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|
package main
import "html/template"
// tmpl is the chat page: one page per room, no build step, no framework.
//
// One room per page is what keeps this simple. Each page opens its own SSE
// stream at /room/{id}/events and therefore has its own Last-Event-ID resume
// cursor, so the protocol below never has to name a room: every frame on a
// stream belongs to that stream's single timeline. Multiplexing all rooms onto
// one stream would give N timelines one scalar cursor and force the client to
// route frames — reintroducing exactly the bookkeeping this design removed.
// Switching rooms is a plain navigation, so the browser handles the teardown.
//
// Everything arrives over that stream as one of four operations — prepend,
// append, update, reset — and each one is a single DOM mutation at a position
// the client does not have to work out:
//
// prepend older history log.prepend(fragment)
// append new messages log.append(fragment)
// update a message changed byId.get(id).replaceWith(...)
// reset view is invalid log.replaceChildren()
//
// This works because the server writes history to the response *before* it
// starts forwarding live events, so the two can never interleave: every batch
// is either entirely above what the client holds or entirely below it, and the
// server knows which. Nothing here sorts, compares or scans for a position, so
// rendering a message costs the same whether the log holds ten rows or ten
// thousand.
//
// Rows are keyed by event_id (UNIQUE in hicli's schema, server-assigned, never
// reused), which is also what the SSE resume cursor carries. Edits and
// redactions are not rows: they arrive as fields of the message they affect,
// which is why they need no position and why there is no "remove" operation.
//
// The styling mirrors source-forge's directory listing rather than a typical
// chat UI: the colour tokens (see sharedStyle) are copied verbatim from
// source-forge/page.go so the two apps look like the same site, and each
// message is one tight listing row with a relative timestamp. No bubbles, no
// avatars.
var tmpl = template.Must(template.New("index").Parse(indexTemplate))
// roomsTmpl renders the landing page: the list of joined rooms.
//
// It is a plain page, not a live stream, and that is a deliberate constraint
// rather than a shortcut. Pushing room-list changes would mean the sync handler
// had to do work for every room in the account on every sync; as it stands it
// drops any room nobody has open after a single map lookup (see viewIfOpen).
// The list re-sorts on each load, which is all the freshness a page you glance
// at before clicking through needs.
var roomsTmpl = template.Must(template.New("rooms").Parse(roomsTemplate))
// sharedStyle is the common look for both pages: the colour tokens are copied
// verbatim from source-forge/page.go so the apps read as the same site, and
// both pages render their content as one tight listing with hairline rules.
const sharedStyle = `
:root {
--bg: #ffffff;
--fg: #1a1a1a;
--muted: #666;
--link: #0b5fff;
--border: #e2e2e2;
}
@media (prefers-color-scheme: dark) {
:root {
--bg: #1a1a1a;
--fg: #dddddd;
--muted: #999;
--link: #6ea8ff;
--border: #333;
}
}
* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
background: var(--bg); color: var(--fg);
font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
line-height: 1.5;
display: flex; flex-direction: column;
}
a { color: var(--link); text-decoration: none; }
a:hover { text-decoration: underline; }
header {
padding: 0.5em 1em; border-bottom: 1px solid var(--border);
background: var(--bg); display: flex; align-items: baseline; gap: 0.6em;
position: sticky; top: 0; z-index: 1;
}
header h1 { font-size: 1.2rem; font-weight: 600; margin: 0; }
header .who { color: var(--muted); font-size: 0.85em; }
header .status { margin-left: auto; font-size: 0.85em; color: var(--muted); }
header .status.live::before { content: "\25cf "; color: #2e7d32; }
header .status.down::before { content: "\25cf "; color: #c62828; }
/* The notification toggle is a plain text button: it is a setting, not an
action, so it should not look like the send button. */
header .notify {
font: inherit; font-size: 0.85em;
background: none; border: 0; padding: 0;
color: var(--muted); cursor: pointer;
}
header .notify:hover:not(:disabled) { text-decoration: underline; }
header .notify:disabled { cursor: default; opacity: 0.7; }
header .notify.on { color: var(--link); }
`
// humanAgoJS is the relative-timestamp helper, shared by both pages so a room's
// last activity is phrased exactly like a message's timestamp. Ported from
// source-forge's humanAgo (serve.go).
const humanAgoJS = `
function humanAgo(ms) {
const secs = Math.floor((Date.now() - ms) / 1000);
if (secs < 60) return "just now";
const units = [
["year", 365 * 24 * 3600],
["month", 30 * 24 * 3600],
["week", 7 * 24 * 3600],
["day", 24 * 3600],
["hour", 3600],
["minute", 60],
];
for (const [name, unitSecs] of units) {
const n = Math.floor(secs / unitSecs);
if (n >= 1) return n + " " + name + (n === 1 ? "" : "s") + " ago";
}
return "just now";
}
// fmtAbs is the absolute timestamp shown on hover.
function fmtAbs(ms) {
const d = new Date(ms);
const pad = (n) => String(n).padStart(2, "0");
return d.getFullYear() + "-" + pad(d.getMonth() + 1) + "-" + pad(d.getDate()) +
" " + pad(d.getHours()) + ":" + pad(d.getMinutes());
}
`
// notifyJS is the desktop-notification client, included by both pages.
//
// It deliberately contains no policy: which messages deserve a notification is
// decided by the account's Matrix push rules, evaluated server-side by hicli
// (see the notification type in serve.go). This code only renders what arrives.
//
// Nor does it coordinate with other tabs. Every tab opens /notifications, but
// the server sends each notification to exactly one of them, so there is no
// deduplication to do here — no SharedWorker, no BroadcastChannel, no lock.
