feat: add local chat provider and CLI

src/javis/core/chat_service.py

@@ -0,0 +1,57 @@
+"""Chat orchestration without interface or provider-specific details."""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+
+from javis.memory.sqlite_store import ChatSession, SQLiteSessionStore
+from javis.providers.base import ChatMessage, LocalModelProvider
+
+
+class SessionProviderMismatchError(RuntimeError):
+    """The active provider cannot safely continue the stored session."""
+
+
+@dataclass(frozen=True, slots=True)
+class LoadedSession:
+    session: ChatSession
+    messages: list[ChatMessage]
+
+
+class ChatService:
+    def __init__(
+        self,
+        store: SQLiteSessionStore,
+        provider: LocalModelProvider,
+    ) -> None:
+        self.store = store
+        self.provider = provider
+
+    def new_session(self) -> ChatSession:
+        return self.store.create_session(self.provider.name, self.provider.model)
+
+    def list_sessions(self) -> list[ChatSession]:
+        return self.store.list_sessions()
+
+    def load_session(self, session_id: str) -> LoadedSession:
+        session = self.store.get_session(session_id)
+        if session.provider != self.provider.name or session.model != self.provider.model:
+            raise SessionProviderMismatchError(
+                "Die Sitzung verwendet "
+                f"{session.provider}/{session.model}, aktiv ist "
+                f"{self.provider.name}/{self.provider.model}."
+            )
+        return LoadedSession(session, self.store.get_messages(session_id))
+
+    def send(self, session_id: str, text: str) -> str:
+        normalized = text.strip()
+        if not normalized:
+            raise ValueError("Eine leere Nachricht wird nicht gesendet.")
+        loaded = self.load_session(session_id)
+        messages = [*loaded.messages, ChatMessage("user", normalized)]
+        response = self.provider.chat(messages)
+        self.store.append_exchange(session_id, normalized, response)
+        return response
+
+    def clear_session(self, session_id: str) -> None:
+        self.store.clear_messages(session_id)