You are given a simple chat room system.

The system has three global data structures:

aways: Dict[str, str] = {}
messages = []
tacos: Dict[str, int] = {}

Implement or explain the function:

def receive(name: str, msg: str):

The function is called every time a user sends a message.

For every received message, the system should first add the original user message to messages in the following format:

"name: msg"

The chat room also supports several bot behaviors.

AwayBot

The system keeps an aways dictionary.

The key is a user name, and the value is that user’s away message.

When any new message mentions a user who is currently away, the system should append an automatic bot response:

"AwayBot: <user> is away: <away_message>"

A user can set themselves as away by sending a message that starts with:

@away

For example:

receive("@alice", "@away having lunch")

This should mark @alice as away with the message:

"having lunch"

The system should also append:

"AwayBot: @alice is now away: having lunch"

MeetBot

A user can start a Google Meet by sending a message that starts with:

@meet

For example:

receive("@alice", "@meet @bob")

The system should append a bot message similar to:

"MeetBot: Google Meet with @alice, and @bob starting at google meet link"

After creating the meeting, both users should be marked as away.

The sender should get an away message like:

"@alice may be in a meeting right now"

The invited user should get an away message like:

"@bob may be in a meeting right now"

TacosBot

The chat room also supports a taco reward command.

A user can give tacos by sending a message that starts with:

@givetaco

The message format is:

@givetaco <number_of_tacos> <receiver>

For example:

receive("@alice", "@givetaco 3 @bob")

The system should add 3 tacos to @bob.

If @bob does not exist in the taco counter yet, initialize their taco count to 0 before adding the new tacos.

Then append a bot message similar to:

"TacosBot: @alice gave @bob 3 🌮s. @bob now has 3 🌮s"

Goal

Given this chat system, implement the receive function so that it correctly:

1. records the original user message,
2. triggers AwayBot when an away user is mentioned,
3. handles the @meet command,
4. handles the @givetaco command,
5. handles the @away command,
6. preserves the final message order in messages.

面试中可以先说整体流程：

每次收到消息，我会先保存原始消息。然后检查当前消息是否提到了 away 用户。接着判断消息是不是 bot command。不同 command 会更新不同的全局状态，并把对应 bot 回复追加到 messages 里。

实现时可以把命令按空格拆开：

parts = msg.split()

这样更容易判断：

parts[0] == "@away"
parts[0] == "@meet"
parts[0] == "@givetaco"

@away 后面的内容可以用空格重新拼起来。@meet 取第二个参数作为被邀请用户。@givetaco 取第二个参数作为数量，第三个参数作为接收人。

边界情况

这题可以简单补充几个边界情况：

如果 command 参数不完整，可以不触发 bot，或者返回错误提示。

如果 taco 数量不是数字，需要跳过或提示格式错误。

如果 mention 检测用 if user in msg，可能会误匹配。例如 @ann 可能匹配到 @anna。更稳的做法是把消息拆成单词后再判断。

总结

这道题的关键是维护三个状态：messages、aways、tacos。

messages 记录输出顺序。

aways 记录用户状态。

tacos 记录累计数量。

整体思路就是：保存原始消息，检查 away mention，解析 command，更新状态，追加 bot 回复。这个结构讲清楚，面试官就能看到候选人对代码逻辑和业务规则的理解。

csoahelp 做的就是这种场景里的实时辅助，题目刚读完就能给出完整思路，现场不用卡壳。

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