// The one thing a tab decides for itself is whether the notification is
// pointless because the user is already looking at that very room.
//
// Permission is requested on a click rather than on load: browsers increasingly
// refuse requestPermission() outside a user gesture (Firefox since 72), and an
// unprompted permission dialog on page load is obnoxious anyway.
const notifyJS = `
const notifyToggle = document.getElementById("notify-toggle");
// Persisted so the choice survives navigation between rooms, which is a full
// page load in this app.
const NOTIFY_KEY = "webchat-notify";
function notifyEnabled() {
return localStorage.getItem(NOTIFY_KEY) === "on" && Notification.permission === "granted";
}
function renderNotifyToggle() {
if (!notifyToggle) return;
if (!("Notification" in window)) {
notifyToggle.textContent = "notifications unsupported";
notifyToggle.disabled = true;
return;
}
if (Notification.permission === "denied") {
notifyToggle.textContent = "notifications blocked";
notifyToggle.disabled = true;
return;
}
notifyToggle.textContent = notifyEnabled() ? "notifications on" : "notifications off";
notifyToggle.classList.toggle("on", notifyEnabled());
}
if (notifyToggle) {
notifyToggle.addEventListener("click", async () => {
if (notifyEnabled()) {
localStorage.setItem(NOTIFY_KEY, "off");
renderNotifyToggle();
return;
}
// Asking again when already granted is a no-op that resolves immediately,
// so this needs no permission check of its own.
const permission = await Notification.requestPermission();
localStorage.setItem(NOTIFY_KEY, permission === "granted" ? "on" : "off");
renderNotifyToggle();
if (permission === "granted") connectNotifications();
});
renderNotifyToggle();
}
// currentRoomID is set by the chat page; the room list leaves it null. It is
// used only to decide whether a click needs to navigate.
var currentRoomID = window.currentRoomID || null;
let notifySource = null;
function connectNotifications() {
if (notifySource || !("Notification" in window)) return;
// The stream is only opened once notifications are actually wanted. Opening
// it regardless would make every idle tab a candidate leader on the server
// and let notifications be routed to a tab that will never show them.
if (!notifyEnabled()) return;
notifySource = new EventSource("/notifications");
notifySource.addEventListener("notify", (e) => {
if (!notifyEnabled()) return;
const n = JSON.parse(e.data);
// No "am I showing this room?" check here on purpose: this tab is usually
// not the one displaying it. The server suppresses notifications for rooms
// some tab reports as visible, which is the only place that knows.
const title = n.highlight ? n.room_name + " — " + n.display : n.room_name;
const notification = new Notification(title, {
body: n.display + ": " + n.body,
// Collapses a burst from one room into a single notification rather than
// stacking one per message.
tag: n.room_id,
silent: !n.sound,
});
notification.addEventListener("click", () => {
window.focus();
if (n.room_id !== currentRoomID) window.location.href = n.path;
notification.close();
});
});
}
connectNotifications();
`
// roomsTemplate is the room list.
//
// Rooms arrive already sorted newest-activity-first (hicli's GetBySortTS), so
// the page does no ordering of its own. Timestamps are rendered client-side
// from the epoch millis, for the same reason the chat page does it: the server
// cannot know the viewer's timezone, and "3 hours ago" has to stay honest on a
// page left open.
const roomsTemplate = `<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>webchat · rooms</title>
<style>` + sharedStyle + `
#rooms { list-style: none; padding: 0; margin: 0; overflow-y: auto; flex: 1; }
#rooms li {
display: grid;
grid-template-columns: 1fr auto;
gap: 0 0.75em;
border-bottom: 1px solid var(--border);
}
/* The link fills the row, so the whole row is the click target. */
#rooms li a {
grid-column: 1 / -1;
display: grid;
grid-template-columns: subgrid;
padding: 0.3em 1em;
color: var(--fg);
}
#rooms li a:hover { background: var(--border); text-decoration: none; }
#rooms .name {
grid-column: 1;
font-weight: 600;
overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
#rooms .ago {
grid-column: 2;
color: var(--muted); font-size: 0.85em; white-space: nowrap;
}
#empty { padding: 1em; color: var(--muted); }
</style>
</head>
<body>
<header>
<h1>webchat</h1>
<span class="who">{{.UserID}}</span>
<button type="button" class="notify" id="notify-toggle" style="margin-left:auto"></button>
</header>
{{if .Rooms}}
<ul id="rooms">
{{range .Rooms}}
<li>
<a href="{{.Path}}">
<span class="name" title="{{.ID}}">{{.Name}}</span>
<span class="ago" data-ts="{{.Activity}}"></span>
</a>
</li>
{{end}}
</ul>
{{else}}
<div id="empty">No rooms yet — the initial sync may still be running. Reload in a moment.</div>
{{end}}
<script>` + humanAgoJS + `
for (const el of document.querySelectorAll("#rooms .ago")) {
const ts = Number(el.dataset.ts);
if (!ts) continue;
el.textContent = humanAgo(ts);
el.title = fmtAbs(ts);
}
` + notifyJS + `
</script>
</body>
</html>
`
const indexTemplate = `<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>webchat{{if .RoomName}} · {{.RoomName}}{{end}}</title>
<style>` + sharedStyle + `
/* The back link sits before the title, so the room name stays the heading. */
header .back { font-size: 0.9em; }
/* The message log, styled after source-forge's ul.listing: hairline
separators and a tight vertical rhythm.
Rows are a grid rather than inline text with a floated timestamp: with a
proportional font, nicks can only be aligned by giving them their own
column, and a float cannot do that. Long messages then wrap inside their
own column instead of running under the nick. */
/* The scroller holds both the message log and the pending-upload list, so
that pending rows sit below every real message without having to be
ordered among them.
