Add a memory buffer implementation

sinner/models/FrameMemoryBuffer.py

@@ -0,0 +1,32 @@
+from typing import Dict
+
+from sinner.models.NumberedFrame import NumberedFrame
+
+
+class FrameMemoryBuffer:
+    def __init__(self, source_name: str, target_name: str) -> None:
+        self.source_name = source_name
+        self.target_name = target_name
+        # In-memory storage structure, organized by source/target combinations
+        self.frames: Dict[int, NumberedFrame] = {}
+
+    def clean(self) -> None:
+        self.frames.clear()
+
+    def add_frame(self, frame: NumberedFrame) -> None:
+        """Adds a frame to the in-memory buffer."""
+        self.frames[frame.index] = frame
+
+    def get_frame(self, frame_index: int, return_previous: bool = True) -> NumberedFrame | None:
+        """Retrieves a frame by its ID from the in-memory buffer, if it exists."""
+        result = self.frames.get(frame_index)
+        if not result and return_previous:
+            # Find the nearest previous frame index
+            closest_prev_index = max((index for index in self.frames.keys() if index < frame_index), default=None)
+            if closest_prev_index is not None:
+                return self.frames[closest_prev_index]
+        return result
+
+    def has_frame(self, frame_index: int) -> bool:
+        """Checks if a frame exists in the in-memory buffer."""
+        return frame_index in self.frames