package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"time"
)

// TelegramSender sends alerts to a Telegram chat via Bot API.
type TelegramSender struct {
	botToken string
	chatID   string
	client   *http.Client
	enabled  bool
}

// NewTelegramSender creates a sender. Returns a no-op sender if token or chatID is empty.
func NewTelegramSender(botToken, chatID string) *TelegramSender {
	return &TelegramSender{
		botToken: botToken,
		chatID:   chatID,
		client: &http.Client{
			Timeout: 10 * time.Second,
			Transport: &http.Transport{
				Proxy: http.ProxyFromEnvironment,
			},
		},
		enabled: botToken != "" && chatID != "",
	}
}

// IsEnabled returns true if both token and chatID are configured.
func (t *TelegramSender) IsEnabled() bool {
	return t.enabled
}

// SendAlert sends a formatted momentum alert to Telegram.
func (t *TelegramSender) SendAlert(alert BinanceAlert) error {
	if !t.enabled {
		return nil
	}

	// Build message
	icon := "🔴"
	directionWord := "暴跌"
	if alert.Direction == "up" {
		icon = "🟢"
		directionWord = "暴涨"
	}
	sign := "+"
	if alert.ChangePct < 0 {
		sign = ""
	}

	text := fmt.Sprintf("%s *%s* %s %s%.2f%% | $%.4f",
		icon, alert.Coin, directionWord, sign, alert.ChangePct, alert.Price)

	payload := map[string]interface{}{
		"chat_id":    t.chatID,
		"text":       text,
		"parse_mode": "Markdown",
	}
	body, _ := json.Marshal(payload)

	url := fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", t.botToken)
	resp, err := t.client.Post(url, "application/json", bytes.NewReader(body))
	if err != nil {
		return fmt.Errorf("telegram API call failed: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != 200 {
		return fmt.Errorf("telegram API returned %d", resp.StatusCode)
	}

	log.Printf("[Telegram] Alert sent: %s %s %.2f%%", alert.Coin, alert.Direction, alert.ChangePct)
	return nil
}