package captcha

import (
	"encoding/base64"
	"fmt"
	"time"

	"ycc-server/pkg/lzkit/crypto"
)

// GenerateEncryptedSceneID 生成加密的场景ID
// 格式: sceneId&timestamp&expireTime -> AES-256-CBC + PKCS7 -> Base64(IV + ciphertext)
func GenerateEncryptedSceneID(sceneId, ekey string, expireSeconds int) (string, error) {
	// 参数校验
	if expireSeconds <= 0 || expireSeconds > 86400 {
		expireSeconds = 3600 // 默认1小时
	}

	// 构建明文: sceneId&timestamp&expireTime
	ts := time.Now().Unix()
	plaintext := fmt.Sprintf("%s&%d&%d", sceneId, ts, expireSeconds)

	// 解码 ekey（Base64 -> 32字节密钥）
	keyBytes, err := base64.StdEncoding.DecodeString(ekey)
	if err != nil {
		return "", fmt.Errorf("decode ekey error: %w", err)
	}

	// 验证密钥长度（AES-256 需要 32 字节）
	if len(keyBytes) != 32 {
		return "", fmt.Errorf("invalid ekey length, need 32 bytes after base64 decode, got %d", len(keyBytes))
	}

	// 使用 AES 加密
	return crypto.AesEncrypt([]byte(plaintext), keyBytes)
}