#!/bin/sh
# Monitor 容器节点（Agent、Probe）的宿主机更新器。用法：monitor-update <check|apply> <组件>   组件 = agent 或 probe
#
# 信任模型（防篡改、防中间人）：
#   - 只接受用发布私钥签名的清单（ECDSA P-256 / SHA-256，对清单文件的原始字节签名）；公钥放在本机，面板和 Registry 都改不了它。
#   - 清单里写的是镜像的 digest：拉取时用 repo@sha256:…，内容寻址，Registry 或链路上的人换不出另一个镜像。
#   - 镜像仓库、组件、服务名都来自本机的配置（/etc/monitor-update/<组件>.conf），清单里写什么都不会改变拉哪个仓库。
#   - 清单的 seq 必须比已安装的大（防止旧清单被重放回滚）。
#   - 业务进程（Agent、Probe）只能往数据目录里写「清单」和「请求」文件，更新由这个宿主机脚本完成，业务进程不执行任何命令。
set -eu

CMD="${1:-}"
COMPONENT="${2:-}"
case "$CMD" in check|apply) ;; *) echo "usage: monitor-update <check|apply> <agent|probe>" >&2; exit 2 ;; esac
case "$COMPONENT" in agent|probe) ;; *) echo "component must be agent or probe" >&2; exit 2 ;; esac

CONF="${MONITOR_UPDATE_CONF_DIR:-/etc/monitor-update}/$COMPONENT.conf"
[ -r "$CONF" ] || { echo "missing $CONF" >&2; exit 2; }
# 配置：DATA_DIR（容器里 /etc/monitor 对应的宿主机目录）、IMAGE_REPO、UNIT、PUBKEY、POLICY（auto|manual）、AUTHFILE（可选）、
#       STATE_DIR（已安装版本的记录）、ENV_FILE（容器单元读取的 IMAGE=… 文件）
# shellcheck disable=SC1090
. "$CONF"
: "${DATA_DIR:?}" "${IMAGE_REPO:?}" "${UNIT:?}" "${PUBKEY:?}" "${ENV_FILE:?}"
POLICY="${POLICY:-manual}"
STATE_DIR="${STATE_DIR:-/var/lib/monitor-update}"
# 业务进程（容器里的 Agent、Probe）可写的目录只有 update/：它在里面放 offer.manifest、offer.sig、apply.request。
# 这个脚本以 root 运行，所以：只读取普通文件（不跟符号链接）、读取之后先复制到自己的临时目录再验证和使用（防止验证之后被换掉），
# 并且绝不往 update/ 里写任何东西；状态写在 root 拥有的 update-status/ 里（业务进程只读）。
UPDATE_DIR="$DATA_DIR/update"
STATUS_DIR="$DATA_DIR/update-status"
STATUS="$STATUS_DIR/status.json"
INSTALLED="$STATE_DIR/$COMPONENT.installed"     # 两行：seq、digest
mkdir -p "$STATE_DIR" "$STATUS_DIR"
chmod 755 "$STATUS_DIR"
WORK="$(mktemp -d)"
trap 'rm -rf "$WORK"' EXIT
OFFER_MANIFEST="$WORK/offer.manifest"
OFFER_SIG="$WORK/offer.sig"

# 把业务进程放的清单和签名复制到临时目录；不是普通文件（缺失、符号链接）就当作没有
fetch_offer() {
  rm -f "$OFFER_MANIFEST" "$OFFER_SIG"
  for name in offer.manifest offer.sig; do
    f="$UPDATE_DIR/$name"
    if [ -f "$f" ] && [ ! -L "$f" ]; then head -c 8192 "$f" > "$WORK/$name"; fi
  done
}

now() { date +%s; }

# 状态文件：Agent / Probe 读它并随心跳报给面板。root 写，业务进程只读。
write_status() { # state available_json error
  tmp="$(mktemp "$STATUS_DIR/.status.XXXXXX")"
  printf '{"state":"%s","current":"%s","available":%s,"error":"%s","at":%s}\n' \
    "$1" "$(current_digest)" "${2:-null}" "$(printf '%s' "${3:-}" | tr -d '"\\\n' | cut -c1-200)" "$(now)" > "$tmp"
  chmod 644 "$tmp"
  mv -f "$tmp" "$STATUS"
}

current_digest() { [ -r "$INSTALLED" ] && sed -n 2p "$INSTALLED" || echo ""; }
installed_seq() { [ -r "$INSTALLED" ] && sed -n 1p "$INSTALLED" || echo 0; }

# 从扁平的清单里取字段（清单由 CI 生成，只有字符串和整数，没有嵌套）
field() { sed -n 's/.*"'"$1"'":"\([^"]*\)".*/\1/p' "$OFFER_MANIFEST" | head -n 1; }
num_field() { sed -n 's/.*"'"$1"'":\([0-9][0-9]*\).*/\1/p' "$OFFER_MANIFEST" | head -n 1; }

