refactor(frontend): use* 関数の格納場所のフォルダ名を composables に変更 (#16004)

* refactor(frontend): use* 関数の格納場所を正式名称（composables）に変更

* migrate

* move useLoading

9 files changed, 967 insertions, 0 deletions

diff --git a/packages/frontend/src/composables/use-chart-tooltip.ts b/packages/frontend/src/composables/use-chart-tooltip.ts
new file mode 100644
index 0000000000..bba64fc6ee
--- /dev/null
+++ b/packages/frontend/src/composables/use-chart-tooltip.ts
@@ -0,0 +1,63 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { onUnmounted, onDeactivated, ref } from 'vue';
+import * as os from '@/os.js';
+import MkChartTooltip from '@/components/MkChartTooltip.vue';
+
+export function useChartTooltip(opts: { position: 'top' | 'middle' } = { position: 'top' }) {
+	const tooltipShowing = ref(false);
+	const tooltipX = ref(0);
+	const tooltipY = ref(0);
+	const tooltipTitle = ref<string | null>(null);
+	const tooltipSeries = ref<{
+		backgroundColor: string;
+		borderColor: string;
+		text: string;
+	}[] | null>(null);
+	const { dispose: disposeTooltipComponent } = os.popup(MkChartTooltip, {
+		showing: tooltipShowing,
+		x: tooltipX,
+		y: tooltipY,
+		title: tooltipTitle,
+		series: tooltipSeries,
+	}, {});
+
+	onUnmounted(() => {
+		disposeTooltipComponent();
+	});
+
+	onDeactivated(() => {
+		tooltipShowing.value = false;
+	});
+
+	function handler(context) {
+		if (context.tooltip.opacity === 0) {
+			tooltipShowing.value = false;
+			return;
+		}
+
+		tooltipTitle.value = context.tooltip.title[0];
+		tooltipSeries.value = context.tooltip.body.map((b, i) => ({
+			backgroundColor: context.tooltip.labelColors[i].backgroundColor,
+			borderColor: context.tooltip.labelColors[i].borderColor,
+			text: b.lines[0],
+		}));
+
+		const rect = context.chart.canvas.getBoundingClientRect();
+
+		tooltipShowing.value = true;
+		tooltipX.value = rect.left + window.scrollX + context.tooltip.caretX;
+		if (opts.position === 'top') {
+			tooltipY.value = rect.top + window.scrollY;
+		} else if (opts.position === 'middle') {
+			tooltipY.value = rect.top + window.scrollY + context.tooltip.caretY;
+		}
+	}
+
+	return {
+		handler,
+	};
+}
diff --git a/packages/frontend/src/composables/use-form.ts b/packages/frontend/src/composables/use-form.ts
new file mode 100644
index 0000000000..1c93557413
--- /dev/null
+++ b/packages/frontend/src/composables/use-form.ts
@@ -0,0 +1,57 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { computed, reactive, watch } from 'vue';
+import type { Reactive } from 'vue';
+import { deepEqual } from '@/utility/deep-equal';
+
+function copy<T>(v: T): T {
+	return JSON.parse(JSON.stringify(v));
+}
+
+function unwrapReactive<T>(v: Reactive<T>): T {
+	return JSON.parse(JSON.stringify(v));
+}
+
+export function useForm<T extends Record<string, any>>(initialState: T, save: (newState: T) => Promise<void>) {
+	const currentState = reactive<T>(copy(initialState));
+	const previousState = reactive<T>(copy(initialState));
+
+	const modifiedStates = reactive<Record<keyof T, boolean>>({} as any);
+	for (const key in currentState) {
+		modifiedStates[key] = false;
+	}
+	const modified = computed(() => Object.values(modifiedStates).some(v => v));
+	const modifiedCount = computed(() => Object.values(modifiedStates).filter(v => v).length);
+
+	watch([currentState, previousState], () => {
+		for (const key in modifiedStates) {
+			modifiedStates[key] = !deepEqual(currentState[key], previousState[key]);
+		}
+	}, { deep: true });
+
+	async function _save() {
+		await save(unwrapReactive(currentState));
+		for (const key in currentState) {
