const {ElemJS, ejs} = require("./basic.js")
const {Subscribable} = require("./store/subscribable.js")
const {store} = require("./store/store.js")
const {Anchor} = require("./anchor.js")
const {Sender} = require("./sender.js")
const lsm = require("./lsm.js")

let debug = false

const NO_MAX = Symbol("NO_MAX")

const dateFormatter = Intl.DateTimeFormat("default", {hour: "numeric", minute: "numeric", day: "numeric", month: "short", year: "numeric"})

let sentIndex = 0

function getTxnId() {
	return Date.now() + (sentIndex++)
}

function eventSearch(list, event, min = 0, max = NO_MAX) {
	if (list.length === 0) return {success: false, i: 0}

	if (max === NO_MAX) max = list.length - 1
	let mid = Math.floor((max + min) / 2)
	// success condition
	if (list[mid] && list[mid].data.event_id === event.data.event_id) return {success: true, i: mid}
	// failed condition
	if (min >= max) {
		while (mid !== -1 && (!list[mid] || list[mid].data.origin_server_ts > event.data.origin_server_ts)) mid--
		return {
			success: false,
			i: mid + 1
		}
	}
	// recurse (below)
	if (list[mid].data.origin_server_ts > event.data.origin_server_ts) return eventSearch(list, event, min, mid - 1)
	// recurse (above)
	else return eventSearch(list, event, mid + 1, max)
}

class Event extends ElemJS {
	constructor(data) {
		super("div")
		this.class("c-message")
		this.data = null
		this.group = null
		this.editedAt = null
		this.update(data)
	}

	// predicates

	canGroup() {
		return this.data.type === "m.room.message"
	}

	// operations

	setGroup(group) {
		this.group = group
	}

	setEdited(time) {
		this.editedAt = time
		this.render()
	}

	update(data) {
		this.data = data
		this.render()
	}

	removeEvent() {
		if (this.group) this.group.removeEvent(this)
		else this.remove()
	}

	render() {
		this.element.classList[this.data.pending ? "add" : "remove"]("c-message--pending")
		if (this.data.type === "m.room.message") {
			this.text(this.data.content.body)
		} else if (this.data.type === "m.room.member") {
			if (this.data.content.membership === "join") {
				this.child(ejs("i").text("joined the room"))
			} else if (this.data.content.membership === "invite") {
				this.child(ejs("i").text(`invited ${this.data.content.displayname} to the room`))
			} else if (this.data.content.membership === "leave") {
				this.child(ejs("i").text("left the room"))
			} else {
				this.child(ejs("i").text("unknown membership event"))
			}
		} else if (this.data.type === "m.room.encrypted") {
			this.child(ejs("i").text("Carbon does not yet support encrypted messages."))
		} else {
			this.child(ejs("i").text(`Unsupported event type ${this.data.type}`))
		}
		if (this.editedAt) {
			this.child(ejs("span").class("c-message__edited").text("(edited)").attribute("title", "at " + dateFormatter.format(this.editedAt)))
		}
	}
}

class EventGroup extends ElemJS {
	constructor(reactive, list) {
		super("div")
		this.class("c-message-group")
		this.reactive = reactive
		this.list = list
		this.data = {
			sender: list[0].data.sender,
			origin_server_ts: list[0].data.origin_server_ts
		}
		this.sender = new Sender(this.reactive.id, this.data.sender)
		this.child(
			this.sender.avatar,
			this.messages = ejs("div").class("c-message-group__messages").child(
				ejs("div").class("c-message-group__intro").child(
					this.sender.name,
					ejs("div").class("c-message-group__date").text(dateFormatter.format(this.data.origin_server_ts))
				),
				...this.list
			)
		)
	}

	addEvent(event) {
		const index = eventSearch(this.list, event).i
		event.setGroup(this)
		this.list.splice(index, 0, event)
		this.messages.childAt(index + 1, event)
	}

	removeEvent(event) {
		const search = eventSearch(this.list, event)
		if (!search.success) throw new Error(`Event ${event.data.event_id} not found in this group`)
		const index = search.i
		// actually remove the event
		this.list.splice(index, 1)
		event.remove() // should get everything else
		if (this.list.length === 0) this.reactive.removeGroup(this)
	}
}


