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SQL support 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.sql;

import com.querydsl.core.types.ConstantImpl;
import com.querydsl.core.types.Expression;
import java.util.ArrayList;
import java.util.List;

/**
 * {@code WindowRows} provides the building of the rows/range part of the window function expression
 *
 * @param  expression type
 * @author tiwe
 */
public class WindowRows {

  private static final String AND = " and";

  private static final String BETWEEN = " between";

  private static final String CURRENT_ROW = " current row";

  private static final String FOLLOWING = " following";

  private static final String PRECEDING = " preceding";

  private static final String UNBOUNDED = " unbounded";

  /** Intermediate step */
  public class Between {

    public BetweenAnd unboundedPreceding() {
      str.append(UNBOUNDED);
      str.append(PRECEDING);
      return new BetweenAnd();
    }

    public BetweenAnd currentRow() {
      str.append(CURRENT_ROW);
      return new BetweenAnd();
    }

    public BetweenAnd preceding(Expression expr) {
      args.add(expr);
      str.append(PRECEDING);
      str.append(" {").append(offset++).append("}");
      return new BetweenAnd();
    }

    public BetweenAnd preceding(int i) {
      return preceding(ConstantImpl.create(i));
    }

    public BetweenAnd following(Expression expr) {
      args.add(expr);
      str.append(FOLLOWING);
      str.append(" {").append(offset++).append("}");
      return new BetweenAnd();
    }

    public BetweenAnd following(int i) {
      return following(ConstantImpl.create(i));
    }
  }

  /** Intermediate step */
  public class BetweenAnd {

    public BetweenAnd() {
      str.append(AND);
    }

    public WindowFunction unboundedFollowing() {
      str.append(UNBOUNDED);
      str.append(FOLLOWING);
      return rv.withRowsOrRange(str.toString(), args);
    }

    public WindowFunction currentRow() {
      str.append(CURRENT_ROW);
      return rv.withRowsOrRange(str.toString(), args);
    }

    public WindowFunction preceding(Expression expr) {
      args.add(expr);
      str.append(PRECEDING);
      str.append(" {").append(offset++).append("}");
      return rv.withRowsOrRange(str.toString(), args);
    }

    public WindowFunction preceding(int i) {
      return preceding(ConstantImpl.create(i));
    }

    public WindowFunction following(Expression expr) {
      args.add(expr);
      str.append(FOLLOWING);
      str.append(" {").append(offset++).append("}");
      return rv.withRowsOrRange(str.toString(), args);
    }

    public WindowFunction following(int i) {
      return following(ConstantImpl.create(i));
    }
  }

  private final WindowFunction rv;

  private final StringBuilder str = new StringBuilder();

  private final List> args = new ArrayList<>();

  private int offset;

  public WindowRows(WindowFunction windowFunction, String prefix, int offset) {
    this.rv = windowFunction;
    this.offset = offset;
    str.append(prefix);
  }

  public Between between() {
    str.append(BETWEEN);
    return new Between();
  }

  public WindowFunction unboundedPreceding() {
    str.append(UNBOUNDED);
    str.append(PRECEDING);
    return rv.withRowsOrRange(str.toString(), args);
  }

  public WindowFunction currentRow() {
    str.append(CURRENT_ROW);
    return rv.withRowsOrRange(str.toString(), args);
  }

  public WindowFunction preceding(Expression expr) {
    args.add(expr);
    str.append(PRECEDING);
    str.append(" {").append(offset++).append("}");
    return rv.withRowsOrRange(str.toString(), args);
  }

  public WindowFunction preceding(int i) {
    return preceding(ConstantImpl.create(i));
  }
}