[Feature Request] Add `possible_actions` and `cannot_dahai` to Mjai Protocol Messages

[Apricot-S]

In the final version of the Mjai protocol (protocol_version == 3), messages sent from the server to the client include possible_actions and cannot_dahai fields.
This field allows the server to explicitly communicate which actions are available to the client, including the set of possible calls, whether winning is allowed, and which tiles cannot be discarded due to kuikae restrictions or after declaring riichi.

Pros

• The client no longer needs to compute its own set of legal actions, reducing implementation complexity.

Cons

• The server must customize outgoing messages for each client.
• Messages sent to clients during a match must be separated from those stored as logs.

Reference

For reference, the corresponding implementation in the original mjai project can be found here:
https://github.com/gimite/mjai/blob/master/lib/mjai/game.rb

[smly]

Thank you for your valuable feedback! I plan to incorporate this request. Regarding the specifications that could lead to computational overhead, I will reconsider them in the v0.3.0 milestone.

[Apricot-S]

Note

オリジナルの mjai プロトコルとの互換性を重視するなら "possible_actions" には "dahai" を含めずに副露と和了のみ含める必要がありますが、互換性を気にしないのであれば "dahai" も含めた方がよいと思われます。

また、Env の文脈で "possible" という用語は "取りうるすべての" という意味らしいので、オリジナルとの互換性を維持する必要が無いのであれば "legal_actions" の方がより適切だと思われます。

参考: mjx-project/mjx#800

[Apricot-S]

cannot_dahai, possible_actions を含んだ mjai プロトコルの形式のドキュメントはこちらにあります。
https://github.com/gotodeploy/mjai-server/blob/master/docs/protocols.md