fix: complete first version issue remediation

gateway/internal/inbound/server_test.go

@@ -1,6 +1,7 @@
 package inbound
 
 import (
+	"bytes"
 	"context"
 	"encoding/json"
 	"log"
@@ -166,6 +167,69 @@ func TestInboundServerAuthenticatesAndSubmits(t *testing.T) {
 	}
 }
 
+func TestPostIncludesAPIErrorResponseBody(t *testing.T) {
+	api := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		w.WriteHeader(http.StatusBadRequest)
+		_, _ = w.Write([]byte(`{"message":"CMPP submit content does not match an approved template and signature","statusCode":400}`))
+	}))
+	defer api.Close()
+
+	err := (Server{APIBaseURL: api.URL}).post(context.Background(), "/inbound/submit", map[string]string{"account": "100001"}, nil)
+	if err == nil || !bytes.Contains([]byte(err.Error()), []byte("CMPP submit content does not match an approved template and signature")) {
+		t.Fatalf("expected API response body in error, got %v", err)
+	}
+}
+
+func TestNormalizeInboundSubmitSupportsCMPP2AndCMPP3(t *testing.T) {
+	tests := []struct {
+		name     string
+		packet   any
+		protocol string
+	}{
+		{name: "cmpp2", packet: &cmpp.Cmpp2SubmitReqPkt{MsgSrc: "100001", SeqId: 20}, protocol: "cmpp20"},
+		{name: "cmpp3", packet: &cmpp.Cmpp3SubmitReqPkt{MsgSrc: "100001", SeqId: 30}, protocol: "cmpp30"},
+	}
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			got, ok := normalizeInboundSubmit(test.packet)
+			if !ok || got.protocol != test.protocol || got.msgSrc != "100001" {
+				t.Fatalf("unexpected normalized packet: %+v ok=%v", got, ok)
+			}
+		})
+	}
+}
+
+func TestSetInboundSubmitResponseSupportsCMPP2AndCMPP3(t *testing.T) {
+	cmpp2 := &cmpp.Cmpp2SubmitRspPkt{}
+	setInboundSubmitResponse(cmpp2, 101, 9)
+	if cmpp2.MsgId != 101 || cmpp2.Result != 9 {
+		t.Fatalf("unexpected CMPP2 response: %+v", cmpp2)
+	}
+	cmpp3 := &cmpp.Cmpp3SubmitRspPkt{}
+	setInboundSubmitResponse(cmpp3, 202, 9)
+	if cmpp3.MsgId != 202 || cmpp3.Result != 9 {
+		t.Fatalf("unexpected CMPP3 response: %+v", cmpp3)
+	}
+}
+
+func TestInboundClientProtocolUsesConnectRequestVersion(t *testing.T) {
+	resetDownstreamRegistry()
+	defer resetDownstreamRegistry()
+	conn := &cmpp.Conn{}
+	downstreamRegistry.byAccount["100001"] = &downstreamSession{
+		account:  "100001",
+		protocol: "cmpp20",
+		conn:     conn,
+	}
+	if got := inboundClientProtocol("100001", conn, "cmpp30"); got != "cmpp20" {
+		t.Fatalf("protocol = %s, want cmpp20", got)
+	}
+	if got := inboundClientProtocol("missing", conn, "cmpp30"); got != "cmpp30" {
+		t.Fatalf("fallback protocol = %s, want cmpp30", got)
+	}
+}
+
 func TestFlushOnlineAccountsFetchesPendingDeliveries(t *testing.T) {
 	resetDownstreamRegistry()
 	defer resetDownstreamRegistry()