// procd-compat: the parts of procd's ubus API that OpenWrt tools call, for
// a system where Shepherd, not procd, is init.
//
//  - `service' object, method `event': {type: "config.change", data:
//    {package: P}} -- sent by reload_config and by rpcd after `uci commit'
//    (LuCI's Save & Apply) -- runs `herd reload S' for each Shepherd service
//    S registered for config P.  procd does this with the reload triggers
//    init scripts declare (procd_add_reload_trigger); here they come from
//    the Guix services, in the config file.  Method `get_data' answers
//    with no data (fw4 asks it for service-provided rules).
//  - `system' object: `board', `info' (LuCI's status page, `ubus call system
//    board'), `reboot'.  Same reply shapes as procd's system.c.
//
// Usage: procd-compat CONFIG.json
//   {"herd": "/.../herd", "reboot": "/.../reboot", "uci": "/.../uci",
//    "triggers": {"firewall": ["firewall"], ...},
//    "release": {"distribution": ..., "version": ..., ...}}

'use strict';

import { connect } from 'ubus';
import * as uloop from 'uloop';
import { readfile, writefile, popen, access, statvfs } from 'fs';
import { md5 } from 'digest';

const config = json(readfile(ARGV[0]) ?? die(`cannot read ${ARGV[0]}\n`));
const triggers = config.triggers ?? {};

function log(msg) {
	warn(`procd-compat: ${msg}\n`);
}


// --- config.change -> herd reload ---------------------------------------

// procd queues triggered actions and runs them after a short delay; do the
// same, so a burst of commits (LuCI applies several configs at once) reloads
// each service once.  herd runs as a child process, one at a time, never
// blocking the loop: a reload may call back into this daemon (fw4 asks
// `service get_data').
const pending = {};
let running = false;

function run_pending() {
	const service = sort(keys(pending))[0];
	if (running || service == null)
		return;
	delete pending[service];
	running = true;
	log(`herd reload ${service}`);
	uloop.process(config.herd, [ 'reload', service ], {}, (rc) => {
		if (rc != 0)
			log(`herd reload ${service} failed (${rc})`);
		running = false;
		run_pending();
	});
}

const reloader = uloop.timer(-1, run_pending);

// reload_config compares `uci show' digests with those of its last run,
// kept in /var/run/config.md5.  rpcd (LuCI's apply and rollback) sends
// config.change itself, so that baseline would go stale and a later
// `uci commit; reload_config' could miss a change back: refresh the
// changed config's line.
const md5file = '/var/run/config.md5';

function refresh_baseline(pkg) {
	const sums = readfile(md5file);
	if (!sums || !match(pkg, /^[A-Za-z0-9_-]+$/) ||
	    !access(`/etc/config/${pkg}`))
		return;

	const p = popen(`${config.uci} show ${pkg} 2>/dev/null`);
	const sum = md5(p.read('all') ?? '');
	p.close();

	const path = `/var/run/config.check/${pkg}`;
	const lines = filter(split(trim(sums), '\n'),
	                     (l) => length(l) && !match(l, regexp(`  ${path}$`)));
	push(lines, `${sum}  ${path}`);
	writefile(md5file, join('\n', lines) + '\n');
}

function config_changed(conn, pkg) {
	refresh_baseline(pkg);

	for (let service in triggers[pkg] ?? [])
		pending[service] = true;

	if (length(pending) && !running)
		reloader.set(1000);

	// Like procd: broadcast it for anyone listening.
	conn.event('config.change', { config: pkg });
}


// --- system board / info ------------------------------------------------

function readline(path) {
	const s = readfile(path);
	return s ? trim(split(s, '\n')[0]) : null;
}

function kv_file(path, sep) {
	const res = {};
	for (let line in split(readfile(path) ?? '', '\n')) {
		const i = index(line, sep);
		if (i > 0)
			res[trim(substr(line, 0, i))] = trim(substr(line, i + 1));
	}
	return res;
}

function rootfs_type() {
	let type = null;
	for (let line in split(readfile('/proc/mounts') ?? '', '\n')) {
		const f = split(line, ' ');
		if (f[1] == '/' && f[0] != 'rootfs')
			type = f[2];
	}
	return type;
}

function board() {
	const cpu = kv_file('/proc/cpuinfo', ':');
	const res = {
		kernel: readline('/proc/sys/kernel/osrelease'),
		hostname: readline('/proc/sys/kernel/hostname'),
		// procd's aarch64 string; "model name" etc. elsewhere.
		system: cpu['CPU revision'] != null
			? sprintf('ARMv8 Processor rev %d', hex(cpu['CPU revision']))
			: cpu['model name'] ?? cpu['system type'] ?? 'unknown',
	};

