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core module for querydsl
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/*
 * Copyright 2011, Mysema Ltd
 * 
 * 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.mysema.query;

import java.io.Serializable;
import java.util.Set;

import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

import com.google.common.base.Objects;
import com.google.common.collect.ImmutableSet;
import com.mysema.query.types.Expression;
import com.mysema.query.types.Predicate;

/**
 * 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 ImmutableSet flags;

    private final Expression target;

    private final JoinType type;

    /**
     * Create a new JoinExpression instance
     * 
     * @param type
     * @param target
     */
    public JoinExpression(JoinType type, Expression target) {
        this(type, target, null, ImmutableSet.of());
    }
            
    
    /**
     * Create a new JoinExpression instance
     * 
     * @param type
     * @param target
     * @param condition
     * @param flags
     */
    public JoinExpression(JoinType type, Expression target, @Nullable Predicate condition, 
            Set flags) {
        this.type = type;
        this.target = target;
        this.condition = condition;
        this.flags = ImmutableSet.copyOf(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;
    }

    public String toString() {
        StringBuilder 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.hashCode(condition, target, type);
    }

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

}