package intelligence_finance

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

// Default API paths - these can be customized after receiving the actual short codes.
const (
	defaultPathInvoiceCreate       = "/api/invoice/create"
	defaultPathInvoiceStatusQuery  = "/api/invoice/status"
	defaultPathPaymentCreate       = "/api/payment/create"
	defaultPathPaymentStatusQuery  = "/api/payment/status"
)

// Client is the intelligence finance API client.
type Client struct {
	baseURL      string
	tenantID     string
	clientID     string
	clientSecret string
	httpClient   *http.Client

	// Paths for each API endpoint (configurable after onboarding).
	pathInvoiceCreate      string
	pathInvoiceStatusQuery string
	pathPaymentCreate      string
	pathPaymentStatusQuery string
}

// ClientOption is a functional option for configuring the Client.
type ClientOption func(*Client)

// WithHTTPClient sets a custom HTTP client.
func WithHTTPClient(httpClient *http.Client) ClientOption {
	return func(c *Client) {
		c.httpClient = httpClient
	}
}

// WithInvoiceCreatePath sets a custom path for the invoice create API.
func WithInvoiceCreatePath(path string) ClientOption {
	return func(c *Client) {
		c.pathInvoiceCreate = path
	}
}

// WithInvoiceStatusQueryPath sets a custom path for the invoice status query API.
func WithInvoiceStatusQueryPath(path string) ClientOption {
	return func(c *Client) {
		c.pathInvoiceStatusQuery = path
	}
}

// WithPaymentCreatePath sets a custom path for the payment create API.
func WithPaymentCreatePath(path string) ClientOption {
	return func(c *Client) {
		c.pathPaymentCreate = path
	}
}

// WithPaymentStatusQueryPath sets a custom path for the payment status query API.
func WithPaymentStatusQueryPath(path string) ClientOption {
	return func(c *Client) {
		c.pathPaymentStatusQuery = path
	}
}

// NewClient creates a new intelligence finance API client.
//   - baseURL: the base URL of the platform API (e.g., "https://api.example.com")
//   - tenantID: the tenant ID assigned by the platform
//   - clientID: the application client ID assigned by the platform
//   - clientSecret: the application client secret assigned by the platform
func NewClient(baseURL, tenantID, clientID, clientSecret string, opts ...ClientOption) *Client {
	c := &Client{
		baseURL:                strings.TrimRight(baseURL, "/"),
		tenantID:               tenantID,
		clientID:               clientID,
		clientSecret:           clientSecret,
		httpClient:             &http.Client{},
		pathInvoiceCreate:      defaultPathInvoiceCreate,
		pathInvoiceStatusQuery: defaultPathInvoiceStatusQuery,
		pathPaymentCreate:      defaultPathPaymentCreate,
		pathPaymentStatusQuery: defaultPathPaymentStatusQuery,
	}
	for _, opt := range opts {
		opt(c)
	}
	return c
}

// doRequest sends an HTTP request with authentication headers and returns the raw response body.
func (c *Client) doRequest(ctx context.Context, path string, request interface{}) ([]byte, error) {
	bodyBytes, err := json.Marshal(request)
	if err != nil {
		return nil, &ErrSigning{Message: "marshal request body", Err: err}
	}

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

	// Set standard headers
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("tenant-id", c.tenantID)
	req.Header.Set("client-id", c.clientID)

	// Generate and set signature headers
	timestamp := GenerateTimestamp()
	nonce, err := GenerateNonce(16)
	if err != nil {
		return nil, &ErrSigning{Message: "generate nonce", Err: err}
	}

	signature := HmacSHA256Base64(c.clientSecret, timestamp+nonce)

	req.Header.Set("x-bfl-signature-timestamp", timestamp)
	req.Header.Set("x-bfl-signature-nonce", nonce)
	req.Header.Set("x-bfl-signature", signature)

	resp, err := c.httpClient.Do(req)
	if err != nil {
		return nil, &ErrNetwork{Err: fmt.Errorf("send request: %w", err)}
	}
	defer resp.Body.Close()

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

	if resp.StatusCode != http.StatusOK {
		return nil, &ErrInvalidResponse{
			Message: fmt.Sprintf("unexpected status code %d: %s", resp.StatusCode, string(respBody)),
		}
	}

	return respBody, nil
}

// parseResponse parses the API response and extracts the data field.
func parseResponse(body []byte, target interface{}) error {
	var apiResp APIResponse
	if err := json.Unmarshal(body, &apiResp); err != nil {
		return &ErrInvalidResponse{Message: fmt.Sprintf("unmarshal response: %v", err)}
	}

	if apiResp.Code != 0 {
		return &APIError{Code: ErrorCode(apiResp.Code), Message: apiResp.Msg}
	}

