package flags

import (
	"crypto/sha256"
	"encoding/binary"
	"errors"
	"fmt"
	"math/rand"
)

func shuffleSliceRandom(slice []string) []string {
	shuffled := make([]string, len(slice))
	copy(shuffled, slice)

	for i := len(shuffled) - 1; i > 0; i-- {
		j := rand.Intn(i + 1)
		shuffled[i], shuffled[j] = shuffled[j], shuffled[i]
	}

	return shuffled
}

func shuffleSlice(slice []string, seed string) []string {
	hasher := sha256.New()
	hasher.Write([]byte(seed))
	hash := hasher.Sum(nil)

	seedInt := int64(binary.LittleEndian.Uint64(hash[:8]))

	r := rand.New(rand.NewSource(seedInt))

	shuffled := make([]string, len(slice))
	copy(shuffled, slice)

	r.Shuffle(len(shuffled), func(i, j int) {
		shuffled[i], shuffled[j] = shuffled[j], shuffled[i]
	})

	return shuffled
}

func filterCountriesByTags(tags []string) (error, []string) {
	var result []string

	for _, tag := range tags {
		isSupported := false
		for _, supportedTag := range supportedTags {
			if tag == supportedTag {
				isSupported = true
			}
		}
		if isSupported == false {
			return errors.New(fmt.Sprintf("unsupported tag %v", tag)), result
		}
	}

	for _, country := range countryCodes {
		for _, tag := range tags {
			for _, cTag := range country.Tags {
				if cTag == tag {
					result = append(result, country.Code)
				}
			}
		}
	}

	return nil, result
}