+			previousState[key] = copy(currentState[key]);
+		}
+	}
+
+	function discard() {
+		for (const key in currentState) {
+			currentState[key] = copy(previousState[key]);
+		}
+	}
+
+	return {
+		state: currentState,
+		savedState: previousState,
+		modifiedStates,
+		modified,
+		modifiedCount,
+		save: _save,
+		discard,
+	};
+}
diff --git a/packages/frontend/src/composables/use-leave-guard.ts b/packages/frontend/src/composables/use-leave-guard.ts
new file mode 100644
index 0000000000..395c12a756
--- /dev/null
+++ b/packages/frontend/src/composables/use-leave-guard.ts
@@ -0,0 +1,50 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import type { Ref } from 'vue';
+
+export function useLeaveGuard(enabled: Ref<boolean>) {
+	/* TODO
+	const setLeaveGuard = inject('setLeaveGuard');
+
+	if (setLeaveGuard) {
+		setLeaveGuard(async () => {
+			if (!enabled.value) return false;
+
+			const { canceled } = await os.confirm({
+				type: 'warning',
+				text: i18n.ts.leaveConfirm,
+			});
+
+			return canceled;
+		});
+	} else {
+		onBeforeRouteLeave(async (to, from) => {
+			if (!enabled.value) return true;
+
+			const { canceled } = await os.confirm({
+				type: 'warning',
+				text: i18n.ts.leaveConfirm,
+			});
+
+			return !canceled;
+		});
+	}
+	*/
+
+	/*
+	function onBeforeLeave(ev: BeforeUnloadEvent) {
+		if (enabled.value) {
+			ev.preventDefault();
+			ev.returnValue = '';
+		}
+	}
+
+	window.addEventListener('beforeunload', onBeforeLeave);
+	onUnmounted(() => {
+		window.removeEventListener('beforeunload', onBeforeLeave);
+	});
+	*/
+}
diff --git a/packages/frontend/src/composables/use-loading.ts b/packages/frontend/src/composables/use-loading.ts
new file mode 100644
index 0000000000..6c6ff6ae0d
--- /dev/null
+++ b/packages/frontend/src/composables/use-loading.ts
@@ -0,0 +1,52 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { computed, h, ref } from 'vue';
+import MkLoading from '@/components/global/MkLoading.vue';
+
+export const useLoading = (props?: {
+	static?: boolean;
+	inline?: boolean;
+	colored?: boolean;
+	mini?: boolean;
+	em?: boolean;
+}) => {
+	const showingCnt = ref(0);
+
+	const show = () => {
+		showingCnt.value++;
+	};
+
+	const close = (force?: boolean) => {
+		if (force) {
+			showingCnt.value = 0;
+		} else {
+			showingCnt.value = Math.max(0, showingCnt.value - 1);
+		}
+	};
+
+	const scope = <T>(fn: () => T) => {
+		show();
+
+		const result = fn();
+		if (result instanceof Promise) {
+			return result.finally(() => close());
+		} else {
+			close();
+			return result;
+		}
+	};
+
+	const showing = computed(() => showingCnt.value > 0);
+	const component = computed(() => showing.value ? h(MkLoading, props) : null);
+
+	return {
+		show,
+		close,
+		scope,
+		component,
+		showing,
+	};
+};
diff --git a/packages/frontend/src/composables/use-mutation-observer.ts b/packages/frontend/src/composables/use-mutation-observer.ts
new file mode 100644
index 0000000000..7b774022dc
--- /dev/null
+++ b/packages/frontend/src/composables/use-mutation-observer.ts
@@ -0,0 +1,21 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { onUnmounted, watch } from 'vue';
+import type { Ref } from 'vue';
+
+export function useMutationObserver(targetNodeRef: Ref<HTMLElement | null | undefined>, options: MutationObserverInit, callback: MutationCallback): void {
+	const observer = new MutationObserver(callback);
+
+	watch(targetNodeRef, (targetNode) => {
+		if (targetNode) {
+			observer.observe(targetNode, options);
+		}
+	}, { immediate: true });
+
+	onUnmounted(() => {
+		observer.disconnect();
+	});
+}
