package wireguard

import (
	"encoding/base64"
	"fmt"
	"log"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"sync"
)

const (
	// KeyLength is the standard WireGuard key length in bytes (32 bytes = 256 bits)
	KeyLength = 32
	// Base64KeyLength is the length of a base64-encoded WireGuard key (44 characters)
	Base64KeyLength = 44
	// TempDir is the directory for temporary key storage
	TempDir = "/tmp/wg-admin"
)

var (
	tempKeys      = make(map[string]bool)
	tempKeysMutex sync.Mutex
)

// KeyPair represents a WireGuard key pair
type KeyPair struct {
	PrivateKey string // Base64-encoded private key
	PublicKey  string // Base64-encoded public key
}

// GeneratePrivateKey generates a new WireGuard private key using wg genkey
func GeneratePrivateKey() (string, error) {
	cmd := exec.Command("wg", "genkey")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("wg genkey failed: %w, output: %s", err, string(output))
	}

	key := string(output)
	if err := ValidateKey(key); err != nil {
		return "", fmt.Errorf("generated invalid private key: %w", err)
	}

	// Store as temporary key
	tempKeyPath := filepath.Join(TempDir, "private.key")
	if err := storeTempKey(tempKeyPath, key); err != nil {
		log.Printf("Warning: failed to store temporary private key: %v", err)
	}

	return key, nil
}

// GeneratePublicKey generates a public key from a private key using wg pubkey
func GeneratePublicKey(privateKey string) (string, error) {
	if err := ValidateKey(privateKey); err != nil {
		return "", fmt.Errorf("invalid private key: %w", err)
	}

	cmd := exec.Command("wg", "pubkey")
	cmd.Stdin = strings.NewReader(privateKey)
	output, err := cmd.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("wg pubkey failed: %w, output: %s", err, string(output))
	}

	key := string(output)
	if err := ValidateKey(key); err != nil {
		return "", fmt.Errorf("generated invalid public key: %w", err)
	}

	// Store as temporary key
	tempKeyPath := filepath.Join(TempDir, "public.key")
	if err := storeTempKey(tempKeyPath, key); err != nil {
		log.Printf("Warning: failed to store temporary public key: %v", err)
	}

	return key, nil
}

// GeneratePSK generates a new pre-shared key using wg genpsk
func GeneratePSK() (string, error) {
	cmd := exec.Command("wg", "genpsk")
	output, err := cmd.CombinedOutput()
	if err != nil {
		return "", fmt.Errorf("wg genpsk failed: %w, output: %s", err, string(output))
	}

	key := string(output)
	if err := ValidateKey(key); err != nil {
		return "", fmt.Errorf("generated invalid PSK: %w", err)
	}

	// Store as temporary key
	tempKeyPath := filepath.Join(TempDir, "psk.key")
	if err := storeTempKey(tempKeyPath, key); err != nil {
		log.Printf("Warning: failed to store temporary PSK: %v", err)
	}

	return key, nil
}

// GenerateKeyPair generates a complete WireGuard key pair (private + public)
func GenerateKeyPair() (*KeyPair, error) {
	privateKey, err := GeneratePrivateKey()
	if err != nil {
		return nil, err
	}

	publicKey, err := GeneratePublicKey(privateKey)
	if err != nil {
		return nil, fmt.Errorf("failed to generate public key: %w", err)
	}

	return &KeyPair{
		PrivateKey: privateKey,
		PublicKey:  publicKey,
	}, nil
}

// ValidateKey validates that a key is properly formatted (44 base64 characters)
func ValidateKey(key string) error {
	// Trim whitespace
	key = strings.TrimSpace(key)

	// Check length (44 base64 characters for 32 bytes)
	if len(key) != Base64KeyLength {
		return fmt.Errorf("invalid key length: expected %d characters, got %d", Base64KeyLength, len(key))
	}

	// Verify it's valid base64
	decoded, err := base64.StdEncoding.DecodeString(key)
	if err != nil {
		return fmt.Errorf("invalid base64 encoding: %w", err)
	}

	// Verify decoded length is 32 bytes
	if len(decoded) != KeyLength {
		return fmt.Errorf("invalid decoded key length: expected %d bytes, got %d", KeyLength, len(decoded))
	}

	return nil
}

// StoreKey atomically writes a key to a file with 0600 permissions
func StoreKey(path string, key string) error {
	// Validate key before storing
	if err := ValidateKey(key); err != nil {
		return fmt.Errorf("invalid key: %w", err)
	}

	// Trim whitespace
	key = strings.TrimSpace(key)

	// Create parent directories if needed
	dir := filepath.Dir(path)
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("failed to create directory %s: %w", dir, err)
	}

	// Write to temporary file
	tempPath := path + ".tmp"
	if err := os.WriteFile(tempPath, []byte(key), 0600); err != nil {
		return fmt.Errorf("failed to write temp file %s: %w", tempPath, err)
	}

	// Atomic rename
	if err := os.Rename(tempPath, path); err != nil {
		os.Remove(tempPath) // Clean up temp file on failure
		return fmt.Errorf("failed to rename temp file to %s: %w", path, err)
	}

	return nil
}

// LoadKey reads a key from a file and validates it
func LoadKey(path string) (string, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return "", fmt.Errorf("failed to read key file %s: %w", path, err)
	}

	key := strings.TrimSpace(string(data))
	if err := ValidateKey(key); err != nil {
		return "", fmt.Errorf("invalid key in file %s: %w", path, err)
	}

	return key, nil
}

// storeTempKey stores a temporary key and tracks it for cleanup
func storeTempKey(path string, key string) error {
	// Create temp directory if needed
	if err := os.MkdirAll(TempDir, 0700); err != nil {
		return fmt.Errorf("failed to create temp directory %s: %w", TempDir, err)
	}

	// Trim whitespace
	key = strings.TrimSpace(key)

	// Write to file with 0600 permissions
	if err := os.WriteFile(path, []byte(key), 0600); err != nil {
		return fmt.Errorf("failed to write temp key to %s: %w", path, err)
	}

	// Track for cleanup
	tempKeysMutex.Lock()
	tempKeys[path] = true
	tempKeysMutex.Unlock()

	return nil
}

// CleanupTempKeys removes all temporary keys
func CleanupTempKeys() error {
	tempKeysMutex.Lock()
	defer tempKeysMutex.Unlock()

	var cleanupErrors []string

	for path := range tempKeys {
		if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
			cleanupErrors = append(cleanupErrors, fmt.Sprintf("%s: %v", path, err))
			log.Printf("Warning: failed to remove temp key %s: %v", path, err)
		}
		delete(tempKeys, path)
	}

	// Also attempt to clean up the temp directory if empty
	if _, err := os.ReadDir(TempDir); err == nil {
		if err := os.Remove(TempDir); err != nil && !os.IsNotExist(err) {
			log.Printf("Warning: failed to remove temp directory %s: %v", TempDir, err)
		}
	}

	if len(cleanupErrors) > 0 {
		return fmt.Errorf("cleanup errors: %s", strings.Join(cleanupErrors, "; "))
	}

	return nil
}