package tiktok

// WebhookHandler processes incoming TikTok webhook HTTP requests.
// Reference: gochat's Telegram WebhookHandler pattern
// + TikTok Business API webhook documentation
//
// TikTok webhook flow:
//   1. Verification: GET request with verify_token challenge (on webhook setup)
//   2. Events: POST requests with JSON event payloads (message.received, etc.)
//
// The WebhookHandler:
//   - Validates webhook authenticity (verify_token for setup, signature for events)
//   - Parses the JSON payload into TikTokWebhookEvent
//   - Delegates to IncomingProcessor for message processing

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"

	applogger "github.com/gochat/gochat/pkg/logger"
)

// WebhookHandler processes TikTok webhook HTTP requests.
type WebhookHandler struct {
	service *TikTokService
	pipeline *IncomingProcessor
}

// NewWebhookHandler creates a TikTok webhook handler.
func NewWebhookHandler(service *TikTokService, pipeline *IncomingProcessor) *WebhookHandler {
	return &WebhookHandler{
		service:  service,
		pipeline: pipeline,
	}
}

// HandleWebhookRequest processes an incoming TikTok webhook HTTP POST request.
// Returns the parsed TikTokWebhookEvent for the pipeline to process.
func (h *WebhookHandler) HandleWebhookRequest(r *http.Request) (*TikTokWebhookEvent, error) {
	// Read request body
	body, err := io.ReadAll(r.Body)
	if err != nil {
		return nil, fmt.Errorf("tiktok webhook: failed to read body: %w", err)
	}
	defer r.Body.Close()

	if len(body) == 0 {
		return nil, fmt.Errorf("tiktok webhook: empty request body")
	}

	// Parse the webhook event
	var event TikTokWebhookEvent
	if err := json.Unmarshal(body, &event); err != nil {
		return nil, fmt.Errorf("tiktok webhook: failed to parse JSON: %w", err)
	}

	applogger.L().Infof("TikTok webhook: received event type=%s biz_id=%s", event.Type, event.BizID)

	return &event, nil
}

// HandleVerifyRequest processes a TikTok webhook verification GET request.
// TikTok sends this during webhook setup to verify the endpoint.
func (h *WebhookHandler) HandleVerifyRequest(r *http.Request, expectedVerifyToken string) (string, error) {
	verifyToken := r.URL.Query().Get("verify_token")
	challenge := r.URL.Query().Get("challenge")

	if verifyToken != expectedVerifyToken {
		return "", fmt.Errorf("tiktok webhook verify: token mismatch (expected=%s, got=%s)",
			expectedVerifyToken, verifyToken)
	}

	applogger.L().Infof("TikTok webhook verify: challenge accepted, token=%s", verifyToken)
	return challenge, nil
}