Staying pinned to the bottom is done with scroll snapping rather than with
JavaScript. #latest is a zero-height marker below the messages carrying
scroll-snap-align: end, so "the bottom" is a snap position;
the spec then requires the container to re-snap to it whenever content is
added, moved or *resized* (css-scroll-snap §4.1.3), which is exactly the
set of events that used to need handling by hand — a new message, an image
finishing decoding, the composer growing under the scroller. Snapping is
"proximity" rather than "mandatory" so that it stops applying once the
user has scrolled away to read something; mandatory would drag them back.
align-content: end keeps a room with less content than viewport height
against the bottom, so a nearly-empty room does not render floating at the
top with the composer stranded below it.
Snapping only engages while the scroller is exactly at the snap position,
so a viewport left a pixel short simply will not follow new messages. That
is not papered over here; it is caught by #sentinel below, which reports
whether the bottom is actually visible after the fact and offers the way
back. The two together are what make the imprecision harmless.
NEVER set scroll-behavior: smooth on this element. Re-snapping honours it
(css-scroll-snap §4.1.3), and an animated scroll adjustment would still be
in flight when the intersection observer samples the result — turning the
check below into a race that reports a spurious "not at the bottom". */
#scroller {
flex: 1; overflow-y: auto;
scroll-snap-type: y proximity;
align-content: end;
}
/* Zero-height, so it takes no space and never shows a gap under the last
message. */
#latest { scroll-snap-align: end; height: 0; }
/* The observed element, deliberately separate from the snap target and last
in the scroller: it is visible exactly when the bottom edge of the newest
message is, which is the "is it entirely in view" question the banner
asks. Asking it with threshold 1.0 on the message itself would instead
wedge the banner open forever on any message taller than the viewport.
1px rather than 0: a zero-area target is well defined (an edge-adjacent
intersection counts, with ratio 1), but a real box removes any dependence
on that corner of the spec. */
#sentinel { height: 1px; }
/* The unread-message banner. Sits directly above the composer, where the eye
already is when typing, and is styled as a quieter variant of a message
row rather than as a notification: it is the message, just not in view
yet. The whole bar is the button, so the click target is the full width.
It appears only when the bottom is genuinely off screen, which means it
doubles as the recovery path when snapping fails to follow a new message
— the case that would otherwise silently lose the conversation. */
#newest {
display: flex; align-items: baseline; gap: 0.6em;
width: 100%; text-align: left;
font: inherit; font-size: 0.9rem;
padding: 0.35em 1em; cursor: pointer;
color: var(--fg); background: var(--border);
border: 0; border-top: 1px solid var(--border);
}
#newest:hover { filter: brightness(1.08); }
#newest .who { font-weight: 600; white-space: nowrap; }
#newest .body {
flex: 1; min-width: 0;
overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
color: var(--muted);
}
#newest .arrow { color: var(--link); font-weight: 600; }
#log {
list-style: none; padding: 0; margin: 0;
font-size: 0.95rem;
}
#log li {
display: grid;
/* The last column is a fixed width, not "auto": the ticker below rewrites
every timestamp once a minute, and "just now" -> "13 minutes ago" in an
auto column would resize the body column and rewrap every message in the
log under the reader. */
grid-template-columns: 9em 1fr 7.5em;
gap: 0 0.75em;
padding: 0.15em 1em;
border-bottom: 1px solid var(--border);
}
#log li .who {
grid-column: 1;
font-weight: 600; color: var(--fg);
text-align: right;
overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
/* Own messages are distinguished only by sender colour — no bubble. */
#log li.own .who { color: var(--link); }
#log li .body {
grid-column: 2;
min-width: 0; /* lets the column actually shrink */
white-space: pre-wrap;
overflow-wrap: anywhere;
}
#log li.error .body { color: var(--muted); font-style: italic; }
#log li .ago {
grid-column: 3;
color: var(--muted); font-size: 0.85em;
white-space: nowrap;
}
/* A redacted message keeps its text (we still have it cached) behind a
marker, rather than vanishing. */
#log li .redacted-marker {
color: var(--muted); font-style: italic;
margin-right: 0.4em;
}
#log li.redacted .body { color: var(--muted); }
/* Edits are sub-rows under the message they revise: the full new text with
the changed words marked, so the message reads as a whole rather than as a
diff fragment. */
#log li .edit {
display: block;
margin-top: 0.15em;
padding-left: 1em;
color: var(--muted);
text-indent: -1em; /* hanging indent, so wraps line up under the text */
}
#log li .edit::before { content: "\21b3\a0"; }
#log li .edit del {
text-decoration: line-through;
opacity: 0.7;
}
#log li .edit ins {
text-decoration: none;
color: var(--fg);
font-weight: 600;
}
#log li .edit .edit-ago { font-size: 0.85em; margin-left: 0.4em; }
/* On narrow screens a 9em nick column eats the message, so stack instead. */
@media (max-width: 40em) {
#log li { grid-template-columns: 1fr 7.5em; }
#log li .who { grid-column: 1; text-align: left; }
#log li .ago { grid-column: 2; }
#log li .body { grid-column: 1 / -1; }
}
/* Attachments. Images are capped so a screenshot does not fill the viewport;
click opens the original.
