__init__.py

from copy import copy
from helium._impl.match_type import PREFIX_IGNORE_CASE
from helium._impl.selenium_wrappers import WebElementWrapper, \
	WebDriverWrapper, FrameIterator, FramesChangedWhileIterating
from helium._impl.util.dictionary import inverse
from helium._impl.util.system import is_windows, get_canonical_os_name
from helium._impl.util.xpath import lower, predicate, predicate_or
from inspect import getfullargspec, ismethod, isfunction
from selenium.common.exceptions import UnexpectedAlertPresentException, \
	ElementNotVisibleException, MoveTargetOutOfBoundsException, \
	WebDriverException, StaleElementReferenceException, \
	NoAlertPresentException, NoSuchWindowException
from selenium.webdriver.common.by import By
from selenium.webdriver.firefox.service import Service as ServiceFirefox
from selenium.webdriver.remote.webelement import WebElement
from selenium.webdriver.support.wait import WebDriverWait
from selenium.webdriver.support.ui import Select
from selenium.webdriver import Chrome, ChromeOptions, Firefox, FirefoxOptions
from time import sleep, time

import atexit
import re

def might_spawn_window(f):
	def f_decorated(self, *args, **kwargs):
		driver = self.require_driver()
		if driver.is_ie() and AlertImpl(driver).exists():
			# Accessing .window_handles in IE when an alert is present raises an
			# UnexpectedAlertPresentException. When DesiredCapability
			# 'unexpectedAlertBehaviour' is not 'ignore' (the default is
			# 'dismiss'), this leads to the alert being closed. Since we don't
			# want to unintentionally close alert dialogs, we therefore do not
			# access .window_handles in IE when an alert is present.
			return f(self, *args, **kwargs)
		window_handles_before = driver.window_handles[:]
		result = f(self, *args, **kwargs)
		# As above, don't access .window_handles in IE if an alert is present:
		if not (driver.is_ie() and AlertImpl(driver).exists()):
			if driver.is_firefox():
				# Unlike Chrome, Firefox does not wait for new windows to open.
				# Give it a little time to do so:
				sleep(.2)
			new_window_handles = [
				h for h in driver.window_handles
				if h not in window_handles_before
			]
			if new_window_handles:
				driver.switch_to.window(new_window_handles[0])
		return result
	return f_decorated

def handle_unexpected_alert(f):
	def f_decorated(*args, **kwargs):
		try:
			return f(*args, **kwargs)
		except UnexpectedAlertPresentException:
			raise UnexpectedAlertPresentException(
				"This command is not supported when an alert is present. To "
				"accept the alert (this usually corresponds to clicking 'OK') "
				"use `Alert().accept()`. To dismiss the alert (ie. 'cancel' "
				"it), use `Alert().dismiss()`. If the alert contains a text "
				"field, you can use write(...) to set its value. "
				"Eg.: `write('hi there!')`."
			)
	return f_decorated

