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/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package io.trino.sql.planner;

import com.google.common.collect.ImmutableMap;
import io.trino.Session;
import io.trino.operator.scalar.TryFunction;
import io.trino.spi.connector.ColumnHandle;
import io.trino.spi.predicate.NullableValue;
import io.trino.sql.PlannerContext;
import io.trino.sql.ir.Booleans;
import io.trino.sql.ir.Constant;
import io.trino.sql.ir.Expression;
import io.trino.sql.ir.optimizer.IrExpressionOptimizer;

import java.util.Map;
import java.util.Set;
import java.util.stream.Collectors;

import static com.google.common.collect.ImmutableSet.toImmutableSet;
import static com.google.common.collect.Sets.intersection;
import static io.trino.sql.ir.optimizer.IrExpressionOptimizer.newPartialEvaluator;
import static java.util.Objects.requireNonNull;

public class LayoutConstraintEvaluator
{
    private final Session session;
    private final Map assignments;
    private final IrExpressionOptimizer evaluator;
    private final Expression expression;
    private final Set arguments;

    public LayoutConstraintEvaluator(PlannerContext plannerContext, Session session, Map assignments, Expression expression)
    {
        this.session = requireNonNull(session, "session is null");
        this.assignments = ImmutableMap.copyOf(requireNonNull(assignments, "assignments is null"));
        evaluator = newPartialEvaluator(plannerContext);
        this.expression = requireNonNull(expression, "expression is null");
        arguments = SymbolsExtractor.extractUnique(expression).stream()
                .map(assignments::get)
                .collect(toImmutableSet());
    }

    public Set getArguments()
    {
        return arguments;
    }

    public boolean isCandidate(Map bindings)
    {
        if (intersection(bindings.keySet(), arguments).isEmpty()) {
            return true;
        }

        Map inputs = assignments.entrySet().stream()
                .filter(entry -> bindings.containsKey(entry.getValue()))
                .collect(Collectors.toMap(
                        Map.Entry::getKey,
                        entry -> {
                            NullableValue value = bindings.get(entry.getValue());
                            return new Constant(entry.getKey().type(), value.getValue());
                        }));

        // Skip pruning if evaluation fails in a recoverable way. Failing here can cause
        // spurious query failures for partitions that would otherwise be filtered out.
        Expression optimized = TryFunction.evaluate(() -> evaluator.process(expression, session, inputs).orElse(expression), Booleans.TRUE);

        // If any conjuncts evaluate to FALSE or null, then the whole predicate will never be true and so the partition should be pruned
        return !(optimized instanceof Constant constant) || Boolean.TRUE.equals(constant.value());
    }
}