The height cap is expressed as a *width* limit derived from the aspect
ratio (--ar, set inline from the event's own w/h) rather than as
max-height. Both would look identical once loaded, but only this reserves
the right amount of space beforehand: the browser sizes the placeholder
from the width and the aspect ratio, so a max-height that turned out to be
the binding constraint would leave the row too tall and shrink it on
decode, shifting everything below. Capping width alone means the computed
height is already <= 24em and nothing moves when the pixels arrive. */
#log li .body img {
display: block; margin: 0.25em 0;
max-width: min(100%, 40em, calc(24em * var(--ar, 1)));
width: auto; height: auto;
border: 1px solid var(--border); border-radius: 4px;
background: var(--border); /* placeholder tint while loading */
}
#log li .body video {
display: block; margin: 0.25em 0;
max-width: min(100%, 40em, calc(24em * var(--ar, 1)));
height: auto;
}
#log li .body audio {
display: block; margin: 0.25em 0;
max-width: min(100%, 40em);
}
#log li .body .file {
display: inline-block; margin: 0.25em 0;
padding: 0.2em 0.5em;
border: 1px solid var(--border); border-radius: 4px;
}
#log li .body .file::before { content: "\1f4c4\a0"; }
#log li .body .size { color: var(--muted); font-size: 0.85em; }
/* Pending uploads live in their own list below the log, so they are always
visually last without needing to be positioned among real messages. */
#pending {
list-style: none; padding: 0; margin: 0;
font-size: 0.95rem;
}
#pending li {
display: grid;
grid-template-columns: 9em 1fr 7.5em;
gap: 0 0.75em;
padding: 0.15em 1em;
border-bottom: 1px solid var(--border);
opacity: 0.6;
}
#pending li .who {
grid-column: 1; font-weight: 600; text-align: right;
overflow: hidden; text-overflow: ellipsis; white-space: nowrap;
}
#pending li .body { grid-column: 2; font-style: italic; color: var(--muted); }
#pending li .ago { grid-column: 3; color: var(--muted); font-size: 0.85em; }
#pending li.error .body { color: #c62828; }
@media (max-width: 40em) {
#pending li { grid-template-columns: 1fr 7.5em; }
#pending li .who { grid-column: 1; text-align: left; }
#pending li .ago { grid-column: 2; }
#pending li .body { grid-column: 1 / -1; }
}
#typing {
padding: 0 1em; font-size: 0.85em; color: var(--muted); min-height: 1.4em;
}
form {
display: flex; gap: 0.5em; padding: 0.6em 1em;
border-top: 1px solid var(--border);
}
#text {
flex: 1; padding: 0.4em 0.5em; color: var(--fg); background: var(--bg);
border: 1px solid var(--border); border-radius: 4px;
font: inherit; font-size: 0.95rem; resize: none; max-height: 8em;
}
#send {
font: inherit; font-size: 0.95rem; padding: 0.4em 1em; cursor: pointer;
color: var(--bg); background: var(--link);
border: 0; border-radius: 4px;
}
#send:hover { opacity: 0.9; }
#send:disabled { opacity: 0.5; cursor: default; }
</style>
</head>
<body>
<header>
<a class="back" href="/" title="all rooms">←</a>
<h1>{{if .RoomName}}{{.RoomName}}{{else}}webchat{{end}}</h1>
<span class="who" title="{{.RoomID}}">{{.UserID}}</span>
<span class="status" id="status">connecting…</span>
<button type="button" class="notify" id="notify-toggle"></button>
</header>
<div id="scroller">
<ul id="log"></ul>
<ul id="pending"></ul>
<div id="latest"></div>
<div id="sentinel"></div>
</div>
<div id="typing"></div>
<button type="button" id="newest" hidden>
<span class="who"></span>
<span class="body"></span>
<span class="arrow">↓</span>
</button>
<form id="composer">
<textarea id="text" rows="1" placeholder="Message…" autocomplete="off" autofocus></textarea>
<button type="submit" id="send">Send</button>
</form>
<script>` + humanAgoJS + `
// Every endpoint this page talks to is scoped to one room, so all of them hang
// off this prefix. Rendering it server-side keeps the frontend ignorant of the
// routing scheme — and of how a room ID has to be escaped in a URL.
const base = "{{.Base}}";
// Read by notifyJS, to suppress notifications for the room already on screen.
window.currentRoomID = "{{.RoomID}}";
// The backlog the server rendered into this page, oldest first, plus the
// timeline boundaries it covers. Rendering it here rather than streaming it is
// what keeps the scroll position sane — see handleIndex in serve.go.
const backlogMsgs = {{.Backlog}};
const backlogNewest = "{{.Newest}}";
const backlogOldest = "{{.Oldest}}";
const backlogHave = {{.Have}};
const scroller = document.getElementById("scroller");
const sentinel = document.getElementById("sentinel");
const newestEl = document.getElementById("newest");
const log = document.getElementById("log");
const pending = document.getElementById("pending");
const statusEl = document.getElementById("status");
const typingEl = document.getElementById("typing");
const form = document.getElementById("composer");
const text = document.getElementById("text");
const sendBtn = document.getElementById("send");
// event_id -> {li, ago, ts}. event_id is UNIQUE in hicli's schema, so this
// doubles as the dedup key. The .ago node is cached here rather than re-queried,
// because the ticker below touches every row once a minute and a querySelector
// per row does not scale to a large backlog.
const rendered = new Map();
function humanSize(bytes) {
if (!bytes) return "";
const units = ["B", "kiB", "MiB", "GiB"];
let n = bytes, i = 0;
while (n >= 1024 && i < units.length - 1) { n /= 1024; i++; }
return (i === 0 ? n : n.toFixed(1)) + " " + units[i];
}
// renderMedia appends the element for an attachment, picking by msgtype.
