package liquibase.sqlgenerator.core;

 import liquibase.database.Database;

 import liquibase.database.core.PostgresDatabase;

 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 FindForeignKeyConstraintsGeneratorPostgres extends

         AbstractSqlGenerator<FindForeignKeyConstraintsStatement> {

     @Override

     public int getPriority() {

         return PRIORITY_DATABASE;

     }

     @Override

     public boolean supports(FindForeignKeyConstraintsStatement statement, Database database) {

         return database instanceof PostgresDatabase;

     }

     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("FK.TABLE_NAME as \"").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_BASE_TABLE_NAME)

                 .append("\", ");

         sb.append("CU.COLUMN_NAME as \"")

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

         sb.append("PK.TABLE_NAME as \"").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_FOREIGN_TABLE_NAME)

                 .append("\", ");

         sb.append("PT.COLUMN_NAME as \"").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_FOREIGN_COLUMN_NAME)

                 .append("\", ");

         sb.append("C.CONSTRAINT_NAME as \"").append(FindForeignKeyConstraintsStatement.RESULT_COLUMN_CONSTRAINT_NAME)

                 .append("\" ");

         sb.append("FROM       INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS C ");

         sb.append("INNER JOIN  INFORMATION_SCHEMA.TABLE_CONSTRAINTS FK ON C.CONSTRAINT_NAME = FK.CONSTRAINT_NAME ");

         sb.append("INNER JOIN      INFORMATION_SCHEMA.TABLE_CONSTRAINTS PK ON C.UNIQUE_CONSTRAINT_NAME = PK.CONSTRAINT_NAME ");

         sb.append("INNER JOIN      INFORMATION_SCHEMA.KEY_COLUMN_USAGE CU ON C.CONSTRAINT_NAME = CU.CONSTRAINT_NAME ");

         sb.append("INNER JOIN  ( ");

         sb.append("  SELECT      i1.TABLE_NAME, i2.COLUMN_NAME ");

         sb.append("  FROM        INFORMATION_SCHEMA.TABLE_CONSTRAINTS i1 ");

         sb.append("  INNER JOIN      INFORMATION_SCHEMA.KEY_COLUMN_USAGE i2 ON i1.CONSTRAINT_NAME = i2.CONSTRAINT_NAME ");

         sb.append("  WHERE       i1.CONSTRAINT_TYPE = 'PRIMARY KEY' ");

         sb.append(") PT ON PT.TABLE_NAME = PK.TABLE_NAME ");

         sb.append("WHERE      FK.TABLE_NAME='").append(statement.getBaseTableName()).append("'");

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

     }

 }