#!/usr/bin/env bash
# Shared alert sender. Source this file; do not execute it.
# Outbound text is limited to service, route, errorCode, count, requestId, time.

ensure_private_dir() {
  local dir="$1"
  mkdir -p -- "$dir"
  if [ "$(uname -s)" = "Linux" ]; then
    chmod 700 "$dir"
  fi
}

load_monitor_env() {
  local file="$1"
  local line key value mode
  [ -n "$file" ] || return 0
  [ -f "$file" ] && [ ! -L "$file" ] || return 0
  if [ "$(uname -s)" = "Linux" ]; then
    mode="$(stat -c %a "$file")"
    [ "$mode" = "600" ] || {
      echo "monitor env must be mode 0600" >&2
      exit 1
    }
  fi
  while IFS= read -r line || [ -n "$line" ]; do
    case "$line" in
      ""|\#*) continue ;;
      FEISHU_WEBHOOK_URL=*|FEISHU_SIGN_SECRET=*)
        key="${line%%=*}"
        value="${line#*=}"
        case "$value" in
          *[$'\n\r`$']*)
            echo "monitor env value is unsafe" >&2
            exit 1
            ;;
        esac
        printf -v "$key" '%s' "$value"
        export "$key"
        ;;
    esac
  done <"$file"
}

feishu_sign() {
  local timestamp="$1"
  local secret="$2"
  local string_to_sign
  string_to_sign="$(printf '%s\n%s' "$timestamp" "$secret")"
  printf '' | openssl dgst -sha256 -hmac "$string_to_sign" -binary | openssl base64 -A
}

webhook_allowed() {
  local url="$1"
  [[ "$url" =~ ^https://open\.(feishu\.cn|larksuite\.com|larkoffice\.com)/open-apis/bot/v2/hook/[A-Za-z0-9-]+$ ]] && return 0
  [[ "$url" =~ ^http://127\.0\.0\.1:[0-9]{1,5}/hook$ ]] && return 0
  return 1
}

alert_line_allowed() {
  local line="$1"
  [[ "$line" =~ ^service=[a-z0-9_-]+[[:space:]]route=(/|/[A-Za-z0-9/_.-]+|-)[[:space:]]errorCode=[a-z][a-z0-9._-]*[[:space:]]count=[0-9]+[[:space:]]requestId=(-|[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}(,[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}){0,4})[[:space:]]time=[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}Z$ ]]
}

post_monitor_alert() {
  local text="$1"
  local state_dir line timestamp sign payload_file response_file pending py curl_status code
  state_dir="${JYOTISHA_MONITOR_STATE_DIR:-/var/lib/jyotisha-monitor}"
  ensure_private_dir "$state_dir"
  pending=""
  while IFS= read -r line || [ -n "$line" ]; do
    [ -n "$line" ] || continue
    alert_line_allowed "$line" || {
      echo "alert text has a field that is not allowed" >&2
      exit 1
    }
    pending="${pending}${line}"$'\n'
  done <<<"$text"
  [ -n "$pending" ] || return 0
  pending="${pending%$'\n'}"

  if [ -z "${FEISHU_WEBHOOK_URL:-}" ]; then
    printf '%s\n' "$pending" >>"$state_dir/alerts.log"
    return 0
  fi
  webhook_allowed "$FEISHU_WEBHOOK_URL" || {
    printf '%s\n' "service=monitor route=- errorCode=webhook_rejected count=1 requestId=- time=$(date -u +%Y-%m-%dT%H:%M:%SZ)" >>"$state_dir/alerts.log"
    return 0
  }

  payload_file="$(mktemp)"
  response_file="$(mktemp)"
  if [ "$(uname -s)" = "Linux" ]; then
    chmod 600 "$payload_file" "$response_file"
  fi
  if [ -n "${FEISHU_SIGN_SECRET:-}" ]; then
    timestamp="$(date +%s)"
    sign="$(feishu_sign "$timestamp" "$FEISHU_SIGN_SECRET")"
    FEISHU_ALERT_TEXT="$text" FEISHU_ALERT_TIMESTAMP="$timestamp" FEISHU_ALERT_SIGN="$sign" \
      python_write_payload "$payload_file" signed
  else
    FEISHU_ALERT_TEXT="$text" python_write_payload "$payload_file" plain
  fi
  if [ -n "${JYOTISHA_PYTHON:-}" ]; then
    py="$JYOTISHA_PYTHON"
  elif command -v python3 >/dev/null 2>&1; then
    py="python3"
  else
    py="python"
  fi
  curl_status=0
  curl --silent --show-error --fail --connect-timeout 10 --max-time 10 \
    -H 'Content-Type: application/json' \
    -H 'Connection: close' \
    --data-binary @"$payload_file" \
    -o "$response_file" \
    "$FEISHU_WEBHOOK_URL" || curl_status=$?
  code=""
  if [ "$curl_status" -eq 0 ]; then
    code="$("$py" - "$response_file" <<'PY'
import json
import sys

try:
    payload = json.load(open(sys.argv[1], encoding="utf-8"))
except Exception:
    print("")
    raise SystemExit(0)
if isinstance(payload, dict) and payload.get("code") == 0:
    print("0")
else:
    print("")
PY
)"
    code="$(printf '%s' "$code" | tr -d '\r')"
  fi
  rm -f -- "$payload_file" "$response_file"
  if [ "$curl_status" -ne 0 ] || [ "$code" != "0" ]; then
    echo "feishu webhook was not accepted" >&2
    return 1
  fi
  printf '%s\n' "$pending" >>"$state_dir/alerts.log"
}

python_write_payload() {
  local destination="$1"
  local mode="$2"
  local py
  export FEISHU_ALERT_TEXT FEISHU_ALERT_TIMESTAMP FEISHU_ALERT_SIGN
  if [ -n "${JYOTISHA_PYTHON:-}" ]; then
    py="$JYOTISHA_PYTHON"
  elif command -v python3 >/dev/null 2>&1; then
    py="python3"
  else
    py="python"
  fi
  "$py" - "$destination" "$mode" <<'PY'
import json
import os
import sys

destination, mode = sys.argv[1], sys.argv[2]
text = os.environ["FEISHU_ALERT_TEXT"]
payload = {"msg_type": "text", "content": {"text": text}}
if mode == "signed":
    payload["timestamp"] = os.environ["FEISHU_ALERT_TIMESTAMP"]
    payload["sign"] = os.environ["FEISHU_ALERT_SIGN"]
with open(destination, "w", encoding="utf-8", newline="\n") as handle:
    json.dump(payload, handle, ensure_ascii=True, separators=(",", ":"))
PY
}