//
// Note on laziness: loading="lazy" only applies to <img> (and <iframe>). The
// equivalent for audio/video is preload="none", which fetches nothing at all
// until the user hits play — strictly better than lazy for our purposes.
function renderMedia(body, msg) {
const m = msg.media;
switch (msg.msgtype) {
case "m.image": {
const img = document.createElement("img");
img.src = m.url;
img.alt = m.filename || msg.body || "image";
img.loading = "lazy";
img.decoding = "async";
// Intrinsic dimensions are what make lazy loading behave: without them
// every unloaded image is zero-height and the scroll position jumps as
// images arrive. --ar additionally lets the CSS express the height cap as
// a width limit, so the space reserved before the image loads is the
// space it ends up taking — see the img rule in the stylesheet.
if (m.w) img.width = m.w;
if (m.h) img.height = m.h;
if (m.w && m.h) img.style.setProperty("--ar", m.w + " / " + m.h);
const link = document.createElement("a");
link.href = m.url;
link.target = "_blank";
link.rel = "noreferrer";
link.appendChild(img);
body.appendChild(link);
return;
}
case "m.video": {
const v = document.createElement("video");
v.src = m.url;
v.controls = true;
v.preload = "none";
if (m.w) v.width = m.w;
if (m.h) v.height = m.h;
if (m.w && m.h) v.style.setProperty("--ar", m.w + " / " + m.h);
body.appendChild(v);
return;
}
case "m.audio": {
const a = document.createElement("audio");
a.src = m.url;
a.controls = true;
a.preload = "none";
body.appendChild(a);
return;
}
default: {
const link = document.createElement("a");
link.className = "file";
link.href = m.url;
link.download = m.filename || "";
link.textContent = m.filename || msg.body || "file";
body.appendChild(link);
if (m.size) {
const size = document.createElement("span");
size.className = "size";
size.textContent = " " + humanSize(m.size);
body.appendChild(size);
}
}
}
}
// diffWords produces a word-level diff between two strings, as a list of
// {type, text} where type is "same", "del" or "ins".
//
// Standard LCS over whitespace-separated tokens. Messages are short, so the
// O(n*m) table is fine; it is capped anyway to keep a pathological paste from
// freezing the tab.
function diffWords(before, after) {
// Whitespace is kept as its own token, so the original spacing (including
// newlines) survives the round trip and reassembling the "same" and "ins"
// parts reproduces the new text exactly.
const a = before.split(/(\s+)/).filter((s) => s !== "");
const b = after.split(/(\s+)/).filter((s) => s !== "");
const MAX = 400;
if (a.length > MAX || b.length > MAX) {
// Too long to diff meaningfully; just show the replacement.
return [{ type: "ins", text: after }];
}
// lcs[i][j] = length of the longest common subsequence of a[i:] and b[j:].
const lcs = Array.from({ length: a.length + 1 }, () => new Uint16Array(b.length + 1));
for (let i = a.length - 1; i >= 0; i--) {
for (let j = b.length - 1; j >= 0; j--) {
lcs[i][j] = a[i] === b[j]
? lcs[i + 1][j + 1] + 1
: Math.max(lcs[i + 1][j], lcs[i][j + 1]);
}
}
const out = [];
const push = (type, tok) => {
const last = out[out.length - 1];
// Merge runs so we emit one element per changed phrase, not per word. The
// tokens already carry their own whitespace, so they concatenate directly.
if (last && last.type === type) last.text += tok;
else out.push({ type: type, text: tok });
};
let i = 0, j = 0;
while (i < a.length && j < b.length) {
if (a[i] === b[j]) { push("same", a[i]); i++; j++; }
else if (lcs[i + 1][j] >= lcs[i][j + 1]) { push("del", a[i]); i++; }
else { push("ins", b[j]); j++; }
}
while (i < a.length) { push("del", a[i]); i++; }
while (j < b.length) { push("ins", b[j]); j++; }
return out;
}
// renderEdit builds one edit sub-row: the whole message as it now reads, with
// the words that changed since the previous version marked up.
function renderEdit(prevBody, e) {
const row = document.createElement("span");
row.className = "edit";
for (const part of diffWords(prevBody, e.body)) {
let node;
if (part.type === "same") node = document.createTextNode(part.text);
else if (part.type === "del") { node = document.createElement("del"); node.textContent = part.text; }
else { node = document.createElement("ins"); node.textContent = part.text; }
row.appendChild(node);
}
const ago = document.createElement("span");
ago.className = "edit-ago";
ago.textContent = "edited " + humanAgo(e.timestamp);
ago.title = fmtAbs(e.timestamp);
row.appendChild(ago);
return row;
}
// mk builds the <li> for one message. It is the only place a row is
// constructed: prepend, append and update all go through it, so a message looks
// the same however it arrived.
function mk(msg) {
const el = document.createElement("li");
el.className = [
msg.is_own ? "own" : "",
msg.error ? "error" : "",
msg.redacted ? "redacted" : "",
].filter((c) => c).join(" ");
const who = document.createElement("span");
who.className = "who";
who.textContent = msg.is_own ? "you" : msg.display;
who.title = msg.sender;
el.appendChild(who);
const body = document.createElement("span");
body.className = "body";
if (msg.redacted) {
const marker = document.createElement("span");
marker.className = "redacted-marker";
marker.textContent = "(redacted)";
body.appendChild(marker);
}
// Text first, then the attachment: an image message's body is just its
// filename, which the element itself already shows, so skip it there.
if (msg.body && !(msg.media && msg.msgtype !== "m.text")) {
body.appendChild(document.createTextNode(msg.body)); // never interpret HTML
}
if (msg.error) body.title = msg.error;
// A redacted message keeps no attachment: the content is gone server-side.
if (msg.media && !msg.redacted) renderMedia(body, msg);
// Edits are shown against the version before them, so each sub-row reads as
// the full message with just that revision's changes marked.
if (msg.edits && !msg.redacted) {
let prev = msg.body;
for (const e of msg.edits) {
body.appendChild(renderEdit(prev, e));
prev = e.body;
}
}
el.appendChild(body);
const ago = document.createElement("span");
ago.className = "ago";
ago.textContent = humanAgo(msg.timestamp);
ago.title = fmtAbs(msg.timestamp);
el.appendChild(ago);
rendered.set(msg.event_id, { li: el, ago: ago, ts: msg.timestamp });
return el;
}
// build turns a batch of messages into one fragment, so the whole batch costs a
// single DOM insertion.
