Repository: projectdiscovery/goflags (go)

Issue:
Add RateLimit flag
## Proposed changes
we can consider adding new flag type in goflags for ratelimit which accepts ratelimit along with unit

```
type RateLimit struct{
   MaxTokens unit
   Duration    time.Duration
}

rls := []RateLimit{}
flag.RateLimitVar(&rls, "-rls",nil,"rate limit along with unit ex:  10/ms , 30/m, 8/s ")
```
ref: https://github.com/projectdiscovery/subfinder/pull/891#pullrequestreview-1525004982

Pull request description:
add ratelimit flag
Closes #122.

Patch:
diff --git a/examples/basic/main.go b/examples/basic/main.go
index f4fc21a..a73d8ae 100644
--- a/examples/basic/main.go
+++ b/examples/basic/main.go
@@ -15,6 +15,7 @@ type Options struct {
 	Address  goflags.StringSlice
 	fileSize goflags.Size
 	duration time.Duration
+	rls      goflags.RateLimitMap
 }
 
 func main() {
@@ -28,6 +29,7 @@ func main() {
 	flagSet.CreateGroup("info", "Info",
 		flagSet.StringVarP(&testOptions.name, "name", "n", "", "name of the user"),
 		flagSet.StringSliceVarP(&testOptions.Email, "email", "e", nil, "email of the user", goflags.CommaSeparatedStringSliceOptions),
+		flagSet.RateLimitMapVarP(&testOptions.rls, "rate-limits", "rls", nil, "rate limits in format k=v/d i.e hackertarget=10/s", goflags.CommaSeparatedStringSliceOptions),
 	)
 	flagSet.CreateGroup("additional", "Additional",
 		flagSet.StringVarP(&testOptions.Phone, "phone", "ph", "", "phone of the user"),
@@ -40,4 +42,7 @@ func main() {
 	if err := flagSet.Parse(); err != nil {
 		log.Fatal(err)
 	}
+
+	// ratelimits value is
+	fmt.Printf("Got RateLimits: %+v\n", testOptions.rls)
 }
diff --git a/ratelimit_var.go b/ratelimit_var.go
new file mode 100644
index 0000000..bcd9cdb
--- /dev/null
+++ b/ratelimit_var.go
@@ -0,0 +1,170 @@
+package goflags
+
+import (
+	"errors"
+	"fmt"
+	"strconv"
+	"strings"
+	"time"
+	"unicode"
+
+	stringsutil "github.com/projectdiscovery/utils/strings"
+	timeutil "github.com/projectdiscovery/utils/time"
+)
+
+var (
+	MaxRateLimitTime   = time.Minute // anything above time.Minute is not practical (for our use case)
+	rateLimitOptionMap map[*RateLimitMap]Options
+)
+
+func init() {
+	rateLimitOptionMap = make(map[*RateLimitMap]Options)
+}
+
+type RateLimit struct {
+	MaxCount uint
+	Duration time.Duration
+}
+
+type RateLimitMap struct {
+	kv map[string]RateLimit
+}
+
+// Set inserts a value to the map. Format: key=value
+func (rateLimitMap *RateLimitMap) Set(value string) error {
+	if rateLimitMap.kv == nil {
+		rateLimitMap.kv = make(map[string]RateLimit)
+	}
+
+	option, ok := rateLimitOptionMap[rateLimitMap]
+	if !ok {
+		option = StringSliceOptions
+	}
+	rateLimits, err := ToStringSlice(value, option)
+	if err != nil {
+		return err
+	}
+
+	for _, rateLimit := range rateLimits {
+		var k, v string
+		if idxSep := strings.Index(rateLimit, kvSep); idxSep > 0 {
+			k = rateLimit[:idxSep]
+			v = rateLimit[idxSep+1:]
+		}
+
+		// note:
+		// - inserting multiple times the same key will override the previous v
+		// - empty string is legitimate rateLimit
+		if k != "" {
+			rateLimit, err := parseRateLimit(v)
+			if err != nil {
+				return err
+			}
+			rateLimitMap.kv[k] = rateLimit
+		}
+	}
+	return nil
+}
+
+// Del removes the specified key
+func (rateLimitMap *RateLimitMap) Del(key string) error {
+	if rateLimitMap.kv == nil {
+		return errors.New("empty runtime map")
+	}
+	delete(rateLimitMap.kv, key)
+	return nil
+}
+
+// IsEmpty specifies if the underlying map is empty
+func (rateLimitMap *RateLimitMap) IsEmpty() bool {
+	return rateLimitMap.kv == nil || len(rateLimitMap.kv) == 0
+}
+
+// AsMap returns the internal map as reference - changes are allowed
+func (rateLimitMap *RateLimitMap) AsMap() map[string]RateLimit {
+	return rateLimitMap.kv
+}
+
+func (rateLimitMap RateLimitMap) String() string {
+	defaultBuilder := &strings.Builder{}
+	defaultBuilder.WriteString("{")
+
+	var items string
+	for k, v := range rateLimitMap.kv {
+		items += fmt.Sprintf("\"%s\":\"%d/%s\",", k, v.MaxCount, v.Duration.String())
+	}
+	defaultBuilder.WriteString(stringsutil.TrimSuffixAny(items, ",", ":"))
+	defaultBuilder.WriteString("}")
+	return defaultBuilder.String()
+}
+
+// RateLimitMapVar adds a ratelimit flag with a longname
+func (flagSet *FlagSet) RateLimitMapVar(field *RateLimitMap, long string, defaultValue []string, usage string, options Options) *FlagData {
+	return flagSet.RateLimitMapVarP(field, long, "", defaultValue, usage, options)
+}
+
+// RateLimitMapVarP adds a ratelimit flag with a short name and long name.
+// It is equivalent to RateLimitMapVar, and also allows specifying ratelimits in days (e.g., "hackertarget=2/d" 2 requests per day, which is equivalent to 24h).
+func (flagSet *FlagSet) RateLimitMapVarP(field *RateLimitMap, long, short string, defaultValue StringSlice, usage string, options Options) *FlagData {
+	if field == nil {
+		panic(fmt.Errorf("field cannot be nil for flag -%v", long))
+	}
+
+	rateLimitOptionMap[field] = options
+	for _, defaultItem := range defaultValue {
+		values, _ := ToStringSlice(defaultItem, options)
+		for _, value := range values {
+			if err := field.Set(value); err != nil {
+				panic(fmt.Errorf("failed to set default value for flag -%v: %v", long, err))
+			}
+		}
+	}
+
+	flagData := &FlagData{
+		usage:        usage,
+		long:         long,
+		defaultValue: defaultValue,
+		skipMarshal:  true,
+	}
+	if short != "" {
+		flagData.short = short
+		flagSet.CommandLine.Var(field, short, usage)
+		flagSet.flagKeys.Set(short, flagData)
+	}
+	flagSet.CommandLine.Var(field, long, usage)
+	flagSet.flagKeys.Set(long, flagData)
+	return flagData
+}
+
+func parseRateLimit(s string) (RateLimit, error) {
+	sArr := strings.Split(s, "/")
+
+	if len(sArr) < 2 {
+		return RateLimit{}, errors.New("parse error: expected format k=v/d (e.g., scanme.sh=10/s got " + s)
+	}
+
+	maxCount, err := strconv.ParseUint(sArr[0], 10, 64)
+	if err != nil {
+		return RateLimit{}, errors.New("parse error: " + err.Error())
+	}
+	timeValue := sArr[1]
+	if len(timeValue) > 0 {
+		// check if time is given ex: 1s
+		// if given value is just s (add prefix 1)
+		firstChar := timeValue[0]
+		if !unicode.IsDigit(rune(firstChar)) {
+			timeValue = "1" + timeValue
+		}
+	}
+
+	duration, err := timeutil.ParseDuration(timeValue)
+	if err != nil {
+		return RateLimit{}, errors.New("parse error: " + err.Error())
+	}
+
+	if MaxRateLimitTime < duration {
+		return RateLimit{}, fmt.Errorf("duration cannot be more than %v but got %v", MaxRateLimitTime, duration)
+	}
+
+	return RateLimit{MaxCount: uint(maxCount), Duration: duration}, nil
+}


