From 7549beaf44f0d326d56e7f5c357cd3c5aaf84a13 Mon Sep 17 00:00:00 2001
From: andig <andi@evcc.io>
Date: Thu, 27 Aug 2026 15:29:50 +0200
Subject: [PATCH] Services: add sunspec/read for reading a point value from a
 device (#33230)

---
 util/service/sunspec.go      | 119 +++++++++++++++++++++++++++++++++++
 util/service/sunspec_test.go |  29 +++++++++
 2 files changed, 148 insertions(+)
 create mode 100644 util/service/sunspec.go
 create mode 100644 util/service/sunspec_test.go

diff --git a/util/service/sunspec.go b/util/service/sunspec.go
new file mode 100644
index 000000000..c7c481c69
--- /dev/null
+++ b/util/service/sunspec.go
@@ -0,0 +1,119 @@
+package service
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/evcc-io/evcc/plugin"
+	"github.com/evcc-io/evcc/server/service"
+	"github.com/evcc-io/evcc/util"
+	"github.com/evcc-io/evcc/util/modbus"
+	"github.com/fatih/structs"
+	"github.com/spf13/cast"
+)
+
+// SunSpecQuery combines modbus settings, sunspec point and additional parameters
+type SunSpecQuery struct {
+	modbus.Settings `mapstructure:",squash"`
+	Value           string  // sunspec point, e.g. 124:0:InOutWRte_RvrtTms
+	Scale           float64 // scaling factor
+	ResultType      string  // type cast (int, float, string)
+}
+
+func init() {
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /read", sunspecRead)
+
+	service.Register("sunspec", mux)
+}
+
+// sunspecRead reads a sunspec point value from a device based on URL parameters
+// Returns single value as array (for UI compatibility)
+func sunspecRead(w http.ResponseWriter, req *http.Request) {
+	// Convert URL query parameters to map for decoding
+	cc := make(map[string]any)
+	for k := range req.URL.Query() {
+		cc[k] = req.URL.Query().Get(k)
+	}
+
+	query := SunSpecQuery{
+		Scale: 1.0,
+	}
+
+	if err := util.DecodeOther(cc, &query); err != nil {
+		jsonError(w, http.StatusBadRequest, err)
+		return
+	}
+
+	// Validate required parameters
+	if (query.URI == "" && query.Device == "") || query.Value == "" {
+		jsonError(w, http.StatusBadRequest, fmt.Errorf("uri or device and value parameters are required"))
+		return
+	}
+
+	// Cache per exact request: distinct id/point/scale/resulttype must not share a converted value
+	cacheKey := "sunspec/" + req.URL.Query().Encode()
+
+	mu.RLock()
+	if entry, ok := cache[cacheKey]; ok && time.Since(entry.timestamp) < cacheTTL {
+		mu.RUnlock()
+		jsonWrite(w, []string{cast.ToString(entry.value)})
+		return
+	}
+	mu.RUnlock()
+
+	// Use background context so connection isn't tied to HTTP request lifecycle
+	value, err := readPointValue(context.TODO(), query)
+	if err != nil {
+		jsonError(w, http.StatusInternalServerError, err)
+		return
+	}
+
+	res := toString(value, query.ResultType)
+
+	mu.Lock()
+	cache[cacheKey] = cacheEntry{
+		value:     res,
+		timestamp: time.Now(),
+	}
+	mu.Unlock()
+
+	jsonWrite(w, []string{res})
+}
+
+// readPointValue reads a sunspec point value by reusing the sunspec plugin
+func readPointValue(ctx context.Context, query SunSpecQuery) (any, error) {
+	// Convert Settings to map (plugin expects Settings fields at top level)
+	cfg := structs.Map(query.Settings)
+
+	cfg["value"] = []string{query.Value}
+	cfg["scale"] = query.Scale
+
+	p, err := plugin.NewModbusSunspecFromConfig(ctx, cfg)
+	if err != nil {
+		return 0, fmt.Errorf("failed to create sunspec plugin: %w", err)
+	}
+
+	g, err := p.(plugin.FloatGetter).FloatGetter()
+	if err != nil {
+		return nil, err
+	}
+
+	var res float64
+	func() {
+		defer func() {
+			if r := recover(); r != nil {
+				err = fmt.Errorf("read failed: %v", r)
+			}
+		}()
+
+		res, err = g()
+	}()
+	if err != nil {
+		return nil, err
+	}
+
+	return res, nil
+}
diff --git a/util/service/sunspec_test.go b/util/service/sunspec_test.go
new file mode 100644
index 000000000..545f7cdf0
--- /dev/null
+++ b/util/service/sunspec_test.go
@@ -0,0 +1,29 @@
+package service
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestSunspecRead_MissingValue(t *testing.T) {
+	// point value is required
+	req := httptest.NewRequest("GET", "/read?uri=192.168.1.1:502&id=1", nil)
+	w := httptest.NewRecorder()
+
+	sunspecRead(w, req)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+}
+
+func TestSunspecRead_MissingConnection(t *testing.T) {
+	// uri or device is required
+	req := httptest.NewRequest("GET", "/read?id=1&value=124:0:InOutWRte_RvrtTms", nil)
+	w := httptest.NewRecorder()
+
+	sunspecRead(w, req)
+
+	assert.Equal(t, http.StatusBadRequest, w.Code)
+}