@fbltd/async/dist/bin/dependency/vanilla/reaction/reaction.js

Miscellaneous async utils

import { Dependency } from "../../dependency.js";
import { symAI } from "../../../constants.js";
import { runFnWithDepCollection } from "./utils.js";
export function reaction(fn, config) {
    let { result, deps } = runFnWithDepCollection(fn);
    const dep = new Dependency(result, config);
    async function subscribe() {
        const stream = { [symAI]: () => {
                let depsArray;
                let beforeValues;
                let obj = {
                    next: async () => {
                        depsArray = Array.from(deps);
                        beforeValues = depsArray.map(dep => dep.value_unsafe);
                        const promises = depsArray.map(dep => dep.next());
                        promises.push(dep.disposePromise);
                        await Promise.race(promises);
                        if (dep.done)
                            return { done: true };
                        let shouldRun = depsArray.some((dep, i) => dep.value_unsafe !== beforeValues[i]);
                        if (shouldRun) {
                            ({ result, deps } = runFnWithDepCollection(fn));
                            return { done: false, value: result };
                        }
                        else {
                            for (let dep of deps) {
                                if (dep.done)
                                    deps.delete(dep);
                            }
                            if (!deps.size)
                                return { done: true };
                            return obj.next();
                        }
                    }
                };
                return obj;
            } };
        for await (let value of stream) {
            dep.value = value;
        }
    }
    subscribe().then(() => dep.dispose());
    return dep;
}