Sketching the implementation of the monad and selections

1 files changed, 93 insertions, 0 deletions

diff --git a/python/src/types/state.py b/python/src/types/state.py
new file mode 100644
index 0000000..ca048aa
--- /dev/null
+++ b/python/src/types/state.py
@@ -0,0 +1,93 @@
+from dataclasses import dataclass
+from pathlib import Path
+
+from .buffer import Buffer
+from .selection import Selection
+
+
+class StateChange:
+    def invert(self) -> "StateChange" | None:
+        return None
+
+
+@dataclass
+class SetCurrentSelection(StateChange):
+    old_selection: Selection
+    new_selection: Selection
+
+    def invert(self) -> "SetCurrentSelection":
+        return SetCurrentSelection(
+            old_selection=self.new_selection,
+            new_selection=self.old_selection,
+        )
+
+
+@dataclass
+class SetCurrentBuffer(StateChange):
+    old_buffer: Buffer
+    new_buffer: Buffer
+
+    def invert(self) -> "SetCurrentBuffer":
+        return SetCurrentBuffer(
+            old_buffer=self.new_buffer,
+            new_buffer=self.old_buffer,
+        )
+
+
+@dataclass
+class ModifyBuffer(StateChange):
+    buffer: Buffer
+    old_start: int
+    old_end: int
+    old_content: str
+    new_content: str
+
+    def invert(self) -> None:
+        # TODO: implement
+        return None
+
+
+@dataclass
+class CreateBuffer(StateChange):
+    buffer: Buffer
+    file: Path | None
+
+
+@dataclass
+class DeleteBuffer(StateChange):
+    buffer: Buffer
+
+
+@dataclass
+class EditorState:
+    current_buffer: Buffer
+    current_selection: Selection
+    buffer_to_file: dict[Buffer, Path | None]
+    history: list[StateChange]
+
+    def commit(self, change: StateChange) -> "EditorState":
+        match change:
+            case SetCurrentSelection(_, new_selection):
+                self.current_selection = new_selection
+            case SetCurrentBuffer(_, new_buffer):
+                self.current_buffer = new_buffer
+            case ModifyBuffer(buffer, old_start, old_end, _, new_content):
+                self.current_buffer.content = (
+                    self.current_buffer.content[:old_start]
+                    + new_content
+                    + self.current_buffer.content[old_end:]
+                )
+            case CreateBuffer(buffer, file):
+                self.buffer_to_file[buffer] = file
+            case DeleteBuffer(buffer):
+                del self.buffer_to_file[buffer]
+        self.history.append(change)
+        return self
+
+    def commit_changes(self, changes: list[StateChange]) -> "EditorState":
+        for change in changes:
+            self.commit(change)
+        return self
+
+
+Result = tuple[Selection, list[StateChange]]