Test patch:
diff --git a/ratelimit_var_test.go b/ratelimit_var_test.go
new file mode 100644
index 0000000..41730cc
--- /dev/null
+++ b/ratelimit_var_test.go
@@ -0,0 +1,93 @@
+package goflags
+
+import (
+	"os"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestRateLimitMapVar(t *testing.T) {
+
+	t.Run("default-value", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.RateLimitMapVarP(&rateLimitMap, "rate-limits", "rls", []string{"hackertarget=1/ms"}, "rate limits", CommaSeparatedStringSliceOptions),
+		)
+		os.Args = []string{
+			os.Args[0],
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Millisecond}, rateLimitMap.AsMap()["hackertarget"])
+		tearDown(t.Name())
+	})
+
+	t.Run("multiple-default-value", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.RateLimitMapVarP(&rateLimitMap, "rate-limits", "rls", []string{"hackertarget=1/s,github=1/ms"}, "rate limits", CommaSeparatedStringSliceOptions),
+		)
+		os.Args = []string{
+			os.Args[0],
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Second}, rateLimitMap.AsMap()["hackertarget"])
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Millisecond}, rateLimitMap.AsMap()["github"])
+		tearDown(t.Name())
+	})
+
+	t.Run("valid-rate-limit", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.RateLimitMapVarP(&rateLimitMap, "rate-limits", "rls", nil, "rate limits", CommaSeparatedStringSliceOptions),
+		)
+		os.Args = []string{
+			os.Args[0],
+			"-rls", "hackertarget=10/m",
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, RateLimit{MaxCount: 10, Duration: time.Minute}, rateLimitMap.AsMap()["hackertarget"])
+
+		tearDown(t.Name())
+	})
+
+	t.Run("valid-rate-limits", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		flagSet := NewFlagSet()
+		flagSet.CreateGroup("Config", "Config",
+			flagSet.RateLimitMapVarP(&rateLimitMap, "rate-limits", "rls", nil, "rate limits", CommaSeparatedStringSliceOptions),
+		)
+		os.Args = []string{
+			os.Args[0],
+			"-rls", "hackertarget=1/s,github=1/ms",
+		}
+		err := flagSet.Parse()
+		assert.Nil(t, err)
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Second}, rateLimitMap.AsMap()["hackertarget"])
+		assert.Equal(t, RateLimit{MaxCount: 1, Duration: time.Millisecond}, rateLimitMap.AsMap()["github"])
+		tearDown(t.Name())
+	})
+
+	t.Run("without-unit", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		err := rateLimitMap.Set("hackertarget=1")
+		assert.NotNil(t, err)
+		assert.ErrorContains(t, err, "parse error")
+		tearDown(t.Name())
+	})
+
+	t.Run("invalid-unit", func(t *testing.T) {
+		var rateLimitMap RateLimitMap
+		err := rateLimitMap.Set("hackertarget=1/x")
+		assert.NotNil(t, err)
+		assert.ErrorContains(t, err, "parse error")
+		tearDown(t.Name())
+	})
+}