package httpserver

import (
	"context"
	"encoding/json"
	"net/http"
	"strings"

	"github.com/TelegramExchange/tgex-backend/tg_parser/internal/usecase"
	"github.com/gotd/td/tgerr"
	"github.com/rs/zerolog/log"
)

type Server struct {
	httpServer *http.Server
}

func New(uc *usecase.UseCase, addr string) *Server {
	mux := http.NewServeMux()
	mux.HandleFunc("/fetch-telegram-channel", func(w http.ResponseWriter, r *http.Request) {
		if r.Method != http.MethodGet {
			http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
			return
		}

		username := strings.TrimSpace(r.URL.Query().Get("username"))
		username = strings.TrimPrefix(username, "@")
		if username == "" {
			http.Error(w, "missing username", http.StatusBadRequest)
			return
		}

		channel, err := uc.FetchChannelMeta(r.Context(), username)
		if err != nil {
			if isNotFoundError(err) {
				http.Error(w, "channel not found", http.StatusNotFound)
				return
			}
			log.Error().Err(err).Str("username", username).Msg("fetch channel meta failed")
			http.Error(w, "internal error", http.StatusInternalServerError)
			return
		}

		resp := struct {
			ID         string `json:"id"`
			TelegramID int64  `json:"telegram_id"`
			Username   string `json:"username"`
			Title      string `json:"title"`
			AccessHash int64  `json:"access_hash"`
			Pts        int    `json:"pts"`
		}{
			ID:         channel.ID.String(),
			TelegramID: channel.TelegramID,
			Username:   channel.Username,
			Title:      channel.Title,
			AccessHash: channel.AccessHash,
			Pts:        channel.Pts,
		}

		w.Header().Set("Content-Type", "application/json")
		if err := json.NewEncoder(w).Encode(resp); err != nil {
			log.Error().Err(err).Msg("encode channel response")
		}
	})

	return &Server{
		httpServer: &http.Server{
			Addr:    addr,
			Handler: mux,
		},
	}
}

func (s *Server) ListenAndServe() error {
	return s.httpServer.ListenAndServe()
}

func (s *Server) Shutdown(ctx context.Context) error {
	return s.httpServer.Shutdown(ctx)
}

func isNotFoundError(err error) bool {
	if tgerr.Is(err, "USERNAME_NOT_OCCUPIED", "USERNAME_INVALID", "CHANNEL_INVALID", "CHANNEL_PRIVATE") {
		return true
	}

	msg := err.Error()
	return strings.Contains(msg, "no chats in resolve result") ||
		strings.Contains(msg, "not a channel")
}