Bare bones of a notification system

flake8/__init__.py

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+__version__ = '3.0.0a1'

flake8/_trie.py

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+"""Independent implementation of a Trie tree."""
+
+__all__ = ('Trie', 'TrieNode')
+
+
+def _iterate_stringlike_objects(string):
+    for i in range(len(string)):
+        yield string[i:i+1]
+
+
+class Trie(object):
+    """The object that manages the trie nodes."""
+
+    def __init__(self):
+        """Initialize an empty trie."""
+        self.root = TrieNode(None, None)
+
+    def add(self, path, node_data):
+        """Add the node data to the path described."""
+        node = self.root
+        for prefix in _iterate_stringlike_objects(path):
+            child = node.find_prefix(prefix)
+            if child is None:
+                child = node.add_child(prefix, [])
+            node = child
+        node.data.append(node_data)
+
+    def find(self, path):
+        """Find a node based on the path provided."""
+        node = self.root
+        for prefix in _iterate_stringlike_objects(path):
+            child = node.find_prefix(prefix)
+            if child is None:
+                return None
+            node = child
+        return node
+
+
+class TrieNode(object):
+    """The majority of the implementation details of a Trie."""
+
+    def __init__(self, prefix, data, children=None):
+        """Initialize a TrieNode with data and children."""
+        self.children = children or {}
+        self.data = data
+        self.prefix = prefix
+
+    def __repr__(self):
+        """Generate an easy to read representation of the node."""
+        return 'TrieNode(prefix={0}, data={1}, children={2})'.format(
+            self.prefix, self.data, dict(self.children)
+        )
+
+    def find_prefix(self, prefix):
+        """Find the prefix in the children of this node.
+
+        :returns: A child matching the prefix or None.
+        :rtype: :class:`~TrieNode` or None
+        """
+        return self.children.get(prefix, None)
+
+    def add_child(self, prefix, data, children=None):
+        """Create and add a new child node.
+
+        :returns: The newly created node
+        :rtype: :class:`~TrieNode`
+        """
+        new_node = TrieNode(prefix, data, children)
+        self.children[prefix] = new_node
+        return new_node
+
+    def traverse(self):
+        """Traverse children of this node in order."""
+        raise NotImplementedError()

flake8/notifier.py

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+from flake8 import _trie
+
+
+class Notifier(object):
+    def __init__(self):
+        self.listeners = _trie.Trie()
+
+    def listeners_for(self, error_code):
+        node = self.listeners.find(error_code)
+        for listener in node.data:
+            yield listener
+        if node.children:
+            for child in node.traverse():
+                for listener in child.data:
+                    yield listener
+
+    def notify(self, error_code, *args, **kwargs):
+        for listener in self.listeners_for(error_code):
+            listener.notify(*args, **kwargs)
+
+    def register_listener(self, error_code, listener):
+        self.listeners.add(error_code, listener)