#!/usr/bin/env perl
# Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
# SPDX-License-Identifier: MIT
#
# install.pl: install nuntius as a systemd service.
#
# nuntius ships as a single static binary. Build it on your workstation, upload
# the binary, the systemd unit, and the .env template to the server, then run
# this script there as root from that directory:
#
#   scp bin/nuntius nuntius.service .env.example user@host:/tmp/nuntius/
#   ssh user@host
#   cd /tmp/nuntius && sudo perl install.pl
#
# It expects ./nuntius and ./nuntius.service (and optionally ./.env.example) in
# the current working directory. Idempotent: re-running is safe. It skips the
# user, config, and .env when they already exist, and never starts the service.

use strict;
use warnings;

my $nuntius_user = 'nuntius';
my $bin_dest     = '/usr/local/bin/nuntius';
my $config_dir   = '/etc/nuntius';
my $config_file  = '/etc/nuntius/config.toml';
my $env_file     = '/etc/nuntius/.env';
my $data_dir     = '/var/lib/nuntius';
my $service_dest = '/etc/systemd/system/nuntius.service';

sub note  { print qq{==> $_[0]\n} }
sub warn_ { print qq{WARN: $_[0]\n} }
sub fail  { print qq{ERROR: $_[0]\n}; exit 1 }

# run executes one child in list form, so no argument is ever word-split or
# globbed, and dies naming the attempt when the child fails.
sub run {
    my (@cmd) = @_;
    system(@cmd) == 0
      or die qq{ERROR: could not run '$cmd[0]': exit code } . ($? >> 8) . qq{\n};
}

# silenced runs a block with STDOUT and STDERR pointed at /dev/null, restored
# afterwards, so the caller sees only what it decides to print.
sub silenced(&) {
    open(my $save_out, '>&', \*STDOUT) or die qq{ERROR: could not save STDOUT: $!\n};
    open(my $save_err, '>&', \*STDERR) or die qq{ERROR: could not save STDERR: $!\n};
    open(STDOUT, '>', '/dev/null') or die qq{ERROR: could not silence STDOUT: $!\n};
    open(STDERR, '>&', \*STDOUT)   or die qq{ERROR: could not silence STDERR: $!\n};
    my $result = $_[0]->();
    open(STDOUT, '>&', $save_out) or die qq{ERROR: could not restore STDOUT: $!\n};
    open(STDERR, '>&', $save_err) or die qq{ERROR: could not restore STDERR: $!\n};
    return $result;
}

sub require_root {
    $> == 0 or fail('Run as root: sudo perl install.pl');
}

sub require_files {
    -f './nuntius'
      or fail('./nuntius binary not found: copy it here first (e.g. rsync bin/nuntius).');
    -f './nuntius.service'
      or fail('./nuntius.service not found: copy it from the repository root.');
}

sub create_user {
    if (silenced { system('id', $nuntius_user) == 0 }) {
        note("User $nuntius_user already exists.");
        return;
    }
    note("Creating system user $nuntius_user...");
    run('useradd', '--system', '--shell', '/usr/sbin/nologin',
        '--home-dir', $data_dir, '--user-group', $nuntius_user);
}

sub create_data_dir {
    note("Setting up $data_dir...");
    unless (-d $data_dir) {
        mkdir($data_dir, 0750) or die qq{ERROR: could not create $data_dir: $!\n};
    }
    my $uid = getpwnam($nuntius_user)
      or die qq{ERROR: could not look up user $nuntius_user\n};
    my $gid = getgrnam($nuntius_user)
      or die qq{ERROR: could not look up group $nuntius_user\n};
    chown($uid, $gid, $data_dir) or die qq{ERROR: could not chown $data_dir: $!\n};
    chmod(0750, $data_dir) or die qq{ERROR: could not chmod $data_dir: $!\n};
}

sub install_binary {
    note("Installing binary to $bin_dest...");
    run('install', '-m', '0755', './nuntius', $bin_dest);
}

sub install_service {
    note("Installing systemd unit $service_dest...");
    run('install', '-m', '0644', './nuntius.service', $service_dest);
}

sub generate_config {
    if (-f $config_file) {
        note("Config $config_file already exists; leaving it untouched.");
        return;
    }

    note("Generating $config_file...");
    unless (-d $config_dir) {
        mkdir($config_dir, 0755) or die qq{ERROR: could not create $config_dir: $!\n};
    }

    # nuntius writes the template config on first start; run it briefly, then
    # let `timeout` send SIGTERM (graceful shutdown). The write happens at
    # startup, before the timeout elapses. timeout exits 124 on SIGTERM and
    # 137 on SIGKILL, so its status is deliberately not checked here.
    silenced { system('timeout', '-k', '5s', '4s', $bin_dest) };

    if (!-f $config_file) {
        warn_("nuntius did not create $config_file; check the uploaded binary.");
    }

    # Fix ownership in case nuntius wrote files as root.
    run('chown', '-R', "$nuntius_user:$nuntius_user", $data_dir);
}

sub install_env {
    if (-f $env_file) {
        note("$env_file already exists; leaving it untouched.");
    }
    elsif (-f './.env.example') {
        note("Creating $env_file from .env.example (edit it!)...");
        run('install', '-m', '0600', './.env.example', $env_file);
        run('chown', "root:$nuntius_user", $env_file);
    }
    else {
        warn_(".env.example not found; skipping $env_file. Create it before starting.");
    }
}

sub enable_service {
    note('Reloading systemd and enabling nuntius...');
    run('systemctl', 'daemon-reload');
    run('systemctl', 'enable', 'nuntius.service');
}

sub final_notes {
    print <<"END_NOTES";

============================================================
nuntius installed and enabled, but NOT started.

Next manual steps:
  1. Set the SMTP password:
       sudo \$EDITOR $env_file
  2. Edit the auto-generated config (smtp.host, smtp.user, allowed_origins):
       sudo \$EDITOR $config_file
  3. Start the service:
       sudo systemctl start nuntius
       sudo journalctl -u nuntius -f
  4. Add the Caddy reverse_proxy directive (see README.md), then:
       sudo caddy validate && sudo systemctl reload caddy
============================================================
END_NOTES
}

require_root();
require_files();
create_user();
create_data_dir();
install_binary();
install_service();
generate_config();
install_env();
enable_service();
final_notes();