# 验签 + 字段校验。成功时设置 M_DIGEST、M_TAG、M_VERSION、M_SEQ；失败返回非 0，原因在 ERR。
verify_offer() {
  ERR=""
  [ -s "$OFFER_MANIFEST" ] && [ -s "$OFFER_SIG" ] || { ERR="no offer"; return 1; }
  [ "$(wc -c < "$OFFER_MANIFEST")" -le 4096 ] || { ERR="manifest too large"; return 1; }
  sigbin="$WORK/sig.bin"
  base64 -d "$OFFER_SIG" > "$sigbin" 2>/dev/null || { ERR="bad signature encoding"; return 1; }
  openssl dgst -sha256 -verify "$PUBKEY" -signature "$sigbin" "$OFFER_MANIFEST" >/dev/null 2>&1 || { ERR="signature check failed"; return 1; }
  [ "$(field component)" = "$COMPONENT" ] || { ERR="manifest is for another component"; return 1; }
  [ "$(field image)" = "$IMAGE_REPO" ] || { ERR="manifest names another repository"; return 1; }
  M_DIGEST="$(field digest)"
  case "$M_DIGEST" in sha256:*) ;; *) ERR="bad digest"; return 1 ;; esac
  [ "${#M_DIGEST}" -eq 71 ] && [ -z "$(printf '%s' "${M_DIGEST#sha256:}" | tr -d '0-9a-f')" ] || { ERR="bad digest"; return 1; }
  M_TAG="$(field tag)"; M_VERSION="$(field version)"; M_SEQ="$(num_field seq)"
  [ -n "$M_SEQ" ] || { ERR="no seq"; return 1; }
  [ "$M_SEQ" -gt "$(installed_seq)" ] || { ERR="stale manifest (seq $M_SEQ <= $(installed_seq))"; return 1; }
}

available_json() { printf '{"version":"%s","tag":"%s","digest":"%s","seq":%s}' "$(printf '%s' "$M_VERSION" | tr -d '"\\')" "$(printf '%s' "$M_TAG" | tr -d '"\\')" "$M_DIGEST" "$M_SEQ"; }

do_check() {
  fetch_offer
  if ! verify_offer; then
    # 没有新清单，或者清单已经安装过：不算错误，只是没有更新
    case "$ERR" in
      "no offer"|"stale manifest"*) write_status up_to_date null "" ;;
      *) write_status invalid null "$ERR"; echo "offer rejected: $ERR" >&2 ;;
    esac
    return 0
  fi
  if [ "$M_DIGEST" = "$(current_digest)" ]; then
    write_status up_to_date null ""
    return 0
  fi
  write_status available "$(available_json)" ""
  echo "update available: $M_TAG ($M_DIGEST)"
  if [ "$POLICY" = auto ]; then do_apply; fi
  return 0
}

do_apply() {
  rm -f "$UPDATE_DIR/apply.request"
  fetch_offer
  verify_offer || { write_status invalid null "$ERR"; echo "refusing to apply: $ERR" >&2; return 1; }
  avail="$(available_json)"
  write_status applying "$avail" ""
  ref="$IMAGE_REPO@$M_DIGEST"
  if [ -n "${AUTHFILE:-}" ]; then export REGISTRY_AUTH_FILE="$AUTHFILE"; fi
  if ! podman pull --quiet "$ref" >/dev/null 2>&1; then
    write_status failed "$avail" "pull failed"; echo "pull failed: $ref" >&2; return 1
  fi
  prev="$(cat "$ENV_FILE" 2>/dev/null || true)"
  printf 'IMAGE=%s\n' "$ref" > "$ENV_FILE.new" && mv -f "$ENV_FILE.new" "$ENV_FILE"
  systemctl restart "$UNIT" || true
  # 健康确认：服务在跑，并且 20 秒内没有再被重启（崩溃循环算失败）
  sleep 5
  before="$(systemctl show -p NRestarts --value "$UNIT" 2>/dev/null || echo 0)"
  sleep 15
  after="$(systemctl show -p NRestarts --value "$UNIT" 2>/dev/null || echo 0)"
  if systemctl is-active --quiet "$UNIT" && [ "$before" = "$after" ]; then
    printf '%s\n%s\n' "$M_SEQ" "$M_DIGEST" > "$INSTALLED"
    write_status up_to_date null ""
    echo "updated to $M_TAG"
    return 0
  fi
  echo "new version did not become healthy, rolling back" >&2
  if [ -n "$prev" ]; then printf '%s\n' "$prev" > "$ENV_FILE"; fi
  systemctl restart "$UNIT" || true
  write_status rolled_back "$avail" "new version did not become healthy"
  return 1
}

case "$CMD" in
  check) do_check ;;
  apply) do_apply ;;
esac