	if target != nil && apiResp.Data != nil {
		// Convert map to JSON then unmarshal into target
		dataBytes, err := json.Marshal(apiResp.Data)
		if err != nil {
			return &ErrInvalidResponse{Message: fmt.Sprintf("marshal data: %v", err)}
		}
		if err := json.Unmarshal(dataBytes, target); err != nil {
			return &ErrInvalidResponse{Message: fmt.Sprintf("unmarshal data: %v", err)}
		}
	}

	return nil
}

// parseResponseRaw parses the API response and returns the raw data field.
func parseResponseRaw(body []byte) (map[string]interface{}, error) {
	var apiResp APIResponse
	if err := json.Unmarshal(body, &apiResp); err != nil {
		return nil, &ErrInvalidResponse{Message: fmt.Sprintf("unmarshal response: %v", err)}
	}

	if apiResp.Code != 0 {
		return nil, &APIError{Code: ErrorCode(apiResp.Code), Message: apiResp.Msg}
	}

	return apiResp.Data, nil
}

// ============================================================
// Interface 1: CreateInvoice - 订单开票接口
// ============================================================

// CreateInvoice submits an invoice creation request for an order.
// It returns the invoice creation response containing status and invoice data.
func (c *Client) CreateInvoice(ctx context.Context, req *InvoiceCreateRequest) (*InvoiceCreateResponse, error) {
	body, err := c.doRequest(ctx, c.pathInvoiceCreate, req)
	if err != nil {
		return nil, err
	}

	var result InvoiceCreateResponse
	if err := parseResponse(body, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ============================================================
// Interface 2: QueryInvoiceStatus - 开票状态查询接口
// ============================================================

// QueryInvoiceStatus queries the invoice status for a given order.
// It returns the invoice status response containing the current status and invoice data.
func (c *Client) QueryInvoiceStatus(ctx context.Context, req *InvoiceStatusQueryRequest) (*InvoiceStatusQueryResponse, error) {
	body, err := c.doRequest(ctx, c.pathInvoiceStatusQuery, req)
	if err != nil {
		return nil, err
	}

	var result InvoiceStatusQueryResponse
	if err := parseResponse(body, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ============================================================
// Interface 3: CreatePaymentOrder - 创建付款单据接口
// ============================================================

// CreatePaymentOrder creates a payment order.
// It returns the response containing the unique payment order code.
func (c *Client) CreatePaymentOrder(ctx context.Context, req *CreatePaymentOrderRequest) (*CreatePaymentOrderResponse, error) {
	body, err := c.doRequest(ctx, c.pathPaymentCreate, req)
	if err != nil {
		return nil, err
	}

	var result CreatePaymentOrderResponse
	if err := parseResponse(body, &result); err != nil {
		return nil, err
	}
	return &result, nil
}

// ============================================================
// Interface 4: Payment Notification Handler (平台回调客户接口)
// ============================================================

// ParsePaymentNotification parses a payment notification request body
// sent by the platform. This is used when the platform calls back to
// the customer's system after a payment is completed.
//
// Usage example in an HTTP handler:
//
//	func handler(w http.ResponseWriter, r *http.Request) {
//	    body, _ := io.ReadAll(r.Body)
//	    notification, err := ParsePaymentNotification(body)
//	    if err != nil {
//	        http.Error(w, "FAILED", http.StatusBadRequest)
//	        return
//	    }
//	    // Process the notification...
//	    w.Write([]byte("SUCCESS"))
//	}
func ParsePaymentNotification(body []byte) (*PaymentNotificationData, error) {
	var notification PaymentNotificationData
	if err := json.Unmarshal(body, &notification); err != nil {
		return nil, &ErrInvalidResponse{Message: fmt.Sprintf("parse payment notification: %v", err)}
	}
	return &notification, nil
}

// ParseGenericNotification parses a generic notification request body
// sent by the platform. The generic notification contains bizType, bizId, and data.
func ParseGenericNotification(body []byte) (*NotificationRequest, error) {
	var notification NotificationRequest
	if err := json.Unmarshal(body, &notification); err != nil {
		return nil, &ErrInvalidResponse{Message: fmt.Sprintf("parse notification: %v", err)}
	}
	return &notification, nil
}

// ============================================================
// Interface 5: QueryPaymentStatus - 支付状态查询接口
// ============================================================

// QueryPaymentStatus queries the payment status for a given payment order.
// The response has the same structure as PaymentNotificationData.
func (c *Client) QueryPaymentStatus(ctx context.Context, req *PaymentStatusQueryRequest) (*PaymentStatusQueryResponse, error) {
	body, err := c.doRequest(ctx, c.pathPaymentStatusQuery, req)
	if err != nil {
		return nil, err
	}

	var result PaymentStatusQueryResponse
	if err := parseResponse(body, &result); err != nil {
		return nil, err
	}
	return &result, nil
}