diff --git a/packages/frontend/src/composables/use-note-capture.ts b/packages/frontend/src/composables/use-note-capture.ts
new file mode 100644
index 0000000000..2f33c25a0a
--- /dev/null
+++ b/packages/frontend/src/composables/use-note-capture.ts
@@ -0,0 +1,283 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { onUnmounted } from 'vue';
+import * as Misskey from 'misskey-js';
+import { EventEmitter } from 'eventemitter3';
+import type { Reactive, Ref } from 'vue';
+import { useStream } from '@/stream.js';
+import { $i } from '@/i.js';
+import { store } from '@/store.js';
+import { misskeyApi } from '@/utility/misskey-api.js';
+import { prefer } from '@/preferences.js';
+import { globalEvents } from '@/events.js';
+
+export const noteEvents = new EventEmitter<{
+	[ev: `reacted:${string}`]: (ctx: { userId: Misskey.entities.User['id']; reaction: string; emoji?: { name: string; url: string; }; }) => void;
+	[ev: `unreacted:${string}`]: (ctx: { userId: Misskey.entities.User['id']; reaction: string; emoji?: { name: string; url: string; }; }) => void;
+	[ev: `pollVoted:${string}`]: (ctx: { userId: Misskey.entities.User['id']; choice: string; }) => void;
+}>();
+
+const fetchEvent = new EventEmitter<{
+	[id: string]: Pick<Misskey.entities.Note, 'reactions' | 'reactionEmojis'>;
+}>();
+
+const pollingQueue = new Map<string, {
+	referenceCount: number;
+	lastAddedAt: number;
+}>();
+
+function pollingEnqueue(note: Pick<Misskey.entities.Note, 'id' | 'createdAt'>) {
+	if (pollingQueue.has(note.id)) {
+		const data = pollingQueue.get(note.id)!;
+		pollingQueue.set(note.id, {
+			...data,
+			referenceCount: data.referenceCount + 1,
+			lastAddedAt: Date.now(),
+		});
+	} else {
+		pollingQueue.set(note.id, {
+			referenceCount: 1,
+			lastAddedAt: Date.now(),
+		});
+	}
+}
+
+function pollingDequeue(note: Pick<Misskey.entities.Note, 'id' | 'createdAt'>) {
+	const data = pollingQueue.get(note.id);
+	if (data == null) return;
+
+	if (data.referenceCount === 1) {
+		pollingQueue.delete(note.id);
+	} else {
+		pollingQueue.set(note.id, {
+			...data,
+			referenceCount: data.referenceCount - 1,
+		});
+	}
+}
+
+const CAPTURE_MAX = 30;
+const MIN_POLLING_INTERVAL = 1000 * 10;
+const POLLING_INTERVAL =
+	prefer.s.pollingInterval === 1 ? MIN_POLLING_INTERVAL * 1.5 * 1.5 :
+	prefer.s.pollingInterval === 2 ? MIN_POLLING_INTERVAL * 1.5 :
+	prefer.s.pollingInterval === 3 ? MIN_POLLING_INTERVAL :
+	MIN_POLLING_INTERVAL;
+
+window.setInterval(() => {
+	const ids = [...pollingQueue.entries()]
+		.filter(([k, v]) => Date.now() - v.lastAddedAt < 1000 * 60 * 5) // 追加されてから一定時間経過したものは省く
+		.map(([k, v]) => k)
+		.sort((a, b) => (a > b ? -1 : 1)) // 新しいものを優先するためにIDで降順ソート
+		.slice(0, CAPTURE_MAX);
+
+	if (ids.length === 0) return;
+	if (window.document.hidden) return;
+
+	// まとめてリクエストするのではなく、個別にHTTPリクエスト投げてCDNにキャッシュさせた方がサーバーの負荷低減には良いかもしれない？
+	misskeyApi('notes/show-partial-bulk', {
+		noteIds: ids,
+	}).then((items) => {
+		for (const item of items) {
+			fetchEvent.emit(item.id, {
+				reactions: item.reactions,
+				reactionEmojis: item.reactionEmojis,
+			});
+		}
+	});
+}, POLLING_INTERVAL);
+
+function pollingSubscribe(props: {
+	note: Pick<Misskey.entities.Note, 'id' | 'createdAt'>;
+	$note: ReactiveNoteData;
+}) {
+	const { note, $note } = props;
+
+	function onFetched(data: Pick<Misskey.entities.Note, 'reactions' | 'reactionEmojis'>): void {
+		$note.reactions = data.reactions;
+		$note.reactionCount = Object.values(data.reactions).reduce((a, b) => a + b, 0);
+		$note.reactionEmojis = data.reactionEmojis;
+	}
+
+	pollingEnqueue(note);
+	fetchEvent.on(note.id, onFetched);