//
// A message we already hold is updated in place and left out of the fragment,
// rather than added a second time. That makes append and prepend idempotent,
// which is what lets the server deliver the same message twice without any
// coordination: the only way to see a duplicate is to be told about one, and
// event_id is unique per event.
function build(msgs) {
const frag = document.createDocumentFragment();
for (const msg of msgs) {
const existing = rendered.get(msg.event_id);
if (existing) {
existing.li.replaceWith(mk(msg));
continue;
}
frag.appendChild(mk(msg));
}
return frag;
}
// applyUpdate re-renders messages in place, keyed by event_id.
//
// An unknown id is dropped, never inserted: the server sends updates for
// whatever changed, which may well be outside the window this client is
// showing, and an update carries no position to insert at.
function applyUpdate(msgs) {
for (const msg of msgs) {
const existing = rendered.get(msg.event_id);
if (!existing) continue;
existing.li.replaceWith(mk(msg));
}
}
// ---------------------------------------------------------------------------
// the unread-message banner
// ---------------------------------------------------------------------------
// Following new messages is the stylesheet's job (see #scroller), but snapping
// only engages while the scroller is exactly at the snap position, so a
// viewport a pixel short of the bottom silently stops following. Rather than
// try to make that precise — measuring scroll offsets by hand is what made the
// old code jump — this watches the *result* and offers a way back when the
// newest message is not on screen, whatever the reason.
//
// Watching beats calculating here because the question is literally "is this
// on screen", which the browser can answer exactly and arithmetic over
// scrollHeight can only approximate.
//
// The banner needs *two* conditions, not one, and conflating them is the
// obvious mistake: showing it whenever the bottom is off screen means reading
// history always carries a banner advertising a message that was read long
// ago. So it appears only when both hold:
//
// an unseen message exists AND the bottom is not in view
//
// newestMsg carries the first. It is set only by messages that arrive over the
// stream — never by the backlog the page was rendered with, which by
// definition was already on screen — and cleared again the moment the bottom
// comes into view, which is what "seen" means here. A null newestMsg makes
// showBanner a no-op, so the position half can fire freely without ever
// producing a banner for something already read.
let newestMsg = null;
// bottomWatch reports whether the very bottom of the log is in view.
//
// It is re-registered on every append rather than left observing, and that is
// load-bearing: an observer reports *transitions*, so one that already knows
// the bottom is off screen stays silent when yet another message arrives off
// screen — exactly when the banner needs updating. Re-registering resets the
// remembered state (a fresh registration starts at threshold index -1, which
// no computed index can equal), which guarantees a callback carrying the
// current answer.
//
// The callback runs after layout, and therefore after snapping has had its
// turn, so it sees the settled result rather than the moment of insertion.
const bottomWatch = new IntersectionObserver((entries) => {
const entry = entries[entries.length - 1];
if (entry.isIntersecting) {
// Reaching the bottom is what marks the newest message as seen, so the
// banner does not come back if the user scrolls up again afterwards.
newestMsg = null;
hideBanner();
} else {
showBanner();
}
}, { root: scroller, threshold: 0 });
// Between appends the registration stays live, so scrolling back down to the
// bottom hides the banner on its own — no scroll handler anywhere.
function watchBottom() {
bottomWatch.unobserve(sentinel); // observe() alone would be a no-op
bottomWatch.observe(sentinel);
}
// bannerText is the one-line preview. Attachments have no useful body (for an
// image it is just the filename), so they get a placeholder, mirroring what
// desktop notifications show — see notificationBody in serve.go.
function bannerText(msg) {
if (msg.media && msg.msgtype !== "m.text") {
switch (msg.msgtype) {
case "m.image": return "[image]";
case "m.video": return "[video]";
case "m.audio": return "[audio]";
default: return "[file]";
}
}
return msg.body || "";
}
function showBanner() {
if (!newestMsg) return;
newestEl.querySelector(".who").textContent =
newestMsg.is_own ? "you" : newestMsg.display;
newestEl.querySelector(".body").textContent = bannerText(newestMsg);
newestEl.hidden = false;
}
function hideBanner() {
newestEl.hidden = true;
}
// Clicking anywhere on the banner returns to the bottom. Landing exactly at
// the bottom is also what re-arms snapping, so following resumes from here.
//
// The message counts as seen from the click, not from the scroll that follows:
// acting on the banner is the acknowledgement. Waiting for the observer to
// confirm arrival would leave it unseen if the scroll came up short, and the
// banner would then reappear for a message the reader has just been taken to.
newestEl.addEventListener("click", () => {
newestMsg = null;
scroller.scrollTop = scroller.scrollHeight;
hideBanner();
});
// reset throws the log away, for when the server tells us our view can no
// longer be reconciled (hicli cleared the room's timeline, or we missed a live
// event). The stream then re-sends history from scratch.
