ResultsPage Class

package PageObjects;
import org.openqa.selenium.By;
import org.openqa.selenium.ElementNotVisibleException;
import org.openqa.selenium.InvalidArgumentException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebElement;
import org.openqa.selenium.support.ui.WebDriverWait;
import framework.LogWriter;
public class ResultsPage 
{
	
  private WebDriver driver;
  private WebDriverWait wait;
	
  private final LogWriter traceLogWriter;
	
  private static final By PAGINATION_TEXT_XPATH = 
        By.xpath("//span[@data-key = 'pagination-text']");
	
  private static final By NEXT_PAGE_XPATH = By.xpath("//a[@data-key = 'next-btn']");
	
  private static final String PAGE_XPATH = "//a[@data-page = '%d']";
	
  public ResultsPage(WebDriver driver)
  {
    this.driver = driver;
    this.wait = new WebDriverWait(driver, 30);
		
    this.traceLogWriter = new LogWriter("./target/logs", 
                                        "trace.log");
  }
	
  public boolean isDisplayed()
  {
    boolean result = wait.until(d -> d.getCurrentUrl()
                                .contains("bibliocommons.com"));
    traceLogWriter.writeToLog("ResultsPage - isDisplayed()");
    return result;		 
  }
	
  public int totalCount()
  {
    wait.until(
     d -> d.findElement(PAGINATION_TEXT_XPATH).isDisplayed());	
	
    WebElement countElement = driver.findElement(PAGINATION_TEXT_XPATH);	
    String countText = countElement.getText();
		
    int i = countText.indexOf("of") + 3;
    int j = countText.indexOf("results") - 1;
    countText = countText.substring(i,  j);
		
    int count = Integer.parseInt(countText);
		
    traceLogWriter.writeToLog("ResultsPage - get TotalCount()");
		
    return count;
  }
	
  public String resultsPerPage()
  {
    wait.until(
     d -> d.findElement(PAGINATION_TEXT_XPATH).isDisplayed());		
		
    WebElement countElement = driver.findElement(PAGINATION_TEXT_XPATH);
    String countText = countElement.getText();
		
    int i = countText.indexOf("of") - 1;
    countText = countText.substring(0, i);
		
    traceLogWriter.writeToLog("ResultsPage() - get ResultsPerPage()");
		
    return countText;
  }
	
  public ResultsPage goToPage(int pageNumber)
  {
     if (pageNumber <= 0)
       throw new InvalidArgumentException(
                    "pageNumber should be > 0");
		
     By pageLocator = By.xpath(
                          String.format(PAGE_XPATH, pageNumber));
		
     wait.until(d -> d.findElement(pageLocator).isDisplayed());		
	
     WebElement page = driver.findElement(pageLocator);
     page.click();
     traceLogWriter.writeToLog("ResultsPage - goToPage()");
			
     String expectedResults = resultsPerPage(pageNumber);	 
     waitUntilResultsPerPageIs(expectedResults);		
		
     return new ResultsPage(driver);
  }
	
	
  public ResultsPage goToNextPage()
  {	
     wait.until(
      d -> d.findElement(NEXT_PAGE_XPATH).isDisplayed());		
     WebElement page = driver.findElement(NEXT_PAGE_XPATH);
     page.click();
     traceLogWriter.writeToLog("ResultsPage - goToNextPage()");
		
     String expectedResults = resultsPerPage(pageNumber());	 
     waitUntilResultsPerPageIs(expectedResults);
						
     return new ResultsPage(driver);
   }
	
   private void waitUntilResultsPerPageIs(String resultsPerPage)
   {
     wait.until(d -> d.findElement(PAGINATION_TEXT_XPATH)
			.getText().contains(resultsPerPage));
   }
 
   private String resultsPerPage(int pageNumber)
   {
     int from = (pageNumber - 1) * 10 + 1;
     int to = pageNumber * 10;
		
     return String.format("%d to %d", from, to);
   }
	
   public int pageNumber()
   {
     String url = driver.getCurrentUrl();
		
     if (!url.contains("page"))
      return 1;
		
     int i = url.indexOf("page=") + 5;
     int j = url.indexOf("&query");
		
     String pageValue = url.substring(i,  j);
		
     return Integer.parseInt(pageValue);
   }
	
}