+
+	onUnmounted(() => {
+		pollingDequeue(note);
+		fetchEvent.off(note.id, onFetched);
+	});
+}
+
+function realtimeSubscribe(props: {
+	note: Pick<Misskey.entities.Note, 'id' | 'createdAt'>;
+}): void {
+	const note = props.note;
+	const connection = useStream();
+
+	function onStreamNoteUpdated(noteData): void {
+		const { type, id, body } = noteData;
+
+		if (id !== note.id) return;
+
+		switch (type) {
+			case 'reacted': {
+				noteEvents.emit(`reacted:${id}`, {
+					userId: body.userId,
+					reaction: body.reaction,
+					emoji: body.emoji,
+				});
+				break;
+			}
+
+			case 'unreacted': {
+				noteEvents.emit(`unreacted:${id}`, {
+					userId: body.userId,
+					reaction: body.reaction,
+					emoji: body.emoji,
+				});
+				break;
+			}
+
+			case 'pollVoted': {
+				noteEvents.emit(`pollVoted:${id}`, {
+					userId: body.userId,
+					choice: body.choice,
+				});
+				break;
+			}
+
+			case 'deleted': {
+				globalEvents.emit('noteDeleted', id);
+				break;
+			}
+		}
+	}
+
+	function capture(withHandler = false): void {
+		connection.send('sr', { id: note.id });
+		if (withHandler) connection.on('noteUpdated', onStreamNoteUpdated);
+	}
+
+	function decapture(withHandler = false): void {
+		connection.send('un', { id: note.id });
+		if (withHandler) connection.off('noteUpdated', onStreamNoteUpdated);
+	}
+
+	function onStreamConnected() {
+		capture(false);
+	}
+
+	capture(true);
+	connection.on('_connected_', onStreamConnected);
+
+	onUnmounted(() => {
+		decapture(true);
+		connection.off('_connected_', onStreamConnected);
+	});
+}
+
+type ReactiveNoteData = Reactive<{
+	reactions: Misskey.entities.Note['reactions'];
+	reactionCount: Misskey.entities.Note['reactionCount'];
+	reactionEmojis: Misskey.entities.Note['reactionEmojis'];
+	myReaction: Misskey.entities.Note['myReaction'];
+	pollChoices: NonNullable<Misskey.entities.Note['poll']>['choices'];
+}>;
+
+export function useNoteCapture(props: {
+	note: Pick<Misskey.entities.Note, 'id' | 'createdAt'>;
+	parentNote: Misskey.entities.Note | null;
+	$note: ReactiveNoteData;
+}) {
+	const { note, parentNote, $note } = props;
+
+	noteEvents.on(`reacted:${note.id}`, onReacted);
+	noteEvents.on(`unreacted:${note.id}`, onUnreacted);
+	noteEvents.on(`pollVoted:${note.id}`, onPollVoted);
+
+	let latestReactedKey: string | null = null;
+	let latestUnreactedKey: string | null = null;
+	let latestPollVotedKey: string | null = null;
+
+	function onReacted(ctx: { userId: Misskey.entities.User['id']; reaction: string; emoji?: { name: string; url: string; }; }): void {
+		const newReactedKey = `${ctx.userId}:${ctx.reaction}`;
+		if (newReactedKey === latestReactedKey) return;
+		latestReactedKey = newReactedKey;
+
+		if (ctx.emoji && !(ctx.emoji.name in $note.reactionEmojis)) {
+			$note.reactionEmojis[ctx.emoji.name] = ctx.emoji.url;
+		}
+
+		const currentCount = $note.reactions[ctx.reaction] || 0;
+
+		$note.reactions[ctx.reaction] = currentCount + 1;
+		$note.reactionCount += 1;
+
+		if ($i && (ctx.userId === $i.id)) {
+			$note.myReaction = ctx.reaction;
+		}
+	}
+
+	function onUnreacted(ctx: { userId: Misskey.entities.User['id']; reaction: string; emoji?: { name: string; url: string; }; }): void {
+		const newUnreactedKey = `${ctx.userId}:${ctx.reaction}`;
+		if (newUnreactedKey === latestUnreactedKey) return;
+		latestUnreactedKey = newUnreactedKey;
+
+		const currentCount = $note.reactions[ctx.reaction] || 0;
+
+		$note.reactions[ctx.reaction] = Math.max(0, currentCount - 1);
+		$note.reactionCount = Math.max(0, $note.reactionCount - 1);
