/*
 * RiskScape™ Copyright New Zealand Institute for Earth Science Limited
 * (Earth Sciences New Zealand) is distributed for research purposes only
 * under the terms of AGPLv3.
 *
 * RiskScape™ Copyright 2026 New Zealand Institute for Earth Science
 * Limited (Earth Sciences New Zealand). All rights reserved. Source code
 * available under the AGPLv3.
 * 
 * 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 for RESEARCH PURPOSES ONLY, in the hope that it will
 * be useful for research and education initiatives.
 * 
 * If you are not a researcher, or you are a researcher who wishes to use this
 * program on terms other than AGPLv3 (including those who wish to restrict the
 * distribution of any source code created using this program), please contact:
 * https://riskscape.org.nz
 * 
 * This program is distributed 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 should have received a copy
 * of the GNU Affero General Public License along with this program.  If not, see
 * <http://www.gnu.org/licenses/>.
 * 
 * By way of summary only, under the AGPLv3:
 *     • Permissions of this strongest copyleft license are conditioned
 *       on making available complete source code of licensed works and
 *       modifications, which include larger works using a licensed work,
 *       under the same license.
 *     • Copyright and license notices must be preserved.
 *     • Contributors provide an express grant of patent rights.
 *     • When a modified version is used to provide a service over a
 *       network, the complete source code of the modified version must be made
 *       available.
 */
package nz.org.riskscape.engine;

import java.util.Iterator;

import lombok.RequiredArgsConstructor;
import nz.org.riskscape.engine.types.Nullable;
import nz.org.riskscape.engine.types.Struct;
import nz.org.riskscape.engine.types.Struct.StructMember;

// puts a new equality method around a struct to allow some special case behaviour around what constitutes
// an equal struct for the purposes of normalization.  That special case is that the types of members themselves
// must be the same objects, not just equal.  Without this, child structs can be substituted out, which can break
// realized expressions  (see Tuple#checkOwner) that construct structs/tuples.
@RequiredArgsConstructor
class RekeyedStruct {

  final Struct source;

  @Override
  public boolean equals(Object obj) {
    if (obj instanceof RekeyedStruct) {
      RekeyedStruct rhs = (RekeyedStruct) obj;
      Iterator<StructMember> lhsMembers = this.source.getMembers().iterator();
      Iterator<StructMember> rhsMembers = rhs.source.getMembers().iterator();

      while (lhsMembers.hasNext()) {
        if (!rhsMembers.hasNext()) {
          return false;
        }

        StructMember lhsMember = lhsMembers.next();
        StructMember rhsMember = rhsMembers.next();

        if (!lhsMember.getKey().equals(rhsMember.getKey())) {
          return false;
        }

        if (Nullable.is(lhsMember.getType()) !=  Nullable.is(rhsMember.getType())) {
          // only one side is nullable, cannot be the same.
          return false;
        }
        // We strip nullable and check that the contained type is the same instance, and don't worry about
        // the nullable being a different instance - it won't affect the results of this method in a deleterious way
        if (Nullable.strip(lhsMember.getType()) != Nullable.strip(rhsMember.getType())) {
          return false;
        }
      }

      // extras on the rhs - not so good, al
      return !rhsMembers.hasNext();
    } else {
      return false;
    }
  }

  @Override
  public int hashCode() {
    return source.hashCode();
  }
}
