package main

import (
	"crypto/aes"
	"crypto/cipher"
	"crypto/rand"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"
)

// cookieKeyPath returns the filesystem path where the local encryption key is stored.
// The key is intentionally NOT stored in recorder_settings.json.
func cookieKeyPath() (string, error) {
	// Prefer ./data (you already use it for models_store.db)
	p, err := resolvePathRelativeToApp("data/cookies.key")
	if err == nil && strings.TrimSpace(p) != "" {
		_ = os.MkdirAll(filepath.Dir(p), 0o755)
		return p, nil
	}

	// Fallback: next to the executable
	p2, err2 := resolvePathRelativeToApp("cookies.key")
	if err2 != nil {
		return "", err2
	}
	_ = os.MkdirAll(filepath.Dir(p2), 0o755)
	return p2, nil
}

func loadOrCreateCookieKey() ([]byte, error) {
	p, err := cookieKeyPath()
	if err != nil {
		return nil, err
	}

	if b, err := os.ReadFile(p); err == nil {
		// accept exactly 32 bytes, or trim if longer
		if len(b) >= 32 {
			return b[:32], nil
		}
	}

	key := make([]byte, 32)
	if _, err := io.ReadFull(rand.Reader, key); err != nil {
		return nil, err
	}
	// 0600 is best-effort; on Windows this is still fine.
	if err := os.WriteFile(p, key, 0o600); err != nil {
		return nil, err
	}
	return key, nil
}

func normalizeCookieMap(in map[string]string) map[string]string {
	out := map[string]string{}
	for k, v := range in {
		kk := strings.ToLower(strings.TrimSpace(k))
		vv := strings.TrimSpace(v)
		if kk == "" || vv == "" {
			continue
		}
		out[kk] = vv
	}
	return out
}

func encryptCookieMap(cookies map[string]string) (string, error) {
	clean := normalizeCookieMap(cookies)
	plain, err := json.Marshal(clean)
	if err != nil {
		return "", err
	}
	return encryptBytesToBase64(plain)
}

func decryptCookieMap(blob string) (map[string]string, error) {
	blob = strings.TrimSpace(blob)
	if blob == "" {
		return map[string]string{}, nil
	}
	plain, err := decryptBase64ToBytes(blob)
	if err != nil {
		return nil, err
	}
	var out map[string]string
	if err := json.Unmarshal(plain, &out); err != nil {
		return nil, err
	}
	return normalizeCookieMap(out), nil
}

func encryptBytesToBase64(plain []byte) (string, error) {
	key, err := loadOrCreateCookieKey()
	if err != nil {
		return "", err
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return "", err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return "", err
	}

	nonce := make([]byte, gcm.NonceSize())
	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
		return "", err
	}
	ciphertext := gcm.Seal(nil, nonce, plain, nil)
	buf := append(nonce, ciphertext...)
	return base64.StdEncoding.EncodeToString(buf), nil
}

func decryptBase64ToBytes(blob string) ([]byte, error) {
	key, err := loadOrCreateCookieKey()
	if err != nil {
		return nil, err
	}
	block, err := aes.NewCipher(key)
	if err != nil {
		return nil, err
	}
	gcm, err := cipher.NewGCM(block)
	if err != nil {
		return nil, err
	}

	buf, err := base64.StdEncoding.DecodeString(blob)
	if err != nil {
		return nil, err
	}
	ns := gcm.NonceSize()
	if len(buf) < ns {
		return nil, fmt.Errorf("encrypted cookies: invalid length")
	}
	nonce := buf[:ns]
	ciphertext := buf[ns:]
	plain, err := gcm.Open(nil, nonce, ciphertext, nil)
	if err != nil {
		return nil, err
	}
	return plain, nil
}