//
// didReset is latched so a later reconnect does not re-offer the backlog the
// page was rendered with: those rows are gone from the DOM, and claiming to
// still hold them would leave a hole. After a reset the stream is the only
// source of history, exactly as it was before the page embedded any.
let didReset = false;
function reset() {
log.replaceChildren();
rendered.clear();
didReset = true;
// The message the banner was advertising is no longer in the log.
newestMsg = null;
hideBanner();
}
// Keep the relative timestamps honest on a long-lived page.
setInterval(() => {
for (const entry of rendered.values()) {
entry.ago.textContent = humanAgo(entry.ts);
}
}, 60000);
// SSE with auto-reconnect. EventSource retries on its own and echoes back the
// last id: it saw as Last-Event-ID — an event ID, which the server re-resolves
// against the current timeline — so there is no manual re-sync on reconnect.
//
// Four message operations, each exactly one DOM mutation. The server always
// knows whether a batch belongs above or below what we hold, so nothing here
// sorts, compares or searches for a position.
// tabID identifies this tab's event stream to the server, so it can report
// whether the room is on screen. Only has to be unique among live streams, and
// deliberately not persisted: a reloaded tab is a new stream.
const tabID = Math.random().toString(36).slice(2) + Date.now().toString(36);
// Tell the server whether this tab is actually showing the room, so it can skip
// notifying about a conversation being read. The server decides this because
// the notification is delivered to a single tab that is usually a different one
// — see the notify handling in serve.go.
//
// sendBeacon on hide: a plain fetch can be cancelled when the page is being
// backgrounded or closed, which is exactly when this matters most.
function reportVisibility() {
const visible = document.visibilityState === "visible";
const body = JSON.stringify({ tab: tabID, visible: visible });
if (!visible && navigator.sendBeacon) {
navigator.sendBeacon(base + "/visibility", new Blob([body], { type: "application/json" }));
return;
}
fetch(base + "/visibility", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: body,
keepalive: true,
}).catch(() => {});
}
document.addEventListener("visibilitychange", reportVisibility);
function connect() {
// Visibility is passed on connect as well as reported later, so a tab opened
// in the background never briefly counts as being on screen.
const params = new URLSearchParams({
tab: tabID,
visible: document.visibilityState === "visible" ? "1" : "0",
});
// Tell the server what the page already rendered, so it neither replays it
// nor skips past it: resume forward from the newest row, and continue
// backwards from the oldest if the page got less than a full backlog.
//
// These are query parameters because EventSource sends Last-Event-ID only on
// a *re*connect — on the first connect there is no header to carry a cursor
// the server never issued. On later reconnects the header is newer than
// these and takes precedence server-side. They are cleared after a reset,
// which throws away the rendered backlog they describe.
if (!didReset) {
if (backlogNewest) params.set("since", backlogNewest);
if (backlogOldest) {
params.set("before", backlogOldest);
params.set("have", String(backlogHave));
}
}
const es = new EventSource(base + "/events?" + params);
es.onopen = () => {
statusEl.textContent = "live";
statusEl.className = "status live";
};
es.onerror = () => {
statusEl.textContent = "reconnecting…";
statusEl.className = "status down";
};
// Older history, walking backwards. Arrives newest-chunk-first, so each
// batch goes above the last.
//
// No scroll handling here, deliberately. Rows are inserted above the
// viewport, and the log is never empty by the time these arrive (the page
// ships with its backlog), so the scroller is scrolled away from its origin
// and CSS scroll anchoring holds the visible content still on its own. The
// code that used to adjust scrollTop by the height difference was double
// compensating: the browser had already made the same adjustment.
es.addEventListener("prepend", (e) => {
const msgs = JSON.parse(e.data).messages;
if (!msgs.length) return;
log.prepend(build(msgs));
});
// New messages, and gap replay after a reconnect. Always oldest-first and
// always newer than everything we hold.
//
// No scroll handling: #latest is a snap position at the bottom of the
// scroller, so adding content below re-snaps to it when the user is at the
// bottom and leaves them alone when they have scrolled away. All this does
// is ask, afterwards, whether the newest message actually ended up on
// screen — and show the banner when it did not.
//
// Note there is no special case for our own messages: one you just sent
// arrives here like any other, so sending while reading history leaves you
// where you are and offers the banner rather than yanking you to the bottom.
es.addEventListener("append", (e) => {
const msgs = JSON.parse(e.data).messages;
if (!msgs.length) return;
log.append(build(msgs));
newestMsg = msgs[msgs.length - 1];
watchBottom();
});
// A message changed: edited, redacted, or finally decrypted.
es.addEventListener("update", (e) => {
applyUpdate(JSON.parse(e.data).messages);
});
// Our view can no longer be reconciled; history follows on this same stream.
es.addEventListener("reset", () => {
reset();
});
es.addEventListener("typing", (e) => {
const users = JSON.parse(e.data).users || [];
typingEl.textContent = users.length
? users.join(", ") + (users.length === 1 ? " is" : " are") + " typing…"
: "";
});
}
form.addEventListener("submit", async (e) => {
e.preventDefault();
const body = text.value.trim();
if (!body) return;
sendBtn.disabled = true;
text.value = "";
text.style.height = "auto";
try {
const res = await fetch(base + "/send", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ text: body }),
});
if (!res.ok) {
text.value = body; // put it back so nothing is lost
alert("send failed: " + (await res.text()));
}
} catch (err) {
text.value = body;
alert("send failed: " + err);
} finally {
sendBtn.disabled = false;
text.focus();
notifyTyping(false);
}
});
// Enter sends, Shift+Enter inserts a newline.
text.addEventListener("keydown", (e) => {
if (e.key === "Enter" && !e.shiftKey) {
e.preventDefault();
form.requestSubmit();
}
});
// Grow the textarea with its content, up to the CSS max-height.
