# Contact messages

Visitor→admin messaging built into the site: a `{contact: Label}` directive
in article Markdown renders a button that opens a chat-style panel; messages
are stored in the kanta database and answered from the admin inbox on `/_a`.
Visitors are anonymous — a localStorage session token identifies their
thread — and everything realtime rides the two existing WebSockets; there is
no REST polling anywhere.

- `pagerite/messages.py` — the feature's core: the strict message renderer,
  thread store ops, wire payloads, both socket protocols and the
  `/_contact/files` upload route.
- `pagerite/data.py` — `Data.contact` (`ContactThread`/`ContactMessage`).
- `pagerite/tracking.py` — the sockets the protocol rides (see below).
- `pagerite/views.py` — the `{contact:}` directive (`_contact_tag`) and the
  on-demand bundle's asset config.
- `frontend/src/contact-main.js` + `ContactPanel.vue` — the visitor panel,
  imported on demand by `pagerite.js` on trigger clicks.
- `frontend/src/Composer.vue` + `richtext.js` — the shared composer and its
  DOM→Markdown serializer.
- `frontend/src/MessagesView.vue` — the admin inbox (the messages tab of
  `AnalyticsView.vue` on `/_a`).

## Trigger

A lone `{contact: Label}` line in article Markdown (the block-directive
machinery of `markdown.py`) renders
`<button class="contact-trigger">Label</button>` ("Contact us" when the
label is empty). `pagerite.js` click-delegates these buttons and lazy-loads
the contact bundle; the editor preview renders the same button inert, and
description/card mining resolves the tag to nothing. The label lives in the
chunk, so translated pages localize it like any other text. Feeds render the
tag as its literal source (no directive context).

## Visitor side

The token is `crypto.randomUUID()` in localStorage
(`pagerite-contact-token`), generated on first use; the server stores only
its blake3 hash as the thread key. Pages are shared/cached renders, so the
thread UI is entirely client-side. A per-browser "seen" timestamp
(`pagerite-contact-seen`) drives the unread dot on trigger buttons when an
admin reply arrives while the panel is closed.

The panel rides the public `/_ws` activity socket via a bridge in
`pagerite.js` (`register`/`send`, sharing its queue and reconnect pacing —
no extra connection). Frames **to** the server:

- `{token}` — register/resync; the current thread state is pushed back.
  `pagerite.js` re-sends this on every socket (re)connect, which is the
  resync mechanism (the socket idle-closes after 5 min and reconnects on
  activity).
- `{token, msg, pow, fr, name?, email?}` — append a message; `msg` is the
  Markdown-subset source, `pow` the solved proof-of-work (below), `fr` the
  page path it was sent from (stored for context). The **first** message
  of a thread must carry `name` and `email` introducing the visitor; the
  identity is stored on the thread and fixed from then on.

Frames **from** the server: `{type: "thread", id, created, unread, name,
email, messages: [{id, t, admin, html, page}]}` — a full thread snapshot
(replace/upsert by `id`); `{type: "pow", challenge, required}` — a fresh
single-use PoW challenge (`required` means the last message was rejected
for a missing/stale solution and should be re-sent once solved); or
`{type: "contact-error", detail}`.

### Proof of work (anti-spam)

Sends are gated by easypow (PBKDF2 challenges, ~5 s solving cost). The
server hands a fresh single-use challenge with every registration/resync
and after every accepted message; the panel solves it in the background
with the bundled solver module (served from the installed package at
`/_contact/easypow.js`, so client and validator versions always match),
typically finishing while the user is still writing. Each message burns
one solution — a send with a missing, stale or already-spent solution is
dropped and answered with a fresh `required` challenge, which the client
solves and retries once. Challenges are a per-connection local in the
`/_ws` handler (RAM only).

## Admin side

Admins watch the inbox as the **messages tab on `/_a`**, served by the
existing `/_api/ws/analytics` socket (admin-gated like all of `/_api`).
Analytics payloads keep their type-less snapshot shape; messaging frames
always carry a `type` field, and that is how the client tells them apart.
On connect the server sends `{type: "threads", threads: [...]}` (100 most
recently active); new messages and replies push single-thread updates.
Admin→server frames: `{type: "reply", id, text}` and `{type: "read", id}`.
Replies are authored with the SSO `remote-user` name and mark the thread
read; `unread` on a thread means its last message is the visitor's and
newer than the admin's last read.

