ebean/src/main/java/com/avaje/ebean/OrderBy.java

package com.avaje.ebean;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Represents an Order By for a Query.
 * <p>
 * Is a ordered list of OrderBy.Property objects each specifying a property and
 * whether it is ascending or descending order.
 * </p>
 * <p>
 * Typically you will not construct an OrderBy yourself but use one that exists
 * on the Query object.
 * </p>
 */
public final class OrderBy<T> implements Serializable {

  private static final long serialVersionUID = 9157089257745730539L;

  private transient Query<T> query;

  private final List<Property> list;

  /**
   * Create an empty OrderBy with no associated query.
   */
  public OrderBy() {
    this.list = new ArrayList<Property>(2);
  }
  
  private OrderBy(List<Property> list) {
    this.list = list;
  }

  /**
   * Create an orderBy parsing the order by clause.
   * <p>
   * The order by clause follows SQL order by clause with comma's between each
   * property and optionally "asc" or "desc" to represent ascending or
   * descending order respectively.
   * </p>
   */
  public OrderBy(String orderByClause) {
    this(null, orderByClause);
  }

  /**
   * Construct with a given query and order by clause.
   */
  public OrderBy(Query<T> query, String orderByClause) {
    this.query = query;
    this.list = new ArrayList<Property>(2);
    parse(orderByClause);
  }

  /**
   * Reverse the ascending/descending order on all the properties.
   */
  public void reverse() {
    for (int i = 0; i < list.size(); i++) {
      list.get(i).reverse();
    }
  }

  /**
   * Add a property with ascending order to this OrderBy.
   */
  public Query<T> asc(String propertyName) {

    list.add(new Property(propertyName, true));
    return query;
  }

  /**
   * Add a property with descending order to this OrderBy.
   */
  public Query<T> desc(String propertyName) {

    list.add(new Property(propertyName, false));
    return query;
  }

  /**
   * Return a copy of this OrderBy with the path trimmed.
   */
  public OrderBy<T> copyWithTrim(String path) {
    List<Property> newList = new ArrayList<Property>(list.size());
    for (int i = 0; i < list.size(); i++) {
      newList.add(list.get(i).copyWithTrim(path));
    }
    return new OrderBy<T>(newList);
  }
  
  /**
   * Return the properties for this OrderBy.
   */
  public List<Property> getProperties() {
    // not returning an Immutable list at this point
    return list;
  }

  /**
   * Return true if this OrderBy does not have any properties.
   */
  public boolean isEmpty() {
    return list.isEmpty();
  }

  /**
   * Return the associated query if there is one.
   */
  public Query<T> getQuery() {
    return query;
  }

  /**
   * Associate this OrderBy with a query.
   */
  public void setQuery(Query<T> query) {
    this.query = query;
  }

  /**
   * Return a copy of the OrderBy.
   */
  public OrderBy<T> copy() {

    OrderBy<T> copy = new OrderBy<T>();
    for (int i = 0; i < list.size(); i++) {
      copy.add(list.get(i).copy());
    }
    return copy;
  }

  /**
   * Add a property to the order by.
   */
  public void add(Property p) {
    list.add(p);
  }

  public String toString() {
    return list.toString();
  }

  /**
   * Returns the OrderBy in string format.
   */
  public String toStringFormat() {
    if (list.isEmpty()) {
      return null;
    }
    StringBuilder sb = new StringBuilder();
    for (int i = 0; i < list.size(); i++) {
      Property property = list.get(i);
      if (i > 0) {
        sb.append(", ");
      }
      sb.append(property.toStringFormat());
    }
    return sb.toString();
  }

  @Override
  public boolean equals(Object obj) {
    if (obj == this) {
      return true;
    }
    if (!(obj instanceof OrderBy<?>)) {
      return false;
    }
    
    OrderBy<?> e = (OrderBy<?>) obj;
    return e.list.equals(list);
  }

  /**
   * Return a hash value for this OrderBy. This can be to determine logical
   * equality for OrderBy clauses.
   */
  public int hashCode() {
    return list.hashCode();
  }

  /**
   * A property and its ascending descending order.
   */
  public static final class Property implements Serializable {

    private static final long serialVersionUID = 1546009780322478077L;

    private String property;

    private boolean ascending;

    public Property(String property, boolean ascending) {
      this.property = property;
      this.ascending = ascending;
    }

    /**
     * Return a copy of this Property with the path trimmed.
     */
    public Property copyWithTrim(String path) {
      return new Property(property.substring(path.length() + 1), ascending);
    }

    public int hashCode() {
      int hc = property.hashCode();
      hc = hc * 31 + (ascending ? 0 : 1);
      return hc;
    }
    
    public boolean equals(Object obj) {
      if (obj == this) {
        return true;
      }
      if (!(obj instanceof Property)) {
        return false;
      }
      
      Property e = (Property) obj;
      return e.ascending == ascending 
          && e.property.equals(property);
    }

    public String toString() {
      return toStringFormat();
    }

    public String toStringFormat() {
      if (ascending) {
        return property;
      } else {
        return property + " desc";
      }
    }

    /**
     * Reverse the ascending/descending order for this property.
     */
    public void reverse() {
      this.ascending = !ascending;
    }

    /**
     * Trim off the pathPrefix.
     */
    public void trim(String pathPrefix) {
      property = property.substring(pathPrefix.length() + 1);
    }

    /**
     * Return a copy of this property.
     */
    public Property copy() {
      return new Property(property, ascending);
    }

    /**
     * Return the property name.
     */
    public String getProperty() {
      return property;
    }

    /**
     * Set the property name.
     */
    public void setProperty(String property) {
      this.property = property;
    }

    /**
     * Return true if the order is ascending.
     */
    public boolean isAscending() {
      return ascending;
    }

    /**
     * Set to true if the order is ascending.
     */
    public void setAscending(boolean ascending) {
      this.ascending = ascending;
    }

  }

  private void parse(String orderByClause) {

    if (orderByClause == null) {
      return;
    }

    String[] chunks = orderByClause.split(",");
    for (int i = 0; i < chunks.length; i++) {

      String[] pairs = chunks[i].split(" ");
      Property p = parseProperty(pairs);
      if (p != null) {
        list.add(p);
      }
    }
  }

  private Property parseProperty(String[] pairs) {
    if (pairs.length == 0) {
      return null;
    }

    ArrayList<String> wordList = new ArrayList<String>(pairs.length);
    for (int i = 0; i < pairs.length; i++) {
      if (!isEmptyString(pairs[i])) {
        wordList.add(pairs[i]);
      }
    }
    if (wordList.isEmpty()) {
      return null;
    }
    if (wordList.size() == 1) {
      return new Property(wordList.get(0), true);
    }
    if (wordList.size() == 2) {
      boolean asc = isAscending(wordList.get(1));
      return new Property(wordList.get(0), asc);
    }
    String m = "Expecting a max of 2 words in [" + Arrays.toString(pairs)
        + "] but got " + wordList.size();
    throw new RuntimeException(m);
  }

  private boolean isAscending(String s) {
    s = s.toLowerCase();
    if (s.startsWith("asc")) {
      return true;
    }
    if (s.startsWith("desc")) {
      return false;
    }
    String m = "Expecting [" + s + "] to be asc or desc?";
    throw new RuntimeException(m);
  }

  private boolean isEmptyString(String s) {
    return s == null || s.length() == 0;
  }
}