/*
* 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.sql;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import javax.annotation.Nullable;
import com.google.common.collect.ImmutableList;
import com.querydsl.core.types.*;
import com.querydsl.core.types.dsl.ComparableExpressionBase;
import com.querydsl.core.types.dsl.Expressions;
import com.querydsl.core.types.dsl.SimpleExpression;
/**
* {@code WindowFirstLast} is a builder for window function expressions
*
* @author tiwe
*
* @param <T>
*/
public class WindowFirstLast<T> extends MutableExpressionBase<T> {
private static final long serialVersionUID = 4107262569593794721L;
private static final String ORDER_BY = "order by ";
private final List<OrderSpecifier<?>> orderBy = new ArrayList<OrderSpecifier<?>>();
@Nullable
private transient volatile SimpleExpression<T> value;
private final Expression<T> target;
private final boolean first;
public WindowFirstLast(WindowOver<T> target, boolean first) {
super(target.getType());
this.target = target;
this.first = first;
}
@Override
public <R,C> R accept(Visitor<R,C> v, C context) {
return getValue().accept(v, context);
}
public WindowFirstLast<T> orderBy(ComparableExpressionBase<?> orderBy) {
value = null;
this.orderBy.add(orderBy.asc());
return this;
}
public WindowFirstLast<T> orderBy(ComparableExpressionBase<?>... orderBy) {
value = null;
for (ComparableExpressionBase<?> e : orderBy) {
this.orderBy.add(e.asc());
}
return this;
}
public WindowFirstLast<T> orderBy(OrderSpecifier<?> orderBy) {
value = null;
this.orderBy.add(orderBy);
return this;
}
public WindowFirstLast<T> orderBy(OrderSpecifier<?>... orderBy) {
value = null;
Collections.addAll(this.orderBy, orderBy);
return this;
}
SimpleExpression<T> getValue() {
if (value == null) {
if (orderBy.isEmpty()) {
// TODO this check should be static
throw new IllegalStateException("No order by arguments given");
}
ImmutableList.Builder<Expression<?>> args = ImmutableList.builder();
StringBuilder builder = new StringBuilder();
builder.append("{0} keep (dense_rank ");
args.add(target);
builder.append(first ? "first " : "last ");
builder.append(ORDER_BY);
builder.append("{1}");
args.add(ExpressionUtils.orderBy(orderBy));
builder.append(")");
value = Expressions.template(target.getType(), builder.toString(), args.build());
}
return value;
}
public WindowFunction<T> over() {
return new WindowFunction<T>(getValue());
}
}