package xyshanghai

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strconv"
	"time"
)

// Client 供应商API客户端
type Client struct {
	baseURL    string
	httpClient *http.Client
	apiKey     *APIKey
}

// Option 客户端配置选项
type Option func(*Client)

// WithBaseURL 设置基础URL
func WithBaseURL(baseURL string) Option {
	return func(c *Client) {
		c.baseURL = baseURL
	}
}

// WithTimeout 设置HTTP超时时间
func WithTimeout(timeout time.Duration) Option {
	return func(c *Client) {
		c.httpClient.Timeout = timeout
	}
}

// WithHTTPClient 设置自定义HTTP客户端
func WithHTTPClient(httpClient *http.Client) Option {
	return func(c *Client) {
		c.httpClient = httpClient
	}
}

// NewClient 创建新的客户端
func NewClient(apiKey *APIKey, opts ...Option) *Client {
	c := &Client{
		httpClient: &http.Client{Timeout: 30 * time.Second},
		apiKey:     apiKey,
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

// doRequest 发送请求并处理响应
func (c *Client) doRequest(ctx context.Context, path string, reqBody interface{}) (*CommonResponse, error) {
	// 序列化业务数据
	plaintext, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("marshal request body: %w", err)
	}

	// SM4加密
	encryptedData, err := SM4Encrypt(c.apiKey.SM4Key, plaintext)
	if err != nil {
		return nil, fmt.Errorf("encrypt data: %w", err)
	}

	// 生成时间戳
	timestamp := strconv.FormatInt(time.Now().UnixMilli(), 10)

	// 生成签名
	sign := SM3Sign(c.apiKey.SM3Salt, timestamp+encryptedData)

	// 构建请求体
	commonReq := CommonRequestBody{EncryptedData: encryptedData}
	reqBytes, err := json.Marshal(commonReq)
	if err != nil {
		return nil, fmt.Errorf("marshal common request: %w", err)
	}

	// 创建HTTP请求
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, c.baseURL+path, bytes.NewReader(reqBytes))
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("timestamp", timestamp)
	req.Header.Set("sign", sign)

	// 发送请求
	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("do request: %w", err)
	}
	defer resp.Body.Close()

	// 读取响应
	respBody, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("read response body: %w", err)
	}

	// 解析公共响应
	var commonResp CommonResponse
	if err := json.Unmarshal(respBody, &commonResp); err != nil {
		return nil, fmt.Errorf("unmarshal common response: %w", err)
	}

	return &commonResp, nil
}

// decryptData 解密响应中的data字段
func (c *Client) decryptData(encryptedData string, target interface{}) error {
	plaintext, err := SM4Decrypt(c.apiKey.SM4Key, encryptedData)
	if err != nil {
		return fmt.Errorf("decrypt data: %w", err)
	}
	if err := json.Unmarshal(plaintext, target); err != nil {
		return fmt.Errorf("unmarshal decrypted data: %w", err)
	}
	return nil
}

// CreateOrder 卡券/直充权益下单
func (c *Client) CreateOrder(ctx context.Context, req *CreateOrderRequest) (*CreateOrderResponse, error) {
	commonResp, err := c.doRequest(ctx, "/order/create", req)
	if err != nil {
		return nil, err
	}

	if commonResp.Code != 0 {
		return nil, NewSDKError(ErrorCode(commonResp.Code), commonResp.Msg, nil)
	}

	if commonResp.Data == nil {
		return nil, NewSDKError(ErrCodeFailure, "response data is nil", nil)
	}

	var resp CreateOrderResponse
	if err := c.decryptData(*commonResp.Data, &resp); err != nil {
		return nil, err
	}
	return &resp, nil
}

// QueryOrder 卡券/直充/微信立减金订单查询
func (c *Client) QueryOrder(ctx context.Context, req *QueryOrderRequest) (*QueryOrderResponse, error) {
	commonResp, err := c.doRequest(ctx, "/order/query", req)
	if err != nil {
		return nil, err
	}

	if commonResp.Code != 0 {
		return nil, NewSDKError(ErrorCode(commonResp.Code), commonResp.Msg, nil)
	}

	if commonResp.Data == nil {
		return nil, NewSDKError(ErrCodeFailure, "response data is nil", nil)
	}

	var resp QueryOrderResponse
	if err := c.decryptData(*commonResp.Data, &resp); err != nil {
		return nil, err
	}
	return &resp, nil
}

// RechargeOrder 微信立减金订单充值
func (c *Client) RechargeOrder(ctx context.Context, req *RechargeOrderRequest) (*RechargeOrderResponse, error) {
	commonResp, err := c.doRequest(ctx, "/order/recharge", req)
	if err != nil {
		return nil, err
	}

	if commonResp.Code != 0 {
		return nil, NewSDKError(ErrorCode(commonResp.Code), commonResp.Msg, nil)
	}

	if commonResp.Data == nil {
		return nil, NewSDKError(ErrCodeFailure, "response data is nil", nil)
	}

	var resp RechargeOrderResponse
	if err := c.decryptData(*commonResp.Data, &resp); err != nil {
		return nil, err
	}
	return &resp, nil
}

// ParseCallbackRequest 解析回调请求，返回业务数据
func (c *Client) ParseCallbackRequest(r *http.Request) (*CallbackRequest, error) {
	// 读取请求体
	body, err := io.ReadAll(r.Body)
	if err != nil {
		return nil, fmt.Errorf("read request body: %w", err)
	}
	defer r.Body.Close()

	// 解析通用请求体
	var commonReq CommonRequestBody
	if err := json.Unmarshal(body, &commonReq); err != nil {
		return nil, fmt.Errorf("unmarshal common request: %w", err)
	}

	// 验证签名（可选）
	timestamp := r.Header.Get("timestamp")
	sign := r.Header.Get("sign")
	expectedSign := SM3Sign(c.apiKey.SM3Salt, timestamp+commonReq.EncryptedData)
	if sign != expectedSign {
		return nil, NewSDKError(ErrCodeFailure, "sign verification failed", nil)
	}

	// 解密业务数据
	plaintext, err := SM4Decrypt(c.apiKey.SM4Key, commonReq.EncryptedData)
	if err != nil {
		return nil, fmt.Errorf("decrypt callback data: %w", err)
	}

	var callbackReq CallbackRequest
	if err := json.Unmarshal(plaintext, &callbackReq); err != nil {
		return nil, fmt.Errorf("unmarshal callback request: %w", err)
	}

	return &callbackReq, nil
}

// CallbackHandler 返回一个http.Handler，用于处理回调通知
func (c *Client) CallbackHandler() http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		callbackReq, err := c.ParseCallbackRequest(r)
		if err != nil {
			http.Error(w, "invalid request", http.StatusBadRequest)
			return
		}

		// 用户需要实现自己的处理逻辑，这里仅返回成功
		// 实际使用时，用户应通过闭包或回调函数注入业务处理
		_ = callbackReq

		// 返回成功
		w.WriteHeader(http.StatusOK)
		w.Write([]byte("ok"))
	})
}