'use strict'
const fs = require('fs').promises
const app = require('express')()
const wg = require('./wireguard')

// Variables
const PORT = 80
const IPV4_CIDR = 16
const IPV4_NET = '10.4'
const IPV6_CIDR = 80
const IPV6_NET = 'fd69:1337:0:420:f4:f4'
const WG_CONFIG_FILE = '/etc/wireguard/wg.conf'
const TLD = 'gf4'
const SERVERS = [
	{
		host: 'ksn',
		ipv4: '10.4.0.1',
		ipv6: 'fd69:1337:0:420:f4:f4::1',
		pubkey: '/LrbvvmXLk2ZmU94JZua+eliqySuJ4QMHApthjvhO3s=',
		endpoint: '172.93.54.60:52348',
		dns: true,
		local: true,
	}, {
		host: 'krow',
		ipv4: '10.4.0.3',
		ipv6: 'fd69:1337:0:420:f4:f4::3',
		pubkey: '6VA79LOmlUaJSD1AiLEMCtnjMRZ7rwRrdbtNSCDtO2k=',
		endpoint: '85.17.214.157:56333',
		dns: true,
	}
]

//TODO: Extract this from SERVERS with dns=true
const DNS_SERVERS = '10.4.0.1, fd69:1337:0:420:f4:f4::1, 10.4.0.3, fd69:1337:0:420:f4:f4::3'

// API
app.get('/', async (req,res) => {
	const privkey = req.query['del']
	const hostname = req.query['add']
	const requester = req.ip.replace('::ffff:','')
	
	// Delete a peer
	if (privkey) {
		console.log(`Deleting ${privkey} from ${req.ip}`)
		res.setHeader('content-type', 'text/plain')
		res.send(`Delete ${privkey}`)
	}

	// Add a peer
	else if (hostname) {
		console.log(`New peer request from ${requester}`)
		
		// Determine user subnet
		let subnet
		if (requester.includes(IPV4_NET)) subnet = requester.split('.').slice(-2,-1)[0]
		else if (requester.includes(IPV6_NET)) subnet = requester.split(':').slice(-2,-1)[0]
		else console.log(`Received add request from ${requester}, which does not appear to be from the network.`)

		// Read wg.conf file for this user's other devices
		const userpeers = (await fs.readFile(WG_CONFIG_FILE)).toString()
		.split('\n\n').filter( (paragraph) => {
			return paragraph.includes('[Peer]')
		}).filter( (peer) => {
			return peer.includes(`${IPV4_NET}.${subnet}`) || peer.includes(`${IPV6_NET}:${subnet}`)
		})
		let found_usernames = []
		let found_ipv6s = []
		let found_ipv4s = []
		for (const userpeer of userpeers) {
			for (const line of userpeer.split('\n')) {
				if (line.includes('[Peer]')) {
					// Check if host exists
					if (line.includes(`# ${hostname}.`)) {
						console.log(`Host already exists for ${hostname}`)
						res.sendStatus(500); return
					}
					found_usernames.push(line.split('.').slice(-2,-1)[0])
				}
				else if (line.includes('AllowedIPs')) {
					const ips = line.split('=')[1].split(',')
					found_ipv4s.push(ips.filter( (ip) => ip.includes(IPV4_NET) ))
					found_ipv6s.push(ips.filter( (ip) => ip.includes(IPV6_NET) ))
				}
			}
		}
		// Check that all IP addresses are in correct subnet or error out
		if (!found_ipv4s.every((found_ipv4) => 
		found_ipv4.toString().includes(`${IPV4_NET}.${subnet}.`))) {
                        console.log(`Found unmatching IPv4 address subnets for ${requester}: ${found_ipv4s}`)
			res.sendStatus(500); return
		} else if (!found_ipv6s.every((found_ipv6) =>
                found_ipv6.toString().includes(`${IPV6_NET}:${subnet}:`))) {
                        console.log(`Found unmatching IPv6 address subnets for ${requester}: ${found_ipv6s}`)
                        res.sendStatus(500); return
		// Check that all usernames are correct or error out
		// https://stackoverflow.com/a/35568895
		} else if (!found_usernames.every( (v,i,r) => v === r[0] )) {
			console.log(`Found unmatching usernames for ${requester}: ${found_usernames.toString()}`)
			res.sendStatus(500); return

		// Everything looks good!  Proceed
		} else {
			const username = found_usernames[0]
			console.log(`${requester} must be ${username}`)

			// Find next available host part in config
			const used_ipv4_hosts = found_ipv4s.map((found_ipv4) => 
				found_ipv4.toString().split('.')[3].split('/')[0])
			const used_ipv6_hosts = found_ipv6s.map((found_ipv6) => 
				found_ipv6.toString().split(':')[3].split('/')[0])
			let host = 1
			while ([...used_ipv4_hosts,...used_ipv6_hosts].includes(host.toString())) host++
			
			// Create IP Addresses and keys
			const ipv4_addr = `${IPV4_NET}.${subnet}.${host}`
			const ipv6_addr = `${IPV6_NET}:${subnet}:${host}`
			const keypair = await wg.generateKeypair()
			const pubkey = keypair[0]
			const privkey = keypair[1]
			
			// Create [Peer] sections for each SERVERS
			let client_peers = []
			let server_peers = {}
			for (const server of SERVERS) {
				const psk = await wg.generatePSK()
				client_peers.push(`
[Peer] # ${server.host}.${TLD}
PublicKey = ${server.pubkey}
PresharedKey = ${psk}
AllowedIPs = ${server.ipv4}/32, ${server.ipv6}/128
Endpoint = ${server.endpoint}
PersistentKeepAlive = 25`)
				const server_config = `\n
[Peer] # ${hostname}.${username}.${TLD}
PublicKey = ${pubkey}
PresharedKey = ${psk}
AllowedIPs = ${ipv4_addr}/32, ${ipv6_addr}/128`
				if (server.local) {
					// Add server_config to wg0.conf
					fs.appendFile(WG_CONFIG_FILE,server_config)
				} else {
					//TODO: Send server_config to `${server.host}.gf4`
					console.log(`Sending config to ${server.host}.gf4`)
				}
			}
	
			//TODO: Nameserver config
	
			// Generate config
			const listen_port = Math.floor(50000 + Math.random() * 10000)
			const config = `[Interface]
PrivateKey = ${privkey}
Address = ${ipv4_addr}/${IPV4_CIDR}, ${ipv6_addr}/${IPV6_CIDR}
DNS = ${DNS_SERVERS}
ListenPort = ${listen_port}
PostUp = resolvectl domain ${TLD} ${TLD}
${client_peers.join('\n')}`
	
			// Send config to user
			res.setHeader('content-type', 'text/plain')
			res.send(config)
		}
	}

	// Invalid querystring
	else { console.log(`Invalid querystring: ${req.query}`) }
}).listen(PORT)