class APIImpl:
	DRIVER_REQUIRED_MESSAGE = \
		"This operation requires a browser window. Please call one of " \
		"the following functions first:\n" \
		" * start_chrome()\n" \
		" * start_firefox()\n" \
		" * set_driver(...)"
	def __init__(self):
		self.driver = None
	def start_firefox_impl(
		self, url=None, headless=False, options=None, profile=None
	):
		firefox_driver = self._start_firefox_driver(headless, options, profile)
		return self._start(firefox_driver, url)
	def _start_firefox_driver(self, headless, options, profile):
		firefox_options = FirefoxOptions() if options is None else options
		if headless:
			firefox_options.add_argument('--headless')
		kwargs = {
			'options': firefox_options
		}
		if profile:
			# This is Deprecated in the driver so only do it (and trigger the
			# warnings) if the user requests it
			kwargs['firefox_profile'] = profile
		service_log_path = 'nul' if is_windows() else '/dev/null'
		service = ServiceFirefox(log_path=service_log_path)
		result = Firefox(service=service, **kwargs)
		return result
	def start_chrome_impl(
		self, url=None, headless=False, maximize=False, options=None
	):
		chrome_driver = self._start_chrome_driver(headless, maximize, options)
		return self._start(chrome_driver, url)
	def _start_chrome_driver(self, headless, maximize, options):
		chrome_options = self._get_chrome_options(headless, maximize, options)
		result = Chrome(options=chrome_options)
		atexit.register(self._kill_service, result.service)
		return result
	def _get_chrome_options(self, headless, maximize, options):
		result = ChromeOptions() if options is None else options
		# Prevent Chrome's debug logs from appearing in our console window:
		result.add_experimental_option('excludeSwitches', ['enable-logging'])
		if headless:
			result.add_argument('--headless')
		elif maximize:
			result.add_argument('--start-maximized')
		return result
	def _kill_service(self, service):
		old = service.send_remote_shutdown_command
		service.send_remote_shutdown_command = lambda: None
		try:
			service.stop()
		finally:
			service.send_remote_shutdown_command = old
	def _start(self, browser, url=None):
		self.set_driver_impl(browser)
		if url is not None:
			self.go_to_impl(url)
		return self.get_driver_impl()
	@might_spawn_window
	@handle_unexpected_alert
	def go_to_impl(self, url):
		if '://' not in url:
			url = 'http://' + url
		self.require_driver().get(url)
	def set_driver_impl(self, driver):
		self.driver = WebDriverWrapper(driver)
	def get_driver_impl(self):
		if self.driver is not None:
			return self.driver.unwrap()
	@might_spawn_window
	@handle_unexpected_alert
	def write_impl(self, text, into=None):
		if into is not None:
			from helium import GUIElement
			if isinstance(into, GUIElement):
				into = into._impl
		self._handle_alerts(
			self._write_no_alert, self._write_with_alert, text, into=into
		)
	def _write_no_alert(self, text, into=None):
		if into:
			if isinstance(into, str):
				into = TextFieldImpl(self.require_driver(), into)
			def _write(elt):
				if hasattr(elt, 'clear') and callable(elt.clear):
					elt.clear()
				elt.send_keys(text)
			self._manipulate(into, _write)
		else:
			self.require_driver().switch_to.active_element.send_keys(text)
	def _write_with_alert(self, text, into=None):
		if into is None:
			into = AlertImpl(self.require_driver())
		if not isinstance(into, AlertImpl):
			raise UnexpectedAlertPresentException(
				"into=%r is not allowed when an alert is present." % into
			)
		into._write(text)
	def _handle_alerts(self, no_alert, with_alert, *args, **kwargs):
		driver = self.require_driver()
		if not AlertImpl(driver).exists():
			return no_alert(*args, **kwargs)
		return with_alert(*args, **kwargs)
	@might_spawn_window
	@handle_unexpected_alert
	def press_impl(self, key):
		self.require_driver().switch_to.active_element.send_keys(key)
	def click_impl(self, element):
		self._perform_mouse_action(element, self._click)
	def doubleclick_impl(self, element):
		self._perform_mouse_action(element, self._doubleclick)
	def hover_impl(self, element):
		self._perform_mouse_action(element, self._hover)
	def rightclick_impl(self, element):
		self._perform_mouse_action(element, self._rightclick)
	def press_mouse_on_impl(self, element):
		self._perform_mouse_action(element, self._press_mouse_on)
	def release_mouse_over_impl(self, element):
		self._perform_mouse_action(element, self._release_mouse_over)
	def _click(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).click().perform()
	def _doubleclick(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).double_click().perform()
	def _hover(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).perform()
	def _rightclick(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).context_click().perform()
	def _press_mouse_on(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).click_and_hold().perform()
	def _release_mouse_over(self, selenium_elt, offset):
		self._move_to_element(selenium_elt, offset).release().perform()
	def _move_to_element(self, element, offset):
		result = self.require_driver().action()
		if offset is not None:
			result.move_to_element_with_offset(
				element,
				offset[0] - element.size['width'] / 2,
				offset[1] - element.size['height'] / 2
			)
		else:
			result.move_to_element(element)
		return result
	def drag_impl(self, element, to):
		with DragHelper(self) as drag_helper:
			self._perform_mouse_action(element, drag_helper.start_dragging)
			self._perform_mouse_action(to, drag_helper.drop_on_target)
	@might_spawn_window
	@handle_unexpected_alert
	def _perform_mouse_action(self, element, action):
		element, offset = self._unwrap_clickable_element(element)
		self._manipulate(element, lambda wew: action(wew.unwrap(), offset))
	def _unwrap_clickable_element(self, elt):
		from helium import HTMLElement, Point
		offset = None
		if isinstance(elt, str):
			elt = ClickableText(self.require_driver(), elt)
		elif isinstance(elt, HTMLElement):
			elt = elt._impl
		elif isinstance(elt, Point):
			elt, offset = self._point_to_element_and_offset(elt)
		return elt, offset
	def _point_to_element_and_offset(self, point):
		driver = self.require_driver()
		element = WebElementWrapper(driver.execute_script(
			'return document.elementFromPoint(%r, %r);' % (point.x, point.y)
		))
		offset = point - (element.location.left, element.location.top)
		if offset == (0, 0) and driver.is_firefox():
			# In some CSS settings (eg. test_point.html), the (0, 0) point of
			# buttons in Firefox is not clickable! The reason for this is that
			# Firefox styles buttons to not be perfect squares, but have an
			# indent in the corners. This workaround makes `click(btn.top_left)`
			# work even when this happens:
			offset = (1, 1)
		return element, offset
	@handle_unexpected_alert
	def find_all_impl(self, predicate):
		return [
			predicate.with_impl(bound_gui_elt_impl)
			for bound_gui_elt_impl in predicate._impl.find_all()
		]
	def scroll_down_impl(self, num_pixels):
		self._scroll_by(0, num_pixels)
	def scroll_up_impl(self, num_pixels):
		self._scroll_by(0, -num_pixels)
	def scroll_right_impl(self, num_pixels):
		self._scroll_by(num_pixels, 0)
	def scroll_left_impl(self, num_pixels):
		self._scroll_by(-num_pixels, 0)
	@handle_unexpected_alert
	def _scroll_by(self, dx_pixels, dy_pixels):
		self.require_driver().execute_script(
			'window.scrollBy(arguments[0], arguments[1]);', dx_pixels, dy_pixels
		)
	@might_spawn_window
	@handle_unexpected_alert
	def select_impl(self, combo_box, value):
		from helium import ComboBox
		if isinstance(combo_box, str):
			combo_box = ComboBoxImpl(self.require_driver(), combo_box)
		elif isinstance(combo_box, ComboBox):
			combo_box = combo_box._impl
		def _select(web_element):
			if isinstance(web_element, WebElementWrapper):
				web_element = web_element.unwrap()
			Select(web_element).select_by_visible_text(value)
		self._manipulate(combo_box, _select)
	def _manipulate(self, gui_or_web_elt, action):
		driver = self.require_driver()
		if hasattr(gui_or_web_elt, 'perform') \
			and callable(gui_or_web_elt.perform):
			driver.last_manipulated_element = gui_or_web_elt.perform(action)
		else:
			if isinstance(gui_or_web_elt, WebElement):
				gui_or_web_elt = WebElementWrapper(gui_or_web_elt)
			action(gui_or_web_elt)
			driver.last_manipulated_element = gui_or_web_elt
	@handle_unexpected_alert
	def drag_file_impl(self, file_path, to):
		to, _ = self._unwrap_clickable_element(to)
		drag_and_drop = DragAndDropFile(self.require_driver(), file_path)
		drag_and_drop.begin()
		try:
			# Some web apps (Gmail in particular) only register for the 'drop'
			# event when user has dragged the file over the document. We
			# therefore simulate this dragging over the document first:
			drag_and_drop.drag_over_document()
			self._manipulate(to, lambda elt: drag_and_drop.drop_on(elt))
		finally:
			drag_and_drop.end()
	@might_spawn_window
	@handle_unexpected_alert
	def attach_file_impl(self, file_path, to=None):
		from helium import Point
		driver = self.require_driver()
		if to is None:
			to = FileInput(driver)
		elif isinstance(to, str):
			to = FileInput(driver, to)
		elif isinstance(to, Point):
			to, _ = self._point_to_element_and_offset(to)
		self._manipulate(to, lambda elt: elt.send_keys(file_path))
	def refresh_impl(self):
		self._handle_alerts(
			self._refresh_no_alert, self._refresh_with_alert
		)
	def _refresh_no_alert(self):
		self.require_driver().refresh()
	def _refresh_with_alert(self):
		AlertImpl(self.require_driver()).accept()
		self._refresh_no_alert()
	def wait_until_impl(self, condition_fn, timeout_secs=10, interval_secs=0.5):
		if ismethod(condition_fn):
			is_bound = condition_fn.__self__ is not None
			args_spec = getfullargspec(condition_fn).args
			unfilled_args = len(args_spec) - (1 if is_bound else 0)
		else:
			if not isfunction(condition_fn):
				condition_fn = condition_fn.__call__
			args_spec = getfullargspec(condition_fn).args
			unfilled_args = len(args_spec)
		condition = \
			condition_fn if unfilled_args else lambda driver: condition_fn()
		wait = WebDriverWait(
			self.require_driver().unwrap(), timeout_secs,
			poll_frequency=interval_secs
		)
		wait.until(condition)
	@handle_unexpected_alert
	def switch_to_impl(self, window):
		driver = self.require_driver()
		from helium import Window
		if isinstance(window, str):
			window = WindowImpl(driver, window)
		elif isinstance(window, Window):
			window = window._impl
		driver.switch_to.window(window.handle)
	def kill_browser_impl(self):
		self.require_driver().quit()
		self.driver = None
	@handle_unexpected_alert
	def highlight_impl(self, element):
		driver = self.require_driver()
		from helium import HTMLElement, Text
		if isinstance(element, str):
			element = Text(element)
		if isinstance(element, HTMLElement):
			element = element._impl
		try:
			element = element.first_occurrence
		except AttributeError:
			pass
		previous_style = element.get_attribute("style")
		if isinstance(element, WebElementWrapper):
			element = element.unwrap()
		driver.execute_script(
			"arguments[0].setAttribute("
				"'style', 'border: 2px solid red; font-weight: bold;'"
			");", element
		)
		driver.execute_script(
			"var target = arguments[0];"
			"var previousStyle = arguments[1];"
			"setTimeout("
				"function() {"
					"target.setAttribute('style', previousStyle);"
				"}, 2000"
			");", element, previous_style
		)
	def require_driver(self):
		if not self.driver:
			raise RuntimeError(self.DRIVER_REQUIRED_MESSAGE)
		return self.driver

