From 5c70b18c08e176c77635659a300c180415ac6eed Mon Sep 17 00:00:00 2001
From: Nurzhan Saktaganov <nurzhan.saktaganov@gmail.com>
Date: Thu, 9 Jan 2025 16:16:16 +0300
Subject: [PATCH] api: implement VshardRouterCallResp.GetTransparent method
 (resolve #22)

---
 CHANGELOG.md                  | 12 ++++++++
 api.go                        | 28 ++++++++++++++++++
 tests/tnt/router_call_test.go | 53 ++++++++++++++++++++++++++++++++++-
 3 files changed, 92 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index f93f6d6..b813173 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,15 @@
+## Unreleased
+
+CHANGES:
+* All PR, issue references in #XYZ format in commits older than 42f363775dfb9eaf7ec2a6ed7a999847752cec00 refer to https://github.com/KaymeKaydex/go-vshard-router.
+
+FEATURES:
+
+* Implement VshardRouterCallResp.GetTransparent method to reuse custom msgpack decoders of direct call (#22).
+
+TESTS:
+* Tests for VshardRouterCallResp.GetTransparent.
+
 ## v1.3.2
 
 CHANGES:
diff --git a/api.go b/api.go
index 712d7c7..eeae65f 100644
--- a/api.go
+++ b/api.go
@@ -1,6 +1,7 @@
 package vshard_router //nolint:revive
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"time"
@@ -228,6 +229,33 @@ func (r VshardRouterCallResp) GetTyped(result []interface{}) error {
 	return nil
 }
 
+// GetTransparent decodes a response from user defined function into result.
+// The response has the same format as a direct call (without vshard router) to this function.
+// If you have some custom decoder for some lua handler's response, you can reuse your decoder using this method.
+// P.S. the maximum length of the response array is cut to 3 elements due to lua vshard storage implementation
+// see https://github.com/tarantool/vshard/blob/dfa2cc8a2aff221d5f421298851a9a229b2e0434/vshard/storage/init.lua#L3130.
+func (r VshardRouterCallResp) GetTransparent(result interface{}) error {
+	// Make a msgpack binary with desired array length.
+	enc := msgpack.GetEncoder()
+	defer msgpack.PutEncoder(enc)
+
+	var buf bytes.Buffer
+	enc.Reset(&buf)
+
+	err := enc.EncodeArrayLen(len(r.rawMessages))
+	if err != nil {
+		return err
+	}
+
+	data := buf.Bytes()
+	for _, rawMessage := range r.rawMessages {
+		data = append(data, rawMessage...)
+	}
+
+	// Call users' custom decoder (if any).
+	return msgpack.Unmarshal(data, result)
+}
+
 // RouterCallImpl Perform shard operation function will restart operation
 // after wrong bucket response until timeout is reached
 // Deprecated: RouterCallImpl is deprecated.
diff --git a/tests/tnt/router_call_test.go b/tests/tnt/router_call_test.go
index 60c797d..4528788 100644
--- a/tests/tnt/router_call_test.go
+++ b/tests/tnt/router_call_test.go
@@ -11,7 +11,7 @@ import (
 	"github.com/tarantool/go-vshard-router/providers/static"
 )
 
-func TestRouterCallProto(t *testing.T) {
+func TestRouterCallImplProto(t *testing.T) {
 	skipOnInvalidRun(t)
 
 	t.Parallel()
@@ -111,3 +111,54 @@ func TestRouterCallProto(t *testing.T) {
 	_, _, err = router.RouterCallImpl(ctx, bucketID, callOpts, "echo", args)
 	require.Nil(t, err, "RouterCallImpl echo finished with no err even on dirty bucket map")
 }
+
+func TestRouterCallProto(t *testing.T) {
+	skipOnInvalidRun(t)
+
+	t.Parallel()
+
+	ctx := context.Background()
+
+	cfg := getCfg()
+
+	router, err := vshardrouter.NewRouter(ctx, vshardrouter.Config{
+		TopologyProvider: static.NewProvider(cfg),
+		DiscoveryTimeout: 5 * time.Second,
+		DiscoveryMode:    vshardrouter.DiscoveryModeOn,
+		TotalBucketCount: totalBucketCount,
+		User:             defaultTntUser,
+		Password:         defaultTntPassword,
+	})
+	require.NoError(t, err, "NewRouter finished successfully")
+
+	bucketID := randBucketID(totalBucketCount)
+
+	rs, err := router.BucketResolve(ctx, bucketID)
+	require.NoError(t, err, "BucketResolve with no err")
+
+	const maxRespLen = 3
+	for argLen := 0; argLen <= maxRespLen; argLen++ {
+		args := []interface{}{}
+
+		for i := 0; i < argLen; i++ {
+			args = append(args, "arg")
+		}
+
+		var routerOpts vshardrouter.VshardRouterCallOptions
+		resp, err := router.CallRW(ctx, bucketID, "echo", args, routerOpts)
+		require.NoError(t, err, "router.CallRW with no err")
+
+		var resViaVshard interface{}
+		var resDirect interface{}
+
+		err = resp.GetTransparent(&resViaVshard)
+		require.NoError(t, err, "GetTransparent with no err")
+
+		var rsOpts vshardrouter.ReplicasetCallOpts
+
+		err = rs.CallAsync(ctx, rsOpts, "echo", args).GetTyped(&resDirect)
+		require.NoError(t, err, "rs.CallAsync.GetTyped with no error")
+
+		require.Equalf(t, resDirect, resViaVshard, "resDirect != resViaVshard on argLen %d", argLen)
+	}
+}