+		if ($note.reactions[ctx.reaction] === 0) delete $note.reactions[ctx.reaction];
+
+		if ($i && (ctx.userId === $i.id)) {
+			$note.myReaction = null;
+		}
+	}
+
+	function onPollVoted(ctx: { userId: Misskey.entities.User['id']; choice: string; }): void {
+		const newPollVotedKey = `${ctx.userId}:${ctx.choice}`;
+		if (newPollVotedKey === latestPollVotedKey) return;
+		latestPollVotedKey = newPollVotedKey;
+
+		const choices = [...$note.pollChoices];
+		choices[ctx.choice] = {
+			...choices[ctx.choice],
+			votes: choices[ctx.choice].votes + 1,
+			...($i && (ctx.userId === $i.id) ? {
+				isVoted: true,
+			} : {}),
+		};
+
+		$note.pollChoices = choices;
+	}
+
+	onUnmounted(() => {
+		noteEvents.off(`reacted:${note.id}`, onReacted);
+		noteEvents.off(`unreacted:${note.id}`, onUnreacted);
+		noteEvents.off(`pollVoted:${note.id}`, onPollVoted);
+	});
+
+	// 投稿からある程度経過している(=タイムラインを遡って表示した)ノートは、イベントが発生する可能性が低いためそもそも購読しない
+	// ただし「リノートされたばかりの過去のノート」(= parentNoteが存在し、かつparentNoteの投稿日時が最近)はイベント発生が考えられるため購読する
+	// TODO: デバイスとサーバーの時計がズレていると不具合の元になるため、ズレを検知して警告を表示するなどのケアが必要かもしれない
+	if (parentNote == null) {
+		if ((Date.now() - new Date(note.createdAt).getTime()) > 1000 * 60 * 5) { // 5min
+			// リノートで表示されているノートでもないし、投稿からある程度経過しているので購読しない
+			return;
+		}
+	} else {
+		if ((Date.now() - new Date(parentNote.createdAt).getTime()) > 1000 * 60 * 5) { // 5min
+			// リノートで表示されているノートだが、リノートされてからある程度経過しているので購読しない
+			return;
+		}
+	}
+
+	if ($i && store.s.realtimeMode) {
+		realtimeSubscribe(props);
+	} else {
+		pollingSubscribe(props);
+	}
+}
diff --git a/packages/frontend/src/composables/use-pagination.ts b/packages/frontend/src/composables/use-pagination.ts
new file mode 100644
index 0000000000..f1042985bf
--- /dev/null
+++ b/packages/frontend/src/composables/use-pagination.ts
@@ -0,0 +1,258 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { computed, isRef, onMounted, ref, shallowRef, triggerRef, watch } from 'vue';
+import * as Misskey from 'misskey-js';
+import type { ComputedRef, DeepReadonly, Ref, ShallowRef } from 'vue';
+import { misskeyApi } from '@/utility/misskey-api.js';
+
+const MAX_ITEMS = 30;
+const MAX_QUEUE_ITEMS = 100;
+const FIRST_FETCH_LIMIT = 15;
+const SECOND_FETCH_LIMIT = 30;
+
+export type MisskeyEntity = {
+	id: string;
+	createdAt: string;
+	_shouldInsertAd_?: boolean;
+	[x: string]: any;
+};
+
+export type PagingCtx<E extends keyof Misskey.Endpoints = keyof Misskey.Endpoints> = {
+	endpoint: E;
+	limit?: number;
+	params?: Misskey.Endpoints[E]['req'] | ComputedRef<Misskey.Endpoints[E]['req']>;
+
+	/**
+	 * 検索APIのような、ページング不可なエンドポイントを利用する場合
+	 * (そのようなAPIをこの関数で使うのは若干矛盾してるけど)
+	 */
+	noPaging?: boolean;
+
+	offsetMode?: boolean;
+
+	baseId?: MisskeyEntity['id'];
+	direction?: 'newer' | 'older';
+};
+
+export function usePagination<T extends MisskeyEntity>(props: {
+	ctx: PagingCtx;
+	useShallowRef?: boolean;
+}) {
+	const items = props.useShallowRef ? shallowRef<T[]>([]) : ref<T[]>([]);
+	let aheadQueue: T[] = [];
+	const queuedAheadItemsCount = ref(0);
+	const fetching = ref(true);
+	const fetchingOlder = ref(false);
+	const canFetchOlder = ref(false);
+	const error = ref(false);
+
+	// パラメータに何らかの変更があった際、再読込したい（チャンネル等のIDが変わったなど）
+	watch(() => [props.ctx.endpoint, props.ctx.params], init, { deep: true });
+
+	function getNewestId(): string | null | undefined {
+		// 様々な要因により並び順は保証されないのでソートが必要
+		if (aheadQueue.length > 0) {
+			return aheadQueue.map(x => x.id).sort().at(-1);
+		}
+		return items.value.map(x => x.id).sort().at(-1);
+	}
+
+	function getOldestId(): string | null | undefined {
+		// 様々な要因により並び順は保証されないのでソートが必要
