31:T61b,md`# Login with comment

⚠️ the V2 is here

The simplest way to securely discover the currently logged in user. Furthermore, the result generates a token you can externally verify for use in backend services. To authenticate, the user just needs to write a code in a publically visible comment.

The returned payload is a Firebase Auth user, signed in using a [custom token](https://firebase.google.com/docs/auth/admin/create-custom-tokens). Thus, the login persists across browser sessions. The host Firebase project is *"endpointserviceusers"*. If you only need to know the logged in user id you can verify these tokens without special access to *"endpointserviceusers"*. If you want to use the token to access **your own backend** Firebase functionality, you should fork this notebook and rebase onto your own Firebase projects (see CONFIG section). An example is done [here](https://observablehq.com/@endpointservices/endpoint-login-with-comment). Overally this is like an Oauth client bit without any params to configure! This should work across all notebook domains. Import with ~~~js import {viewof user, verifyIdToken} from '@endpointservices/login-with-comment' ~~~ Instanciate the login prompt with ~~~js viewof user ~~~ a minimal working example in a 3rd party notebook is [here](https://observablehq.com/@tdlgkjfhdljovtttqrzu/login-with-comment-example) `32:T1673,createLogin = () => { // When no-one is logged in we want don't want the cell to resolve, so we return a promise // We want that promise to be resolved next time we get a value let firstResolve; const updateResult = () => { const newValue = userFirebase.auth().currentUser; if (firstResolve) { firstResolve(newValue); } if (!newValue) { if (!firstResolve) userUi.value = new Promise((resolve) => (firstResolve = resolve)); else userUi.value = undefined; } else { userUi.value = newValue; } userUi.dispatchEvent( new CustomEvent("input", { bubbles: true, detail: { user: userUi.value || null } }) ); }; const userUi = html`${viewroutine(async function* () { let response; let err = ""; const actionWas = (action) => response && response.actions.includes(action); // On a new page refresh the currentUser is unkown and we have to listen to the auth state change to discover // the initial state. This article explains it well // https://medium.com/firebase-developers/why-is-my-currentuser-null-in-firebase-auth-4701791f74f0 if (!mutable authStateKnown) { let ready = null; const isReady = new Promise((resolve) => (ready = resolve)); userFirebase.auth().onAuthStateChanged(ready); await isReady; mutable authStateKnown = true; } await new Promise((r) => r()); // micro tick so userUi initializes while (true) { try { // update overall view state updateResult(); if (!userFirebase.auth().currentUser) { const loginUi = screen({ actions: ["login"] }); // We need to see if someone logs in via a side channel const unsubscribe = userFirebase.auth().onAuthStateChanged((user) => { if (user) loginUi.dispatchEvent(new Event("input", { bubbles: true })); }); response = yield* ask(loginUi); unsubscribe(); } else { const logoutUi = screen({ actions: ["logout"] }); // We need to see if someone logout ivia a side channel const unsubscribe = userFirebase.auth().onAuthStateChanged((user) => { if (!user) logoutUi.dispatchEvent(new Event("input", { bubbles: true })); }); response = yield* ask(logoutUi); unsubscribe(); } if (actionWas("logout")) { console.log("Logging out"); yield screen({ info: md`Logging out...` }); await userFirebase.auth().signOut(); } if (actionWas("login")) { console.log("login"); const privateCode = randomId(64); const publicCode = await hash(privateCode); yield screen({ info: md`Preparing...` }); await prepare(publicCode); let relmeauth = false; while (!userFirebase.auth().currentUser) { while (!actionWas("verify")) { console.log("prompt verify"); response = yield* ask( screen({ info: md`1. ${err}Add comment containing **${publicCode}** to this notebook using the cell burger menu to the left. 2. Click login to complete login.

\n⚠️ Logging in discloses your [Observable](https://observablehq.com/) username to the notebook author. ${actionWas("copy") ? "\ncopied to clipboard" : ""}`, actions: ["copy", "verify"], toggles: [ { code: "profile_relmeauth", label: html`[optional] scan for teams?`, value: relmeauth, caption: html`

how does scanning work?

${md`From your Observablehq profile URL we look for weblinks to team profile URLs, and if those profile URLs also weblink to your profile URL we consider you to have admin access for that team (see [relmeauth](https://observablehq.com/@endpointservices/auth#observable_features))`}

${style()}${['...', inner()]}

`\n}","pinned":true,"hidden":false,"mode":"ojs"},{"id":1245,"value":"screen ","pinned":true,"hidden":false,"mode":"ojs"},{"id":487,"value":"$35","pinned":false,"hidden":false,"mode":"ojs"},{"id":615,"value":"container(() => htl.html`

\n \n ${button({\n action: \"login\",\n label: \"Comment signin\",\n icon: chatIcon\n })}${button({\n action: \"copy\",\n label: \"Copy\",\n icon: copyIcon\n })}\n \n \n

write a comment containing code 'dasdasdasdas' in a comment
\n ⚠️ comment not found (try again?)

\n`)","pinned":true,"hidden":false,"mode":"ojs"},{"id":820,"value":"content = ({\n labels: {\n copy: \"Copy to clipboard\",\n login: \"Login with comment\",\n logout: () =>\n `Logout ${userFirebase\n .auth()\n .currentUser.uid.replace(\"observablehq|\", '')}`,\n verify: \"Login\"\n },\n icons: {\n copy: copyIcon,\n login: chatIcon\n }\n})","pinned":true,"hidden":false,"mode":"ojs"},{"id":1185,"value":"expandContent = (val) => typeof val === 'function' ? val() : val;","pinned":true,"hidden":false,"mode":"ojs"},{"id":814,"value":"viewof testScreen = screen({\n info: \"Please copy code\",\n actions: [\"login\", \"verify\"],\n toggles: [\n {\n code: \"profile_relmeauth\",\n label: html`[optional] scan for teams?`,\n value: true,\n caption: html`

how does scanning work?

\n ${md`From your Observablehq profile URL we look for weblinks to team profile URLs, and if those profile URLs also weblink to your profile URL we consider you to have admin access for that team. (related [relmeauth](https://observablehq.com/@endpointservices/auth#observable_features))`}\n

`\n }\n ]\n})","pinned":true,"hidden":false,"mode":"ojs"},{"id":850,"value":"testScreen","pinned":true,"hidden":false,"mode":"ojs"},{"id":29,"value":"screen = ({ info, actions = [], toggles = [] } = {}) =>\n container(\n () => view`

\n \n ${[\n \"actions\",\n actions.map(action =>\n button({\n action,\n label: expandContent(content.labels[action]),\n icon: content.icons[action]\n })\n )\n ]}\n \n${info ? html`

${info}

` : ''}\n${[\n '...',\n Object.fromEntries(\n toggles.map(toggle => {\n return [\n toggle.code,\n view`

${[\n '...',\n stopPropagation(\n Inputs.toggle({ label: toggle.label, value: toggle.value })\n )\n ]}

${toggle.caption}