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core module for querydsl
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/*
 * Copyright 2015, The Querydsl Team (http://www.querydsl.com/team)
 *
 * 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 com.querydsl.core;

import com.querydsl.core.annotations.Immutable;
import com.querydsl.core.types.Expression;
import com.querydsl.core.types.Predicate;
import com.querydsl.core.util.CollectionUtils;
import java.io.Serializable;
import java.util.Collections;
import java.util.Objects;
import java.util.Set;
import org.jetbrains.annotations.Nullable;

/**
 * {@code JoinExpression} is a join element in a {@link Query} instance.
 *
 * @author tiwe
 */
@Immutable
public final class JoinExpression implements Serializable {

  private static final long serialVersionUID = -1131755765747174886L;

  @Nullable private final Predicate condition;

  private final Set flags;

  private final Expression target;

  private final JoinType type;

  /**
   * Create a new JoinExpression instance
   *
   * @param type type of join
   * @param target target of join
   */
  public JoinExpression(JoinType type, Expression target) {
    this(type, target, null, Collections.emptySet());
  }

  /**
   * Create a new JoinExpression instance
   *
   * @param type type of join
   * @param target target of join
   * @param condition join condition or null, if none is used
   * @param flags join flags
   */
  public JoinExpression(
      JoinType type, Expression target, @Nullable Predicate condition, Set flags) {
    this.type = type;
    this.target = target;
    this.condition = condition;
    this.flags = CollectionUtils.unmodifiableSet(flags);
  }

  @Nullable
  public Predicate getCondition() {
    return condition;
  }

  public Expression getTarget() {
    return target;
  }

  public JoinType getType() {
    return type;
  }

  public boolean hasFlag(JoinFlag flag) {
    return flags.contains(flag);
  }

  public Set getFlags() {
    return flags;
  }

  @Override
  public String toString() {
    var builder = new StringBuilder();
    builder.append(type).append(" ").append(target);
    if (condition != null) {
      builder.append(" on ").append(condition);
    }
    return builder.toString();
  }

  @Override
  public int hashCode() {
    return Objects.hash(condition, target, type);
  }

  @Override
  public boolean equals(Object o) {
    if (o == this) {
      return true;
    } else if (o instanceof JoinExpression) {
      var j = (JoinExpression) o;
      return Objects.equals(condition, j.condition)
          && Objects.equals(target, j.target)
          && Objects.equals(type, j.type);
    } else {
      return false;
    }
  }
}