/** Displays a spinner and creates an event to notify timeline to load more messages */
class LoadMore extends ElemJS {
	constructor(id) {
		super("div")
		this.class("c-message-notice")
		this.id = id

		this.child(
			ejs("div").class("c-message-notice__inner").child(
				ejs("span").class("loading-icon"),
				ejs("span").text("Loading more...")
			)
		)
		const intersection_observer = new IntersectionObserver(e => this.intersectionHandler(e))
		intersection_observer.observe(this.element)
	}

	intersectionHandler(e) {
		if (e.some(e => e.isIntersecting)) {
			store.rooms.get(this.id).value().timeline.loadScrollback()
		}
	}
}

class ReactiveTimeline extends ElemJS {
	constructor(id, list) {
		super("div")
		this.class("c-event-groups")
		this.id = id
		this.list = list
		this.loadMore = new LoadMore(this.id)
		this.render()
	}

	addEvent(event) {
		this.loadMore.remove()
		// if (debug) console.log("running search", this.list, event)
		// if (debug) debugger;
		const search = eventSearch(this.list, event)
		// console.log(search, this.list.map(l => l.data.sender), event.data)
		if (!search.success) {
			if (search.i >= 1) {
				// add at end
				this.tryAddGroups(event, [search.i - 1, search.i])
			} else {
				// add at start
				this.tryAddGroups(event, [0, -1])
			}
		} else {
			this.tryAddGroups(event, [search.i])
		}
		this.loadMore = new LoadMore(this.id)
		this.childAt(0, this.loadMore)
	}

	tryAddGroups(event, indices) {
		const success = indices.some(i => {
			if (!this.list[i]) {
				// if (printed++ < 100) console.log("tryadd success, created group")
				const group = new EventGroup(this, [event])
				if (i === -1) {
					// here, -1 means at the start, before the first group
					i = 0 // jank but it does the trick
				}
				this.list.splice(i, 0, group)
				this.childAt(i, group)
				event.setGroup(group)
				return true
			} else if (this.list[i] && this.list[i].data.sender === event.data.sender) {
				// if (printed++ < 100) console.log("tryadd success, using existing group")
				this.list[i].addEvent(event)
				return true
			}
		})
		if (!success) console.log("tryadd failure", indices, this.list.map(l => l.data.sender), event.data)
	}

	removeGroup(group) {
		const index = this.list.indexOf(group)
		this.list.splice(index, 1)
		group.remove() // should get everything else
	}

	render() {
		this.clearChildren()
		this.child(this.loadMore)
		this.list.forEach(group => this.child(group))
		this.anchor = new Anchor()
		this.child(this.anchor)
	}
}

class Timeline extends Subscribable {
	constructor(room) {
		super()
		Object.assign(this.events, {
			beforeChange: [],
			afterChange: [],
			beforeScrollbackLoad: [],
			afterScrollbackLoad: [],
		})
		Object.assign(this.eventDeps, {
			beforeChange: [],
			afterChange: [],
			beforeScrollbackLoad: [],
			afterScrollbackLoad: [],
		})
		this.room = room
		this.id = this.room.id
		this.list = []
		this.map = new Map()
		this.reactiveTimeline = new ReactiveTimeline(this.id, [])
		this.latest = 0
		this.pending = new Set()
		this.pendingEdits = []
		this.from = null
	}

	updateStateEvents(events) {
		for (const eventData of events) {
			let id = eventData.event_id
			if (eventData.type === "m.room.member") {
				// update members
				if (eventData.membership !== "leave") {
					const member = this.room.members.get(eventData.state_key)
					// only use the latest state
					if (!member.exists() || eventData.origin_server_ts > member.data.origin_server_ts) {
						member.set(eventData)
					}
				}
			}
		}
	}

