/*
 * 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.rl.ast;

import java.util.Optional;
import java.util.function.Consumer;

import nz.org.riskscape.dsl.Token;
import nz.org.riskscape.engine.util.Pair;

/**
 * Minimal amount that all bits of an abstract syntax tree must return
 * TODO could consider moving this (or at least parts of this) to the DSL package?
 */
public interface AST {

  /**
   * @return a string that can be reparsed and will equal this ast, although the original source may not be identical
   */
  String toSource();

  /**
   * Functional style instanceof method
   */
  default <T extends AST> Optional<T> isA(Class<T> type) {
    if (type.isInstance(this)) {
      return Optional.of(type.cast(this));
    } else {
      return Optional.empty();
    }
  }

  /**
   * @return a pair of tokens that represent the start and end of this expression, to be used when giving users
   * information about where errors have occurred.  If the expression has been rebuilt then the boundary may
   * be empty or it may be from the original AST. Intended for use in problems to trace errors back to
   * their source.
   */
  Optional<Pair<Token, Token>> getBoundary();

  /**
   * Functional if/else helper that emulates case-classes to run different handlers depending on whether this part of
   * the AST belongs to a pipeline (PipelineAST) or an expression (Expression).
   */
  default void switchType(Consumer<Expression> ifExpression, Consumer<PipelineAST> ifPipeline) {
    if (this instanceof Expression expr) {
      ifExpression.accept(expr);
    } else if (this instanceof PipelineAST pipeline) {
      ifPipeline.accept(pipeline);
    } else {
      throw new AssertionError("Unexpected type: " + this);
    }
  }
}
