const {ElemJS, ejs, q} = require("./basic.js")
const {store} = require("./store/store.js")
const lsm = require("./lsm.js")

function markFullyRead(roomID, eventID) {
	return fetch(`${lsm.get("domain")}/_matrix/client/r0/rooms/${roomID}/read_markers?access_token=${lsm.get("access_token")}`, {
		method: "POST",
		body: JSON.stringify({
			"m.fully_read": eventID,
			"m.read": eventID
		})
	})
}

class ReadBanner extends ElemJS {
	constructor() {
		super(q("#c-chat-banner"))

		this.newMessages = ejs("span")
		this.child(
			ejs("div").class("c-chat-banner__inner").child(
				ejs("button").class("c-chat-banner__part").on("click", this.jumpTo.bind(this)).child(
					ejs("div").class("c-chat-banner__part-inner")
						.child(this.newMessages)
						.addText(" new messages")
				),
				ejs("button").class("c-chat-banner__part", "c-chat-banner__last").on("click", this.markRead.bind(this)).child(
					ejs("div").class("c-chat-banner__part-inner").text("Mark as read")
				)
			)
		)

		store.activeRoom.subscribe("changeSelf", this.render.bind(this))
		store.notificationsChange.subscribe("changeSelf", this.render.bind(this))
		this.render()
	}

	async jumpTo() {
		if (!store.activeRoom.exists()) return
		const timeline = store.activeRoom.value().timeline
		const readMarker = timeline.readMarker
		while (true) {
			if (readMarker.attached) {
				readMarker.element.scrollIntoView({behavior: "smooth", block: "center"})
				return
			} else {
				q("#c-chat-messages").scrollTo({
					top: 0,
					left: 0,
					behavior: "smooth"
				})
				await new Promise(resolve => {
					const unsubscribe = timeline.subscribe("afterScrollbackLoad", () => {
						unsubscribe()
						resolve()
					})
				})
			}
		}
	}

	markRead() {
		if (!store.activeRoom.exists()) return
		const timeline = store.activeRoom.value().timeline
		markFullyRead(timeline.id, timeline.latestEventID)
	}

	render() {
		let count = 0
		if (store.activeRoom.exists()) {
			count = store.activeRoom.value().number.state.unreads
		}
		if (count !== 0) {
			this.newMessages.text(count)
			this.class("c-chat-banner--active")
		} else {
			this.removeClass("c-chat-banner--active")
		}
	}
}
const readBanner = new ReadBanner()

class ReadMarker extends ElemJS {
	constructor(timeline) {
		super("div")

		this.class("c-read-marker")
		this.loadingIcon = ejs("div")
			.class("c-read-marker__loading", "loading-icon")
			.style("display", "none")
		this.child(
			ejs("div").class("c-read-marker__inner").child(
				ejs("div").class("c-read-marker__text").child(this.loadingIcon).addText("New")
			)
		)

		let processing = false
		const observer = new IntersectionObserver(entries => {
			const entry = entries[0]
			if (!entry.isIntersecting) return
			if (processing) return
			processing = true
			this.loadingIcon.style("display", "")
			markFullyRead(this.timeline.id, this.timeline.latestEventID).then(() => {
				this.loadingIcon.style("display", "none")
				processing = false
			})
		}, {
			root: document.getElementById("c-chat-messages"),
			rootMargin: "-80px 0px 0px 0px", // marker must be this distance inside the top of the screen to be counted as read
			threshold: 0.01
		})
		observer.observe(this.element)

		this.attached = false
		this.timeline = timeline
		this.timeline.userReads.get(lsm.get("mx_user_id")).subscribe("changeSelf", (_, eventID) => {
			// read marker updated, attach to it
			const event = this.timeline.map.get(eventID)
			this.attach(event)
		})
		this.timeline.subscribe("afterChange", () => {
			// timeline has new events, attach to last read one
			const eventID = this.timeline.userReads.get(lsm.get("mx_user_id")).value()
			const event = this.timeline.map.get(eventID)
			this.attach(event)
		})
	}

	attach(event) {
		if (event && event.data.origin_server_ts !== this.timeline.latest) {
			this.class("c-read-marker--attached")
			event.element.insertAdjacentElement("beforeend", this.element)
			this.attached = true
		} else {
			this.removeClass("c-read-marker--attached")
			this.attached = false
		}
		if (store.activeRoom.value() === this.timeline.room) {
			readBanner.render()
		}
	}
}

module.exports = {
	ReadMarker,
	readBanner,
	markFullyRead
}