# SchemaValidator.java

    /*
    ** Module   : SchemaValidator.java
    ** Abstract : Validates dynamically added tables and checks if they can be represented as an ORM.
    **
    ** Copyright (c) 2022-2024, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------------Description---------------------------------------
    ** 001 BS  20221230 Created initial version.
    ** 002 BS  20230331 Added validations for sequences.
    ** 003 OM  20240412 Added sorting direction for index components.
    ** 004 OM  20240516 Throw StopConditionException() in the mutable database failed validation.
    */

    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** This program 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.  See the
    ** GNU Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
    **     You must preserve all legal notices or author attributions in the covered
    **     work or Appropriate Legal Notices displayed by works containing the covered
    **     work.  You may not remove from the covered work any author or developer
    **     credit already included within the covered work.
    **
    **   1. No License To Use Trademarks.
    **
    **     This license does not grant any license or rights to use the trademarks
    **     Golden Code, FWD, any Golden Code or FWD logo, or any other trademarks
    **     of Golden Code Development Corporation. You are not authorized to use the
    **     name Golden Code, FWD, or the names of any author or contributor, for
    **     publicity purposes without written authorization.
    **
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    **
    **     You may not represent yourself as Golden Code Development Corporation or FWD.
    **
    **     You may not represent yourself for publicity purposes as associated with
    **     Golden Code Development Corporation, FWD, or any author or contributor to
    **     the covered work, without written authorization.
    **
    **   3. No Misrepresentation of Source or Origin.
    **
    **     You may not represent the covered work as solely your work.  All modified
    **     versions of the covered work must be marked in a reasonable way to make it
    **     clear that the modified work is not originating from Golden Code Development
    **     Corporation or FWD.  All modified versions must contain the notices of
    **     attribution required in this license.
    */

    package com.goldencode.p2j.persist.orm.schema;

    import com.goldencode.p2j.persist.*;
    import com.goldencode.p2j.persist.orm.*;
    import com.goldencode.p2j.persist.orm.schema.element.*;
    import com.goldencode.p2j.util.*;
    import java.util.*;
    import java.util.function.*;

    /**
     * Validates dynamically added tables and checks if they can be represented as an ORM.
     */
    public class SchemaValidator
    {
       /**
        * Validation rules. Key is an error message, value is a runnable function that returns a validation result
        * as a boolean value.
        *
        * Validation function convention:
        *   <code>FALSE</code> means no violation
        *   <code>TRUE</code> means violation is detected, an error will be reported
        */
       private static final Map<String, Function<Table, Boolean>> RULES = new HashMap<>();

       /** Record ID (recid) column name. */
       public static final String RECID = Session.PK;

       static
       {
          RULES.put("Table {table} needs to have at least one attribute",
                    table -> table.getAttributes().isEmpty());
          RULES.put("Surrogate primary key must be present. Table {table} needs to have a " + RECID + " column",
                    table -> table.getAttributes().stream()
                                  .noneMatch(attribute -> attribute.getName().equalsIgnoreCase(RECID)));
          RULES.put("Table {table} needs to have more columns than just " + RECID,
                    table -> table.getAttributes().stream()
                                  .allMatch(attribute -> attribute.getName().equalsIgnoreCase(RECID)));
          RULES.put("Table {table} has column " + RECID + " indexed incorrectly. " +
                    "Column " + RECID + " can only appear at the end of the index.",
             table -> table.getIndexes().stream().anyMatch(index -> {
                List<Tuple<String, Boolean>> columns = index.getColumns();
                if (!columns.isEmpty())
                {
                   boolean recidUsed = columns.stream().anyMatch(s -> s.getKey().equalsIgnoreCase(RECID));
                   String lastColumnName = columns.get(columns.size() - 1).getKey();

                   // RECID is indexed, but not at the end
                   return recidUsed && !lastColumnName.equalsIgnoreCase(RECID);
                }
                // This should not happen (databases should not create indexes with no columns), but just in case.
                return false;
             })
          );
       }

       /**
        * Apply validation rules on given table.
        *
        * @param   table
        *          Table to validate
        *
        * @throws  ErrorConditionException
        *          Exception is thrown in case of a failed validation
        */
       public static void validate(Table table)
       throws ErrorConditionException
       {
          for (Map.Entry<String, Function<Table, Boolean>> entry : RULES.entrySet())
          {
             if (entry.getValue().apply(table))
             {
                throw new StopConditionException(entry.getKey().replace("{table}", table.getName()));
             }
          }
       }

       /**
        * Apply validation rules on sequences. Currently just check that p2j_id_generator_sequence exists.
        *
        * @param   sequences
        *          Sequence list to validate
        *
        * @throws  ErrorConditionException
        *          Exception is thrown in case of a failed validation
        */
       public static void validate(Collection<Sequence> sequences)
       throws ErrorConditionException
       {
          if (sequences.stream()
                       .noneMatch(sequence -> sequence.getName().equalsIgnoreCase(Persistence.ID_GEN_SEQUENCE)))
          {
             throw new StopConditionException(
                   "Sequence " + Persistence.ID_GEN_SEQUENCE + " is not defined in database.");
          }
       }
    }