package auth

import (
	"crypto/rand"
	"crypto/subtle"
	"encoding/base64"
	"fmt"
	"strings"

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

const (
	argon2Time    = 3
	argon2Memory  = 65536
	argon2Threads = 4
	argon2KeyLen  = 32
)

func HashPassword(password string) (string, error) {
	salt := make([]byte, 16)
	_, err := rand.Read(salt)

	if err != nil {
		return "", err
	}

	hash := argon2.IDKey([]byte(password), salt, argon2Time, argon2Memory, argon2Threads, argon2KeyLen)

	hashedPassword := fmt.Sprintf("$argon2id$v=%d$m=%d,t=%d,p=%d$%s$%s",
		argon2.Version, argon2Memory, argon2Time, argon2Threads,
		base64.RawStdEncoding.EncodeToString(salt),
		base64.RawStdEncoding.EncodeToString(hash),
	)

	return hashedPassword, nil
}

func VerifyPassword(hashedPassword, password string) bool {
	// Parse the Argon2 hash format: $argon2id$v=19$m=65536,t=3,p=4$salt$hash
	parts := strings.Split(hashedPassword, "$")
	if len(parts) != 6 {
		return false
	}

	// Extract parameters
	var memory, time, threads uint32
	var version int

	fmt.Sscanf(parts[2], "v=%d", &version)
	fmt.Sscanf(parts[3], "m=%d,t=%d,p=%d", &memory, &time, &threads)

	salt, err := base64.RawStdEncoding.DecodeString(parts[4])
	if err != nil {
		return false
	}

	hash, err := base64.RawStdEncoding.DecodeString(parts[5])
	if err != nil {
		return false
	}

	// Generate hash with the same parameters
	derivedKey := argon2.IDKey([]byte(password), salt, time, memory, uint8(threads), uint32(len(hash)))

	// Compare hashes using constant time comparison
	return subtle.ConstantTimeCompare(hash, derivedKey) == 1
}