package telegram

import (
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strings"
	"time"
)

// Sender abstracts the actual Telegram Bot API call so the service layer
// can be unit-tested without making real network requests.
type Sender interface {
	Send(ctx context.Context, botToken, chatID, text string) error
}

type httpSender struct {
	client *http.Client
}

func NewHTTPSender() Sender {
	return &httpSender{client: &http.Client{Timeout: 10 * time.Second}}
}

func (s *httpSender) Send(ctx context.Context, botToken, chatID, text string) error {
	if botToken == "" || chatID == "" {
		return fmt.Errorf("telegram bot token and chat id must be configured")
	}

	endpoint := fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", botToken)
	form := url.Values{
		"chat_id": {chatID},
		"text":    {text},
	}

	req, err := http.NewRequestWithContext(ctx, http.MethodPost, endpoint, strings.NewReader(form.Encode()))
	if err != nil {
		return fmt.Errorf("build telegram request: %w", err)
	}
	req.Header.Set("Content-Type", "application/x-www-form-urlencoded")

	resp, err := s.client.Do(req)
	if err != nil {
		return fmt.Errorf("call telegram api: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 {
		body, _ := io.ReadAll(io.LimitReader(resp.Body, 4096))
		return fmt.Errorf("telegram api returned status %d: %s", resp.StatusCode, string(body))
	}
	return nil
}