package intelligence_finance_v1

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

const (
	// DefaultTimeout 默认请求超时时间
	DefaultTimeout = 30 * time.Second
	// DefaultNonceLength 默认随机数长度
	DefaultNonceLength = 16
	// HeaderTenantID 租户ID请求头
	HeaderTenantID = "tenant-id"
	// HeaderClientID 应用标识请求头
	HeaderClientID = "client-id"
	// HeaderSignatureTimestamp 签名时间戳请求头
	HeaderSignatureTimestamp = "x-bfl-signature-timestamp"
	// HeaderSignatureNonce 签名随机数请求头
	HeaderSignatureNonce = "x-bfl-signature-nonce"
	// HeaderSignature 签名信息请求头
	HeaderSignature = "x-bfl-signature"
	// ClientIDDingTalk 钉钉AI表格的固定 client-id
	ClientIDDingTalk = "dd-ai-table"
)

// Client 业财连接 SDK 客户端
// 用于调用平台提供的接口（订单开票、开票状态查询、创建付款单据、支付状态查询）
// 以及处理平台回调通知
type Client struct {
	// BaseURL 平台接口基础地址
	BaseURL string
	// TenantID 平台分配的租户唯一标识
	TenantID string
	// ClientID 平台分配的应用标识
	ClientID string
	// ClientSecret 平台分配的密钥，用于签名
	ClientSecret string
	// HTTPClient HTTP 客户端
	HTTPClient *http.Client
	// NonceLength 随机数长度
	NonceLength int
}

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

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

// WithNonceLength 设置随机数长度
func WithNonceLength(length int) ClientOption {
	return func(c *Client) {
		c.NonceLength = length
	}
}

// NewClient 创建一个新的业财连接客户端
// baseURL: 平台接口基础地址（如 "https://api.example.com"）
// tenantID: 平台分配的租户唯一标识
// clientID: 平台分配的应用标识（钉钉AI表格固定为 "dd-ai-table"）
// clientSecret: 平台分配的密钥
func NewClient(baseURL, tenantID, clientID, clientSecret string, opts ...ClientOption) *Client {
	c := &Client{
		BaseURL:      baseURL,
		TenantID:     tenantID,
		ClientID:     clientID,
		ClientSecret: clientSecret,
		HTTPClient: &http.Client{
			Timeout: DefaultTimeout,
		},
		NonceLength: DefaultNonceLength,
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

// NewDingTalkClient 创建一个钉钉AI表格专用的客户端
// baseURL: 平台接口基础地址
// tenantID: 平台分配的租户唯一标识
// clientSecret: 平台分配的密钥（在钉钉AI表格中配置为 APPSecret）
// 注意：钉钉AI表格的 client-id 固定为 "dd-ai-table"，签名由AI表格自动完成
func NewDingTalkClient(baseURL, tenantID, clientSecret string, opts ...ClientOption) *Client {
	return NewClient(baseURL, tenantID, ClientIDDingTalk, clientSecret, opts...)
}

// ============================================================================
// 签名相关方法
// ============================================================================

// buildSignature 构建请求签名
// 签名算法：HmacSHA256(client-secret, timestamp + nonce)，结果 Base64 编码
func (c *Client) buildSignature(timestamp, nonce string) string {
	data := timestamp + nonce
	return HmacSHA256Sign(c.ClientSecret, data)
}

// setAuthHeaders 设置认证请求头
func (c *Client) setAuthHeaders(req *http.Request, timestamp, nonce string) {
	req.Header.Set(HeaderTenantID, c.TenantID)
	req.Header.Set(HeaderClientID, c.ClientID)
	req.Header.Set(HeaderSignatureTimestamp, timestamp)
	req.Header.Set(HeaderSignatureNonce, nonce)
	req.Header.Set(HeaderSignature, c.buildSignature(timestamp, nonce))
	req.Header.Set("Content-Type", "application/json")
}

// ============================================================================
// 内部 HTTP 请求方法
// ============================================================================

// doRequest 执行带签名的 POST 请求
func (c *Client) doRequest(ctx context.Context, path string, requestBody interface{}) (*commonResponse, error) {
	bodyBytes, err := json.Marshal(requestBody)
	if err != nil {
		return nil, fmt.Errorf("marshal request body: %w", err)
	}

	url := c.BaseURL + path
	req, err := http.NewRequestWithContext(ctx, http.MethodPost, url, bytes.NewReader(bodyBytes))
	if err != nil {
		return nil, fmt.Errorf("create request: %w", err)
	}

	timestamp := GenerateTimestamp()
	nonce, err := GenerateNonce(c.NonceLength)
	if err != nil {
		return nil, fmt.Errorf("generate nonce: %w", err)
	}

	c.setAuthHeaders(req, timestamp, nonce)

	resp, err := c.HTTPClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("execute request: %w", err)
	}
	defer resp.Body.Close()

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

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		return nil, fmt.Errorf("unexpected HTTP status: %d, body: %s", resp.StatusCode, string(respBody))
	}

	var commonResp commonResponse
	if err := json.Unmarshal(respBody, &commonResp); err != nil {
		return nil, fmt.Errorf("unmarshal response: %w", err)
	}

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

	return &commonResp, nil
}

// ============================================================================
// 接口 1：订单开票
// ============================================================================

// CreateInvoice 提交订单开票请求
// path: 接口路径（接口短码，由平台对接时分配）
// req: 开票请求参数
// 返回开票响应，包含开票状态和发票数据列表
func (c *Client) CreateInvoice(ctx context.Context, path string, req *InvoiceRequest) (*InvoiceResponse, error) {
	commonResp, err := c.doRequest(ctx, path, req)
	if err != nil {
		return nil, err
	}

