package liquibase.precondition.core;

 import liquibase.changelog.ChangeSet;

 import liquibase.changelog.DatabaseChangeLog;

 import liquibase.database.Database;

 import liquibase.database.DatabaseConnection;

 import liquibase.exception.DatabaseException;

 import liquibase.exception.PreconditionErrorException;

 import liquibase.exception.PreconditionFailedException;

 import liquibase.exception.ValidationErrors;

 import liquibase.exception.Warnings;

 import liquibase.executor.ExecutorService;

 import liquibase.precondition.Precondition;

 import liquibase.statement.core.RawSqlStatement;

 public class SqlPrecondition implements Precondition {

     private String expectedResult;

     private String sql;

     public String getExpectedResult() {

         return expectedResult;

     }

     public void setExpectedResult(String expectedResult) {

         this.expectedResult = expectedResult;

     }

     public String getSql() {

         return sql;

     }

     public void setSql(String sql) {

         this.sql = sql;

     }

     @Override

     public Warnings warn(Database database) {

         return new Warnings();

     }

     @Override

     public ValidationErrors validate(Database database) {

         return new ValidationErrors();

     }

     @Override

     public void check(Database database, DatabaseChangeLog changeLog, ChangeSet changeSet)

             throws PreconditionFailedException, PreconditionErrorException {

         DatabaseConnection connection = database.getConnection();

         try {

             String result = (String) ExecutorService.getInstance().getExecutor(database)

                     .queryForObject(new RawSqlStatement(getSql().replaceFirst(";$", "")), String.class);

             if (result == null) {

                 throw new PreconditionFailedException("No rows returned from SQL Precondition", changeLog, this);

             }

             if (!expectedResult.equals(result)) {

                 throw new PreconditionFailedException("SQL Precondition failed.  Expected '" + expectedResult

                         + "' got '" + result + "'", changeLog, this);

             }

         } catch (DatabaseException e) {

             throw new PreconditionErrorException(e, changeLog, this);

         }

     }

     @Override

     public String getName() {

         return "sqlCheck";

     }

 }