feat: add dynamic fields handler to INFO command

app/server.go

@@ -8,6 +8,7 @@ import (
 	"log"
 	"os"
 	"os/signal"
+	"strings"
 	"syscall"
 	"time"
 
@@ -20,6 +21,7 @@ var (
 	port       = flag.String("port", "6379", "listening port")
 	dir        = flag.String("dir", "/tmp/redis", "data directory")
 	dbFilename = flag.String("dbfilename", "dump.rdb", "database filename")
+	replicaOf  = flag.String("replicaof", "", "replica of another redis server")
 )
 
 func run(ctx context.Context, _ io.Writer, _ []string) error {
@@ -30,10 +32,14 @@ func run(ctx context.Context, _ io.Writer, _ []string) error {
 	signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM, syscall.SIGQUIT)
 	defer signal.Stop(sigCh)
 	cfg := config.NewConfig()
+	if *replicaOf != "" && len(strings.Split(*replicaOf, " ")) != 2 {
+		return fmt.Errorf("invalid replicaof flag, expected format: replicaof <host> <port>")
+	}
 	err := cfg.SetBatch(map[string]string{
 		config.ListenAddrKey: fmt.Sprintf(":%s", *port),
 		config.DirKey:        *dir,
 		config.DBFilenameKey: *dbFilename,
+		config.ReplicaOfKey:  *replicaOf,
 	})
 	if err != nil {
 		return err

internal/app/server/config/config.go

@@ -11,12 +11,14 @@ const (
 	ListenAddrKey = "LISTENADDR"
 	DirKey        = "DIR"
 	DBFilenameKey = "DBFILENAME"
+	ReplicaOfKey  = "REPLICAOF"
 )
 
 var supportedOptions = map[string]struct{}{
 	ListenAddrKey: {},
 	DirKey:        {},
 	DBFilenameKey: {},
+	ReplicaOfKey:  {},
 }
 
 type Config struct {
@@ -52,6 +54,9 @@ func (c *Config) SetBatch(pairs map[string]string) error {
 		if _, exists := supportedOptions[strings.ToUpper(key)]; !exists {
 			return fmt.Errorf("%s for %s", ErrOptionNotFound, key)
 		}
+		if value == "" {
+			continue
+		}
 		c.options[key] = value
 	}
 	return nil

pkg/command/command.go

@@ -61,7 +61,7 @@ func NewCommandFactory(kv keyval.KV, cfg *config.Config) *CommandFactory {
 			"set":    &Set{kv: kv},
 			"get":    &Get{kv: kv},
 			"hello":  &Hello{},
-			"info":   &Info{},
+			"info":   &Info{cfg: cfg},
 			"client": &ClientCmd{},
 			"config": &ConfigCmd{cfg: cfg},
 			"keys":   &Keys{kv: kv},

pkg/command/info.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"strings"
 
+	"github.com/codecrafters-io/redis-starter-go/internal/app/server/config"
 	"github.com/codecrafters-io/redis-starter-go/internal/client"
 	"github.com/codecrafters-io/redis-starter-go/pkg/resp"
 )
@@ -13,52 +14,82 @@ const (
 	REPLICATION = "replication"
 )
 
-var (
-	sections = map[string]map[string]string{
-		SERVER: {
+type DynamicFieldHandler func(*config.Config) string
+
+type SectionInfo struct {
+	StaticFields  map[string]string
+	DynamicFields map[string]DynamicFieldHandler
+}
+
+var sections = map[string]SectionInfo{
+	SERVER: {
+		StaticFields: map[string]string{
 			"src_version":    "1.0.0",
 			"redis_version":  "7.4-rc1",
 			"redis_git_sha1": "random-sha1",
 			"redis_build_id": "20240616",
 			"redis_mode":     "standalone",
 		},
-		REPLICATION: {
-			"role": "master",
+	},
+	REPLICATION: {
+		DynamicFields: map[string]DynamicFieldHandler{
+			"role": determineRole,
 		},
-	}
-)
+	},
+}
 
 type Info struct {
+	cfg *config.Config
 }
 
 func (h *Info) Execute(c *client.Client, wr *resp.Writer, args []*resp.Resp) error {
 	argsLen := len(args)
 	if argsLen > 1 {
 		return wr.WriteError(fmt.Errorf("wrong number of arguments for 'info' command"))
 	}
+
 	str := strings.Builder{}
+
 	if argsLen == 1 {
-		str.WriteString(buildSectionString(args[0].String(), sections[args[0].String()]))
-		return wr.WriteString(str.String())
-	}
-	for sectionName, section := range sections {
-		str.WriteString(buildSectionString(sectionName, section))
-		str.WriteString("\r\n")
+		sectionName := args[0].String()
+		if sectionInfo, exists := sections[sectionName]; exists {
+			str.WriteString(buildSectionString(sectionName, sectionInfo, h.cfg))
+		}
+	} else {
+		for sectionName, sectionInfo := range sections {
+			str.WriteString(buildSectionString(sectionName, sectionInfo, h.cfg))
+			str.WriteString("\r\n")
+		}
 	}
 
 	return wr.WriteValue(str.String())
 }
 
-func buildSectionString(sectionName string, section map[string]string) string {
+func buildSectionString(sectionName string, sectionInfo SectionInfo, cfg *config.Config) string {
 	// # Server\r\nupstash_version:1.10.5\r\n,etc.
 	var sb strings.Builder
 	sb.WriteString(fmt.Sprintf("# %s\r\n", sectionName))
-	for key, value := range section {
+
+	for key, value := range sectionInfo.StaticFields {
+		sb.WriteString(fmt.Sprintf("%s:%s\r\n", key, value))
+	}
+
+	for key, handler := range sectionInfo.DynamicFields {
+		value := handler(cfg)
 		sb.WriteString(fmt.Sprintf("%s:%s\r\n", key, value))
 	}
+
 	return sb.String()
 }
 
 func (h *Info) IsBlocking(_ []*resp.Resp) bool {
 	return false
 }
+
+func determineRole(cfg *config.Config) string {
+	_, err := cfg.Get(config.ReplicaOfKey)
+	if err == nil {
+		return "slave"
+	}
+	return "master"
+}