class DragHelper:
	def __init__(self, api_impl):
		self.api_impl = api_impl
		self.is_html_5_drag = None
	def __enter__(self):
		self._execute_script(
			"window.helium = {};"
			"window.helium.dragHelper = {"
			"    createEvent: function(type) {"
			"        var event = document.createEvent('CustomEvent');"
			"        event.initCustomEvent(type, true, true, null);"
			"        event.dataTransfer = {"
			"            data: {},"
			"            setData: function(type, val) {"
			"                this.data[type] = val;"
			"            },"
			"            getData: function(type) {"
			"                return this.data[type];"
			"            }"
			"        };"
			"        return event;"
			"    }"
			"};"
		)
		return self
	def start_dragging(self, element, offset):
		if self._attempt_html_5_drag(element):
			self.is_html_5_drag = True
		else:
			self.api_impl._press_mouse_on(element, offset)
	def drop_on_target(self, target, offset):
		if self.is_html_5_drag:
			self._complete_html_5_drag(target)
		else:
			self.api_impl._release_mouse_over(target, offset)
	def _attempt_html_5_drag(self, element_to_drag):
		return self._execute_script(
			"var source = arguments[0];"
			"function getDraggableParent(element) {"
			"    var previousParent = null;"
			"    while (element != null && element != previousParent) {"
			"        previousParent = element;"
			"        if ('draggable' in element) {"
			"            var draggable = element.draggable;"
			"            if (draggable === true)"
			"                return element;"
			"            if (typeof draggable == 'string' "
			"                    || draggable instanceof String)"
			"                if (draggable.toLowerCase() == 'true')"
			"                    return element;"
			"        }"
			"        element = element.parentNode;"
			"    }"
			"    return null;"
			"}"
			"var draggableParent = getDraggableParent(source);"
			"if (draggableParent == null)"
			"    return false;"
			"window.helium.dragHelper.draggedElement = draggableParent;"
			"var dragStart = window.helium.dragHelper.createEvent('dragstart');"
			"source.dispatchEvent(dragStart);"
			"window.helium.dragHelper.dataTransfer = dragStart.dataTransfer;"
			"return true;",
			element_to_drag
		)
	def _complete_html_5_drag(self, on):
		self._execute_script(
			"var target = arguments[0];"
			"var drop = window.helium.dragHelper.createEvent('drop');"
			"drop.dataTransfer = window.helium.dragHelper.dataTransfer;"
			"target.dispatchEvent(drop);"
			"var dragEnd = window.helium.dragHelper.createEvent('dragend');"
			"dragEnd.dataTransfer = window.helium.dragHelper.dataTransfer;"
			"window.helium.dragHelper.draggedElement.dispatchEvent(dragEnd);",
			on
		)
	def __exit__(self, *_):
		self._execute_script("delete window.helium;")
	def _execute_script(self, script, *args):
		return self.api_impl.require_driver().execute_script(script, *args)

