package pay

import (
	"context"
	"crypto/rand"
	"encoding/hex"
	"strings"
	"time"

	commonpb "gitea.haiyihy.com/hy/chatappcommon/proto"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

// Service 实现支付下单逻辑，当前只返回模拟结果，不写数据库。
type Service struct{}

// New 创建支付服务。
func New() *Service {
	return &Service{}
}

// Pay 校验支付参数并返回模拟支付结果。
func (s *Service) Pay(_ context.Context, request *commonpb.PayRequest) (*commonpb.PayResponse, error) {
	orderNo := strings.TrimSpace(request.GetOrderNo())
	userID := strings.TrimSpace(request.GetUserId())
	amount := strings.TrimSpace(request.GetAmount())
	currency := strings.TrimSpace(request.GetCurrency())
	payMethod := strings.TrimSpace(request.GetPayMethod())
	subject := strings.TrimSpace(request.GetSubject())

	if orderNo == "" {
		return nil, status.Error(codes.InvalidArgument, "order_no is required")
	}
	if userID == "" {
		return nil, status.Error(codes.InvalidArgument, "user_id is required")
	}
	if amount == "" {
		return nil, status.Error(codes.InvalidArgument, "amount is required")
	}
	if currency == "" {
		currency = "USD"
	}
	if payMethod == "" {
		payMethod = "unknown"
	}

	return &commonpb.PayResponse{
		PaymentId: "pay_" + randomID(),
		OrderNo:   orderNo,
		UserId:    userID,
		Status:    "processing",
		Amount:    amount,
		Currency:  currency,
		PayMethod: payMethod,
		Subject:   subject,
		CreatedAt: time.Now().UTC().Format(time.RFC3339),
	}, nil
}

func randomID() string {
	buffer := make([]byte, 8)
	if _, err := rand.Read(buffer); err == nil {
		return hex.EncodeToString(buffer)
	}
	return "fallback"
}