Add a few more JSON instances

[TristanCacqueray]

• part of Add missing ToJSON instances #347

[xsebek]

Wow, Generic is great! 👍

Please just change the description to "- part of #347" as I think this does not add all missing ToJSON instances.

My main interest is the World which has only a parser in Scenario but is missing a serializer.

[TristanCacqueray]

I think it's worth using Generic, however it seems to double, or maybe triple, the build time. Let me try adding instances for World.

[TristanCacqueray]

I guess the alternative to Generic would be to use Data.Aeson.TH, though I'm not familiar with it.

[xsebek]

This is a bit surprising since we have the FromJSONE instance above.

That one requires the entity map and also does not allow specifying robot ID nor some other fields like the log.

I am not sure what this ToJSON instance produces, but I would like it to match the FromJSONE.
Though if the generated instance is reasonable maybe it could be useful and we could align them later.

[TristanCacqueray]

To be honest, I have no idea, I just typed on the keyboard until GHC could link the binary :-)

[byorgey]

Note, when I made the FromJSONE instances I was just interested in putting in enough functionality to be able to describe robots in the ways that I wanted in scenario description files. But if there are fields that are still missing we can definitely add them.

[TristanCacqueray]

Here are the missing instances to be able to serialize the GameState:

instance FromJSONKey (V2 Int64)
instance ToJSONKey (V2 Int64)

instance FromJSON (Array Int Text)
instance ToJSON (Array Int Text)

instance FromJSON (W.World Int Entity)
instance ToJSON (W.World Int Entity)

instance FromJSON ScenarioCollection
instance ToJSON ScenarioCollection

instance FromJSON StdGen
instance ToJSON StdGen

[TristanCacqueray]

Oh well, build time are back to the 5min range (they went up to 15min in the previous checks)

[xsebek]

• V2 Int64 is just a pair, should be easy to serialize it as a two-element list (which we read in scenarios)
• Array Int Text is just an efficient Map in my mind
• World Int Entity this one requires a bit of work
  • you need to serialize chunks of the world and the entity palette (in the scenarios we only do one chunk)
  • we would need to express our WorldFunction as a data type and use that as the generator - but maybe we can pretend that it is always either test world 2 or one entity everywhere for now 🙂
• ScenarioCollection IMHO this should be in UI state, it is a bit annoying that a broken scenario does not let me run any test
• StdGen its current state can be shown, but it does not have a read instance 😕

[byorgey]

• ScenarioCollection IMHO this should be in UI state, it is a bit annoying that a broken scenario does not let me run any test

Agreed, let's move it.

[byorgey]

• StdGen its current state can be shown, but it does not have a read instance confused

Relevant: https://www.reddit.com/r/haskell/comments/ponow7/saving_and_loading_a_stdgen/hcxvrcp/?utm_source=reddit&utm_medium=web2x&context=3

https://discourse.haskell.org/t/save-and-restore-random-number-generator-freeze-thaw/4751/9

[TristanCacqueray]

Actually we may not want to serialize the StdGen. What matters is to be able to recreate the world, so we should record the initial seed, and use it to regenerate the same world, but how random number are produced could be random across reload.

[xsebek]

Actually we may not want to serialize the StdGen.

Counterexample: A player submits a bug report with a saved game and it depends on a random number somewhere.
If you want to randomize it again, you can just call random once more or we could ignore it at loading if the player wants to.

We already allow a custom seed, so keeping the current random generator in saves seems natural. 🤷‍♂️

[byorgey]

I was going to say the same thing re: saving the StdGen. I agree it's not strictly necessary as far as gameplay goes but it would help with reproducibility, and we might as well.

[TristanCacqueray]

@byorgey if that's ok with you, i'd like to merge this PR for #537

[byorgey]

Sounds good to me!