## Message format and the XSS model

Bodies are a **Markdown subset** — emphasis, links, lists, code, plus
`/_f/` image and file references — serialized client-side from a
constrained contenteditable composer (plain-text paste only; formatting
via toolbar; uploads insert image/attachment-chip nodes).

**No user HTML is ever rendered or sanitized.** Sanitizing arbitrary HTML
is unwinnable, so the design never attempts it: the composer serializes to
*text*, and the server re-renders that text with a strict `MarkdownIt`
instance (`messages.py`): `html=False` (the page renderer's trusted-author
raw passthrough does not apply here), no plugins. Every byte of the stored
`html` is markdown-it output from the constrained grammar. markdown-it
also validates link protocols (`javascript:` & co. never become `href`s);
the link rule adds `rel="nofollow ugc noopener"` + `target="_blank"` (and
`download` + a chip class for `/_f/` attachment links); images are
restricted to `/_f/` store names, anything else collapses to its alt text.
Both panels inject this server-rendered HTML verbatim (`v-html`) — the one
injection point, fed only by the strict renderer.

## Uploads

`PUT /_contact/files/{name}` (public, like the messaging socket) stores
panel uploads in the content-addressed file store. Images (raster and
SVG) go through the usual AVIF/WebP/JPEG derivative pipeline and inline
in the message — SVGs included: the extension-less link negotiates
raster derivatives, and even an as-is-served `.svg` is script-inert
inside an `<img>`. Everything else (videos, archives, html, exe…) is
stored as an inert `{hash}.file` blob — the original extension is
dropped on disk, so the store can never be double-click-executed — and
linked as `/_f/{hash}/{original-name}`; the `.file` suffix exists only
on the filesystem and is rejected in URLs. Serving is strictly
separated: `/_f/{name}` serves media only (hash with or without
extension), `.orig.` originals stay blocked, and the filename-carrying
route serves only `{name}.file` blobs (never media, never by hash).
Every `/_f/` response carries `content-disposition: attachment` (no
filename needed — the URL's last segment names the download) and
`x-content-type-options: nosniff`, so a store file can never be
rendered or sniffed into something executable in the site's origin;
subresource fetches (`<img>`, `<video>`, favicons) ignore the
disposition, so inline media is unaffected. The chip anchors
additionally carry a `download` attribute. Uploads are deliberately
**not** PoW-gated (the transfer rate is the real cost there); the gates
are a session-shaped `x-contact-token` header, a 20 MB size cap, and a
pending-upload quota — 10 un-sent files per session, answered 429 (not
403, which could trip auth flows). Every upload stays *pending* per
session: a sent message strikes the files it references off the pending
set, and when the session's last socket closes the remaining pending
files are deleted from the store. Admin uploads from the same composer
go to the admin-gated `/_api/files` instead. Files left behind by a
server restart (the pending set is RAM-only) still linger — no GC.

## Storage

`Data.contact: dict[bytes, ContactThread]` in the kanta database, keyed by
the 12-byte blake3 hash of the session token (never the token itself). A
thread is `created`, `admin_read`, the visitor's self-entered
`name`/`email` (required with the first message, fixed afterwards) and
`messages: dict[str, ContactMessage]` keyed by a sortable timestamp-random
id (dict-keyed, so a save's database diff touches only the appended
message). Each message stores `t`, the Markdown source `md`, its strict
rendering `html`, `admin` ("" = visitor, else the SSO name) and `page`.
Appends are single transactions (`contact` / `contact:reply` /
`contact:read`).

## Limits and deliberate gaps (MVP)

- Message source ≤ 8000 chars; uploads ≤ 20 MB and ≤ 10 pending per
  session; payloads cap at 100 threads × last 200 messages.
- No thread moderation (delete/block), no orphan-upload GC for files
  orphaned by a server restart, and panel strings are English-only.