/*
 * The notch — top-centre, floating, never reserving.
 *
 * The load-bearing rule in this file is that nothing here touches
 * `.os-area`. The desktop has one work-area rectangle now
 * (`src/work-area/index.ts`, carved out of the area by the dock),
 * and it stays useful only while few things carve it; a notch that
 * reserved height would be a second claimant on the top edge for
 * the sake of a pill a window may cover. It floats, and it gets out
 * of the way instead.
 *
 * Getting out of the way is also what the stacking order says: the
 * notch is on the desk, under the window layer, so a window reaching
 * the top edge covers the pill instead of the pill hanging over it.
 */

/*
 * Anchored to the SHELL, not the viewport. `.os-shell` starts below
 * the admin bar when the user keeps it, and at the viewport top when
 * they don't, so an absolutely-positioned notch lands correctly in
 * every admin-bar mode without knowing which one is on. Fixed
 * positioning put it under the bar, which paints above the shell.
 */
.os-notch {
	position: absolute;
	top: 0;
	left: 50%;
	transform: translateX( -50% );
	z-index: var( --os-z-notch, 60 );

	display: flex;
	align-items: center;
	gap: 7px;
	max-width: min( 420px, 60vw );
	height: 34px;
	padding: 0 14px;
	/*
	 * A hairline all the way round except the top, where the pill meets
	 * the screen edge and a line would draw a lid on it. Without the
	 * border the surface disappeared into the default wallpaper — Void
	 * on Void, with only the shadow separating them.
	 */
	border: 1px solid var( --os-ui-border-strong, rgba( 255, 251, 255, 0.22 ) );
	border-top: 0;
	/* Square at the top, round below — it reads as hanging from the
	   screen edge rather than floating near it. */
	border-radius: 0 0 15px 15px;
	background: var( --os-ui-surface-raised, rgba( 20, 18, 24, 0.92 ) );
	box-shadow: 0 2px 12px rgba( 0, 0, 0, 0.4 );
	color: var( --os-ui-fg, #fffbff );
	font-size: 13px;
	line-height: 1;
	cursor: pointer;
	/* `width` is not animated: the pill is sized by its content, and
	   transitioning an auto width does nothing. The message's own
	   max-width is what opens and closes. */
	transition: background 160ms ease, opacity 160ms ease,
		border-color 160ms ease, top 180ms ease,
		visibility 0s linear 160ms;
}

.os-notch:hover,
.os-notch:focus-visible {
	background: var( --os-ui-surface-elevated, rgba( 32, 29, 38, 0.96 ) );
	border-color: var( --os-ui-accent-dim, rgba( 242, 82, 252, 0.5 ) );
}

.os-notch:focus-visible {
	outline: 2px solid var( --os-ui-accent, #f252fc );
	outline-offset: -2px;
}

.os-notch__glyph {
	display: flex;
	flex: 0 0 auto;
	width: 18px;
	height: 18px;
}

.os-notch__glyph svg {
	width: 100%;
	height: 100%;
	fill: currentColor;
}

/*
 * The resting label. It yields to a message rather than sitting
 * beside one — the notch says one thing at a time, and "Site
 * assistant · Saving…" would be two.
 */
.os-notch__label {
	overflow: hidden;
	max-width: 160px;
	white-space: nowrap;
	text-overflow: ellipsis;
	transition: max-width 200ms ease, opacity 120ms ease;
}

.os-notch--speaking .os-notch__label {
	max-width: 0;
	opacity: 0;
}

/*
 * The message is always in the DOM (it is an `aria-live` region and
 * has to be, to be announced reliably); it is its WIDTH that opens.
 * `max-width` rather than `display` so there is something to animate
 * and so the live region is never removed from the accessibility tree.
 */
.os-notch__message {
	overflow: hidden;
	max-width: 0;
	white-space: nowrap;
	text-overflow: ellipsis;
	transition: max-width 200ms ease;
}

.os-notch--speaking .os-notch__message {
	max-width: 320px;
}

/*
 * Overview is the shell talking about itself — a zoomed-out view of
 * every window and desktop. A pill hanging over that view is chrome
 * on top of chrome, and it lands squarely on the desktop thumbnails.
 * Mio steps aside for the same reason and in the same way.
 *
 * `visibility` alongside the fade so it stops taking clicks on the way
 * out; a transparent button over a desktop thumbnail still swallows
 * the click that was meant to switch desktops.
 */
.os-shell:has( .os-area--overview ) .os-notch {
	opacity: 0;
	visibility: hidden;
	/* No delay on the way OUT — the pill must stop taking clicks the
	   moment it starts fading, not after. The delay in the base rule
	   is what holds it visible while it fades back IN. */
	transition-delay: 0s;
}

/* Solo mode is one window freed into a native OS window — the shell's
   own chrome has no place in it. */
body.os-solo .os-notch {
	display: none;
}

@media ( prefers-reduced-motion: reduce ) {
	.os-notch,
	.os-notch__label,
	.os-notch__message {
		transition-duration: 1ms;
	}
}

/*
 * Auto-hide admin bar.
 *
 * The shell starts at the viewport top in this mode (the bar is out of
 * flow), so the notch would be underneath the bar whenever it rolls
 * down. It steps down to sit below it instead, on the bar's own timing.
 */
body.os-active.os-admin-bar-dynamic:has( #wpadminbar:hover ) .os-notch,
body.os-active.os-admin-bar-dynamic:has( #wpadminbar:focus-within ) .os-notch,
body.os-active.os-admin-bar-dynamic:has( .os-notch:hover ) .os-notch,
body.os-active.os-admin-bar-dynamic:has( .os-notch:focus-visible ) .os-notch {
	/* The bar's measured edge (src/admin-bar-height.ts), Core's token
	   behind it — a host that made the bar taller moved this step too. */
	top: var( --os-admin-bar-height, var( --wp-admin--admin-bar--height, 32px ) );
}

/*
 * The hover bridge, and it is what makes the step stable.
 *
 * Hovering the notch is one of the things that rolls the bar down, and
 * the notch answers by moving 32px away from the pointer — which ends
 * the hover, retracts the bar, and brings the notch back up under the
 * pointer to start again. This claims the space the notch vacates, so
 * the pointer is still over the element after the step. Hovering a
 * pseudo-element counts as hovering its owner, the same trick the
 * bar's own reveal zone uses.
 *
 * Only in this mode: nothing moves in the other two, and a permanent
 * 32px hit area hanging off the notch would swallow clicks meant for
 * whatever is behind it.
 */
body.os-active.os-admin-bar-dynamic .os-notch::before {
	content: "";
	position: absolute;
	inset-inline: 0;
	inset-block-end: 100%;
	height: var( --os-admin-bar-height, var( --wp-admin--admin-bar--height, 32px ) );
}