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/*
Copyright 2007-2009 WebDriver committers
Copyright 2007-2009 Google Inc.

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 org.openqa.selenium.internal.seleniumemulation;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.base.Charsets;
import com.google.common.collect.Maps;
import com.google.common.io.Resources;

import com.thoughtworks.selenium.SeleniumException;

import org.openqa.selenium.By;
import org.openqa.selenium.JavascriptExecutor;
import org.openqa.selenium.NoSuchElementException;
import org.openqa.selenium.WebDriver;
import org.openqa.selenium.WebDriverException;
import org.openqa.selenium.WebElement;

import java.io.IOException;
import java.net.URL;
import java.util.Map;
import java.util.logging.Logger;

public class ElementFinder {
  private final static Logger log = Logger.getLogger(ElementFinder.class.getName());
  private final String findElement;
  private final String sizzle;
  private final Map additionalLocators = Maps.newHashMap();

  @VisibleForTesting
  protected ElementFinder() {
    findElement = null;
    sizzle = null;
  }

  public ElementFinder(JavascriptLibrary library) {
    String rawScript = library.getSeleniumScript("findElement.js");
    findElement = "return (" + rawScript + ")(arguments[0]);";

    String linkTextLocator =
        "return (" + library.getSeleniumScript("linkLocator.js") +
            ").call(null, arguments[0], document)";
    add("link", linkTextLocator);

    try {
      URL url =
          Resources.getResource(getClass().getPackage().getName().replace(".", "/") + "/sizzle.js");
      sizzle = Resources.toString(url, Charsets.UTF_8) +
          "var results = []; " +
          "try { Sizzle(arguments[0], document, results);} " +
          "catch (ignored) {} " +
          "return results.length ? results[0] : null;";
      add("sizzle", sizzle);
    } catch (IOException e) {
      throw new SeleniumException("Cannot read sizzle");
    }
  }

  public WebElement findElement(WebDriver driver, String locator) {
    WebElement toReturn = null;

    String strategy = searchAdditionalStrategies(locator);
    if (strategy != null) {
      String actualLocator = locator.substring(locator.indexOf('=') + 1);
      // TODO(simon): Recurse into child documents

      try {
        toReturn =
            (WebElement) ((JavascriptExecutor) driver).executeScript(strategy, actualLocator);

        if (toReturn == null) {
          throw new SeleniumException("Element " + locator + " not found");
        }

        return toReturn;
      } catch (WebDriverException e) {
        throw new SeleniumException("Element " + locator + " not found");
      }
    }

    try {
      toReturn = findElementDirectlyIfNecessary(driver, locator);
      if (toReturn != null) {
        return toReturn;
      }
      return (WebElement) ((JavascriptExecutor) driver).executeScript(findElement, locator);
    } catch (WebDriverException e) {
      throw new SeleniumException("Element " + locator + " not found", e);
    }
  }

  public void add(String strategyName, String implementation) {
    additionalLocators.put(strategyName, implementation);
  }

  private String searchAdditionalStrategies(String locator) {
    int index = locator.indexOf('=');
    if (index == -1) {
      return null;
    }


    String key = locator.substring(0, index);
    return additionalLocators.get(key);
  }

  private WebElement findElementDirectlyIfNecessary(WebDriver driver, String locator) {
    if (locator.startsWith("xpath=")) {
      return xpathWizardry(driver, locator.substring("xpath=".length()));
    }
    if (locator.startsWith("//")) {
      return xpathWizardry(driver, locator);
    }

    if (locator.startsWith("css=")) {
      String selector = locator.substring("css=".length());
      try {
        return driver.findElement(By.cssSelector(selector));
      } catch (WebDriverException e) {
        return fallbackToSizzle(driver, selector);
      }
    }

    return null;
  }

  private WebElement xpathWizardry(WebDriver driver, String xpath) {
    try {
      return driver.findElement(By.xpath(xpath));
    } catch (WebDriverException ignored) {
      // Because we have inconsistent return values
    }

    if (xpath.endsWith("/")) {
      return driver.findElement(By.xpath(xpath.substring(0, xpath.length() - 1)));
    }

    throw new NoSuchElementException("Cannot find an element with the xpath: " + xpath);
  }

  private WebElement fallbackToSizzle(WebDriver driver, String locator) {
    WebElement toReturn = (WebElement) ((JavascriptExecutor) driver).executeScript(sizzle, locator);
    if (toReturn != null) {
      log.warning("You are using a Sizzle locator as a CSS Selector. " +
          "Please use the Sizzle library directly via the JavascriptExecutor or a plain CSS " +
          "selector. Your locator was: " + locator);
      return toReturn;
    }
    throw new NoSuchElementException("Cannot locate element even after falling back to Sizzle: " +
        locator);
  }
}