text.addEventListener("input", () => {
text.style.height = "auto";
text.style.height = Math.min(text.scrollHeight, 128) + "px";
});
// Throttled typing notifications.
let typingSent = 0;
function notifyTyping(on) {
const now = Date.now();
if (on && now - typingSent < 4000) return;
typingSent = on ? now : 0;
fetch(base + "/typing", {
method: "POST",
headers: { "Content-Type": "application/json" },
body: JSON.stringify({ typing: on }),
}).catch(() => {});
}
text.addEventListener("input", () => notifyTyping(text.value.length > 0));
// ---------------------------------------------------------------------------
// paste-to-send images
// ---------------------------------------------------------------------------
// The homeserver's m.upload.size. Oversized pastes are shrunk to fit rather
// than rejected — see fitToLimit.
const uploadLimit = {{.UploadLimit}};
// Downscaling happens here rather than on the server because the browser has
// already decoded the image in order to offer it as a paste, and because
// attachment encryption is length-preserving: once encrypted, the server cannot
// shrink anything without decrypting and re-encrypting.
//
// An image that already fits is uploaded byte-for-byte untouched, so the common
// case (a screenshot) stays lossless PNG. Only images that would otherwise be
// rejected outright get re-encoded.
async function fitToLimit(file, bitmap) {
if (file.size <= uploadLimit) {
return { blob: file, type: file.type, w: bitmap.width, h: bitmap.height };
}
// JPEG size is not a predictable function of quality or scale, so this
// converges by measurement instead of arithmetic: shrink, re-encode, check,
// repeat. Bounded attempts, because a pathological input should fail loudly
// rather than spin.
let scale = Math.sqrt(uploadLimit / file.size);
let quality = 0.9;
for (let attempt = 0; attempt < 6; attempt++) {
const w = Math.max(1, Math.round(bitmap.width * scale));
const h = Math.max(1, Math.round(bitmap.height * scale));
const canvas = document.createElement("canvas");
canvas.width = w;
canvas.height = h;
const ctx = canvas.getContext("2d");
// JPEG has no alpha: without this, transparent regions turn black. Fill
// with the page background so a transparent screenshot still looks right.
ctx.fillStyle = getComputedStyle(document.body).backgroundColor || "#fff";
ctx.fillRect(0, 0, w, h);
ctx.drawImage(bitmap, 0, 0, w, h);
const blob = await new Promise((res) => canvas.toBlob(res, "image/jpeg", quality));
if (!blob) throw new Error("could not re-encode image");
if (blob.size <= uploadLimit) {
return { blob: blob, type: "image/jpeg", w: w, h: h };
}
// Overshot: back off on both axes and try again.
scale *= 0.8;
quality = Math.max(0.4, quality - 0.1);
}
throw new Error("image is too large to send");
}
// Pending rows live in their own list below the log, so they are always visually
// last without needing a position among real messages. They are keyed separately
// too: the sent event comes back with a server-assigned event_id that cannot be
// predicted here, so the placeholder is removed rather than updated in place.
function addPendingRow(label) {
const li = document.createElement("li");
const who = document.createElement("span");
who.className = "who";
who.textContent = "you";
const bodyEl = document.createElement("span");
bodyEl.className = "body";
bodyEl.textContent = label;
const ago = document.createElement("span");
ago.className = "ago";
ago.textContent = "sending…";
li.append(who, bodyEl, ago);
pending.appendChild(li);
return { li: li, body: bodyEl, ago: ago };
}
async function uploadImage(file) {
const row = addPendingRow("uploading image…");
try {
const bitmap = await createImageBitmap(file);
const fitted = await fitToLimit(file, bitmap);
bitmap.close();
const name = file.name ||
("pasted-" + new Date().toISOString().replace(/[:.]/g, "-") +
(fitted.type === "image/png" ? ".png" : ".jpg"));
const params = new URLSearchParams({
w: fitted.w, h: fitted.h, filename: name,
});
const res = await fetch(base + "/upload?" + params, {
method: "POST",
headers: { "Content-Type": fitted.type },
body: fitted.blob,
});
if (!res.ok) throw new Error(await res.text());
// The message itself arrives over SSE like any other, so the placeholder
// just goes away.
row.li.remove();
} catch (err) {
row.li.classList.add("error");
row.body.textContent = "upload failed: " + err.message;
row.ago.textContent = "failed";
}
}
// Render the embedded backlog before connecting, so the page is complete at
// first paint and the stream has nothing to catch up on in the common case.
//
// The one explicit scroll in the app. Scroll snapping cannot do this: a snap
// position is only re-snapped to once the container *is* snapped to it, and a
// freshly loaded page sits at scrollTop 0. This puts it at the bottom, and
// snapping keeps it there from then on.
if (backlogMsgs.length) {
log.append(build(backlogMsgs));
scroller.scrollTop = scroller.scrollHeight;
}
// Start watching regardless of whether there was a backlog, so the banner is
// correct from the first message in an empty room too. The initial callback
// fires whether or not the bottom is visible, which is what establishes the
// starting state rather than assuming it.
//
// Note this deliberately leaves newestMsg null: the backlog was on the page
// before it was ever displayed, so none of it is unseen. Were it set here, a
// room whose last message is taller than the viewport would greet the reader
// with a banner announcing a message they are already looking at.
watchBottom();
text.addEventListener("paste", (e) => {
const files = [];
for (const item of e.clipboardData.items) {
if (item.kind === "file") {
const file = item.getAsFile();
if (file && file.type.startsWith("image/")) files.push(file);
}
}
if (files.length === 0) return; // plain text paste: leave it alone
e.preventDefault();
for (const file of files) uploadImage(file);
});
connect();
` + notifyJS + `
</script>
</body>
</html>
`
|