#!/usr/bin/env bash
# startb: start a command in the background with journald or file logging fallback.
# Usage:
#   startb [--log logfile] COMMAND [ARGS...]
# Environment:
#   STARTB_LOGFILE=... to force a log file.

set -euo pipefail

# PATH may be incomplete from systemd login env; restore from interactive shell.
PATH=$(zsh -c -i 'echo $PATH')
export PATH

SCRIPT_NAME="${0##*/}"

usage() {
  cat <<EOF
Usage: ${SCRIPT_NAME} [--log logfile] COMMAND [ARGS...]

--log logfile  Write logs to this file instead of journald.
Environment variable STARTB_LOGFILE can also provide a logfile path.
EOF
  exit 1
}

if [ $# -lt 1 ]; then
  usage
fi

LOG_FILE=${STARTB_LOGFILE:-}

if [ "$1" = "--log" ] || [ "$1" = "-l" ]; then
  shift
  if [ $# -lt 1 ]; then
    echo "Error: --log requires a logfile path." >&2
    usage
  fi
  LOG_FILE=$1
  shift
fi

if [ $# -lt 1 ]; then
  usage
fi

COMMAND=("$@")
UNIT_BASE=$(basename "${COMMAND[0]}")
UNIT_BASE=${UNIT_BASE:-cmd}
UNIT_NAME="${UNIT_BASE}-$(date +%Y%m%d_%H%M%S_%N)"

log_to_file() {
  local path=$1
  mkdir -p "$(dirname "$path")" 2>/dev/null || true
  touch "$path" || {
    echo "Failed to touch logfile: $path" >&2
    return 1
  }

  nohup setsid "${COMMAND[@]}" >>"$path" 2>&1 &
  local pid=$!
  disown "$pid" 2>/dev/null || true
  echo "$UNIT_NAME started in background (pid=$pid), logs: $path"
  return 0
}

log_to_journal() {
  # 不按雪叶那样写基本记录不到输出，懒得调了，直接屏蔽。
  # if command -v systemd-run >/dev/null 2>&1; then
  #   systemd-run --user --scope --unit="$UNIT_NAME" -- "${COMMAND[@]}" >/dev/null 2>&1 &
  #   local pid=$!
  #   echo "$UNIT_NAME started in systemd scope (pid=$pid), journald logging enabled"
  #   return 0
  # fi

  if command -v systemd-cat >/dev/null 2>&1; then
    nohup setsid systemd-cat -t "$UNIT_BASE" -- "${COMMAND[@]}" >/dev/null 2>&1 &
    local pid=$!
    disown "$pid" 2>/dev/null || true
    echo "$UNIT_BASE started with systemd-cat (pid=$pid), journald logging enabled"
    return 0
  fi

  return 1
}

if [ -n "$LOG_FILE" ]; then
  log_to_file "$LOG_FILE" || exit 1
  exit 0
fi

if log_to_journal; then
  exit 0
fi

# Fallback log path when journald is unavailable.
LOG_FILE="/tmp/${USER:-unknown}/startb/${UNIT_NAME}.log"
log_to_file "$LOG_FILE"