package captcha

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

	lzcrypto "tyc-server/pkg/lzkit/crypto"
)

// GenerateEncryptedSceneID 按阿里云文档生成 EncryptedSceneId（仅适用于 V3 架构加密模式）。
// 明文格式: sceneId&timestamp&expireTime
// 加密: AES-256-CBC + PKCS7Padding，结果为 Base64( IV(16字节) + ciphertext )
func GenerateEncryptedSceneID(sceneId, ekey string, expireSeconds int) (string, error) {
	if expireSeconds <= 0 || expireSeconds > 86400 {
		expireSeconds = 3600
	}

	ts := time.Now().Unix() // 秒级时间戳
	plaintext := fmt.Sprintf("%s&%d&%d", sceneId, ts, expireSeconds)

	keyBytes, err := base64.StdEncoding.DecodeString(ekey)
	if err != nil {
		return "", fmt.Errorf("decode ekey error: %w", err)
	}
	if len(keyBytes) != 32 {
		return "", fmt.Errorf("invalid ekey length, need 32 bytes after base64 decode, got %d", len(keyBytes))
	}

	// 复用已有的 AES-CBC + PKCS7 实现，输出即为 Base64(IV + ciphertext)
	return lzcrypto.AesEncrypt([]byte(plaintext), keyBytes)
}
