/*
 * 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.defaults.function;

import java.util.List;

import nz.org.riskscape.engine.Tuple;
import nz.org.riskscape.engine.coverage.TypedCoverage;
import nz.org.riskscape.engine.data.coverage.MappedCoverage;
import nz.org.riskscape.engine.function.ArgumentList;
import nz.org.riskscape.engine.function.BaseRealizableFunction;
import nz.org.riskscape.engine.function.RiskscapeFunction;
import nz.org.riskscape.engine.rl.RealizationContext;
import nz.org.riskscape.engine.rl.RealizedExpression;
import nz.org.riskscape.engine.rl.ScopedLambdaExpression;
import nz.org.riskscape.engine.types.CoverageType;
import nz.org.riskscape.engine.types.LambdaType;
import nz.org.riskscape.engine.types.Nullable;
import nz.org.riskscape.engine.types.ScopedLambdaType;
import nz.org.riskscape.engine.types.Struct;
import nz.org.riskscape.engine.types.Type;
import nz.org.riskscape.problem.ProblemException;
import nz.org.riskscape.problem.ResultOrProblems;
import nz.org.riskscape.rl.ast.ExpressionProblems;
import nz.org.riskscape.rl.ast.FunctionCall;
import nz.org.riskscape.rl.ast.Lambda;

/**
 * Function that applies a mapping expression to values sampled from the given
 * coverage. This lets you perform simple conversions, e.g. changing the units
 * from centimetres to metres.
 */
public class MapCoverage extends BaseRealizableFunction {

  public MapCoverage() {
    super(ArgumentList.create("coverage", CoverageType.WILD, "expression", new LambdaType("sampled")),
        CoverageType.WILD);
  }

  @Override
  public ResultOrProblems<RiskscapeFunction> realize(RealizationContext context, FunctionCall functionCall,
      List<Type> argumentTypes) {

    return ProblemException.catching(() -> {
      CoverageType coverageType = arguments.getRequiredAs(argumentTypes, 0, CoverageType.class).getOrThrow();
      ScopedLambdaType lambdaType = arguments.getRequiredAs(argumentTypes, 1, ScopedLambdaType.class).getOrThrow();

      Lambda lambda = functionCall.getArguments().get(1).getExpression().isA(Lambda.class).get();
      if (lambdaType.getArity() != 1) {
        throw new ProblemException(ExpressionProblems.get().lambdaArityError(lambda, lambdaType.getArity(), 1));
      }

      Struct lambdaScopeType = lambdaType.buildCallingScopeType(coverageType.getContainedType());
      RealizedExpression realizedLambda =
          context.getExpressionRealizer().realize(lambdaScopeType, lambda.getExpression()).getOrThrow();

      // preserve the nullability of the coverage itself (the realized expression
      // should always determine nullability correctly for the coverage's contained type)
      Type returnType = Nullable.rewrap(argumentTypes.get(0), t -> new CoverageType(realizedLambda.getResultType()));

      return RiskscapeFunction.create(this, argumentTypes, returnType, args -> {
        TypedCoverage coverage = (TypedCoverage) args.get(0);
        ScopedLambdaExpression givenLambda = (ScopedLambdaExpression) args.get(1);
        Tuple scope = givenLambda.buildCallingScope(lambdaScopeType);

        if (coverage == null) {
          return null;
        }

        return new MappedCoverage(coverage, realizedLambda, lambdaType.getArgs().get(0), scope);
      });
    });
  }

}
