caddy-domain.sh

#!/usr/bin/env bash
# Manage domains on a Caddy reverse proxy via its admin API.
#
# Configure via environment:
#   CADDY_API  (default: http://10.0.0.1:2019)
#
# Usage:
#   caddy-domain add <domain> <backend>     Add a domain route
#   caddy-domain remove <domain>            Remove a domain route
#   caddy-domain list                       List all configured domains
#
# Examples:
#   caddy-domain add app.example.com 10.0.0.200:8000
#   caddy-domain add docs.example.com 10.0.0.300:3001
#   caddy-domain remove app.example.com
#   caddy-domain list

set -euo pipefail

CADDY_API="${CADDY_API:-http://10.0.0.1:2019}"

usage() {
  echo "Usage:"
  echo "  caddy-domain add <domain> <backend>   e.g. caddy-domain add app.example.com 10.0.0.200:8000"
  echo "  caddy-domain remove <domain>           e.g. caddy-domain remove app.example.com"
  echo "  caddy-domain list                      List all configured domains"
  exit 1
}

check_api() {
  if ! curl -sf "$CADDY_API/config/" >/dev/null 2>&1; then
    echo "Error: Cannot reach Caddy API at $CADDY_API" >&2
    echo "Is Caddy running on the host with the admin API enabled?" >&2
    exit 1
  fi
}

cmd_add() {
  local domain="$1"
  local backend="$2"

  check_api

  local route_json
  route_json=$(cat <<ENDJSON
{
  "@id": "$domain",
  "match": [{"host": ["$domain"]}],
  "handle": [{
    "handler": "reverse_proxy",
    "upstreams": [{"dial": "$backend"}]
  }],
  "terminal": true
}
ENDJSON
)

  # Try to update existing route by ID
  local http_code
  http_code=$(curl -sf -o /dev/null -w "%{http_code}" \
    -X POST \
    -H "Content-Type: application/json" \
    -d "$route_json" \
    "$CADDY_API/id/$domain" 2>/dev/null) || true

  if [ "$http_code" = "200" ]; then
    echo "Updated: $domain -> $backend"
    return
  fi

  # If the id doesn't exist, POST to the routes array
  local server_name
  server_name=$(curl -sf "$CADDY_API/config/apps/http/servers/" 2>/dev/null \
    | python3 -c "import sys,json; print(list(json.load(sys.stdin).keys())[0])" 2>/dev/null) || server_name="srv0"

  http_code=$(curl -sf -o /dev/null -w "%{http_code}" \
    -X POST \
    -H "Content-Type: application/json" \
    -d "$route_json" \
    "$CADDY_API/config/apps/http/servers/$server_name/routes" 2>/dev/null) || true

  if [ "$http_code" = "200" ]; then
    echo "Added: $domain -> $backend"
  else
    echo "Error: Failed to add route (HTTP $http_code)" >&2
    echo "You may need to set up the initial Caddy config on the host first." >&2
    exit 1
  fi
}

cmd_remove() {
  local domain="$1"

  check_api

  local http_code
  http_code=$(curl -sf -o /dev/null -w "%{http_code}" \
    -X DELETE \
    "$CADDY_API/id/$domain" 2>/dev/null) || true

  if [ "$http_code" = "200" ]; then
    echo "Removed: $domain"
  else
    echo "Error: Domain '$domain' not found or could not be removed (HTTP $http_code)" >&2
    exit 1
  fi
}

cmd_list() {
  check_api

  echo "Configured domains:"
  echo ""

  curl -sf "$CADDY_API/config/apps/http/servers/" 2>/dev/null \
    | python3 -c "
import sys, json

def find_upstreams(handlers):
    backends = []
    for h in handlers:
        if h.get('handler') == 'reverse_proxy':
            for u in h.get('upstreams', []):
                backends.append(u.get('dial', '?'))
        if h.get('handler') == 'subroute':
            for sub in h.get('routes', []):
                backends.extend(find_upstreams(sub.get('handle', [])))
    return backends

servers = json.load(sys.stdin)
for srv_name, srv in servers.items():
    for r in srv.get('routes', []):
        hosts = []
        for m in r.get('match', []):
            hosts.extend(m.get('host', []))
        backends = find_upstreams(r.get('handle', []))
        for host in hosts:
            print(f'  {host} -> {\", \".join(backends)}')
" 2>/dev/null || echo "  (no routes configured or could not parse config)"
}

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

case "$1" in
  add)
    [ $# -ne 3 ] && usage
    cmd_add "$2" "$3"
    ;;
  remove)
    [ $# -ne 2 ] && usage
    cmd_remove "$2"
    ;;
  list)
    cmd_list
    ;;
  *)
    usage
    ;;
esac