+		return items.value.map(x => x.id).sort().at(0);
+	}
+
+	async function init(): Promise<void> {
+		items.value = [];
+		aheadQueue = [];
+		queuedAheadItemsCount.value = 0;
+		fetching.value = true;
+		const params = props.ctx.params ? isRef(props.ctx.params) ? props.ctx.params.value : props.ctx.params : {};
+
+		await misskeyApi<T[]>(props.ctx.endpoint, {
+			...params,
+			limit: props.ctx.limit ?? FIRST_FETCH_LIMIT,
+			allowPartial: true,
+			...(props.ctx.baseId && props.ctx.direction === 'newer' ? {
+				sinceId: props.ctx.baseId,
+			} : props.ctx.baseId && props.ctx.direction === 'older' ? {
+				untilId: props.ctx.baseId,
+			} : {}),
+		}).then(res => {
+			// 逆順で返ってくるので
+			if (props.ctx.baseId && props.ctx.direction === 'newer') {
+				res.reverse();
+			}
+
+			for (let i = 0; i < res.length; i++) {
+				const item = res[i];
+				if (i === 3) item._shouldInsertAd_ = true;
+			}
+
+			if (res.length === 0 || props.ctx.noPaging) {
+				pushItems(res);
+				canFetchOlder.value = false;
+			} else {
+				pushItems(res);
+				canFetchOlder.value = true;
+			}
+
+			error.value = false;
+			fetching.value = false;
+		}, err => {
+			error.value = true;
+			fetching.value = false;
+		});
+	}
+
+	function reload(): Promise<void> {
+		return init();
+	}
+
+	async function fetchOlder(): Promise<void> {
+		if (!canFetchOlder.value || fetching.value || fetchingOlder.value || items.value.length === 0) return;
+		fetchingOlder.value = true;
+		const params = props.ctx.params ? isRef(props.ctx.params) ? props.ctx.params.value : props.ctx.params : {};
+		await misskeyApi<T[]>(props.ctx.endpoint, {
+			...params,
+			limit: SECOND_FETCH_LIMIT,
+			...(props.ctx.offsetMode ? {
+				offset: items.value.length,
+			} : {
+				untilId: getOldestId(),
+			}),
+		}).then(res => {
+			for (let i = 0; i < res.length; i++) {
+				const item = res[i];
+				if (i === 10) item._shouldInsertAd_ = true;
+			}
+
+			if (res.length === 0) {
+				canFetchOlder.value = false;
+				fetchingOlder.value = false;
+			} else {
+				pushItems(res);
+				canFetchOlder.value = true;
+				fetchingOlder.value = false;
+			}
+		}, err => {
+			fetchingOlder.value = false;
+		});
+	}
+
+	async function fetchNewer(options: {
+		toQueue?: boolean;
+	} = {}): Promise<void> {
+		const params = props.ctx.params ? isRef(props.ctx.params) ? props.ctx.params.value : props.ctx.params : {};
+		await misskeyApi<T[]>(props.ctx.endpoint, {
+			...params,
+			limit: SECOND_FETCH_LIMIT,
+			...(props.ctx.offsetMode ? {
+				offset: items.value.length,
+			} : {
+				sinceId: getNewestId(),
+			}),
+		}).then(res => {
+			if (res.length === 0) return; // これやらないと余計なre-renderが走る
+
+			if (options.toQueue) {
+				aheadQueue.unshift(...res.toReversed());
+				if (aheadQueue.length > MAX_QUEUE_ITEMS) {
+					aheadQueue = aheadQueue.slice(0, MAX_QUEUE_ITEMS);
+				}
+				queuedAheadItemsCount.value = aheadQueue.length;
+			} else {
+				unshiftItems(res.toReversed());
+			}
+		});
+	}
+
+	function trim(trigger = true) {
+		if (items.value.length >= MAX_ITEMS) canFetchOlder.value = true;
+		items.value = items.value.slice(0, MAX_ITEMS);
+		if (props.useShallowRef && trigger) triggerRef(items);
+	}
+
+	function unshiftItems(newItems: T[]) {
+		if (newItems.length === 0) return; // これやらないと余計なre-renderが走る
+		items.value.unshift(...newItems.filter(x => !items.value.some(y => y.id === x.id))); // ストリーミングやポーリングのタイミングによっては重複することがあるため
+		trim(false);
+		if (props.useShallowRef) triggerRef(items);
+	}
+
+	function pushItems(oldItems: T[]) {
+		if (oldItems.length === 0) return; // これやらないと余計なre-renderが走る
