#!/bin/sh
# @file write-as.sh
# @description Server mode, one Linux user per account (S3): installed as
# /opt/agenthub/libexec/write-as. The dashboard runs it AS a member through
# sudo (`sudo -n -u ah-<name> /opt/agenthub/libexec/write-as <path> [mode]`)
# for every change it makes inside that member's home — the file editor, a
# `.gitignore` line, the files a pane reads (prompt, proxy settings, context
# copies, drops, a session's launch file) — because the dashboard itself may
# never write, chmod or delete there: the member can swap any name in their
# own home, and a write by another account would follow the swap. As the
# member this can only do what the member could. Content comes on stdin,
# never in argv (sudo logs argv). Modes:
#   (none)   stdin into the file in place (keeps its mode and owner)
#   append   stdin appended
#   replace  stdin into a new 0644 file renamed over the path (atomic)
#   private  same, 0600
#   mkdir    the directory, 0755, parents included
#   remove   the path, recursively (rm never follows a symlink it removes)
#   move     the path to the 3rd argument (rename; never onto an existing
#            name — checked just before, and the dashboard checks first)
#   copy     the path, recursively, to the 3rd argument (symlinks copied as
#            links, never followed; mode and times kept; never onto an
#            existing name)
# @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
set -eu
usage() {
  echo "usage: write-as <absolute path> [append|replace|private|mkdir|remove] | <path> move|copy <absolute dest>" >&2
  exit 2
}
case "${2:-}" in
  move|copy) [ $# -eq 3 ] || usage ;;
  *) { [ $# -ge 1 ] && [ $# -le 2 ]; } || usage ;;
esac
for p in "$1" "${3:-/}"; do
  case "$p" in
    /*) ;;
    *) echo "write-as: an absolute path is required" >&2; exit 2 ;;
  esac
done
swap() {
  t=$(mktemp "$1.XXXXXX")
  cat >"$t" && chmod "$2" "$t" && mv -f "$t" "$1" || { rm -f "$t"; exit 1; }
}
case "${2:-}" in
  "") exec cat >"$1" ;;
  append) exec cat >>"$1" ;;
  replace) swap "$1" 0644 ;;
  private) swap "$1" 0600 ;;
  mkdir) exec mkdir -p -m 0755 -- "$1" ;;
  remove) exec rm -rf -- "$1" ;;
  move)
    [ -e "$3" ] || [ -L "$3" ] && { echo "write-as: $3 exists" >&2; exit 1; }
    exec mv -T -- "$1" "$3" ;;
  copy)
    [ -e "$3" ] || [ -L "$3" ] && { echo "write-as: $3 exists" >&2; exit 1; }
    exec cp -R -P -T --preserve=mode,timestamps -- "$1" "$3" ;;
  *) echo "write-as: unknown mode: $2" >&2; exit 2 ;;
esac