feat: add WeCom payload renderer

internal/server/wecom_notification.go

@@ -0,0 +1,54 @@
+package server
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"net/http"
+	"strings"
+)
+
+var wecomTemplateVariableNames = []string{
+	"event",
+	"title",
+	"message",
+	"timestamp",
+	"content",
+	"number",
+	"device_id",
+	"device_name",
+	"device_label",
+	"time",
+}
+
+type wecomTemplateValues map[string]string
+
+func renderWecomPayload(template string, values wecomTemplateValues) ([]byte, error) {
+	for _, name := range wecomTemplateVariableNames {
+		encoded, err := json.Marshal(values[name])
+		if err != nil {
+			return nil, fmt.Errorf("encode WeCom template value %q: %w", name, err)
+		}
+		template = strings.ReplaceAll(template, "{{"+name+"}}", string(encoded))
+	}
+	if strings.Contains(template, "{{") {
+		return nil, errors.New("wecom.payload_template contains an unsupported variable")
+	}
+
+	var payload map[string]json.RawMessage
+	if err := json.Unmarshal([]byte(template), &payload); err != nil || len(payload) == 0 {
+		return nil, errors.New("wecom.payload_template must render to a non-empty JSON object")
+	}
+	return []byte(template), nil
+}
+
+func validateWecomResponse(status int, body []byte) error {
+	var result struct {
+		ErrCode *int `json:"errcode"`
+	}
+	if status < http.StatusOK || status >= http.StatusMultipleChoices ||
+		json.Unmarshal(body, &result) != nil || result.ErrCode == nil || *result.ErrCode != 0 {
+		return fmt.Errorf("%w: WeCom response was not successful", errProviderRejected)
+	}
+	return nil
+}

internal/server/wecom_notification_test.go

@@ -0,0 +1,56 @@
+package server
+
+import (
+	"errors"
+	"net/http"
+	"testing"
+)
+
+func TestRenderWecomPayloadEscapesTemplateValues(t *testing.T) {
+	payload, err := renderWecomPayload(
+		`{"msgtype":"text","text":{"content":{{message}},"number":{{number}}}}`,
+		wecomTemplateValues{
+			"message": "quote: \"\nline",
+			"number":  "+447386",
+		},
+	)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := string(payload), `{"msgtype":"text","text":{"content":"quote: \"\nline","number":"+447386"}}`; got != want {
+		t.Fatalf("payload = %s, want %s", got, want)
+	}
+}
+
+func TestRenderWecomPayloadRejectsInvalidTemplate(t *testing.T) {
+	for _, template := range []string{
+		`{"text":{{unknown}}}`,
+		`[]`,
+		`{"msgtype":"text"`,
+	} {
+		t.Run(template, func(t *testing.T) {
+			if _, err := renderWecomPayload(template, wecomTemplateValues{}); err == nil {
+				t.Fatalf("template %q was accepted", template)
+			}
+		})
+	}
+}
+
+func TestValidateWecomResponse(t *testing.T) {
+	if err := validateWecomResponse(http.StatusOK, []byte(`{"errcode":0,"errmsg":"ok"}`)); err != nil {
+		t.Fatalf("successful response = %v", err)
+	}
+	for _, response := range []struct {
+		status int
+		body   string
+	}{
+		{http.StatusBadGateway, `{"errcode":0}`},
+		{http.StatusOK, `{"errcode":40058,"errmsg":"invalid"}`},
+		{http.StatusOK, `{}`},
+		{http.StatusOK, `not-json`},
+	} {
+		if err := validateWecomResponse(response.status, []byte(response.body)); !errors.Is(err, errProviderRejected) {
+			t.Fatalf("validateWecomResponse(%d, %s) = %v", response.status, response.body, err)
+		}
+	}
+}