feat: add rpc_find_match for basic 2-player matchmaking

- Implement rpc_find_match Nakama RPC function
- Search for existing authoritative TicTacToe matches via MatchList
- Return first match with available slot (size < 2)
- Create new match using MatchCreate when none available
- Add request/response structs for future extensibility
- Log match search, selection, and creation flow
- Gracefully handle optional JSON payload and invalid input

plugins/main.go

@@ -34,6 +34,10 @@ func InitModule(
 		logger.Error("Failed to register RPC: %v", err)
 		return err
 	}
+	if err := initializer.RegisterRpc("rpc_find_match", rpcFindMatch); err != nil {
+		logger.Error("RegisterRpc rpc_find_match failed: %v", err)
+		return err
+	}
 
 	logger.Info("Go module loaded successfully!")
 	return nil

plugins/matchmaking.go

@@ -0,0 +1,70 @@
+package main
+
+import (
+	"context"
+	"database/sql"
+	"encoding/json"
+
+	"github.com/heroiclabs/nakama-common/runtime"
+)
+
+type FindMatchRequest struct{}
+
+type FindMatchResponse struct {
+	MatchID string `json:"match_id"`
+}
+
+func rpcFindMatch(
+	ctx context.Context,
+	logger runtime.Logger,
+	db *sql.DB,
+	nk runtime.NakamaModule,
+	payload string,
+) (string, error) {
+
+	logger.Info("rpc_find_match called")
+
+	var req FindMatchRequest
+	if payload != "" {
+		if err := json.Unmarshal([]byte(payload), &req); err != nil {
+			logger.Warn("rpc_find_match: invalid request payload: %v", err)
+		}
+	}
+
+	const limit = 10
+	authoritative := true
+	labelFilter := "tictactoe" // must match MatchInit label
+	var minSize, maxSize *int  // nil = no constraint
+
+	matches, err := nk.MatchList(
+		ctx,
+		limit,
+		authoritative,
+		labelFilter,
+		minSize,
+		maxSize,
+		"", // query
+	)
+	if err != nil {
+		logger.Error("rpc_find_match: MatchList failed: %v", err)
+		return "", runtime.NewError("internal error", 13)
+	}
+
+	for _, m := range matches {
+		if m.Size < 2 {
+			logger.Info("rpc_find_match: found match %s with size=%d", m.MatchId, m.Size)
+			out, _ := json.Marshal(FindMatchResponse{MatchID: m.MatchId})
+			return string(out), nil
+		}
+	}
+
+	matchID, err := nk.MatchCreate(ctx, "tictactoe", map[string]interface{}{})
+	if err != nil {
+		logger.Error("rpc_find_match: MatchCreate failed: %v", err)
+		return "", runtime.NewError("internal error", 13)
+	}
+
+	logger.Info("rpc_find_match: created new match %s", matchID)
+	out, _ := json.Marshal(FindMatchResponse{MatchID: matchID})
+	return string(out), nil
+}