1 files changed, 156 insertions, 0 deletions
diff --git a/src/components/LeftSidebar/ConversationsList/ConversationsListVirtual.vue b/src/components/LeftSidebar/ConversationsList/ConversationsListVirtual.vue
new file mode 100644
index 000000000..1a9e73cbd
--- /dev/null
+++ b/src/components/LeftSidebar/ConversationsList/ConversationsListVirtual.vue
@@ -0,0 +1,156 @@
+<!--
+  - @copyright Copyright (c) 2023 Grigorii Shartsev <me@shgk.me>
+  -
+  - @author Grigorii Shartsev <me@shgk.me>
+  -
+  - @license AGPL-3.0-or-later
+  -
+  - This program is free software: you can redistribute it and/or modify
+  - it under the terms of the GNU Affero General Public License as
+  - published by the Free Software Foundation, either version 3 of the
+  - License, or (at your option) any later version.
+  -
+  - This program is distributed in the hope that it will be useful,
+  - but WITHOUT ANY WARRANTY; without even the implied warranty of
+  - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+  - GNU Affero General Public License for more details.
+  -
+  - You should have received a copy of the GNU Affero General Public License
+  - along with this program. If not, see <http://www.gnu.org/licenses/>.
+  -->
+
+<template>
+	<RecycleScroller ref="scroller"
+		item-tag="ul"
+		:items="conversations"
+		:item-size="CONVERSATION_ITEM_SIZE"
+		key-field="token">
+		<template #default="{ item }">
+			<Conversation :item="item" />
+		</template>
+		<template #after>
+			<LoadingPlaceholder v-if="loading" type="conversations" />
+		</template>
+	</RecycleScroller>
+</template>
+
+<script>
+import { RecycleScroller } from 'vue-virtual-scroller'
+
+import Conversation from './Conversation.vue'
+import LoadingPlaceholder from '../../LoadingPlaceholder.vue'
+
+import 'vue-virtual-scroller/dist/vue-virtual-scroller.css'
+
+const CONVERSATION_ITEM_SIZE = 66
+
+export default {
+	name: 'ConversationsListVirtual',
+
+	components: {
+		LoadingPlaceholder,
+		Conversation,
+		RecycleScroller,
+	},
+
+	props: {
+		conversations: {
+			type: Array,
+			required: true,
+		},
+
+		loading: {
+			type: Boolean,
+			default: false,
+		},
+	},
+
+	setup() {
+		return {
+			CONVERSATION_ITEM_SIZE,
+		}
+	},
+
+	methods: {
+		/**
+		 * Get an index of the first fully visible conversation in viewport
+		 *
+		 * @public
+		 * @return {number}
+		 */
+		getFirstItemInViewportIndex() {
+			// (ceil to include partially) of (absolute number of items above viewport) + 1 (next item is in viewport) - 1 (index starts from 0)
+			return Math.ceil(this.$refs.scroller.$el.scrollTop / CONVERSATION_ITEM_SIZE)
+		},
+
+		/**
+		 * Get an index of the last fully visible conversation in viewport
+		 *
+		 * @public
+		 * @return {number}
+		 */
+		getLastItemInViewportIndex() {
+			// (floor to include only fully visible) of (absolute number of items below and in viewport) - 1 (index starts from 0)
+			return Math.floor((this.$refs.scroller.$el.scrollTop + this.$refs.scroller.$el.clientHeight) / CONVERSATION_ITEM_SIZE) - 1
+		},
+
+		/**
+		 * Scroll to conversation by index
+		 *
+		 * @public
+		 * @param {number} index - index of conversation to scroll to
+		 * @return {Promise<void>}
+		 */
+		async scrollToItem(index) {
+			const firstItemIndex = this.getFirstItemInViewportIndex()
+			const lastItemIndex = this.getLastItemInViewportIndex()
+
+			const viewportHeight = this.$refs.scroller.$el.clientHeight
+
+			/**
+			 * Scroll to a position with smooth scroll imitation
+			 *
+			 * @param {number} to - target position
+			 * @return {void}
+			 */
+			const doScroll = (to) => {
+				const ITEMS_TO_BORDER_AFTER_SCROLL = 1
+				const padding = ITEMS_TO_BORDER_AFTER_SCROLL * CONVERSATION_ITEM_SIZE
+				const from = this.$refs.scroller.$el.scrollTop
+				const direction = from < to ? 1 : -1
+
+				// If we are far from the target - instantly scroll to a close position
+				if (Math.abs(from - to) > viewportHeight) {
+					this.$refs.scroller.scrollToPosition(to - direction * viewportHeight)
+				}
+
+				// Scroll to the target with smooth scroll
+				this.$refs.scroller.$el.scrollTo({
+					top: to + padding * direction,
+					behavior: 'smooth',
+				})
+			}
+
+			if (index < firstItemIndex) { // Item is above
+				await doScroll(index * CONVERSATION_ITEM_SIZE)
+			} else if (index > lastItemIndex) { // Item is below
+				// Position of item + item's height and move to bottom
+				await doScroll((index + 1) * CONVERSATION_ITEM_SIZE - viewportHeight)
+			}
+		},
+
+		/**
+		 * Scroll to conversation by token
+		 *
+		 * @param {string} token - token of conversation to scroll to
+		 * @return {void}
+		 */
+		scrollToConversation(token) {
+			const index = this.conversations.findIndex(conversation => conversation.token === token)
+			if (index !== -1) {
+				this.scrollToItem(index)
+			}
+		},
+	},
+}
+</script>