package wireguard

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

	"golang.org/x/crypto/curve25519"
)

type ServerConfig struct {
	PrivateKey string
	PublicKey  string
	Port       int
	Interface  string
	Address    string
}

type ClientConfig struct {
	PrivateKey      string
	PublicKey       string
	Address         string
	ServerIP        string
	ServerPort      int
	ServerPublicKey string
	AllowedIPs      string
	Endpoint        string
}

func GenerateServerConfig(port int, interfaceName, address string) (*ServerConfig, error) {
	privateKey, publicKey, err := generateKeyPair()
	if err != nil {
		return nil, fmt.Errorf("failed to generate key pair: %w", err)
	}

	return &ServerConfig{
		PrivateKey: privateKey,
		PublicKey:  publicKey,
		Port:       port,
		Interface:  interfaceName,
		Address:    address,
	}, nil
}

func (sc *ServerConfig) ToConfigFile() string {
	return fmt.Sprintf(`[Interface]
PrivateKey = %s
Address = %s
ListenPort = %d

`, sc.PrivateKey, sc.Address, sc.Port)
}

func GenerateClientConfig(serverIP string, serverPort int, serverPublicKey, clientPrivateKey, clientPublicKey, clientAddress, allowedIPs string) *ClientConfig {
	return &ClientConfig{
		PrivateKey:      clientPrivateKey,
		PublicKey:       clientPublicKey,
		Address:         clientAddress,
		ServerIP:        serverIP,
		ServerPort:       serverPort,
		ServerPublicKey: serverPublicKey,
		AllowedIPs:        allowedIPs,
		Endpoint:         fmt.Sprintf("%s:%d", serverIP, serverPort),
	}
}

func (cc *ClientConfig) ToConfigFile() string {
	return fmt.Sprintf(`[Interface]
PrivateKey = %s
Address = %s

[Peer]
PublicKey = %s
Endpoint = %s
AllowedIPs = %s
PersistentKeepalive = 25

`, cc.PrivateKey, cc.Address, cc.ServerPublicKey, cc.Endpoint, cc.AllowedIPs)
}

func generateKeyPair() (string, string, error) {
	var privateKey [32]byte
	if _, err := rand.Read(privateKey[:]); err != nil {
		return "", "", fmt.Errorf("failed to generate private key: %w", err)
	}

	privateKey[0] &= 248
	privateKey[31] &= 127
	privateKey[31] |= 64

	var publicKey [32]byte
	curve25519.ScalarBaseMult(&publicKey, &privateKey)

	privateKeyBase64 := base64.StdEncoding.EncodeToString(privateKey[:])
	publicKeyBase64 := base64.StdEncoding.EncodeToString(publicKey[:])

	return privateKeyBase64, publicKeyBase64, nil
}

func GenerateClientKeyPair() (string, string, error) {
	return generateKeyPair()
}