优化目录结构

domain.py

@@ -0,0 +1,67 @@
+from datetime import datetime
+from typing import Annotated, Literal
+
+from pydantic import BaseModel, ConfigDict, Field, model_validator
+
+
+class ToolFunctionCall(BaseModel):
+    name: str
+    arguments: str
+
+
+class ToolCall(BaseModel):
+    id: str
+    type: Literal["function"] = "function"
+    function: ToolFunctionCall
+
+
+class UserMessage(BaseModel):
+    role: Literal["user"] = "user"
+    content: str
+    created_at: datetime
+
+
+class AssistantMessage(BaseModel):
+    role: Literal["assistant"] = "assistant"
+    content: str | None = None
+    tool_calls: list[ToolCall] = Field(default_factory=list)
+    created_at: datetime
+
+
+class ToolMessage(BaseModel):
+    role: Literal["tool"] = "tool"
+    content: str
+    tool_call_id: str
+    name: str
+    is_error: bool = False
+    created_at: datetime
+
+
+Message = Annotated[
+    UserMessage | AssistantMessage | ToolMessage,
+    Field(discriminator="role"),
+]
+
+
+class Session(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+
+    session_id: str
+    system_prompt: str
+    created_at: datetime
+    updated_at: datetime
+    messages: list[Message] = Field(default_factory=list)
+
+    @model_validator(mode="before")
+    @classmethod
+    def add_timestamp_to_legacy_messages(cls, data: object) -> object:
+        if not isinstance(data, dict):
+            return data
+
+        fallback = data.get("created_at")
+        messages = data.get("messages")
+        if fallback is not None and isinstance(messages, list):
+            for message in messages:
+                if isinstance(message, dict):
+                    message.setdefault("created_at", fallback)
+        return data