import 'npm:iterator-polyfill'
// Polyfill AsyncIterator

import { FreshContext } from '$fresh/server.ts'
import { Contact, type Mail, send } from '@cohabit/cohamail/mod.ts'
import { magicLinkTemplate } from '@cohabit/cohamail/templates/mod.ts'
import { SessionHandlers } from '../../../src/session/mod.ts'
import { respondApi } from '../../../src/utils.ts'
import { sleep } from '@jotsr/delayed'
import { User } from '@cohabit/ressources_manager/src/models/mod.ts'
import { db } from '../../../src/db/mod.ts'

type MagicLinkInfos = {
	remoteId: string
	email: string
	timestamp: number
}

export async function getUserByMail(email: string): Promise<User | undefined> {
	const [user] = await db.ressource.user
		.list((user) => user.mail === email)
		.take(1)
		.toArray()

	return user
}

export const handler: SessionHandlers = {
	async POST(request, ctx) {
		const { email } = await request.json() as { email: string }

		// check email before continue
		if (!/\S+@\S+\.\S+/.test(email)) {
			return respondApi('error', new SyntaxError('empty or invalid email'), 400)
		}

		const user = await getUserByMail(email)

		// generate magic link
		const token = crypto.randomUUID()
		const endpoint =
			`${ctx.url.origin}/api/magiclink?token=${token}&redirect=/profil`

		// save token to session
		ctx.state.session.flash<MagicLinkInfos>(`MAGIC_LINK__${token}`, {
			email,
			remoteId: remoteId(request, ctx),
			timestamp: Date.now(),
		})

		// send mail to user
		try {
			if (user) {
				const ip = ctx.remoteAddr.hostname
				const device = request.headers.get('Sec-Ch-Ua-Platform') ?? undefined

				await sendMagicLink(user, { device, ip, endpoint })
			} else {
				//! perform wait to prevent time attacks
				await sleep(Math.random() * 5_000 + 2_000) //between 2s and 7s
			}
			return respondApi('success')
		} catch (error) {
			console.error('MAGIC_LINK_SENDING', error)
			return respondApi(
				'error',
				new Error(`unable to send mail to ${email}`),
				500,
			)
		}
	},
	async GET(request, ctx) {
		const token = ctx.url.searchParams.get('token')
		const redirect = ctx.url.searchParams.get('redirect')

		// no token
		if (token === null) {
			return respondApi('error', 'no token provided', 400)
		}
		// wrong or timeout token
		const entry = ctx.state.session.get<MagicLinkInfos>(`MAGIC_LINK__${token}`)

		const lifespan = Date.now() - 10 * 60 * 1_000 // ten minutes

		if (entry === undefined || entry.timestamp < lifespan) {
			return respondApi('error', 'wrong token or timeout exceeded', 401)
		}

		// check remote id (same user/machine that has query the token)
		if (entry.remoteId === remoteId(request, ctx)) {
			const user = await getUserByMail(entry.email)
			ctx.state.session.set('user', user)

			if (redirect) {
				return Response.redirect(new URL(redirect, ctx.basePath))
			}

			return respondApi('success', user)
		}

		return respondApi(
			'error',
			new Error(
				'invalid id, use the same device/ip to query token and verify token',
			),
			401,
		)
	},
}

function remoteId(
	{ headers }: { headers: Headers },
	{ remoteAddr }: { remoteAddr: FreshContext['remoteAddr'] },
): string {
	const forwardedAddress = headers.get('X-FORWARDED-FOR')
	const forwardedProto = headers.get('X-FORWARDED-PROTO')

	if (forwardedAddress && forwardedProto) {
		return `${forwardedProto}://${forwardedAddress}`
	}

	return `(${remoteAddr.transport}):${remoteAddr.hostname}:${remoteAddr.port}`
}

async function sendMagicLink(
	{ firstname, lastname, mail }: User,
	{ device, ip, endpoint }: { device?: string; ip?: string; endpoint: string },
): Promise<void> {
	const message: Mail = {
		from: Contact.expand('contact'),
		to: [Contact.fromString(`${firstname} ${lastname} <${mail}>`)],
		subject: 'Lien de connection pour FabLab Coh@bit',
		body: magicLinkTemplate.builder({
			device,
			ip,
			endpoint,
		})!,
		options: {
			cc: [],
			cci: [],
			attachments: [],
		},
	}

	await send(message)
}