from __future__ import annotations

import typing
import datetime


from .. import operator, entities, cmdmgr, errors


@operator.operator_class(
    name="last",
    help="切换到前一个对话",
    usage='!last'
)
class LastOperator(operator.CommandOperator):

    async def execute(
        self,
        context: entities.ExecuteContext
    ) -> typing.AsyncGenerator[entities.CommandReturn, None]:
        
        if context.session.conversations:
            # 找到当前会话的上一个会话
            for index in range(len(context.session.conversations)-1, -1, -1):
                if context.session.conversations[index] == context.session.using_conversation:
                    if index == 0:
                        yield entities.CommandReturn(error=errors.CommandOperationError('已经是第一个对话了'))
                        return
                    else:
                        context.session.using_conversation = context.session.conversations[index-1]
                        time_str = context.session.using_conversation.create_time.strftime("%Y-%m-%d %H:%M:%S")

                        yield entities.CommandReturn(text=f"已切换到上一个对话: {index} {time_str}: {context.session.using_conversation.messages[0].readable_str()}")
                        return
        else:
            yield entities.CommandReturn(error=errors.CommandOperationError('当前没有对话'))