Add user configured context to actions

[krispya]

From @Ctrlmonster:

Any chance we could pass our own type into createActions (with the default just being world), similar to how directed lets you define what goes into the system args?

Example: I'd like to define action stores for levels and it'd be nice to be able to control the signature for calling the store. Right now it can only be world, which feels unnecessary restrictive given that I'm defining the function and am responsible for providing the args

// define a store that takes in world and extra args (in this case a level entity)
const LevelActions = createActions((world: World, level: Entity) => ({
  spawn() {
    const entity = world.spawn();
    entity.add(PartOfLevel(level));
    return entity;
  },
  destroy() {
    world.query(PartOfLevel(level)).forEach(e => e.destroy());
  }
}));


// ---
// somewhere else when using the store
const {spawn, destroy} = LevelActions(world, someLevelEntity);
...

[krispya]

From me: Maybe we can make the second arg a context.

const levelActions = createActions<{ level: Entity }>((world, context) => {
    spawn() {
        const entity = world.spawn();
        entity.add(PartOfLevel(context.level));
        return entity;
    }
})

const { spawn } = levelActions(world, { level })

const { spawn } = useActions(levelActions, { level })

[krispya]

I have bad news. TS doesn't allow for partial inference so an API like this where you explicitly type one generic for the context means that it can no longer infer the actions type. Annoying! Currying is too ugly but another way is to force strongly typing the context arg so it can get picked up by inference, ie:

// We have to strongly type it here or it is not usable. 
const levelActions = createActions((world, context: { level: Entity }) => {
    spawn() {
        const entity = world.spawn();
        entity.add(PartOfLevel(context.level));
        return entity;
    }
})

Otherwise, there has to be some kind of Zustand style middleware thing which I am not a big fan of.

Hopefully there is some movement on this in TS: microsoft/TypeScript#26242

[krispya]

Here is that PR: #78

[krispya]

Here is what it looks like with an additional function call to add the context. It is more explicit which is nice, but also pretty much exists just for TS which feels bad.

import { createActions, withContext } from 'koota'

const actions = createActions(
    withContext<{ count: number }>(
        (world, context) => ({
            addToCount: (amount: number) => {
                context.count += amount;
            },
            resetCount: () => {
                context.count = 0;
            },
        })
));