#!/bin/bash
# like `start /b` in Windows CMD.

# goddamn nvm-sh !!!
# have to update PATH before launch
PATH=$(zsh -c -i 'echo $PATH')
export PATH

# https://vescrity.github.io/post/systemd-desktop-suspend/
#systemd-run --user --scope --slice=YukiLauncher.slice --unit="$1-$$".scope /bin/sh -c '"$@"' _ "$@"

# Generated by GitHub Copilot.
# start-bg-journal.sh - start a command as a detached daemon and send stdout/stderr to systemd-journald
#
# Features:
#  - Sends stdout+stderr to journald using systemd-cat when available.
#  - Falls back to writing into a logfile if systemd-cat isn't present or if --log is passed.
#  - Uses setsid to detach, closes inherited file descriptors (best-effort),
#    redirects stdin to /dev/null, and execs the target command.
#  - Supports PID file, umask, and a syslog identifier (tag) and priority for journald.
#  - Uses positional args ($@) for the command; uses $$ in auto-generated names and prints the child PID ($!).
#
# Usage:
#   start-bg-journal.sh [ -t TAG ] [ -r PRIORITY ] [ -l LOGFILE | -d LOGDIR ] [ -p PIDFILE ] [ -u UMASK ] -- command [args...]
#
# Examples:
#   ./start-bg-journal.sh -t myapp -- /usr/bin/myapp --config /etc/myapp.conf
#   ./start-bg-journal.sh -l ./my.log -- /usr/bin/myapp arg1 arg2
#   ./start-bg-journal.sh -p /run/myapp.pid -t myapp -r info -- /usr/bin/myapp
set -euo pipefail

progname=$(basename "$0")

usage() {
  cat <<EOF
Usage: $progname [ -t TAG ] [ -r PRIORITY ] [ -l LOGFILE | -d LOGDIR ] [ -p PIDFILE ] [ -u UMASK ] -- command [args...]

Start command [args...] as a background daemon, sending stdout+stderr to systemd-journald (via systemd-cat)
when available. If systemd-cat is not available or if -l/--log is provided, logs are written to a logfile.

Options:
  -t, --tag TAG        Tag / SYSLOG_IDENTIFIER used by systemd-cat (default: basename(command))
  -r, --priority PRIO  Journal priority (emerg, alert, crit, err, warning, notice, info, debug)
  -l, --log LOGFILE    Write stdout+stderr to LOGFILE instead of journald
  -d, --dir LOGDIR     Directory for autogenerated log files (default: /tmp/$USER/runner)
  -p, --pidfile PATH   Write daemon PID to PATH
  -u, --umask UMASK    Set umask for the daemon (default: 0022)
  -h, --help           Show this help and exit

When no -l is provided and journald is available, output goes to journald.
When -l is not provided and journald is not available, a logfile is auto-generated:
  <LOGDIR>/<command>.<YYYYMMDD-HHMMSS>.pid<$$>.log
EOF
  exit 1
}

# Defaults
logdir="/tmp/$USER/runner"
logfile=""
pidfile=""
umask_val="0022"
tag=""
priority=""

# Parse options up to --
while [[ $# -gt 0 ]]; do
  case "$1" in
    -t|--tag)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      tag="$2"; shift 2 ;;
    -r|--priority)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      priority="$2"; shift 2 ;;
    -l|--log)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      logfile="$2"; shift 2 ;;
    -d|--dir)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      logdir="$2"; shift 2 ;;
    -p|--pidfile)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      pidfile="$2"; shift 2 ;;
    -u|--umask)
      if [[ $# -lt 2 ]]; then echo "Missing argument for $1"; usage; fi
      umask_val="$2"; shift 2 ;;
    -h|--help)
      usage ;;
    --)
      shift; break ;;
    -*)
      echo "Unknown option: $1"; usage ;;
    *)
      break ;;
  esac
done

if [[ $# -eq 0 ]]; then
  echo "Error: no command specified."
  usage
fi

# Build command array from remaining args.
cmd=( "$@" )
cmd_basename=$(basename "${cmd[0]}")
timestamp=$(date +%Y%m%d-%H%M%S)

# If tag not set, default to command basename
if [[ -z "$tag" ]]; then
  tag="${cmd_basename}"
fi

# Detect systemd-cat
systemd_cat_path=""
if command -v systemd-cat >/dev/null 2>&1; then
  systemd_cat_path=$(command -v systemd-cat)
fi

# If user provided logfile explicitly, force file mode
use_journal=false
if [[ -n "${logfile}" ]]; then
  use_journal=false
else
  if [[ -n "${systemd_cat_path}" ]]; then
    use_journal=true
  else
    use_journal=false
  fi
fi

# Prepare logfile if needed
mkdir -p -- "${logdir}"
if ! $use_journal; then
  if [[ -z "${logfile}" ]]; then
    logfile="${logdir}/${cmd_basename}.${timestamp}.pid$$.log"
  fi
  # Ensure file exists and is writable
  : > "${logfile}" || { echo "Cannot write to log file: ${logfile}"; exit 1; }
fi

# Helper: quote command for printing
quoted_cmd() {
  local i out=""
  for i in "$@"; do
    printf -v i "%q" "$i"
    out="${out} ${i}"
  done
  printf '%s' "${out# }"
}

