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Client library for Java for accessing ads APIs including DFP. If you want to use this library, you must also include another Maven artifact to specify which framework you would like to use it with. For example, to use DFP with Axis, you should include the "dfp-axis" artifact.
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// Copyright 2012 Google Inc. All Rights Reserved.
//
// 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.google.api.ads.admanager.lib.utils;

import com.google.common.base.Preconditions;
import com.google.common.base.Strings;
import com.google.common.collect.Maps;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.util.Collections;
import java.util.Map;

/**
 * {@code QueryBuilder} allows for queries to be constructed in parts.
 *
 * @param  the type of the API Value
 */
public class QueryBuilder implements QueryBuilderInterface {

  protected static final String SELECT = "SELECT";
  protected static final String FROM = "FROM";
  protected static final String WHERE = "WHERE";
  protected static final String LIMIT = "LIMIT";
  protected static final String OFFSET = "OFFSET";
  protected static final String ORDER_BY = "ORDER BY";

  protected String select;
  protected String from;
  protected String where;
  protected Integer limit = null;
  protected Integer offset = null;
  protected String orderBy;

  protected Map valueMap;

  /**
   * Constructs a query builder.
   */
  public QueryBuilder() {
    valueMap = Maps.newHashMap();
  }

  /**
   * Removes the {@code keyword} from the {@code clause} if present. Will
   * remove {@code keyword + " "}.
   * @param clause the clause to remove from
   * @param keyword the keyword to remove
   * @return a new string with the keyword + " " removed
   */
  static String removeKeyword(String clause, String keyword) {
    keyword = keyword + " ";
    if (clause.regionMatches(true, 0, keyword, 0, keyword.length())) {
      return clause.substring(keyword.length());
    }
    return clause;
  }

  /**
   * Sets the statement SELECT clause in the form of "a,b" or "*". Only necessary for statements
   * being sent to the {@code PublisherQueryLanguageService}. The "SELECT " keyword will be ignored.
   *
   * @param columns the statement select clause without "SELECT"
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder select(String columns) {
    Preconditions.checkNotNull(columns, "SELECT clause cannot be null");
    columns = removeKeyword(columns, SELECT);
    this.select = columns;
    return this;
  }

  /**
   * Sets the statement FROM clause in the form of "table". Only necessary for statements being sent
   * to the {@code PublisherQueryLanguageService}. The "FROM " keyword will be ignored.
   *
   * @param table the statement from clause without "FROM"
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder from(String table) {
    Preconditions.checkNotNull(table, "FROM clause cannot be null");
    table = removeKeyword(table, FROM);
    this.from = table;
    return this;
  }

  /**
   * Sets the statement WHERE clause in the form of

   * 

   * "WHERE <condition> {[AND | OR] <condition> ...}" 

   * 

   * e.g. "a = b OR b = c". The "WHERE " keyword will be ignored.
   *
   * @param conditions the statement query without "WHERE"
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder where(String conditions) {
    Preconditions.checkNotNull(conditions, "WHERE clause cannot be null");
    conditions = removeKeyword(conditions, WHERE);
    this.where = conditions;
    return this;
  }

  /**
   * Sets the statement LIMIT clause in the form of

   * 

   * "LIMIT <count>" 

   * 

   * e.g. 1000.
   *
   * @param count the statement limit
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder limit(Integer count) {
    this.limit = count;
    return this;
  }

  /**
   * Sets the statement OFFSET clause in the form of

   * 

   * "OFFSET <count>" 

   * 

   * e.g. 200.
   *
   * @param count the statement offset
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder offset(Integer count) {
    this.offset = count;
    return this;
  }

  /**
   * Increases the offset by the {@code amount}.
   *
   * @param amount the amount to increase the offset
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder increaseOffsetBy(Integer amount) {
    if (offset == null) {
      offset = 0;
    }
    this.offset += amount;
    return this;
  }

  /**
   * Gets the current offset.
   * @return the current offset
   */
  @Override
  public Integer getOffset() {
    return this.offset;
  }

  /**
   * Removes the limit and offset from the query.
   *
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder removeLimitAndOffset() {
    offset = null;
    limit = null;
    return this;
  }

  /**
   * Sets the statement ORDER BY clause in the form of

   * 

   * "ORDER BY <property> [ASC | DESC]" 

   * 

   * e.g. "type ASC, lastModifiedDateTime DESC". The "ORDER BY " keyword will be ignored.
   *
   * @param orderBy the statement order by without "ORDER BY"
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder orderBy(String orderBy) {
    Preconditions.checkNotNull(orderBy, "ORDER BY clause cannot be null");
    orderBy = removeKeyword(orderBy, ORDER_BY);
    this.orderBy = orderBy;
    return this;
  }

  /**
   * Adds a value to the statement in the form of a {@code Value}.
   *
   * @param key the value key
   * @param value the value
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  @Override
  public QueryBuilder withBindVariableValue(String key, V value) {
    valueMap.put(key, value);
    return this;
  }

  /**
   * Adds all key value mappings.
   *
   * @param values the mappings of key to value of type 
   * @return a reference to this object
   */
  @CanIgnoreReturnValue
  public QueryBuilder withBindVariableValues(Map values) {
    valueMap.putAll(values);
    return this;
  }

  /**
   * Returns an unmodifiable form of the key to value map.
   */
  @Override
  public Map getBindVariableMap() {
    return Collections.unmodifiableMap(valueMap);
  }

  /**
   * Checks that the query is valid.
   */
  protected void validateQuery() {
    Preconditions.checkState(limit != null || (limit == null && offset == null),
        "OFFSET cannot be set if LIMIT is not set.");
  }

  /**
   * Builds the query from the clauses.
   * @return the c query
   */
  @Override
  public String buildQuery() {
    validateQuery();

    StringBuilder stringBuilder = new StringBuilder();
    if (!Strings.isNullOrEmpty(select)) {
      stringBuilder = stringBuilder.append(SELECT).append(" ").append(select).append(" ");
    }
    if (!Strings.isNullOrEmpty(from)) {
      stringBuilder = stringBuilder.append(FROM).append(" ").append(from).append(" ");
    }
    if (!Strings.isNullOrEmpty(where)) {
      stringBuilder = stringBuilder.append(WHERE).append(" ").append(where).append(" ");
    }
    if (!Strings.isNullOrEmpty(orderBy)) {
      stringBuilder = stringBuilder.append(ORDER_BY).append(" ").append(orderBy).append(" ");
    }
    if (limit != null) {
      stringBuilder = stringBuilder.append(LIMIT).append(" ").append(limit).append(" ");
    }
    if (offset != null) {
      stringBuilder = stringBuilder.append(OFFSET).append(" ").append(offset).append(" ");
    }
    return stringBuilder.toString().trim();
  }
}