CONSTRAINT_SCHEMA ");

         sb.append("AND RC.CONSTRAINT_NAME = KCU.CONSTRAINT_NAME ");

         sb.append("AND RC.TABLE_NAME = '").append(statement.getBaseTableName()).append("' ");

         try {

             sb.append("AND RC.CONSTRAINT_SCHEMA = '").append(database.convertRequestedSchemaToSchema(null)).append("'");

         } catch (DatabaseException e) {

             throw new UnexpectedLiquibaseException(e);

         }

         sb.append("LIMIT 1");

         return new Sql[] { new UnparsedSql(sb.toString()) };

     }

 }