Fix withdraw increment (#26)

* Fix: made increment/is_spent more specific
* fix: make safe `increment_withdraw_link `
* fix: remove old fix
* chore: code format

---------

Co-authored-by: benarc <ben@arc.wales>

helpers.py

@@ -0,0 +1,49 @@
+from threading import Lock
+from typing import Dict
+
+
+class CounterLock:
+    def __init__(self):
+        self.counter = 0
+        self.lock = Lock()
+
+    def acquire(self) -> bool:
+        self.counter += 1
+        return self.lock.acquire()
+
+    def release(self) -> None:
+        self.counter -= 1
+        return self.lock.release()
+
+    @property
+    def no_more_waiters(self) -> bool:
+        return self.counter == 0
+
+
+class NamedLock:
+    _lock = Lock()
+    _locks: Dict[str, CounterLock] = {}
+
+    def acquire(self, name: str) -> bool:
+        self._lock.acquire()
+
+        if name not in self._locks:
+            self._locks[name] = CounterLock()
+
+        self._lock.release()
+
+        return self._locks[name].acquire()
+
+
+
+    def release(self, name: str):
+        self._lock.acquire()
+
+        if name not in self._locks:
+            return self._lock.release()
+
+        self._locks[name].release()
+        if self._locks[name].no_more_waiters:
+            del self._locks[name]
+
+        return self._lock.release()