From a6c3d1f029333fc08fbe70c49b1846ea9a7ad674 Mon Sep 17 00:00:00 2001
From: Gergely Polonkai <gergely@polonkai.eu>
Date: Fri, 6 May 2022 14:11:28 +0200
Subject: [PATCH] [Draft] in-memory replica

---
 earthsnake/replica/__init__.py | 13 +++++-
 earthsnake/replica/memory.py   | 82 ++++++++++++++++++++++++++++++++++
 2 files changed, 94 insertions(+), 1 deletion(-)
 create mode 100644 earthsnake/replica/memory.py

diff --git a/earthsnake/replica/__init__.py b/earthsnake/replica/__init__.py
index 23bba6e..a36a689 100644
--- a/earthsnake/replica/__init__.py
+++ b/earthsnake/replica/__init__.py
@@ -1,6 +1,7 @@
 """Replica related things"""
 
 from abc import ABC, abstractmethod
+from enum import Enum, auto
 from typing import List, Optional
 
 from ..document import Document
@@ -10,6 +11,11 @@ from ..query import Query
 from ..share import Share
 
 
+class HistoryMode(Enum):
+    ALL = auto()
+    LATEST = auto()
+
+
 class IngestEvent:
     pass
 
@@ -44,7 +50,12 @@ class Replica(ABC):
         """Returns the maximum local index of all stored documents"""
 
     @abstractmethod
-    def get_docs_after_local_index(self) -> List[Document]:
+    def get_docs_after_local_index(
+        self,
+        history_mode: HistoryMode,
+        start_after: int,
+        limit: Optional[int] = None,
+    ) -> List[Document]:
         """Get all documents after a specific local index"""
 
     @abstractmethod
diff --git a/earthsnake/replica/memory.py b/earthsnake/replica/memory.py
new file mode 100644
index 0000000..86495bd
--- /dev/null
+++ b/earthsnake/replica/memory.py
@@ -0,0 +1,82 @@
+from typing import Dict, List, Tuple
+
+from ..document import Document
+from ..exc import ReplicaIsClosedError
+from ..identity import Identity
+from ..query import HistoryMode, Query
+from ..path import Path
+from ..share import Share
+from . import Replica
+
+
+class InMemoryReplica(Replica):
+    def __init__(self, share: Share, **driver_kwargs):
+        self.share = share
+        self._is_closed = False
+        self._max_local_index = -1
+        # Local Index <=> Document pairs
+        self._documents: List[Tuple[int, Document]] = {}
+
+    @property
+    def is_closed(self):
+        return self._is_closed
+
+    def close(self, erase: bool = False):
+        if erase:
+            self._local_index = -1
+            self._documents = []
+
+        self._is_closed = True
+
+    @property
+    def max_local_index(self) -> int:
+        return self._max_local_index
+
+    def _get_all_docs(self) -> List[Document]:
+        if self._is_closed:
+            raise ReplicaIsClosedError()
+
+        return [document for _, document in self._documents]
+
+    def _get_latest_docs(self) -> List[Document]:
+        if self._is_closed:
+            raise ReplicaIsClosedError()
+
+        docs_by_path: Dict[str, Document] = {}
+
+        for document in self._documents:
+            if (
+                str(document.path) not in docs_by_path
+                or docs_by_path[str(document.path)].timestamp <= document.timestamp
+            ):
+                docs_by_path[str(document.path)] = document
+
+        return list(docs_by_path.values())
+
+    def query_docs(self, query: Query) -> List[Document]:
+        if self._is_closed:
+            raise ReplicaIsClosedError()
+
+        if query.history_mode == HistoryMode.ALL:
+            docs = self._get_all_docs()
+        else:
+            docs = self._get_latest_docs()
+
+        docs_to_local_index = {
+            document: local_index for document, local_index in self.docs_by_local_index
+        }
+
+        return query({docs_to_local_index[document]: document for document in docs})
+
+    def upsert(self, new_document: Document) -> None:
+        if self._is_closed:
+            raise ReplicaIsClosedError()
+
+        self._local_index += 1
+
+        self._documents = [
+            (local_index, document)
+            for local_index, document in self._documents
+            if document.author != new_document.author or document.path != new_document.path
+        ]
+        self._documents.append((self._local_index, new_document))