	updateEvents(events) {
		this.broadcast("beforeChange")
		// handle state events
		this.updateStateEvents(events)
		for (const eventData of events) {
			// set variables
			this.latest = Math.max(this.latest, eventData.origin_server_ts)
			let id = eventData.event_id
			// handle local echoes
			if (eventData.sender === lsm.get("mx_user_id") && eventData.content && this.pending.has(eventData.content["chat.carbon.message.pending_id"])) {
				const target = this.map.get(eventData.content["chat.carbon.message.pending_id"])
				this.map.set(id, target)
				this.map.delete(eventData.content["chat.carbon.message.pending_id"])
			}
			// handle timeline events
			if (this.map.has(id)) {
				// update existing event
				this.map.get(id).update(eventData)
			} else {
				// skip displaying events that we don't know how to
				if (eventData.type === "m.reaction") {
					continue
				}
				// skip redacted events
				if (eventData.unsigned && eventData.unsigned.redacted_by) {
					continue
				}
				// handle redactions
				if (eventData.type === "m.room.redaction") {
					if (this.map.has(eventData.redacts)) this.map.get(eventData.redacts).removeEvent()
					continue
				}
				// handle edits
				if (eventData.type === "m.room.message" && eventData.content["m.relates_to"] && eventData.content["m.relates_to"].rel_type === "m.replace") {
					this.pendingEdits.push(eventData)
					continue
				}
				// add new event
				const event = new Event(eventData)
				this.map.set(id, event)
				this.reactiveTimeline.addEvent(event)
			}
		}
		// apply edits
		this.pendingEdits = this.pendingEdits.filter(eventData => {
			const replaces = eventData.content["m.relates_to"].event_id
			if (this.map.has(replaces)) {
				const event = this.map.get(replaces)
				event.data.content = eventData.content["m.new_content"]
				event.setEdited(eventData.origin_server_ts)
				event.update(event.data)
				return false // handled; remove from list
			} else {
				return true // we don't have the event it edits yet; keep in list
			}
		})
		this.broadcast("afterChange")
	}

	removeEvent(id) {
		if (!this.map.has(id)) throw new Error(`Tried to delete event ID ${id} which does not exist`)
		this.map.get(id).removeEvent()
		this.map.delete(id)
	}

	getTimeline() {
		return this.reactiveTimeline
	}

	async loadScrollback() {
		debug = true
		if (!this.from) throw new Error("Can't load scrollback, no from token")
		const url = new URL(`${lsm.get("domain")}/_matrix/client/r0/rooms/${this.id}/messages`)
		url.searchParams.set("access_token", lsm.get("access_token"))
		url.searchParams.set("from", this.from)
		url.searchParams.set("dir", "b")
		url.searchParams.set("limit", "20")
		const filter = {
			lazy_load_members: true
		}
		url.searchParams.set("filter", JSON.stringify(filter))

		const root = await fetch(url.toString()).then(res => res.json())

		this.broadcast("beforeScrollbackLoad")

		this.from = root.end
		// console.log(this.updateEvents, root.chunk)
		if (root.state) this.updateStateEvents(root.state)
		if (root.chunk.length) {
			// there are events to display
			this.updateEvents(root.chunk)
		} else {
			// we reached the top of the scrollback
			this.reactiveTimeline.loadMore.remove()
		}
		this.broadcast("afterScrollbackLoad")
	}

	send(body) {
		const tx = getTxnId()
		const id = `pending$${tx}`
		this.pending.add(id)
		const content = {
			msgtype: "m.text",
			body,
			"chat.carbon.message.pending_id": id
		}
		const fakeEvent = {
			type: "m.room.message",
			origin_server_ts: Date.now(),
			event_id: id,
			sender: lsm.get("mx_user_id"),
			content,
			pending: true
		}
		this.updateEvents([fakeEvent])
		return fetch(`${lsm.get("domain")}/_matrix/client/r0/rooms/${this.id}/send/m.room.message/${tx}?access_token=${lsm.get("access_token")}`, {
			method: "PUT",
			body: JSON.stringify(content),
			headers: {
				"Content-Type": "application/json"
			}
		})
	}
}

module.exports = {Timeline}