From 1a2833ed53c42a8c6a326bd52b3c735e3c682c5f Mon Sep 17 00:00:00 2001
From: Tulir Asokan <tulir@maunium.net>
Date: Wed, 4 Dec 2024 01:22:16 +0200
Subject: [PATCH] web/main: add support for back button

---
 web/src/api/statestore/main.ts |  4 ++--
 web/src/ui/MainScreen.tsx      | 17 +++++++++++++++--
 web/src/ui/modal/Lightbox.tsx  | 22 +++++++++++++++++++---
 web/src/ui/modal/Modal.tsx     | 21 ++++++++++++++++++++-
 4 files changed, 56 insertions(+), 8 deletions(-)

diff --git a/web/src/api/statestore/main.ts b/web/src/api/statestore/main.ts
index fc77e6a..52bea6a 100644
--- a/web/src/api/statestore/main.ts
+++ b/web/src/api/statestore/main.ts
@@ -81,7 +81,7 @@ export class StateStore {
 	readonly localPreferenceCache: Preferences = getLocalStoragePreferences("global_prefs", this.preferenceSub.notify)
 	serverPreferenceCache: Preferences = {}
 	switchRoom?: (roomID: RoomID | null) => void
-	activeRoomID?: RoomID
+	activeRoomID: RoomID | null = null
 	imageAuthToken?: string
 
 	getFilteredRoomList(): RoomListEntry[] {
@@ -397,6 +397,6 @@ export class StateStore {
 		this.#watchedRoomEmojiPacks = null
 		this.#personalEmojiPack = null
 		this.serverPreferenceCache = {}
-		this.activeRoomID = undefined
+		this.activeRoomID = null
 	}
 }
diff --git a/web/src/ui/MainScreen.tsx b/web/src/ui/MainScreen.tsx
index 8272bb5..5434682 100644
--- a/web/src/ui/MainScreen.tsx
+++ b/web/src/ui/MainScreen.tsx
@@ -62,13 +62,13 @@ class ContextFields implements MainScreenContextFields {
 		client.store.switchRoom = this.setActiveRoom
 	}
 
-	setActiveRoom = (roomID: RoomID | null) => {
+	setActiveRoom = (roomID: RoomID | null, pushState = true) => {
 		console.log("Switching to room", roomID)
 		const room = (roomID && this.client.store.rooms.get(roomID)) || null
 		window.activeRoom = room
 		this.directSetActiveRoom(room)
 		this.setRightPanel(null)
-		this.client.store.activeRoomID = room?.roomID
+		this.client.store.activeRoomID = room?.roomID ?? null
 		this.keybindings.activeRoom = room
 		if (room) {
 			room.lastOpened = Date.now()
@@ -80,6 +80,9 @@ class ContextFields implements MainScreenContextFields {
 				.querySelector(`div.room-entry[data-room-id="${CSS.escape(room.roomID)}"]`)
 				?.scrollIntoView({ block: "nearest" })
 		}
+		if (pushState) {
+			history.pushState({ room_id: roomID }, "")
+		}
 	}
 
 	clickRoom = (evt: React.MouseEvent) => {
@@ -120,6 +123,16 @@ const MainScreen = () => {
 	useLayoutEffect(() => {
 		window.mainScreenContext = context
 	}, [context])
+	useEffect(() => {
+		const listener = (evt: PopStateEvent) => {
+			const roomID = evt.state?.room_id ?? null
+			if (roomID !== client.store.activeRoomID) {
+				context.setActiveRoom(roomID, false)
+			}
+		}
+		window.addEventListener("popstate", listener)
+		return () => window.removeEventListener("popstate", listener)
+	}, [context, client])
 	useEffect(() => context.keybindings.listen(), [context])
 	useInsertionEffect(() => {
 		const styleTags = document.createElement("style")
diff --git a/web/src/ui/modal/Lightbox.tsx b/web/src/ui/modal/Lightbox.tsx
index 82384fc..a6d9164 100644
--- a/web/src/ui/modal/Lightbox.tsx
+++ b/web/src/ui/modal/Lightbox.tsx
@@ -44,18 +44,34 @@ export const LightboxWrapper = ({ children }: { children: React.ReactNode }) =>
 			if (!target.src) {
 				return
 			}
-			setParams({
+			params = {
 				src: target.src,
 				alt: target.alt,
-			})
+			}
+			setParams(params)
 		} else {
 			setParams(params as LightboxParams)
 		}
+		history.pushState({ ...(history.state ?? {}), lightbox: params }, "")
 	}, [])
 	useLayoutEffect(() => {
 		window.openLightbox = onOpen
+		const listener = (evt: PopStateEvent) => {
+			if (evt.state?.lightbox) {
+				setParams(evt.state.lightbox)
+			} else {
+				setParams(null)
+			}
+		}
+		window.addEventListener("popstate", listener)
+		return () => window.removeEventListener("popstate", listener)
 	}, [onOpen])
-	const onClose = useCallback(() => setParams(null), [])
+	const onClose = useCallback(() => {
+		setParams(null)
+		if (params?.src && history.state?.lightbox?.src === params?.src) {
+			history.back()
+		}
+	}, [params])
 	return <>
 		<LightboxContext value={onOpen}>
 			{children}
diff --git a/web/src/ui/modal/Modal.tsx b/web/src/ui/modal/Modal.tsx
index 5a1df7e..52ee783 100644
--- a/web/src/ui/modal/Modal.tsx
+++ b/web/src/ui/modal/Modal.tsx
@@ -41,18 +41,37 @@ export const ModalWrapper = ({ children }: { children: React.ReactNode }) => {
 			return
 		}
 		setState(null)
+		if (history.state?.modal) {
+			history.back()
+		}
 	}, [])
 	const onKeyWrapper = useCallback((evt: React.KeyboardEvent<HTMLDivElement>) => {
 		if (evt.key === "Escape") {
 			setState(null)
+			if (history.state?.modal) {
+				history.back()
+			}
 		}
 		evt.stopPropagation()
 	}, [])
+	const openModal = useCallback((newState: ModalState) => {
+		if (!history.state?.modal) {
+			history.pushState({ ...(history.state ?? {}), modal: true }, "")
+		}
+		setState(newState)
+	}, [])
 	const wrapperRef = useRef<HTMLDivElement>(null)
 	useLayoutEffect(() => {
 		if (wrapperRef.current && (!document.activeElement || !wrapperRef.current.contains(document.activeElement))) {
 			wrapperRef.current.focus()
 		}
+		const listener = (evt: PopStateEvent) => {
+			if (!evt.state?.modal) {
+				setState(null)
+			}
+		}
+		window.addEventListener("popstate", listener)
+		return () => window.removeEventListener("popstate", listener)
 	}, [state])
 	let modal: JSX.Element | null = null
 	if (state) {
@@ -74,7 +93,7 @@ export const ModalWrapper = ({ children }: { children: React.ReactNode }) => {
 			{content}
 		</div>
 	}
-	return <ModalContext value={setState}>
+	return <ModalContext value={openModal}>
 		{children}
 		{modal}
 	</ModalContext>