From c18edd106b8f0fef560d354a08f971555410c44f Mon Sep 17 00:00:00 2001
From: Hazelnoot <acomputerdog@gmail.com>
Date: Wed, 28 May 2025 02:04:08 -0400
Subject: [PATCH] implement de-duplication for MkUrlPreview

---
 .../frontend/src/components/MkUrlPreview.vue  | 93 +++++++++++++++++--
 1 file changed, 87 insertions(+), 6 deletions(-)

diff --git a/packages/frontend/src/components/MkUrlPreview.vue b/packages/frontend/src/components/MkUrlPreview.vue
index 69a1540600..eb4a4efa33 100644
--- a/packages/frontend/src/components/MkUrlPreview.vue
+++ b/packages/frontend/src/components/MkUrlPreview.vue
@@ -4,7 +4,8 @@ SPDX-License-Identifier: AGPL-3.0-only
 -->
 
 <template>
-<template v-if="player.url && playerEnabled">
+<div v-if="groupLockout" style="display: none"></div>
+<template v-else-if="player.url && playerEnabled">
 	<div
 		:class="$style.player"
 		:style="player.width ? `padding: ${(player.height || 0) / player.width * 100}% 0 0` : `padding: ${(player.height || 0)}px 0 0`"
@@ -76,7 +77,7 @@ SPDX-License-Identifier: AGPL-3.0-only
 	</I18n>
 	<p v-else-if="linkAttribution" :class="$style.linkAttribution"><MkEllipsis/></p>
 
-	<template v-if="showActions">
+	<template v-if="showActions && !groupLockout">
 		<div v-if="tweetId" :class="$style.action">
 			<MkButton :small="true" inline @click="tweetExpanded = true">
 				<i class="ti ti-brand-x"></i> {{ i18n.ts.expandTweet }}
@@ -99,8 +100,53 @@ SPDX-License-Identifier: AGPL-3.0-only
 </div>
 </template>
 
+<script lang="ts">
+/**
+ * Links a group of previews to de-duplicate the results.
+ * Between all MkUrlPreview instances that share a group, each URL and Note are guaranteed to appear only once.
+ */
+export class PreviewGroup {
+	private readonly urls = new Map<string, number>();
+	private readonly noteIds = new Map<string, number>();
+
+	public claimUrl(url: string, componentUid: number): boolean {
+		return this.claim(this.urls, url, componentUid);
+	}
+
+	public claimNoteId(noteId: string, componentUid: number): boolean {
+		return this.claim(this.noteIds, noteId, componentUid);
+	}
+
+	private claim(group: Map<string, number>, key: string, uid: number): boolean {
+		const claim = group.get(key);
+
+		// Already claimed
+		if (claim != null && claim !== uid) {
+			return false;
+		}
+
+		group.set(key, uid);
+		return true;
+	}
+
+	public releaseUrl(url: string, componentUid: number): void {
+		this.release(this.urls, url, componentUid);
+	}
+
+	public releaseNoteId(noteId: string, componentUid: number): void {
+		this.release(this.noteIds, noteId, componentUid);
+	}
+
+	private release(group: Map<string, number>, key: string, uid: number): void {
+		if (group.get(key) === uid) {
+			group.delete(key);
+		}
+	}
+}
+</script>
+
 <script lang="ts" setup>
-import { defineAsyncComponent, onDeactivated, onUnmounted, ref } from 'vue';
+import { defineAsyncComponent, onDeactivated, onUnmounted, ref, getCurrentInstance } from 'vue';
 import { url as local } from '@@/js/config.js';
 import { versatileLang } from '@@/js/intl-const.js';
 import * as Misskey from 'misskey-js';
@@ -119,6 +165,11 @@ import DynamicNoteSimple from '@/components/DynamicNoteSimple.vue';
 import { $i } from '@/i';
 import { userPage } from '@/filters/user.js';
 
