var thunkDispatcherRef = {
    dispatch: function () {}
}

/**
 * The angular injection middleware allows our redux actions to return functions.
 *
 * The function will be executed with regular angular dependency injection, allowing
 * you to use angular services in Redux actions.
 *
 * The redux-thunk also operates on actions that return functions. We interact with
 * thunk by: 1) Adding a provider for the `dispatch` function used by thunk. 2) Carefully
 * checking the arguments, and if a `dispatch` argument exists, passing redux-thunk a
 * function that will correctly execute the angular function with the new dispatch funcion.
 */
function angularInjectionMiddleware($injector) {
    return store => next => action => {
        if (typeof action === 'function') {
            let injectionsRequired = $injector.annotate(action);
            if (injectionsRequired.indexOf('dispatch') > -1) {
                if (injectionsRequired.length === 1) {
                    // Only a dispatch action, pass directly on to redux-thunk.
                    next(action);
                } else {
                    // We need to run `next`, which will be with redux-thunk.
                    // This will give us the dispatch method, which we can then use in angular injection.
                    let actionForThunk = function (dispatch) {
                        thunkDispatcherRef.dispatch = dispatch;
                        return $injector.invoke(action);
                    }
                    return next(actionForThunk)
                }
            } else {
                // Angular action only, with no `dispatch` argument, so we can return a value and ignore thunk.
                return next($injector.invoke(action));
            }

        } else {
            return next(action);
        }
    }
}

angular.module('myApp').factory('dispatch', function () {
    return thunkDispatcherRef.dispatch;
});

angular.module('myApp').factory('angularInjectionMiddleware', angularInjectionMiddleware);

export default angularInjectionMiddleware;