+		items.value.push(...oldItems);
+		if (props.useShallowRef) triggerRef(items);
+	}
+
+	function prepend(item: T) {
+		if (items.value.some(x => x.id === item.id)) return;
+		items.value.unshift(item);
+		trim(false);
+		if (props.useShallowRef) triggerRef(items);
+	}
+
+	function enqueue(item: T) {
+		aheadQueue.unshift(item);
+		if (aheadQueue.length > MAX_QUEUE_ITEMS) {
+			aheadQueue.pop();
+		}
+		queuedAheadItemsCount.value = aheadQueue.length;
+	}
+
+	function releaseQueue() {
+		if (aheadQueue.length === 0) return; // これやらないと余計なre-renderが走る
+		unshiftItems(aheadQueue);
+		aheadQueue = [];
+		queuedAheadItemsCount.value = 0;
+	}
+
+	function removeItem(id: string) {
+		// TODO: queueからも消す
+
+		const index = items.value.findIndex(x => x.id === id);
+		if (index !== -1) {
+			items.value.splice(index, 1);
+			if (props.useShallowRef) triggerRef(items);
+		}
+	}
+
+	function updateItem(id: string, updator: (item: T) => T) {
+		// TODO: queueのも更新
+
+		const index = items.value.findIndex(x => x.id === id);
+		if (index !== -1) {
+			const item = items.value[index]!;
+			items.value[index] = updator(item);
+			if (props.useShallowRef) triggerRef(items);
+		}
+	}
+
+	onMounted(() => {
+		init();
+	});
+
+	return {
+		items: items as DeepReadonly<ShallowRef<T[]>>,
+		queuedAheadItemsCount,
+		fetching,
+		fetchingOlder,
+		canFetchOlder,
+		init,
+		reload,
+		fetchOlder,
+		fetchNewer,
+		unshiftItems,
+		prepend,
+		trim,
+		removeItem,
+		updateItem,
+		enqueue,
+		releaseQueue,
+		error,
+	};
+}
diff --git a/packages/frontend/src/composables/use-scroll-position-keeper.ts b/packages/frontend/src/composables/use-scroll-position-keeper.ts
new file mode 100644
index 0000000000..b584171cbe
--- /dev/null
+++ b/packages/frontend/src/composables/use-scroll-position-keeper.ts
@@ -0,0 +1,77 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { throttle } from 'throttle-debounce';
+import { nextTick, onActivated, onDeactivated, onUnmounted, watch } from 'vue';
+import type { Ref } from 'vue';
+
+// note render skippingがオンだとズレるため、遷移直前にスクロール範囲に表示されているdata-scroll-anchor要素を特定して、復元時に当該要素までスクロールするようにする
+
+// TODO: data-scroll-anchor がひとつも存在しない場合、または手動で useAnchor みたいなフラグをfalseで呼ばれた場合、単純にスクロール位置を使用する処理にフォールバックするようにする
+
+export function useScrollPositionKeeper(scrollContainerRef: Ref<HTMLElement | null | undefined>): void {
+	let anchorId: string | null = null;
+	let ready = true;
+
+	watch(scrollContainerRef, (el) => {
+		if (!el) return;
+
+		const onScroll = () => {
+			if (!el) return;
+			if (!ready) return;
+
+			const scrollContainerRect = el.getBoundingClientRect();
+			const viewPosition = scrollContainerRect.height / 2;
+
+			const anchorEls = el.querySelectorAll('[data-scroll-anchor]');
+			for (let i = anchorEls.length - 1; i > -1; i--) { // 下から見た方が速い
+				const anchorEl = anchorEls[i] as HTMLElement;
+				const anchorRect = anchorEl.getBoundingClientRect();
+				const anchorTop = anchorRect.top;
+				const anchorBottom = anchorRect.bottom;
+				if (anchorTop <= viewPosition && anchorBottom >= viewPosition) {
+					anchorId = anchorEl.getAttribute('data-scroll-anchor');
+					break;
+				}
+			}
+		};
+
+		// ほんとはscrollイベントじゃなくてonBeforeDeactivatedでやりたい
+		// https://github.com/vuejs/vue/issues/9454
+		// https://github.com/vuejs/rfcs/pull/284
+		el.addEventListener('scroll', throttle(1000, onScroll), { passive: true });
+	}, {
+		immediate: true,
+	});
+
+	const restore = () => {
+		if (!anchorId) return;
+		const scrollContainer = scrollContainerRef.value;
+		if (!scrollContainer) return;
