Sentry Raven Middleware for Redux

import Raven from "raven-js";
import { createStore, applyMiddleware, combineReducers } from "redux";
import createRavenMiddleware from "raven-for-redux";

// Mock reducer for demonstration
const initialState = { count: 0, user: { id: 1, name: 'Guest' } };
function reducer(state = initialState, action) {
  switch (action.type) {
    case 'INCREMENT':
      return { ...state, count: state.count + 1 };
    case 'LOGIN':
      return { ...state, user: action.payload };
    default:
      return state;
  }
}

// Initialize Raven (or mock it for local development without a DSN)
const SENTRY_DSN = process.env.SENTRY_DSN ?? "https://examplePublicKey@o0.ingest.sentry.io/0";
// In a real application, you would always provide a valid DSN.
Raven.config(SENTRY_DSN).install();

const store = createStore(
    reducer,
    applyMiddleware(
        // Middlewares that intercept or emit actions should generally precede raven-for-redux.
        createRavenMiddleware(Raven, {
            breadcrumbMessageFromAction: action => action.type,
            breadcrumbDataFromAction: action => ({ actionPayload: action.payload }),
            stateContext: state => ({ user: state.user }),
            actionFilter: action => action.type !== 'IGNORE_THIS_ACTION'
        })
    )
);

// Dispatch some actions to generate breadcrumbs
store.dispatch({ type: 'INCREMENT' });
store.dispatch({ type: 'LOGIN', payload: { id: 123, name: 'Alice' } });
store.dispatch({ type: 'INCREMENT' });
store.dispatch({ type: 'IGNORE_THIS_ACTION' }); // This action will be filtered out

// Simulate an error to capture state and breadcrumbs
try {
  throw new Error("Simulated error during user interaction!");
} catch (e) {
  Raven.captureException(e);
}

console.log('Final State:', store.getState());
// In a real app, console.logs would typically be replaced by actual Sentry reports.