lbry-desktop/ui/js/reducers/availability.js

import * as types from 'constants/action_types';

const reducers = {};
const defaultState = {};

reducers[types.FETCH_AVAILABILITY_STARTED] = function(state, action) {
	const { uri } = action.data;
	const newFetching = Object.assign({}, state.fetching);

	newFetching[uri] = true;

	return Object.assign({}, state, {
		fetching: newFetching
	});
};

reducers[types.FETCH_AVAILABILITY_COMPLETED] = function(state, action) {
	const { uri, availability } = action.data;

	const newFetching = Object.assign({}, state.fetching);
	const newAvailabilityByUri = Object.assign({}, state.byUri);

	delete newFetching[uri];
	newAvailabilityByUri[uri] = availability;

	return Object.assign({}, state, {
		fetching: newFetching,
		byUri: newAvailabilityByUri
	});
};

export default function reducer(state = defaultState, action) {
	const handler = reducers[action.type];
	if (handler) return handler(state, action);
	return state;
}