+		const scrollAnchorEl = scrollContainer.querySelector(`[data-scroll-anchor="${anchorId}"]`);
+		if (!scrollAnchorEl) return;
+		scrollAnchorEl.scrollIntoView({
+			behavior: 'instant',
+			block: 'center',
+			inline: 'center',
+		});
+	};
+
+	onDeactivated(() => {
+		ready = false;
+	});
+
+	onActivated(() => {
+		restore();
+		nextTick(() => {
+			restore();
+			window.setTimeout(() => {
+				restore();
+
+				ready = true;
+			}, 100);
+		});
+	});
+}
diff --git a/packages/frontend/src/composables/use-tooltip.ts b/packages/frontend/src/composables/use-tooltip.ts
new file mode 100644
index 0000000000..af76a3a1e8
--- /dev/null
+++ b/packages/frontend/src/composables/use-tooltip.ts
@@ -0,0 +1,106 @@
+/*
+ * SPDX-FileCopyrightText: syuilo and misskey-project
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+import { ref, watch, onUnmounted } from 'vue';
+import type { Ref } from 'vue';
+
+export function useTooltip(
+	elRef: Ref<HTMLElement | { $el: HTMLElement } | null | undefined>,
+	onShow: (showing: Ref<boolean>) => void,
+	delay = 300,
+): void {
+	let isHovering = false;
+
+	// iOS(Androidも？)では、要素をタップした直後に(おせっかいで)mouseoverイベントを発火させたりするため、それを無視するためのフラグ
+	// 無視しないと、画面に触れてないのにツールチップが出たりし、ユーザビリティが損なわれる
+	// TODO: 一度でもタップすると二度とマウスでツールチップ出せなくなるのをどうにかする 定期的にfalseに戻すとか...？
+	let shouldIgnoreMouseover = false;
+
+	let timeoutId: number;
+
+	let changeShowingState: (() => void) | null;
+
+	let autoHidingTimer;
+
+	const open = () => {
+		close();
+		if (!isHovering) return;
+		if (elRef.value == null) return;
+		const el = elRef.value instanceof Element ? elRef.value : elRef.value.$el;
+		if (!window.document.body.contains(el)) return; // openしようとしたときに既に元要素がDOMから消えている場合があるため
+
+		const showing = ref(true);
+		onShow(showing);
+		changeShowingState = () => {
+			showing.value = false;
+		};
+
+		autoHidingTimer = window.setInterval(() => {
+			if (elRef.value == null || !window.document.body.contains(elRef.value instanceof Element ? elRef.value : elRef.value.$el)) {
+				if (!isHovering) return;
+				isHovering = false;
+				window.clearTimeout(timeoutId);
+				close();
+				window.clearInterval(autoHidingTimer);
+			}
+		}, 1000);
+	};
+
+	const close = () => {
+		if (changeShowingState != null) {
+			changeShowingState();
+			changeShowingState = null;
+		}
+	};
+
+	const onMouseover = () => {
+		if (isHovering) return;
+		if (shouldIgnoreMouseover) return;
+		isHovering = true;
+		timeoutId = window.setTimeout(open, delay);
+	};
+
+	const onMouseleave = () => {
+		if (!isHovering) return;
+		isHovering = false;
+		window.clearTimeout(timeoutId);
+		window.clearInterval(autoHidingTimer);
+		close();
+	};
+
+	const onTouchstart = () => {
+		shouldIgnoreMouseover = true;
+		if (isHovering) return;
+		isHovering = true;
+		timeoutId = window.setTimeout(open, delay);
+	};
+
+	const onTouchend = () => {
+		if (!isHovering) return;
+		isHovering = false;
+		window.clearTimeout(timeoutId);
+		window.clearInterval(autoHidingTimer);
+		close();
+	};
+
+	const stop = watch(elRef, () => {
+		if (elRef.value) {
+			stop();
+			const el = elRef.value instanceof Element ? elRef.value : elRef.value.$el;
+			el.addEventListener('mouseover', onMouseover, { passive: true });
+			el.addEventListener('mouseleave', onMouseleave, { passive: true });
+			el.addEventListener('touchstart', onTouchstart, { passive: true });
+			el.addEventListener('touchend', onTouchend, { passive: true });
+			el.addEventListener('click', close, { passive: true });
+		}
+	}, {
+		immediate: true,
+		flush: 'post',
+	});
+
+	onUnmounted(() => {
+		close();
+	});
+}