# AstExternalizble.java

    /*
    ** Module   : AstExternalizble.java
    ** Abstract : Allow serialization for an AST, to database.
    **
    ** Copyright (c) 2020-2023, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- ---------------------------------Description----------------------------------
    ** 001 CA  20200412 Created initial version, for incremental conversion support.
    ** 002 CA  20200416 Reduce the memory footprint for incremental conversion.
    ** 003 CA  20210423 Added 'getAstId'.
    ** 004 CA  20230127 Performance improvement for incremental conversion.
    */
    /*
    ** 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.
    **
    **   2. No Misrepresentation of Affiliation.
    **
    **     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.convert.db;

    import java.io.*;

    import com.goldencode.ast.*;
    import com.goldencode.p2j.pattern.*;

    /**
     * For AST values for a db-backed collection, this allows the serialization to the database.
     * <p>
     * Only the AST ID will be stored.
     */
    public class AstExternalizble
    implements CustomExternalizable
    {
       /**
        * The associated AST node. This can be <code>null</code> and resolved by {@link #getValue()},
        * if the AST is loaded from disk.
        */
       private Aast ast = null;

       /** The AST ID. */
       private Long astId = null;

       /**
        * Flag indicating if this serialized instance requires special processing.
        * <p>
        * WARNING: {@link AstExternalizble} is used only by 'tmpTabNodes', which sets the {@link #special} flag
        * only for ASTs with <code>authoritative</code> annotation.
        */
       private boolean special = false;

       /**
        * Default c'tor, for deserialization purposes.
        */
       public AstExternalizble()
       {
          // no-op
       }

       /**
        * Create a new instance and map it to the specified AST.
        * <p>
        * This c'tor is used via reflection.
        *
        * @param    value
        *           The AST instance.
        */
       public AstExternalizble(Object value)
       {
          this.astId = ((Aast) value).getId();

          AstManager mgr = AstManager.get();
          long treeId = mgr.getTreeId(astId);
          String treeName = mgr.getTreeName(treeId);

          if (treeName == null)
          {
             this.ast = (Aast) value;
          }
          else
          {
             File file = new File(treeName);
             if (!(file.exists() && file.isFile()))
             {
                this.ast = (Aast) value;
             }
          }

          this.special = Boolean.TRUE.equals(((Aast) value).getAnnotation("authoritative"));
       }

       /**
        * Get the {@link #astId}.
        *
        * @return   See above.
        */
       public Long getAstId()
       {
          return astId;
       }

       /**
        * Compact this instance.
        *
        * @param    fileId
        *           The AST file ID which has finished processing.
        */
       @Override
       public void compact(long fileId)
       {
          if (ast == null)
          {
             return;
          }

          AstManager mgr = AstManager.get();
          long treeId = mgr.getTreeId(astId);
          if (treeId == fileId)
          {
             this.ast = null;
          }
       }

       /**
        * Get the value to be stored in a collection, after it was deserialized from the database.
        *
        * @return   See above.
        */
       @Override
       public Object getValue()
       {
          if (ast == null)
          {
             // TODO: if AST doesn't exist, don't initialize... throw exception?

             AstSymbolResolver resolver = AstSymbolResolver.getResolver();
             ast = resolver.getAst(astId);

             if (ast == null)
             {
                AstManager mgr = AstManager.get();
                long treeId = mgr.getTreeId(astId);
                Aast tree = mgr.loadTree(mgr.getTreeName(treeId));
                // keep a copy of this tree registered
                resolver.registerTree(tree.duplicate());

                this.ast = resolver.getAst(astId);
             }
          }

          return ast;
       }

       /**
        * Write this instance to stream.
        *
        * @param  out
        *         The object output stream.
        */
       @Override
       public void writeExternal(ObjectOutput out) throws IOException
       {
          out.writeObject(astId);
          out.writeByte(special ? 1 : 0);
       }

       /**
        * Restore this instance by re-loading the AST with the given ID.
        *
        * @param    in
        *           The object input stream.
        */
       @Override
       public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
       {
          this.astId = (Long) in.readObject();
          this.special = in.readByte() == 1;
       }

       /**
        * Get the state of the {@link #special} flag.
        *
        * @return   See above.
        */
       public boolean isSpecial()
       {
          return special;
       }
    }