Initial modeling of a separate finder class with examples

- Created base Finder class which has placeholders for find and pre_find_action
  methods. Also has a couple utility methods. Still need to figure out a couple
  shared methods from the old ElementFinder class.
- Created (Element)Finder class which would allow for a list of (element)finders
  instead of just one. This is the central key to be able to look, for example,
  both in the ShadowDOM and in the regular DOM. This might not be the final model
  for the list but thought I would start with a iterative class.
- Also I would really like to use the ElementFinder name for this Finder class as
  it better describes the very specific function of finding an element. And then
  rename the original ElementFinder to something more generic. Having difficulty
  though trying to figure out that generic name .. something about both parsing
  locators strings and finding the elements.
- Copied/Moved core find method into the DefaultFinder class.
- Made a rough model for a separate Strategy class. Not sure if this is the right
  model for this due to reuse across several places I think this might be the way
  to go.

I am still trying to figure out if all these class need to be ContextAware. Overall
though this seems to be a good rough start ..

src/SeleniumLibrary/locators/elementfinder.py

@@ -29,6 +29,159 @@
 from .customlocator import CustomLocator
 
 
+class Finder():
+    def __int__(self):
+        """Placeholder to Finder class instantation method """
+        pass
+
+    def pre_find_action(self):
+        """Placeholder for the pre_find_action method"""
+        pass
+
+    def find(self):
+        """Placeholder for the find method"""
+        pass
+
+    def _is_webelement(self, element):
+        # Hook for unit tests
+        return isinstance(element, (WebElement, EventFiringWebElement))
+
+
+    def _parse_locator(self, locator):
+        if re.match(r"\(*//", locator):
+            return "xpath", locator
+        index = self._get_locator_separator_index(locator)
+        if index != -1:
+            prefix = locator[:index].strip()
+            if prefix in self._strategies:
+                return prefix, locator[index + 1 :].lstrip()
+        return "default", locator
+
+
+class FinderList():
+    def __iter__(self):
+        pass
+
+    def __getitem__(self, item):
+        pass
+
+    def __len__(self):
+        pass
+
+class DefaultFinder(Finder):
+    def find(self, locator, tag=None, first_only=True, required=True, parent=None):
+        element_type = "Element" if not tag else tag.capitalize()
+        if parent and not self._is_webelement(parent):
+            raise ValueError(
+                f"Parent must be Selenium WebElement but it was {type(parent)}."
+            )
+        if self._is_webelement(locator):
+            return locator
+        prefix, criteria = self._parse_locator(locator)
+        strategy = self._strategies[prefix]
+        tag, constraints = self._get_tag_and_constraints(tag)
+        elements = strategy(criteria, tag, constraints, parent=parent or self.driver)
+        if required and not elements:
+            raise ElementNotFound(f"{element_type} with locator '{locator}' not found.")
+        if first_only:
+            if not elements:
+                return None
+            return elements[0]
+        return elements
+
+
+    def _get_tag_and_constraints(self, tag):
+        if tag is None:
+            return None, {}
+        tag = tag.lower()
+        constraints = {}
+        if tag == "link":
+            tag = "a"
+        if tag == "partial link":
+            tag = "a"
+        elif tag == "image":
+            tag = "img"
+        elif tag == "list":
+            tag = "select"
+        elif tag == "radio button":
+            tag = "input"
+            constraints["type"] = "radio"
+        elif tag == "checkbox":
+            tag = "input"
+            constraints["type"] = "checkbox"
+        elif tag == "text field":
+            tag = "input"
+            constraints["type"] = [
+                "date",
+                "datetime-local",
+                "email",
+                "month",
+                "number",
+                "password",
+                "search",
+                "tel",
+                "text",
+                "time",
+                "url",
+                "week",
+                "file",
+            ]
+        elif tag == "file upload":
+            tag = "input"
+            constraints["type"] = "file"
+        elif tag == "text area":
+            tag = "textarea"
+        return tag, constraints
+
+
+class Strategies:
+    def __init__(self):
+        strategies = {
+            "identifier": ElementFinder._find_by_identifier,
+            "id": ElementFinder._find_by_id,
+            "name": ElementFinder._find_by_name,
+            "xpath": ElementFinder._find_by_xpath,
+            "dom": ElementFinder._find_by_dom,
+            "link": ElementFinder._find_by_link_text,
+            "partial link": ElementFinder._find_by_partial_link_text,
+            "css": ElementFinder._find_by_css_selector,
+            "class": ElementFinder._find_by_class_name,
+            "jquery": ElementFinder._find_by_jquery_selector,
+            "sizzle": ElementFinder._find_by_jquery_selector,
+            "tag": ElementFinder._find_by_tag_name,
+            "scLocator": ElementFinder._find_by_sc_locator,
+            "data": ElementFinder._find_by_data_locator,
+            "default": ElementFinder._find_by_default,
+        }
+        self._strategies = NormalizedDict(
+            initial=strategies, caseless=True, spaceless=True
+        )
+        self._default_strategies = list(strategies)
+    def register(self, strategy_name, strategy_keyword, persist=False):
+        strategy = CustomLocator(self.ctx, strategy_name, strategy_keyword)
+        if strategy.name in self._strategies:
+            raise RuntimeError(
+                f"The custom locator '{strategy.name}' cannot be registered. "
+                "A locator of that name already exists."
+            )
+        self._strategies[strategy.name] = strategy.find
+        if is_falsy(persist):
+            # Unregister after current scope ends
+            events.on("scope_end", "current", self.unregister, strategy.name)
+
+    def unregister(self, strategy_name):
+        if strategy_name in self._default_strategies:
+            raise RuntimeError(
+                f"Cannot unregister the default strategy '{strategy_name}'."
+            )
+        if strategy_name not in self._strategies:
+            raise RuntimeError(
+                f"Cannot unregister the non-registered strategy '{strategy_name}'."
+            )
+        del self._strategies[strategy_name]
+
+
+
 class ElementFinder(ContextAware):
     def __init__(self, ctx):
         ContextAware.__init__(self, ctx)