#!/usr/bin/env bash
# install.sh — Linux installer for the restic-manager agent.
#
# Usage (paste in shell):
#   curl -fsSL https://restic.lab.example/install.sh | \
#     sudo RM_SERVER=https://restic.lab.example RM_TOKEN=<one-time-token> sh
#
# What it does:
#   1. detects arch (amd64 / arm64)
#   2. fetches the matching agent binary from the server
#   3. creates the restic-manager-agent service user
#   4. lays down /etc/restic-manager/, /var/lib/restic-manager/
#   5. enrolls (POST /api/agents/enroll) using RM_TOKEN
#   6. installs the systemd unit, enables, starts
#   7. surfaces (but does NOT disable) any existing restic timers /
#      cron entries so the operator can decide what to do
#
# Idempotent — safe to re-run; will refuse if already enrolled
# unless RM_FORCE_REENROLL=1 is set.

set -euo pipefail

: "${RM_SERVER:?must be set, e.g. https://restic.lab.example}"
: "${RM_TOKEN:?must be set, the one-time token from the operator UI}"
: "${RM_INSTALL_PREFIX:=/usr/local/bin}"
: "${RM_CONFIG_DIR:=/etc/restic-manager}"
: "${RM_STATE_DIR:=/var/lib/restic-manager}"
: "${RM_USER:=restic-manager-agent}"
: "${RM_GROUP:=restic-manager-agent}"
: "${RM_FORCE_REENROLL:=0}"

require_root() {
  if [ "$(id -u)" -ne 0 ]; then
    echo "install.sh: must be run as root" >&2
    exit 1
  fi
}

detect_arch() {
  case "$(uname -m)" in
    x86_64|amd64) echo amd64 ;;
    aarch64|arm64) echo arm64 ;;
    *) echo "unsupported architecture: $(uname -m)" >&2; exit 1 ;;
  esac
}

ensure_user() {
  if ! getent group "$RM_GROUP" >/dev/null; then
    groupadd --system "$RM_GROUP"
  fi
  if ! getent passwd "$RM_USER" >/dev/null; then
    useradd --system --gid "$RM_GROUP" \
      --home-dir "$RM_STATE_DIR" --no-create-home \
      --shell /usr/sbin/nologin \
      "$RM_USER"
  fi
}

ensure_dirs() {
  install -d -m 0750 -o "$RM_USER" -g "$RM_GROUP" "$RM_CONFIG_DIR"
  install -d -m 0750 -o "$RM_USER" -g "$RM_GROUP" "$RM_STATE_DIR"
}

detect_existing_schedulers() {
  echo
  echo "==> Scanning for existing restic schedules (we will NOT touch them)"
  local found=0
  if command -v systemctl >/dev/null 2>&1; then
    while IFS= read -r unit; do
      [ -n "$unit" ] || continue
      echo "    [systemd] $unit"
      echo "              disable with: systemctl disable --now $unit"
      found=1
    done < <(systemctl list-unit-files --no-legend --type=timer 2>/dev/null \
              | awk 'tolower($1) ~ /restic/ {print $1}')
  fi
  for f in /etc/cron.d/* /etc/cron.daily/* /etc/cron.hourly/* /etc/cron.weekly/*; do
    [ -f "$f" ] || continue
    if grep -qiI restic "$f" 2>/dev/null; then
      echo "    [cron] $f"
      echo "           review and remove or rename if you want this agent to take over"
      found=1
    fi
  done
  if root_cron=$(crontab -l 2>/dev/null); then
    if echo "$root_cron" | grep -qi restic; then
      echo "    [crontab -l] root crontab contains a restic entry"
      echo "                 review with: crontab -l"
      found=1
    fi
  fi
  if [ $found -eq 0 ]; then
    echo "    (none found)"
  fi
  echo
}

download_agent() {
  local arch out
  arch=$(detect_arch)
  out="$RM_INSTALL_PREFIX/restic-manager-agent"

  echo "==> Downloading restic-manager-agent (linux/$arch) from $RM_SERVER"
  # The server's /agent/binary endpoint serves the matching binary
  # for the requesting agent's arch. (P1-31; until then this URL
  # may need to be a static download.)
  curl -fsSL --retry 3 \
    "$RM_SERVER/agent/binary?os=linux&arch=$arch" \
    -o "$out.new"
  chmod +x "$out.new"
  mv -f "$out.new" "$out"
  echo "    installed $out ($(file -b "$out" | head -1))"
}

enroll_agent() {
  local cfg="$RM_CONFIG_DIR/agent.yaml"
  if [ -s "$cfg" ] && [ "$RM_FORCE_REENROLL" != "1" ]; then
    echo "==> $cfg already exists; skipping enrollment"
    echo "    (set RM_FORCE_REENROLL=1 to overwrite)"
    return
  fi

  echo "==> Enrolling agent with $RM_SERVER"
  sudo -u "$RM_USER" \
    "$RM_INSTALL_PREFIX/restic-manager-agent" \
      -config "$cfg" \
      -enroll-server "$RM_SERVER" \
      -enroll-token "$RM_TOKEN"
}

install_unit() {
  local unit="/etc/systemd/system/restic-manager-agent.service"
  echo "==> Installing systemd unit at $unit"
  curl -fsSL --retry 3 \
    "$RM_SERVER/install/restic-manager-agent.service" \
    -o "$unit"
  chmod 0644 "$unit"
  systemctl daemon-reload
  systemctl enable --now restic-manager-agent.service
  echo "    started; tail with: journalctl -fu restic-manager-agent"
}

main() {
  require_root
  ensure_user
  ensure_dirs
  download_agent
  detect_existing_schedulers
  enroll_agent
  install_unit
  echo
  echo "==> done."
  echo "    config:    $RM_CONFIG_DIR/agent.yaml"
  echo "    binary:    $RM_INSTALL_PREFIX/restic-manager-agent"
  echo "    service:   systemctl status restic-manager-agent"
  echo "    logs:      journalctl -fu restic-manager-agent"
}

main "$@"