# Build the inner script to run under setsid. We inject expanded variables from outer shell.
if $use_journal; then
  # Compose systemd-cat args (escape tag and priority safely)
  # Note: we rely on simple token expansion; tag/priority are validated minimally below.
  journal_args=()
  journal_args+=( "-t" )
  journal_args+=( "$tag" )
  if [[ -n "$priority" ]]; then
    journal_args+=( "-p" )
    journal_args+=( "$priority" )
  fi

  # Validate priority loosely (allow common names or numeric)
  case "$priority" in
    ""|emerg|alert|crit|err|warning|notice|info|debug|0|1|2|3|4|5|6|7) ;;
    *)
      echo "Warning: unknown priority '$priority' — journald may reject it." >&2 ;;
  esac

  # Prepare a single string of quoted journal args for insertion into the -c script
  # We need to protect values with single quotes if they contain special chars.
  journal_args_escaped=""
  for a in "${journal_args[@]}"; do
    # replace every single quote with '\'"\''
    a_escaped=${a//\'/\'"\'"\'}
    journal_args_escaped="$journal_args_escaped '$a_escaped'"
  done

  inner_script=$(cat <<'EOF'
umask __UMASK__
cd / || true

# Close fds (best-effort)
if [ -d /proc/self/fd ]; then
  for fdpath in /proc/self/fd/*; do
    fdnum=${fdpath##*/}
    case "$fdnum" in
      0|1|2) continue ;;
    esac
    eval "exec ${fdnum}>&-" 2>/dev/null || true
  done
else
  maxfd=$(ulimit -n 2>/dev/null || echo 256)
  case "$maxfd" in (*[!0-9]*|"") maxfd=256 ;; esac
  fd=3
  while [ "$fd" -le "$maxfd" ]; do
    eval "exec ${fd}>&-" 2>/dev/null || true
    fd=$((fd+1))
  done
fi

# Redirect stdio: stdin -> /dev/null, stdout+stderr -> systemd-cat (journal)
exec </dev/null
# Note: the systemd-cat command and its args are inserted by the outer script.
exec > >( __SYSTEMD_CAT__ ) 2>&1

# Exec the target command; "$@" expands to the command and its args passed after --
exec "$@"
EOF
)

  # Substitute placeholders with safe values
  inner_script=${inner_script//'__UMASK__'/"$umask_val"}
  # Build the systemd-cat invocation string (path + args) — shell-escaped
  # We need a single token string like: /bin/systemd-cat -t 'tag' -p 'priority'
  systemd_cat_cmd="$(printf '%s' "$systemd_cat_path")$journal_args_escaped"
  # Replace placeholder __SYSTEMD_CAT__ with the built command
  inner_script=${inner_script//'__SYSTEMD_CAT__'/"$systemd_cat_cmd"}

  # Start the detached process via setsid
  setsid bash -c "$inner_script" -- "${cmd[@]}" &
else
  # Fallback: redirect to logfile (file mode)
  inner_script=$(cat <<'EOF'
umask __UMASK__
cd / || true

# Close fds (best-effort)
if [ -d /proc/self/fd ]; then
  for fdpath in /proc/self/fd/*; do
    fdnum=${fdpath##*/}
    case "$fdnum" in
      0|1|2) continue ;;
    esac
    eval "exec ${fdnum}>&-" 2>/dev/null || true
  done
else
  maxfd=$(ulimit -n 2>/dev/null || echo 256)
  case "$maxfd" in (*[!0-9]*|"") maxfd=256 ;; esac
  fd=3
  while [ "$fd" -le "$maxfd" ]; do
    eval "exec ${fd}>&-" 2>/dev/null || true
    fd=$((fd+1))
  done
fi

exec </dev/null
exec > "__LOGFILE__" 2>&1

exec "$@"
EOF
)
  inner_script=${inner_script//'__UMASK__'/"$umask_val"}
  # Escape logfile path for safe insertion (single-quote style)
  log_escaped=${logfile//\'/\'"\'"\'}
  inner_script=${inner_script//'__LOGFILE__'/"'$log_escaped'"}
  setsid bash -c "$inner_script" -- "${cmd[@]}" &
fi

child_pid=$!

# Try to disown if supported
if command -v disown >/dev/null 2>&1; then
  disown "$child_pid" 2>/dev/null || true
fi

# Optionally write pidfile
if [[ -n "${pidfile}" ]]; then
  mkdir -p -- "$(dirname "${pidfile}")"
  printf '%s\n' "${child_pid}" > "${pidfile}"
fi

echo "Started command: $(quoted_cmd "${cmd[@]}")"
echo "Script PID: $$"
echo "Daemon PID: ${child_pid}"
if $use_journal; then
  echo "Output destination: systemd-journald (via $(printf '%s' "$systemd_cat_path"))"
  echo "Journal tag: ${tag}"
  if [[ -n "${priority}" ]]; then
    echo "Journal priority: ${priority}"
  fi
else
  echo "Log file: ${logfile}"
fi
if [[ -n "${pidfile}" ]]; then
  echo "PID file: ${pidfile}"
fi
echo "Started at: $(date --iso-8601=seconds 2>/dev/null || date +%Y-%m-%dT%H:%M:%S%z)"

if ! $use_journal; then
  echo
  echo "To follow the log: tail -F ${logfile}"
else
  echo
  echo "To view logs for this tag: journalctl -t ${tag} -f"
fi