	// Device tree, as procd: the model string, and the first compatible
	// entry with commas as dashes ("raspberrypi-4-model-b").
	const model = readline('/proc/device-tree/model');
	if (model)
		res.model = replace(model, /\0+$/, '');
	const compat = readfile('/proc/device-tree/compatible');
	if (compat)
		res.board_name = replace(split(compat, '\0')[0], /,/g, '-');

	res.rootfs_type = rootfs_type();
	res.release = config.release ?? {};
	return res;
}

function meminfo() {
	const m = kv_file('/proc/meminfo', ':');
	const bytes = (k) => +split(m[k] ?? '0', ' ')[0] * 1024;
	return {
		memory: {
			total: bytes('MemTotal'),
			free: bytes('MemFree'),
			shared: bytes('Shmem'),
			buffered: bytes('Buffers'),
			available: bytes('MemAvailable'),
			cached: bytes('Cached'),
		},
		swap: {
			total: bytes('SwapTotal'),
			free: bytes('SwapFree'),
		},
	};
}

function fsinfo(path) {
	const s = statvfs(path);
	if (!s)
		return null;
	const k = (n) => int(n * s.frsize / 1024);
	return {
		total: k(s.blocks),
		free: k(s.bfree),
		used: k(s.blocks - s.bfree),
		avail: k(s.bavail),
	};
}

function info() {
	const now = time();
	const mem = meminfo();
	// sysinfo(2) loads: fixed point, 1 << 16 = 1.0.
	const load = map(slice(split(readline('/proc/loadavg'), ' '), 0, 3),
	                 (l) => int(+l * 65536));
	const res = {
		// Seconds since the epoch, shifted by the UTC offset (procd:
		// now + tm_gmtoff).
		localtime: now + (now - timelocal(gmtime(now))),
		uptime: int(+split(readline('/proc/uptime'), ' ')[0]),
		load,
		memory: mem.memory,
	};
	for (let fs in [ [ '/', 'root' ], [ '/tmp', 'tmp' ] ]) {
		const i = fsinfo(fs[0]);
		if (i)
			res[fs[1]] = i;
	}
	res.swap = mem.swap;
	return res;
}


// --- ubus ---------------------------------------------------------------

uloop.init();

const conn = connect() ?? die('cannot connect to ubus\n');

// ucode rejects arguments a method doesn't declare (INVALID_ARGUMENT), and
// calls through uhttpd/rpcd (LuCI) carry the caller's session id: every
// method declares it.
const session = { ubus_rpc_session: '' };

const service_obj = conn.publish('service', {
	event: {
		args: { ...session, type: '', data: {} },
		call: (req) => {
			const ev = req.args.type, data = req.args.data;
			if (ev == null || data == null)
				return req.reply(null, 2);  // UBUS_STATUS_INVALID_ARGUMENT
			if (ev == 'config.change' && type(data.package) == 'string')
				config_changed(conn, data.package);
			req.reply(null, 0);
		},
	},
	// Data that procd services register (procd_open_data), e.g. firewall
	// rules for fw4; none here.  fw4 calls it on every start and reload.
	get_data: {
		args: { ...session, name: '', instance: '', type: '' },
		call: () => ({}),
	},
});

const system_obj = conn.publish('system', {
	board: { args: session, call: () => board() },
	info: { args: session, call: () => info() },
	reboot: {
		args: session,
		call: (req) => {
			req.reply(null, 0);
			log('reboot requested over ubus');
			uloop.timer(1000, () => system([ config.reboot ]));
		},
	},
});

if (!service_obj || !system_obj)
	die(`cannot publish objects: ${conn.error()}\n`);

log(`running; triggers for: ${join(' ', sort(keys(triggers)))}`);
uloop.run();