@hexworks/cobalt-state
Version:
State machine utility for Cobalt.
54 lines • 2.6 kB
JavaScript
/* eslint-disable @typescript-eslint/ban-types */
import { safeParseAsync } from "@hexworks/cobalt-core";
import * as RTE from "fp-ts/ReaderTaskEither";
import { pipe } from "fp-ts/lib/function";
import { Map } from "immutable";
import { ThisIsABugError, UnknownEventError, UnknownStateError, } from ".";
import { StateTransitionError } from "./errors/StateTransitionError";
export const newStateMachine = (possibleStates) => {
const supportedStates = possibleStates.reduce((map, state) => map.set(state.name, state), Map());
const supportedEventTypes = possibleStates
.flatMap((state) => Object.keys(state.transitions))
.toSet();
const enter = (stateInstance) => {
const { state, data } = stateInstance;
const stateName = state.name;
const expectedState = supportedStates.get(stateName);
if (!expectedState || expectedState !== state) {
return RTE.left(new UnknownStateError(stateName));
}
return pipe(RTE.fromTaskEither(safeParseAsync(state.schema)(data)), RTE.chain(() => state.onEntry(data)), RTE.map((data) => ({
...stateInstance,
data,
})));
};
const dispatch = (stateInstance, event) => {
const { state, data } = stateInstance;
const stateName = state.name;
const expectedState = supportedStates.get(stateName);
const eventType = event.type;
if (expectedState && expectedState === state) {
const transitions = state.transitions[eventType];
if (transitions) {
const transition = transitions.find((t) => t.condition(data, event));
if (transition) {
return pipe(RTE.fromTaskEither(safeParseAsync(state.schema)(data)), RTE.chain(() => state.onExit(data)), RTE.chain((d) => transition.transitionTo(d, event)), RTE.chain((stateInstance) => pipe(stateInstance.state.onEntry(stateInstance.data), RTE.map((data) => ({
...stateInstance,
data,
})))), RTE.mapLeft((e) => new StateTransitionError(state.name, e)));
}
else {
return RTE.left(new ThisIsABugError(event, data));
}
}
else {
return RTE.left(new UnknownEventError(state.name, event.type));
}
}
else {
return RTE.left(new UnknownStateError(stateName));
}
};
return { supportedStates, supportedEventTypes, enter, dispatch };
};
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