class DragAndDropFile:
	def __init__(self, driver, file_path):
		self.driver = driver
		self.file_path = file_path
		self.file_input_element = None
		self.dragover_event = None
	def begin(self):
		self._create_file_input_element()
		try:
			self.file_input_element.send_keys(self.file_path)
		except:
			self.end()
			raise
	def _create_file_input_element(self):
		# The input needs to be visible to Selenium to allow sending keys to it
		# in Firefox and IE.
		# According to http://stackoverflow.com/questions/6101461/
		# Selenium criteria whether an element is visible or not are the
		# following:
		#  - visibility != hidden
		#  - display != none (is also checked against every parent element)
		#  - opacity != 0
		#  - height and width are both > 0
		#  - for an input, the attribute type != hidden
		# So let's make sure its all good!
		self.file_input_element = self.driver.execute_script(
			"var input = document.createElement('input');"
			"input.type = 'file';"
			"input.style.display = 'block';"
			"input.style.opacity = '1';"
			"input.style.visibility = 'visible';"
			"input.style.height = '1px';"
			"input.style.width = '1px';"
			"if (document.body.childElementCount > 0) { "
			"  document.body.insertBefore(input, document.body.childNodes[0]);"
			"} else { "
			"  document.body.appendChild(input);"
			"}"
			"return input;"
		)
	def drag_over_document(self):
		# According to the HTML5 spec, we need to dispatch the dragenter event
		# once, and then the dragover event continuously, every 350+-200ms:
		# http://www.w3.org/html/wg/drafts/html/master/editing.html#current-drag
		# -operation
		# Especially IE implements this spec very tightly, and considers the
		# dragging to be over if no dragover event occurs for more than ~1sec.
		# We thus need to ensure that we keep dispatching the dragover event.

		# This line used to read `_dispatch_event(..., to='document')`. However,
		# this doesn't work when adding a photo to a tweet on Twitter.
		# Dispatching the event to document.body fixes this, and also works for
		# Gmail:
		self._dispatch_event('dragenter', to='document.body')
		self.dragover_event = self._prepare_continuous_event(
			'dragover', 'document', interval_msecs=300
		)
		self.dragover_event.start()
	def _dispatch_event(self, event_name, to):
		script, args = self._prepare_dispatch_event(event_name, to)
		self.driver.execute_script(script, *args)
	def _prepare_continuous_event(self, event_name, to, interval_msecs):
		script, args = self._prepare_dispatch_event(event_name, to)
		return JavaScriptInterval(self.driver, script, args, interval_msecs)
	def _prepare_dispatch_event(self, event_name, to):
		script = \
			"var files = arguments[0].files;" \
			"var items = [];" \
			"var types = [];" \
			"for (var i = 0; i < files.length; i++) {" \
			"   items[i] = {kind: 'file', type: files[i].type};" \
			"   types[i] = 'Files';" \
			"}" \
			"var event = document.createEvent('CustomEvent');" \
			"event.initCustomEvent(arguments[1], true, true, 0);" \
			"event.dataTransfer = {" \
			"	files: files," \
			"	items: items," \
			"	types: types" \
			"};" \
			"arguments[2].dispatchEvent(event);"
		if isinstance(to, str):
			script = script.replace('arguments[2]', to)
			args = self.file_input_element, event_name,
		else:
			args = self.file_input_element, event_name, to.unwrap()
		return script, args
	def drop_on(self, target):
		self.dragover_event.stop()
		self._dispatch_event('drop', to=target)
	def end(self):
		if self.file_input_element is not None:
			self.driver.execute_script(
				"arguments[0].parentNode.removeChild(arguments[0]);",
				self.file_input_element
			)
		self.file_input_element = None

class JavaScriptInterval:
	def __init__(self, driver, script, args, interval_msecs):
		self.driver = driver
		self.script = script
		self.args = args
		self.interval_msecs = interval_msecs
		self._interval_id = None
	def start(self):
		setinterval_script = (
			"var originalArguments = arguments;"
			"return setInterval(function() {"
			"	arguments = originalArguments;"
			"	%s"
			"}, %d);"
		) % (self.script, self.interval_msecs)
		self._interval_id = \
			self.driver.execute_script(setinterval_script, *self.args)
	def stop(self):
		self.driver.execute_script(
			"clearInterval(arguments[0]);", self._interval_id
		)
		self._interval_id = None

