package auth

import (
	"crypto/rand"
	"crypto/sha256"
	"strings"
	"time"
)

const sessionExpiresInSeconds = 60 * 60 * 24 // 1 day

func GenerateSecureRandomString() (string, error) {
	// Human readable alphabet (a-z, 0-9 without l, o, 0, 1 to avoid confusion)
	alphabet := "abcdefghijklmnpqrstuvwxyz23456789"

	// Generate 24 bytes = 192 bits of entropy.
	// We're only going to use 5 bits per byte so the total entropy will be 192 * 5 / 8 = 120 bits
	bytes := make([]byte, 24)
	_, err := rand.Read(bytes)
	if err != nil {
		return "", err
	}

	var id strings.Builder
	for _, b := range bytes {
		// >> 3 "removes" the right-most 3 bits of the byte
		id.WriteByte(alphabet[b>>3])
	}
	return id.String(), nil
}

func HashSecret(secret string) []byte {
	hash := sha256.Sum256([]byte(secret))
	return hash[:]
}

func CheckExpiration(expirarion time.Time) bool {
	return time.Since(expirarion).Seconds() >= sessionExpiresInSeconds
}