package argon2

import (
	// Standard
	"crypto/subtle"
	"encoding/base64"
	"errors"
	"fmt"
	"strings"

	// Standard Extended
	"golang.org/x/crypto/argon2"
)

// Check Hash
func (algorithm Algorithm) CheckHash(data []byte, hashToCheck string) (bool, error) {
	// Hash Information
	var version int
	var memory uint32
	var threads uint8
	var time uint32
	// Hash Parts
	hashParts := strings.Split(hashToCheck, "$")
	// Validate Hash Parts
	if len(hashParts) != 6 {
		return false, errors.New("the hash is invalid")
	}
	// Get Version
	_, err := fmt.Sscanf(hashParts[2], "v=%d", &version)
	// Handle Error
	if err != nil {
		return false, err
	}
	// Validate Version
	if version != argon2.Version {
		return false, errors.New("incompatible version")
	}
	// Get Other Hash Information
	_, err = fmt.Sscanf(hashParts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)
	// Handle Error
	if err != nil {
		return false, err
	}
	// Salt
	salt, err := base64.RawStdEncoding.Strict().DecodeString(hashParts[4])
	// Handle Error
	if err != nil {
		return false, err
	}
	// Hash
	hash, err := base64.RawStdEncoding.Strict().DecodeString(hashParts[5])
	// Handle Error
	if err != nil {
		return false, err
	}
	// Return Match
	return subtle.ConstantTimeCompare(argon2.IDKey(data, salt, time, memory, threads, uint32(len(hash))), hash) == 1, err
}