class GUIElementImpl:
	def __init__(self, driver):
		self._bound_occurrence = None
		self._driver = driver
	def find_all(self):
		if self._is_bound():
			yield self
		else:
			for occurrence in self.find_all_occurrences():
				yield self.bound_to_occurrence(occurrence)
	def _is_bound(self):
		return self._bound_occurrence is not None
	def find_all_occurrences(self):
		raise NotImplementedError()
	def bound_to_occurrence(self, occurrence):
		result = copy(self)
		result._bound_occurrence = occurrence
		return result
	def exists(self):
		try:
			next(self.find_all())
		except StopIteration:
			return False
		else:
			return True
	@property
	def first_occurrence(self):
		if not self._is_bound():
			self._bind_to_first_occurrence()
		return self._bound_occurrence
	def _bind_to_first_occurrence(self):
		self.perform(lambda _: None)
		# _perform_no_wait(...) below now sets _bound_occurrence.
	def perform(self, action):
		from helium import Config
		end_time = time() + Config.implicit_wait_secs
		# Try to perform `action` at least once:
		result = self._perform_no_wait(action)
		while result is None and time() < end_time:
			result = self._perform_no_wait(action)
		if result is not None:
			return result
		raise LookupError()
	def _perform_no_wait(self, action):
		for bound_gui_elt_impl in self.find_all():
			occurrence = bound_gui_elt_impl.first_occurrence
			try:
				action(occurrence)
			except Exception as e:
				if self.should_ignore_exception(e):
					continue
				else:
					raise
			else:
				self._bound_occurrence = occurrence
				return occurrence
	def should_ignore_exception(self, exception):
		if isinstance(exception, ElementNotVisibleException):
			return True
		if isinstance(exception, MoveTargetOutOfBoundsException):
			return True
		if isinstance(exception, StaleElementReferenceException):
			return True
		if isinstance(exception, WebDriverException):
			msg = exception.msg
			if 'is not clickable at point' in msg \
				and 'Other element would receive the click' in msg:
				# This can happen when the element has moved.
				return True
		return False

class HTMLElementImpl(GUIElementImpl):
	def __init__(
			self, driver, below=None, to_right_of=None, above=None,
			to_left_of=None
	):
		super(HTMLElementImpl, self).__init__(driver)
		self.below = self._unwrap_element(below)
		self.to_right_of = self._unwrap_element(to_right_of)
		self.above = self._unwrap_element(above)
		self.to_left_of = self._unwrap_element(to_left_of)
		self.matches = PREFIX_IGNORE_CASE()
	def find_anywhere_in_curr_frame(self):
		raise NotImplementedError()
	@property
	def width(self):
		return self.first_occurrence.location.width
	@property
	def height(self):
		return self.first_occurrence.location.height
	@property
	def x(self):
		return self.first_occurrence.location.left
	@property
	def y(self):
		return self.first_occurrence.location.top
	@property
	def top_left(self):
		from helium import Point
		return Point(self.x, self.y)
	@property
	def web_element(self):
		return self.first_occurrence.unwrap()
	def find_all_occurrences(self):
		self._handle_closed_window()
		self._driver.switch_to.default_content()
		already_yielded = set()
		for frame_index in FrameIterator(self._driver):
			for occurrence in self._find_all_in_curr_frame():
				if occurrence.target in already_yielded:
					# We have seen this element before, but its frame had a
					# different index. This means that the frames have changed.
					# Abort:
					return
				occurrence.frame_index = frame_index
				yield occurrence
				already_yielded.add(occurrence.target)
	def _handle_closed_window(self):
		window_handles = self._driver.window_handles
		try:
			curr_window_handle = self._driver.current_window_handle
		except NoSuchWindowException:
			window_has_been_closed = True
		else:
			window_has_been_closed = curr_window_handle not in window_handles
		if window_has_been_closed:
			self._driver.switch_to.window(window_handles[0])
	def _find_all_in_curr_frame(self):
		search_regions = self._get_search_regions_in_curr_frame()
		for occurrence in self.find_anywhere_in_curr_frame():
			if not occurrence.is_displayed():
				continue
			if self._is_in_any_search_region(occurrence, search_regions):
				yield occurrence
	def _get_search_regions_in_curr_frame(self):
		result = []
		if self.below:
			result.append([
				elt.location.is_above
				for elt in self.below._find_all_in_curr_frame()
			])
		if self.to_right_of:
			result.append([
				elt.location.is_to_left_of
				for elt in self.to_right_of._find_all_in_curr_frame()
			])
		if self.above:
			result.append([
				elt.location.is_below
				for elt in self.above._find_all_in_curr_frame()
			])
		if self.to_left_of:
			result.append([
				elt.location.is_to_right_of
				for elt in self.to_left_of._find_all_in_curr_frame()
			])
		return result
	def _is_in_any_search_region(self, element, search_regions):
		for direction in search_regions:
			found = False
			for search_region in direction:
				if search_region(element.location):
					found = True
					break
			if not found:
				return False
		return True
	def _is_enabled(self):
		"""
		Useful for subclasses.
		"""
		return self.first_occurrence.get_attribute('disabled') is None
	def _unwrap_element(self, element):
		if isinstance(element, str):
			return TextImpl(self._driver, element)
		from helium import HTMLElement
		if isinstance(element, HTMLElement):
			return element._impl
		return element

class SImpl(HTMLElementImpl):
	def __init__(self, driver, selector, **kwargs):
		super(SImpl, self).__init__(driver, **kwargs)
		self.selector = selector
	def find_anywhere_in_curr_frame(self):
		wrap = lambda web_elements: list(map(WebElementWrapper, web_elements))
		if self.selector.startswith('@'):
			return wrap(self._driver.find_elements(By.NAME, self.selector[1:]))
		if self.selector.startswith('//'):
			return wrap(self._driver.find_elements(By.XPATH, self.selector))
		return wrap(self._driver.find_elements(By.CSS_SELECTOR, self.selector))

