Add file backend

Author: realsuayip

pcontract/backends.py

@@ -0,0 +1,54 @@
+import pickle
+from pathlib import Path
+from typing import TypeVar
+
+from pcontract.data import Collection
+
+T = TypeVar("T", bound="FileBackend")
+
+
+class FileBackend:
+    def __init__(self, filename: str | Path = None) -> None:
+        if isinstance(filename, str):
+            filename = Path(filename)
+
+        self._filename = filename
+        self._file = None
+        self._collection = None
+
+    def init(self, *args, **kwargs) -> None:
+        if self._collection:
+            raise ValueError("The collection is already initialized.")
+
+        self._collection = Collection.init(*args, **kwargs)
+        self._filename = self._collection.uuid
+        self._dump()
+
+    def branch(self, *args, **kwargs) -> None:
+        self._collection.branch(*args, **kwargs)
+        self._dump()
+
+    def explain(self):
+        return self._collection.explain()
+
+    def gantt(self):
+        return self._collection.gantt()
+
+    def __enter__(self: T) -> T:
+        if self._filename is not None:
+            with open(self._filename, "rb") as f:
+                self._collection = pickle.load(f)
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        if self._file is not None:
+            self._file.close()
+
+    def _dump(self):
+        if self._file is None:
+            self._file = open(self._filename, "wb")
+        pickle.dump(self._collection, self._file)
+
+
+def file(filename: str | Path = None) -> FileBackend:
+    return FileBackend(filename)

pcontract/data.py

@@ -93,6 +93,7 @@ def __init__(
     ) -> None:
         self.items: list[Branch] = items
         self.klass: Type[Branch] = klass
+        self.uuid: str = uuid.uuid4().hex
 
     def __repr__(self) -> str:
         return "<%s %s>" % (self.__class__.__name__, repr(self.items))