package handler

import (
	"crypto/subtle"
	"log"
	"net/http"

	"homework-manager/internal/service"

	"github.com/gin-gonic/gin"
)

// TelegramHandler handles incoming Telegram webhook requests.
type TelegramHandler struct {
	telegramService *service.TelegramService
	webhookSecret   string
}

// NewTelegramHandler creates a TelegramHandler.
func NewTelegramHandler(telegramService *service.TelegramService, webhookSecret string) *TelegramHandler {
	return &TelegramHandler{
		telegramService: telegramService,
		webhookSecret:   webhookSecret,
	}
}

// Webhook is the endpoint registered as the Telegram bot webhook.
// POST /api/telegram/webhook
func (h *TelegramHandler) Webhook(c *gin.Context) {
	if h.webhookSecret == "" {
		c.Status(http.StatusServiceUnavailable)
		return
	}
	secret := c.GetHeader("X-Telegram-Bot-Api-Secret-Token")
	if subtle.ConstantTimeCompare([]byte(secret), []byte(h.webhookSecret)) != 1 {
		c.Status(http.StatusUnauthorized)
		return
	}

	var update service.TelegramUpdate
	if err := c.ShouldBindJSON(&update); err != nil {
		c.Status(http.StatusBadRequest)
		return
	}

	// Process asynchronously so Telegram gets a 200 within its timeout window.
	go func() {
		defer func() {
			if r := recover(); r != nil {
				log.Printf("telegram HandleUpdate panic: %v", r)
			}
		}()
		h.telegramService.HandleUpdate(update)
	}()

	c.Status(http.StatusOK)
}