# Guestbook Example

This capsule shows an intentionally shared feed. Guests and signed-in users can post. Everyone who can use the app can read the same entries.

## What It Shows

- An `entries` table with `body`, `authorId: userId()`, `authorName`, and `authorPicture`.
- A shared `entries` query ordered by newest first.
- A `sign` mutation that trims and bounds user input.
- Server-side authorship from `ctx.auth`, not from client-submitted fields.
- A Preact UI using `useAuth`, `createClient<typeof app>()`, and `<SignInWithGoogle />`.

## Server Pattern

Use shared feeds when every user can read the same rows:

```ts
queries: {
  entries: query(async (ctx) => ctx.db.entries.withIndex("by_creation").order("desc").take(50))
}
```

Still keep writes server-authoritative:

```ts
const author = ctx.auth.requireIdentity();
await ctx.db.entries.insert({
  body: trimmed,
  authorId: author.userId,
  authorName: author.displayName,
  authorPicture: author.picture ?? ""
});
```

Do not accept `authorId`, `authorName`, `authorPicture`, or other trusted metadata from the client.

Sharing comes from the query's lack of an owner filter. It does not use a shared guest ID or a fake global user. The `authorId` reference follows a guest to their account on sign-in. `authorName` and `authorPicture` are stored snapshots, so reference transfer does not replace them.

To allow only signed-in accounts to post, use `ctx.auth.requireSignedIn()` in the `sign` mutation. To require sign-in before reading or writing any app data, set `auth: { requireSignIn: true }` on the capsule.

## Run It

Run the checked-in example:

```sh
npx lakebed dev examples/guestbook
```

Open:

```txt
http://localhost:3000
```

To see shared updates from named local test identities, open:

```txt
http://localhost:3000/?lakebed_guest=alice
http://localhost:3000/?lakebed_guest=bob
```

Named overrides cannot upgrade to accounts. Use the default browser session with no override to test guest upgrades.

Then inspect state:

```sh
npx lakebed db dump --port 3000
npx lakebed logs --port 3000
```