Templates: add http service for parameter choices (#32951)

templates/definition/tariff/pvnode-v2.yaml

@@ -15,16 +15,17 @@ requirements:
 group: solar
 
 params:
-  - name: site_id
-    description:
-      en: Site ID
-      de: Standort-ID
-    required: true
   - name: apikey
     description:
       en: pvnode API key
       de: pvnode API Key
     required: true
+  - name: site_id
+    description:
+      en: Site ID
+      de: Standort-ID
+    required: true
+    service: http/get?uri=https://api.pvnode.com/v2/sites/&token={apikey}&jq=[.[].id]
   - name: forecast_days
     description:
       en: Forecast days

util/service/http.go

@@ -0,0 +1,75 @@
+package service
+
+import (
+	"errors"
+	"net/http"
+
+	"github.com/evcc-io/evcc/server/service"
+	"github.com/evcc-io/evcc/util"
+	"github.com/evcc-io/evcc/util/jq"
+	"github.com/evcc-io/evcc/util/request"
+	"github.com/evcc-io/evcc/util/transport"
+	"github.com/itchyny/gojq"
+	"github.com/spf13/cast"
+)
+
+func init() {
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /get", httpGet)
+
+	service.Register("http", mux)
+}
+
+// httpGet reads uri and extracts the choices using the jq query, driving
+// selection of remote resources in templates. The config UI polls while the
+// form is filled, hence a rejected request yields an empty list.
+func httpGet(w http.ResponseWriter, req *http.Request) {
+	q := req.URL.Query()
+
+	uri := q.Get("uri")
+	if uri == "" {
+		jsonError(w, http.StatusBadRequest, errors.New("missing uri"))
+		return
+	}
+
+	expr := q.Get("jq")
+	if expr == "" {
+		expr = "."
+	}
+
+	query, err := gojq.Parse(expr)
+	if err != nil {
+		jsonError(w, http.StatusBadRequest, err)
+		return
+	}
+
+	log := util.NewLogger("http")
+	client := request.NewHelper(log)
+
+	if token := q.Get("token"); token != "" {
+		log.Redact(token)
+		client.Transport = transport.BearerAuth(token, client.Transport)
+	}
+
+	res := []string{}
+	defer func() { jsonWrite(w, res) }()
+
+	body, err := client.GetBody(uri)
+	if err != nil {
+		return
+	}
+
+	val, err := jq.Query(query, body)
+	if err != nil {
+		return
+	}
+
+	if slice, ok := val.([]any); ok {
+		for _, v := range slice {
+			res = append(res, cast.ToString(v))
+		}
+		return
+	}
+
+	res = append(res, cast.ToString(val))
+}