class HTMLElementIdentifiedByXPath(HTMLElementImpl):
	def find_anywhere_in_curr_frame(self):
		x_path = self.get_xpath()
		return self._sort_search_result(
			list(map(
				WebElementWrapper, self._driver.find_elements(By.XPATH, x_path)
			))
		)
	def _sort_search_result(self, search_result):
		keys_to_result_items = []
		for web_elt in search_result:
			try:
				key = self.get_sort_index(web_elt)
			except StaleElementReferenceException:
				pass
			else:
				keys_to_result_items.append((key, web_elt))
		sort_key = lambda tpl: tpl[0]
		keys_to_result_items.sort(key=sort_key)
		result_item = lambda tpl: tpl[1]
		return list(map(result_item, keys_to_result_items))
	def get_xpath(self):
		raise NotImplementedError()
	def get_sort_index(self, web_element):
		return self._driver.get_distance_to_last_manipulated(web_element) + 1

class HTMLElementContainingText(HTMLElementIdentifiedByXPath):
	def __init__(self, driver, text=None, **kwargs):
		super(HTMLElementContainingText, self).__init__(driver, **kwargs)
		self.search_text = text
	def get_xpath(self):
		xpath_base = "//" + self.get_xpath_node_selector() + \
					 predicate(self.matches.xpath('.', self.search_text))
		return '%s[not(self::script)][not(.%s)]' % (xpath_base, xpath_base)
	def get_xpath_node_selector(self):
		return '*'

class TextImpl(HTMLElementContainingText):
	def __init__(self, driver, text=None, include_free_text=True, **kwargs):
		super(TextImpl, self).__init__(driver, text, **kwargs)
		self.include_free_text = include_free_text
	@property
	def value(self):
		return self.first_occurrence.text
	def get_xpath(self):
		button_impl = ButtonImpl(self._driver, self.search_text)
		link_impl = LinkImpl(self._driver, self.search_text)
		components = [
			self._get_search_text_xpath(),
			button_impl.get_input_button_xpath(),
			link_impl.get_xpath()
		]
		if self.search_text and self.include_free_text:
			components.append(
				FreeText(self._driver, self.search_text).get_xpath()
			)
		return ' | '.join(components)
	def _get_search_text_xpath(self):
		if self.search_text:
			result = super(TextImpl, self).get_xpath()
		else:
			no_descendant_with_same_text = \
				"not(.//*[normalize-space(.)=normalize-space(self::*)])"
			result = '//*[text() and %s]' % no_descendant_with_same_text
		return result + "[not(self::option)]" + \
		       ("" if self.include_free_text else "[count(*) <= 1]")

class FreeText(HTMLElementContainingText):
	def get_xpath_node_selector(self):
		return 'text()'
	def get_xpath(self):
		return super(FreeText, self).get_xpath() + '/..'

class LinkImpl(HTMLElementContainingText):
	def get_xpath_node_selector(self):
		return 'a'
	def get_xpath(self):
		return super(LinkImpl, self).get_xpath() + ' | ' + \
			   "//a" + \
			   predicate(self.matches.xpath('@title', self.search_text)) + \
			   ' | ' + "//*[@role='link']" + \
			   predicate(self.matches.xpath('.', self.search_text))
	@property
	def href(self):
		return self.web_element.get_attribute('href')

class ListItemImpl(HTMLElementContainingText):
	def get_xpath_node_selector(self):
		return 'li'

class ButtonImpl(HTMLElementContainingText):
	def get_xpath_node_selector(self):
		return 'button'
	def is_enabled(self):
		aria_disabled = self.first_occurrence.get_attribute('aria-disabled')
		return self._is_enabled() \
			and (not aria_disabled or aria_disabled.lower() == 'false')
	def get_xpath(self):
		has_aria_label = self.matches.xpath('@aria-label', self.search_text)
		has_text = self.matches.xpath('.', self.search_text)
		has_text_or_aria_label = predicate_or(has_aria_label, has_text)
		return ' | '.join([
			super(ButtonImpl, self).get_xpath(), self.get_input_button_xpath(),
			"//*[@role='button']" + has_text_or_aria_label,
			"//button" + predicate(has_aria_label)
		])
	def get_input_button_xpath(self):
		if self.search_text:
			has_value = self.matches.xpath('@value', self.search_text)
			has_label = self.matches.xpath('@label', self.search_text)
			has_aria_label = self.matches.xpath('@aria-label', self.search_text)
			has_title = self.matches.xpath('@title', self.search_text)
			has_text = \
				predicate_or(has_value, has_label, has_aria_label, has_title)
		else:
			has_text = ''
		return "//input[@type='submit' or @type='button']" + has_text

class ImageImpl(HTMLElementIdentifiedByXPath):
	def __init__(self, driver, alt, **kwargs):
		super(ImageImpl, self).__init__(driver, **kwargs)
		self.alt = alt
	def get_xpath(self):
		return "//img" + predicate(self.matches.xpath('@alt', self.alt))

