/*
 * 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
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 */
package nz.org.riskscape.engine.rl;

import static org.hamcrest.Matchers.*;
import static org.junit.Assert.*;

import java.util.List;

import org.hamcrest.Matcher;
import org.junit.Before;
import org.junit.Test;

import nz.org.riskscape.engine.Assert;
import nz.org.riskscape.engine.function.StringFunctions;
import nz.org.riskscape.engine.types.Struct;

public class DefaultExpressionRealizerConstantTest extends BaseExpressionRealizerTest {

  @Before
  public void setup() {
    project.getFunctionSet().insertFirst(new DefaultOperators());
    project.getFunctionSet().addAll(MathsFunctions.FUNCTIONS);
    project.getFunctionSet().addAll(StringFunctions.FUNCTIONS);
    project.getFunctionSet().addAll(LanguageFunctions.FUNCTIONS);
  }

  @Test
  public void literalNumberIsConstant() {
    realize("42");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), is(42L));
  }

  @Test
  public void literalListIsConstant() {
    realize("[1, 2, 3]");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), allOf(
        equalTo(List.of(1L, 2L, 3L)),
        sameInstance(realized.evaluateConstant())
    ));
  }

  @Test
  public void literalStructIsConstant() {
    realize("{a: 1, b: 'text'}");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), allOf(
        equalTo(tuple("{a: 1, b: 'text'}")),
        sameInstance(realized.evaluateConstant())
    ));
  }

  @Test
  public void literalBinaryOperationIsConstant() {
    realize("1 + 2");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), is(3L));
  }

  @Test
  public void bracketedLiteralIsConstant() {
    realize("(42)");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), is(42L));
  }

  @Test
  public void nestedLiteralStructIsConstant() {
    realize("{a: [1, 2], b: {x: 3}}");

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), sameInstance(realized.evaluateConstant()));
  }

  @Test
  public void propertyAccessIsNotConstant() {
    evaluate("foo", tuple("{foo: 1}"));
    assertThat(realized, notConstant());

    Assert.assertThrows(IllegalStateException.class, () -> realized.evaluateConstant());
  }

  @Test
  public void functionCallWithNoArgsIsNotConstantUnlessYouEvaluateItConstantly() {
    realize("maxint()");
    assertThat(realized, notConstant());

    Assert.assertThrows(IllegalStateException.class, () -> realized.evaluateConstant());

    // but if we realize it via the realizeConstant method, it is!  But this must be opted in to
    realized = realizer.realizeConstant(realized.getExpression()).get();

    assertThat(realized, isConstant());
  }

  @Test
  public void functionCallWithConstantOperandIsNotConstantUnlessYouEvaluateItConstantly() {
    evaluate("str({x: 5})", tuple("{x: 5}"));
    assertThat(realized, notConstant());

    Assert.assertThrows(IllegalStateException.class, () -> realized.evaluateConstant());

    // again, it's opt-in, try again with realizeConstant and it works
    realized = realizer.realizeConstant(realized.getExpression()).get();

    assertThat(realized, isConstant());
    assertThat(realized.evaluateConstant(), sameInstance(realized.evaluateConstant()));
  }

  @Test
  public void functionCallWithPropertyAccessCanNeverBeConstant() {
    evaluate("str(x)", tuple("{x: 5}"));
    assertThat(realized, notConstant());

    Assert.assertThrows(IllegalStateException.class, () -> realized.evaluateConstant());

    assertFalse(realizer.realizeConstant(expr).isPresent());
  }

  @Test
  public void functionCallThatThrowsCanBeConstant() throws Exception {
    realized = realizer.realizeConstant(parse("cast('foo', 'integer')")).get();

    assertThat(realized, isConstant());
    Assert.assertThrows(EvalException.class, () -> realized.evaluateConstant());
  }

  @Test
  public void lambdaIsNotConstant() {
    realize("x -> x + 1");
    assertThat(realized, notConstant());

    // NB: this one is weird - it will realize constantly, but it probably shouldn't...
  }

  @Test
  public void binaryOperationIsNotConstantIfSomeIsNotLiteral() {
    evaluate("x + 5", tuple("{x: 10}"));
    assertThat(realized, notConstant());

    // nope
    assertFalse(realizer.realizeConstant(expr).isPresent());
  }

  private void realize(String expression) {
    realize(Struct.EMPTY_STRUCT, parse(expression));
  }

  private Matcher<RealizedExpression> notConstant() {
    return hasProperty("constant", is(false));
  }

  private Matcher<RealizedExpression> isConstant() {
    return hasProperty("constant", is(true));
  }
}
