import crypto from "crypto"

export interface AlipayConfig {
  appId: string
  partnerId: string
  key: string
  returnUrl: string
  notifyUrl: string
}

export class AlipayService {
  constructor(private config: AlipayConfig) {}

  // 创建支付宝订单
  createOrder(params: {
    outTradeNo: string
    subject: string
    totalAmount: number
    body?: string
  }) {
    const orderInfo = {
      app_id: this.config.appId,
      method: "alipay.trade.wap.pay",
      format: "JSON",
      charset: "utf-8",
      sign_type: "MD5",
      timestamp: new Date().toISOString().slice(0, 19).replace("T", " "),
      version: "1.0",
      notify_url: this.config.notifyUrl,
      return_url: this.config.returnUrl,
      biz_content: JSON.stringify({
        out_trade_no: params.outTradeNo,
        product_code: "QUICK_WAP_WAY",
        total_amount: params.totalAmount.toFixed(2),
        subject: params.subject,
        body: params.body || params.subject,
      }),
    }

    const sign = this.generateSign(orderInfo)
    return {
      ...orderInfo,
      sign,
      paymentUrl: this.buildPaymentUrl(orderInfo, sign),
    }
  }

  // 生成签名
  generateSign(params: Record<string, string>): string {
    const sortedKeys = Object.keys(params).sort()
    const signString = sortedKeys
      .filter((key) => params[key] && key !== "sign")
      .map((key) => `${key}=${params[key]}`)
      .join("&")

    const signWithKey = `${signString}${this.config.key}`
    return crypto.createHash("md5").update(signWithKey, "utf8").digest("hex")
  }

  // 验证回调签名
  verifySign(params: Record<string, string>): boolean {
    const receivedSign = params.sign
    if (!receivedSign) return false

    const calculatedSign = this.generateSign(params)
    return receivedSign.toLowerCase() === calculatedSign.toLowerCase()
  }

  // 构建支付URL
  private buildPaymentUrl(params: Record<string, string>, sign: string): string {
    const gateway = "https://openapi.alipay.com/gateway.do"
    const queryParams = new URLSearchParams({ ...params, sign })
    return `${gateway}?${queryParams.toString()}`
  }
}