package utils

import (
	"encoding/json"
	"fmt"
	"math/rand"
	"strings"
	"time"
)

const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"
const (
	letterIdxBits = 6                    // 6 bits to represent a letter index
	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
)

func RandString(n int) string {
	var src = rand.NewSource(time.Now().UnixNano())
	sb := strings.Builder{}
	sb.Grow(n)
	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
		if remain == 0 {
			cache, remain = src.Int63(), letterIdxMax
		}
		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
			sb.WriteByte(letterBytes[idx])
			i--
		}
		cache >>= letterIdxBits
		remain--
	}
	return sb.String()
}

func RandInt(s int, e int) int {
	var integer int
	for {
		integer = rand.Intn(e)
		if integer > s {
			break
		}
	}
	return integer
}

func PrettyPrintJSON(s interface{}) {
	switch v := s.(type) {
	case string:
		var j map[string]interface{}
		if err := json.Unmarshal([]byte(v), &j); err != nil {
			panic(err)
		}
		jsonString, err := json.Marshal(j)
		if err != nil {
			panic(err)
		}
		fmt.Println(string(jsonString))
	default:
		jsonString, err := json.MarshalIndent(s, "", "  ")
		if err != nil {
			panic(err)
		}
		fmt.Println(string(jsonString))
	}
}