Factor out config

main.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"flag"
 	"fmt"
 	"io"
@@ -46,38 +47,71 @@ func isFlagPassed(name string) bool {
 	return found
 }
 
-func realMain() int {
-	var err error
-
-	host := flag.String("host", "127.0.0.1", "Server host")
-	port := flag.Int("port", 6379, "Server port")
-	db := flag.Uint("db", 0, "only dump this database (default: all databases)")
-	filter := flag.String("filter", "*", "Key filter to use")
-	noscan := flag.Bool("noscan", false, "Use KEYS * instead of SCAN - for Redis <=2.8")
-	batchSize := flag.Int("batchSize", 1000, "HSET/RPUSH/SADD/ZADD only add 'batchSize' items at a time")
-	nWorkers := flag.Int("n", 10, "Parallel workers")
-	withTTL := flag.Bool("ttl", true, "Preserve Keys TTL")
-	output := flag.String("output", "resp", "Output type - can be resp or commands")
-	silent := flag.Bool("s", false, "Silent mode (disable logging of progress / stats)")
-
-	tls := flag.Bool("tls", false, "Establish a secure TLS connection")
-	caCert := flag.String("cacert", "", "CA Certificate file to verify with")
-	cert := flag.String("cert", "", "Private key file to authenticate with")
-	key := flag.String("key", "", "SSL private key file path")
+type Config struct {
+	host      string
+	port      int
+	db        *uint
+	filter    string
+	noscan    bool
+	batchSize int
+	nWorkers  int
+	withTTL   bool
+	output    string
+	silent    bool
+	tls       bool
+	caCert    string
+	cert      string
+	key       string
+}
 
-	flag.Parse()
+func FromFlags(progName string, args []string) (Config, error) {
+	c := Config{}
+
+	flags := flag.NewFlagSet(progName, flag.ExitOnError)
+	var buf bytes.Buffer
+	flags.SetOutput(&buf)
+
+	flags.StringVar(&c.host, "host", "127.0.0.1", "Server host")
+	flags.IntVar(&c.port, "port", 6379, "Server port")
+	flags.UintVar(c.db, "db", 0, "only dump this database (default: all databases)")
+	flags.StringVar(&c.filter, "filter", "*", "Key filter to use")
+	flags.BoolVar(&c.noscan, "noscan", false, "Use KEYS * instead of SCAN - for Redis <=2.8")
+	flags.IntVar(&c.batchSize, "batchSize", 1000, "HSET/RPUSH/SADD/ZADD only add 'batchSize' items at a time")
+	flags.IntVar(&c.nWorkers, "n", 10, "Parallel workers")
+	flags.BoolVar(&c.withTTL, "ttl", true, "Preserve Keys TTL")
+	flags.StringVar(&c.output, "output", "resp", "Output type - can be resp or commands")
+	flags.BoolVar(&c.silent, "s", false, "Silent mode (disable logging of progress / stats)")
+	flags.BoolVar(&c.tls, "tls", false, "Establish a secure TLS connection")
+	flags.StringVar(&c.caCert, "cacert", "", "CA Certificate file to verify with")
+	flags.StringVar(&c.cert, "cert", "", "Private key file to authenticate with")
+	flags.StringVar(&c.key, "key", "", "SSL private key file path")
+	flags.Usage = func() {
+		fmt.Fprintf(os.Stderr, "Usage: %s [OPTION]... [FILE OR FOLDER]...\n", progName)
+
+		flags.SetOutput(os.Stderr)
+		flags.PrintDefaults()
+	}
 
 	if !isFlagPassed("db") {
-		db = nil
+		c.db = nil
 	}
 
+	err := flags.Parse(args)
+	return c, err
+}
+
+func realMain() int {
+	var err error
+
+	c, _ := FromFlags(os.Args[0], os.Args[1:])
+
 	var tlshandler *redisdump.TlsHandler = nil
-	if isFlagPassed("tls") {
-		tlshandler = redisdump.NewTlsHandler(*caCert, *cert, *key)
+	if c.tls == true {
+		tlshandler = redisdump.NewTlsHandler(c.caCert, c.cert, c.key)
 	}
 
 	var serializer func([]string) string
-	switch *output {
+	switch c.output {
 	case "resp":
 		serializer = redisdump.RESPSerializer
 
@@ -97,29 +131,29 @@ func realMain() int {
 	defer func() {
 		close(progressNotifs)
 		wg.Wait()
-		if !(*silent) {
+		if !(c.silent) {
 			fmt.Fprint(os.Stderr, "\n")
 		}
 	}()
 
 	pl := newProgressLogger()
 	go func() {
 		for n := range progressNotifs {
-			if !(*silent) {
+			if !(c.silent) {
 				pl.drawProgress(os.Stderr, n.Db, n.Done)
 			}
 		}
 		wg.Done()
 	}()
 
 	logger := log.New(os.Stdout, "", 0)
-	if db == nil {
-		if err = redisdump.DumpServer(*host, *port, url.QueryEscape(redisPassword), tlshandler, *filter, *nWorkers, *withTTL, *batchSize, *noscan, logger, serializer, progressNotifs); err != nil {
+	if c.db == nil {
+		if err = redisdump.DumpServer(c.host, c.port, url.QueryEscape(redisPassword), tlshandler, c.filter, c.nWorkers, c.withTTL, c.batchSize, c.noscan, logger, serializer, progressNotifs); err != nil {
 			fmt.Fprintf(os.Stderr, "%s", err)
 			return 1
 		}
 	} else {
-		if err = redisdump.DumpDB(*host, *port, url.QueryEscape(redisPassword), tlshandler, uint8(*db), *filter, *nWorkers, *withTTL, *batchSize, *noscan, logger, serializer, progressNotifs); err != nil {
+		if err = redisdump.DumpDB(c.host, c.port, url.QueryEscape(redisPassword), tlshandler, uint8(*c.db), c.filter, c.nWorkers, c.withTTL, c.batchSize, c.noscan, logger, serializer, progressNotifs); err != nil {
 			fmt.Fprintf(os.Stderr, "%s", err)
 			return 1
 		}