+const uid = getCurrentInstance()?.uid ?? -1;
+if (uid === -1) {
+	console.warn('[MkUrlPreview] Component has null instance??');
+}
+
 type SummalyResult = Awaited<ReturnType<typeof summaly>>;
 
 const props = withDefaults(defineProps<{
@@ -128,17 +179,24 @@ const props = withDefaults(defineProps<{
 	showAsQuote?: boolean;
 	showActions?: boolean;
 	skipNoteIds?: (string | undefined)[];
+	group?: PreviewGroup;
 }>(), {
 	detail: false,
 	compact: false,
 	showAsQuote: false,
 	showActions: true,
 	skipNoteIds: undefined,
+	group: undefined,
 });
 
+const emit = defineEmits<{
+	(event: 'loaded', preview: SummalyResult & { haveNoteLocally?: boolean } | null, note: Misskey.entities.Note | null): void;
+}>();
+
 const MOBILE_THRESHOLD = 500;
 const isMobile = ref(deviceKind === 'smartphone' || window.innerWidth <= MOBILE_THRESHOLD);
 
+const groupLockout = ref<boolean>(false);
 const hidePreview = ref<boolean>(false);
 const maybeRelativeUrl = maybeMakeRelative(props.url, local);
 const self = maybeRelativeUrl !== props.url;
@@ -170,6 +228,7 @@ const tweetHeight = ref(150);
 const unknownUrl = ref(false);
 const theNote = ref<Misskey.entities.Note | null>(null);
 const fetchingTheNote = ref(false);
+const preview = ref<SummalyResult & { haveNoteLocally?: boolean } | null>(null);
 
 onDeactivated(() => {
 	playerEnabled.value = false;
@@ -190,6 +249,9 @@ async function fetchNote() {
 			hidePreview.value = true;
 			return;
 		}
+		if (props.group && !props.group.claimNoteId(response['object'].id, uid)) {
+			groupLockout.value = true;
+		}
 		theNote.value = response['object'];
 	} catch (err) {
 		if (_DEV_) {
@@ -216,7 +278,16 @@ if (requestUrl.hostname === 'music.youtube.com' && requestUrl.pathname.match('^/
 
 requestUrl.hash = '';
 
-function refresh(withFetch = false) {
+const refresh = (withFetch = false) => {
+	// Release URL/noteID when refreshing, in case it changes.
+	// (Could happen since redirects are allowed.)
+	if (preview.value && props.group) {
+		props.group.releaseUrl(preview.value.url, uid);
+	}
+	if (theNote.value && props.group) {
+		props.group.releaseNoteId(theNote.value.id, uid);
+	}
+
 	const params = new URLSearchParams({
 		url: requestUrl.href,
 		lang: versatileLang,
@@ -243,6 +314,7 @@ function refresh(withFetch = false) {
 				userId: string,
 			}
 		} | null) => {
+			preview.value = info;
 			unknownUrl.value = info == null;
 			title.value = info?.title ?? null;
 			description.value = info?.description ?? null;
@@ -257,6 +329,7 @@ function refresh(withFetch = false) {
 			};
 			sensitive.value = info?.sensitive ?? false;
 			activityPub.value = info?.activityPub ?? null;
+			groupLockout.value = info != null && props.group != null && !props.group.claimUrl(info.url, uid);
 			linkAttribution.value = info?.linkAttribution ?? null;
 			if (linkAttribution.value) {
 				try {
@@ -275,8 +348,9 @@ function refresh(withFetch = false) {
 		})
 		.finally(() => {
 			fetching.value = null;
+			emit('loaded', preview.value, theNote.value);
 		});
-}
+};
 
 function adjustTweetHeight(message: MessageEvent) {
 	if (message.origin !== 'https://platform.twitter.com') return;
@@ -301,6 +375,13 @@ window.addEventListener('message', adjustTweetHeight);
 
 onUnmounted(() => {
 	window.removeEventListener('message', adjustTweetHeight);
+
+	if (preview.value && props.group) {
+		props.group.releaseUrl(preview.value.url, uid);
+	}
+	if (theNote.value && props.group) {
+		props.group.releaseNoteId(theNote.value.id, uid);
+	}
 });
 
 // Load initial data
@@ -388,7 +469,7 @@ refresh();
 .body {
 	position: relative;
 	box-sizing: border-box;
-	padding: 16px;
+	padding: 16px !important; // Unfortunately needed to win a specificity race with MkNoteSimple / SkNoteSimple
 }
 
 .header {