	// 将 data 字段重新序列化后反序列化为 InvoiceResponse
	dataBytes, err := json.Marshal(commonResp.Data)
	if err != nil {
		return nil, fmt.Errorf("marshal response data: %w", err)
	}

	var invoiceResp InvoiceResponse
	if err := json.Unmarshal(dataBytes, &invoiceResp); err != nil {
		return nil, fmt.Errorf("unmarshal invoice response: %w", err)
	}

	return &invoiceResp, nil
}

// ============================================================================
// 接口 2：开票状态查询
// ============================================================================

// QueryInvoiceStatus 查询订单开票状态
// path: 接口路径（接口短码，由平台对接时分配）
// req: 查询请求参数
// 返回开票状态查询响应
func (c *Client) QueryInvoiceStatus(ctx context.Context, path string, req *InvoiceStatusQueryRequest) (*InvoiceStatusQueryResponse, error) {
	commonResp, err := c.doRequest(ctx, path, req)
	if err != nil {
		return nil, err
	}

	dataBytes, err := json.Marshal(commonResp.Data)
	if err != nil {
		return nil, fmt.Errorf("marshal response data: %w", err)
	}

	var statusResp InvoiceStatusQueryResponse
	if err := json.Unmarshal(dataBytes, &statusResp); err != nil {
		return nil, fmt.Errorf("unmarshal invoice status response: %w", err)
	}

	return &statusResp, nil
}

// ============================================================================
// 接口 3：创建付款单据
// ============================================================================

// CreatePaymentDocument 创建付款单据
// path: 接口路径（接口短码，由平台对接时分配）
// req: 付款单据请求参数
// 返回创建结果，包含单据唯一标识
func (c *Client) CreatePaymentDocument(ctx context.Context, path string, req *PaymentDocumentRequest) (*PaymentDocumentResponse, error) {
	commonResp, err := c.doRequest(ctx, path, req)
	if err != nil {
		return nil, err
	}

	dataBytes, err := json.Marshal(commonResp.Data)
	if err != nil {
		return nil, fmt.Errorf("marshal response data: %w", err)
	}

	var paymentResp PaymentDocumentResponse
	if err := json.Unmarshal(dataBytes, &paymentResp); err != nil {
		return nil, fmt.Errorf("unmarshal payment document response: %w", err)
	}

	return &paymentResp, nil
}

// ============================================================================
// 接口 5：支付状态查询
// ============================================================================

// QueryPaymentStatus 查询支付状态
// path: 接口路径（接口短码，由平台对接时分配）
// req: 查询请求参数
// 返回支付状态信息，结构与支付通知一致
func (c *Client) QueryPaymentStatus(ctx context.Context, path string, req *PaymentStatusQueryRequest) (*PaymentStatusQueryResponse, error) {
	commonResp, err := c.doRequest(ctx, path, req)
	if err != nil {
		return nil, err
	}

	dataBytes, err := json.Marshal(commonResp.Data)
	if err != nil {
		return nil, fmt.Errorf("marshal response data: %w", err)
	}

	var paymentStatusResp PaymentStatusQueryResponse
	if err := json.Unmarshal(dataBytes, &paymentStatusResp); err != nil {
		return nil, fmt.Errorf("unmarshal payment status response: %w", err)
	}

	return &paymentStatusResp, nil
}

// ============================================================================
// 回调通知处理（接口 4：支付完成通知）
// ============================================================================

// ParsePaymentNotification 从 HTTP 请求中解析支付完成通知
// 该方法用于客户接收平台回调时使用
func ParsePaymentNotification(r *http.Request) (*PaymentNotification, error) {
	if r.Method != http.MethodPost {
		return nil, fmt.Errorf("invalid HTTP method: %s, expected POST", r.Method)
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		return nil, fmt.Errorf("read notification body: %w", err)
	}
	defer r.Body.Close()

	var notification PaymentNotification
	if err := json.Unmarshal(body, &notification); err != nil {
		return nil, fmt.Errorf("unmarshal payment notification: %w", err)
	}

	return &notification, nil
}

// ParseGeneralNotification 从 HTTP 请求中解析通用通知
func ParseGeneralNotification(r *http.Request) (*GeneralNotification, error) {
	if r.Method != http.MethodPost {
		return nil, fmt.Errorf("invalid HTTP method: %s, expected POST", r.Method)
	}

	body, err := io.ReadAll(r.Body)
	if err != nil {
		return nil, fmt.Errorf("read notification body: %w", err)
	}
	defer r.Body.Close()

	var notification GeneralNotification
	if err := json.Unmarshal(body, &notification); err != nil {
		return nil, fmt.Errorf("unmarshal general notification: %w", err)
	}

	return &notification, nil
}

// VerifyNotificationSignature 验证回调通知签名
// payload: 原始请求体
// signature: 请求中的签名
// secret: 客户在平台配置的验签密钥
// 使用 HmacSHA256 算法验证
func VerifyNotificationSignature(payload []byte, signature, secret string) bool {
	return HmacSHA256Verify(secret, string(payload), signature)
}

// WriteNotificationResponse 写入通知响应
// success: true 返回 "SUCCESS"，false 返回 "FAILED"
func WriteNotificationResponse(w http.ResponseWriter, success bool) {
	w.Header().Set("Content-Type", "text/plain; charset=utf-8")
	if success {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(NotificationSuccess))
	} else {
		w.WriteHeader(http.StatusOK)
		w.Write([]byte(NotificationFailed))
	}
}