class LabelledElement(HTMLElementImpl):
	SECONDARY_SEARCH_DIMENSION_PENALTY_FACTOR = 1.5
	def __init__(self, driver, label=None, **kwargs):
		super(LabelledElement, self).__init__(driver, **kwargs)
		self.label = label
	def find_anywhere_in_curr_frame(self):
		if not self.label:
			result = self._find_elts()
		else:
			labels = TextImpl(
				self._driver, self.label, include_free_text=False
			).find_anywhere_in_curr_frame()
			if labels:
				result = list(self._filter_elts_belonging_to_labels(
					self._find_elts(), labels
				))
			else:
				result = self._find_elts_by_free_text()
		return sorted(result, key=self._driver.get_distance_to_last_manipulated)
	def _find_elts(self, xpath=None):
		if xpath is None:
			xpath = self.get_xpath()
		return list(map(
			WebElementWrapper, self._driver.find_elements(By.XPATH, xpath)
		))
	def _find_elts_by_free_text(self):
		elt_types = [
			xpath.strip().lstrip('/') for xpath in self.get_xpath().split('|')
		]
		labels = '//text()' + predicate(self.matches.xpath('.', self.label))
		xpath = ' | '.join(
			[(labels + '/%s::' + elt_type + '[1]')
			 % ('preceding-sibling'
			    if 'checkbox' in elt_type or 'radio' in elt_type
			    else 'following')
			 for elt_type in elt_types]
		)
		return self._find_elts(xpath)
	def get_xpath(self):
		raise NotImplementedError()
	def get_primary_search_direction(self):
		return 'to_right_of'
	def get_secondary_search_direction(self):
		return 'below'
	def _filter_elts_belonging_to_labels(self, all_elts, labels):
		for label, elt in self._get_labels_with_explicit_elts(all_elts, labels):
			yield elt
			labels.remove(label)
			all_elts.remove(elt)
		labels_to_elts = self._get_related_elts(all_elts, labels)
		labels_to_elts = self._ensure_at_most_one_label_per_elt(labels_to_elts)
		self._retain_closest(labels_to_elts)
		for elts_for_label in list(labels_to_elts.values()):
			assert len(elts_for_label) <= 1
			if elts_for_label:
				yield next(iter(elts_for_label))
	def _get_labels_with_explicit_elts(self, all_elts, labels):
		for label in labels:
			if label.tag_name == 'label':
				label_target = label.get_attribute('for')
				if label_target:
					for elt in all_elts:
						elt_id = elt.get_attribute('id')
						if elt_id.lower() == label_target.lower():
							yield label, elt
	def _get_related_elts(self, all_elts, labels):
		result = {}
		for label in labels:
			for elt in all_elts:
				if self._are_related(elt, label):
					if label not in result:
						result[label] = set()
					result[label].add(elt)
		return result
	def _are_related(self, elt, label):
		if elt.location.intersects(label.location):
			return True
		prim_search_dir = self.get_primary_search_direction()
		sec_search_dir = self.get_secondary_search_direction()
		return label.location.distance_to(elt.location) <= 150 and (
			elt.location.is_in_direction(prim_search_dir, label.location) or
			elt.location.is_in_direction(sec_search_dir, label.location)
		)
	def _ensure_at_most_one_label_per_elt(self, labels_to_elts):
		elts_to_labels = inverse(labels_to_elts)
		self._retain_closest(elts_to_labels)
		return inverse(elts_to_labels)
	def _retain_closest(self, pivots_to_elts):
		for pivot, elts in list(pivots_to_elts.items()):
			if elts:
				# Would like to use a set literal {...} here, but this is not
				# supported in Python 2.6. Thus we need to use set([...]).
				pivots_to_elts[pivot] = set([self._find_closest(pivot, elts)])
	def _find_closest(self, to_pivot, among_elts):
		remaining_elts = iter(among_elts)
		result = next(remaining_elts)
		result_distance = self._compute_distance(result, to_pivot)
		for element in remaining_elts:
			element_distance = self._compute_distance(element, to_pivot)
			if element_distance < result_distance:
				result = element
				result_distance = element_distance
		return result
	def _compute_distance(self, elt_1, elt_2):
		loc_1 = elt_1.location
		loc_2 = elt_2.location
		if loc_1.is_in_direction(self.get_secondary_search_direction(), loc_2):
			factor = self.SECONDARY_SEARCH_DIMENSION_PENALTY_FACTOR
		else:
			factor = 1
		return factor * loc_1.distance_to(loc_2)

class CompositeElement(HTMLElementImpl):
	def __init__(self, driver, *args, **kwargs):
		super(CompositeElement, self).__init__(driver, **kwargs)
		self.args = [driver] + list(args)
		self.kwargs = kwargs
		self._first_element = None
	@property
	def first_element(self):
		if self._first_element is None:
			self._bind_to_first_occurrence()
			# find_anywhere_in_curr_frame() below now sets _first_element
		return self._first_element
	def find_anywhere_in_curr_frame(self):
		already_yielded = []
		for element in self.get_elements():
			for bound_gui_elt_impl in element.find_anywhere_in_curr_frame():
				if self._first_element is None:
					self._first_element = element
				if bound_gui_elt_impl not in already_yielded:
					yield bound_gui_elt_impl
					already_yielded.append(bound_gui_elt_impl)
	def get_elements(self):
		for element_type in self.get_element_types():
			yield element_type(*self.args, **self.kwargs)
	def get_element_types(self):
		raise NotImplementedError()

class ClickableText(CompositeElement):
	def get_element_types(self):
		return [ButtonImpl, TextImpl, ImageImpl]

class TextFieldImpl(CompositeElement):
	def get_element_types(self):
		return [
			StandardTextFieldWithPlaceholder, StandardTextFieldWithLabel,
			AriaTextFieldWithLabel
		]
	@property
	def value(self):
		return self.first_element.value
	def is_enabled(self):
		return self.first_element.is_enabled()
	def is_editable(self):
		return self.first_element.is_editable()

class StandardTextFieldWithLabel(LabelledElement):
	@property
	def value(self):
		return self.first_occurrence.get_attribute('value') or ''
	def is_enabled(self):
		return self._is_enabled()
	def is_editable(self):
		return self.first_occurrence.get_attribute('readOnly') is None
	def get_xpath(self):
		return \
			"//input[%s='text' or %s='email' or %s='password' or %s='number' " \
			"or %s='tel' or string-length(@type)=0]" % ((lower('@type'), ) * 5)\
			+ " | //textarea | //*[@contenteditable='true']"

class AriaTextFieldWithLabel(LabelledElement):
	@property
	def value(self):
		return self.first_occurrence.text
	def is_enabled(self):
		return self._is_enabled()
	def is_editable(self):
		return self.first_occurrence.get_attribute('readOnly') is None
	def get_xpath(self):
		return "//*[@role='textbox']"

class StandardTextFieldWithPlaceholder(HTMLElementIdentifiedByXPath):
	def __init__(self, driver, label, **kwargs):
		super(StandardTextFieldWithPlaceholder, self).__init__(driver, **kwargs)
		self.label = label
	@property
	def value(self):
		return self.first_occurrence.get_attribute('value') or ''
	def is_enabled(self):
		return self._is_enabled()
	def is_editable(self):
		return self.first_occurrence.get_attribute('readOnly') is None
	def get_xpath(self):
		return "(%s)%s" % (
			StandardTextFieldWithLabel(self.label).get_xpath(),
			predicate(self.matches.xpath('@placeholder', self.label))
		)

class FileInput(LabelledElement):
	def get_xpath(self):
		return "//input[@type='file']"

class ComboBoxImpl(CompositeElement):
	def get_element_types(self):
		return [ComboBoxIdentifiedByDisplayedValue, ComboBoxIdentifiedByLabel]
	def is_editable(self):
		return self.first_occurrence.tag_name != 'select'
	@property
	def value(self):
		selected_value = self._select_driver.first_selected_option
		if selected_value:
			return selected_value.text
		return None
	@property
	def options(self):
		return [option.text for option in self._select_driver.options]
	@property
	def _select_driver(self):
		return Select(self.web_element)

class ComboBoxIdentifiedByLabel(LabelledElement):
	def get_xpath(self):
		return "//select | //input[@list]"

class ComboBoxIdentifiedByDisplayedValue(HTMLElementContainingText):
	def get_xpath_node_selector(self):
		return 'option'
	def get_xpath(self):
		option_xpath = \
			super(ComboBoxIdentifiedByDisplayedValue, self).get_xpath()
		return option_xpath + '/ancestor::select[1]'
	def find_anywhere_in_curr_frame(self):
		all_cbs_with_a_matching_value = super(
			ComboBoxIdentifiedByDisplayedValue, self
		).find_anywhere_in_curr_frame()
		result = []
		for cb in all_cbs_with_a_matching_value:
			for selected_option in Select(cb.unwrap()).all_selected_options:
				if self.matches.text(selected_option.text, self.search_text):
					result.append(cb)
					break
		return result

class CheckBoxImpl(LabelledElement):
	def is_enabled(self):
		return self._is_enabled()
	def is_checked(self):
		return self.first_occurrence.get_attribute('checked') is not None
	def get_xpath(self):
		return "//input[@type='checkbox']"
	def get_primary_search_direction(self):
		return 'to_left_of'
	def get_secondary_search_direction(self):
		return 'to_right_of'

class RadioButtonImpl(LabelledElement):
	def is_selected(self):
		return self.first_occurrence.get_attribute('checked') is not None
	def get_xpath(self):
		return "//input[@type='radio']"
	def get_primary_search_direction(self):
		return 'to_left_of'
	def get_secondary_search_direction(self):
		return 'to_right_of'

class WindowImpl(GUIElementImpl):
	def __init__(self, driver, title=None):
		super(WindowImpl, self).__init__(driver)
		self.search_title = title
	def find_all_occurrences(self):
		result_scores = []
		for handle in self._driver.window_handles:
			window = WindowImpl.SeleniumWindow(self._driver, handle)
			if self.search_title is None:
				result_scores.append((0, window))
			else:
				title = window.title
				if title.startswith(self.search_title):
					score = len(title) - len(self.search_title)
					result_scores.append((score, window))
		score = lambda tpl: tpl[0]
		result_scores.sort(key=score)
		for score, window in result_scores:
			yield window
	@property
	def title(self):
		return self.first_occurrence.title
	@property
	def handle(self):
		return self.first_occurrence.handle
	class SeleniumWindow:
		def __init__(self, driver, handle):
			self.driver = driver
			self.handle = handle
			self._window_handle_before = None
		@property
		def title(self):
			with self:
				return self.driver.title
		def __enter__(self):
			try:
				self._window_handle_before = self.driver.current_window_handle
			except NoSuchWindowException as window_closed:
				do_switch = True
			else:
				do_switch = self._window_handle_before != self.handle
			if do_switch:
				self.driver.switch_to.window(self.handle)
		def __exit__(self, *_):
			if self._window_handle_before and \
				self.driver.current_window_handle != self._window_handle_before:
				self.driver.switch_to.window(self._window_handle_before)

class AlertImpl(GUIElementImpl):
	def __init__(self, driver, search_text=None):
		super(AlertImpl, self).__init__(driver)
		self.search_text = search_text
	def find_all_occurrences(self):
		try:
			result = self._driver.switch_to.alert
			text = result.text
			if self.search_text is None or text.startswith(self.search_text):
				yield result
		except NoAlertPresentException:
			pass
	@property
	def text(self):
		return self.first_occurrence.text
	def accept(self):
		first_occurrence = self.first_occurrence
		try:
			first_occurrence.accept()
		except WebDriverException as e:
			# Attempt to work around Selenium issue 3544:
			# https://code.google.com/p/selenium/issues/detail?id=3544
			msg = e.msg
			if msg and re.match(
					r"a\.document\.getElementsByTagName\([^\)]*\)\[0\] is "
					r"undefined", msg
			):
				sleep(0.25)
				first_occurrence.accept()
			else:
				raise
	def dismiss(self):
		self.first_occurrence.dismiss()
	def _write(self, text):
		self.first_occurrence.send_keys(text)