package alerts

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

// Config holds Telegram bot settings from config.json.
type Config struct {
	Enabled  bool   `json:"enabled"`
	BotToken string `json:"bot_token"`
	ChatID   string `json:"chat_id"`
}

// Notifier sends operator alerts via Telegram Bot API.
type Notifier struct {
	cfg    Config
	client *http.Client
	mu     sync.Mutex
	last   time.Time
}

func New(cfg Config) *Notifier {
	return &Notifier{
		cfg: cfg,
		client: &http.Client{
			Timeout: 10 * time.Second,
		},
	}
}

// Enabled reports whether Telegram alerts are configured.
func (n *Notifier) Enabled() bool {
	return n != nil && n.cfg.Enabled && n.cfg.BotToken != "" && n.cfg.ChatID != ""
}

// Send posts a message to the configured chat (best-effort, non-blocking caller).
func (n *Notifier) Send(text string) {
	if !n.Enabled() {
		return
	}

	go func() {
		if err := n.sendSync(text); err != nil {
			log.Printf("telegram alert: %v", err)
		}
	}()
}

func (n *Notifier) sendSync(text string) error {
	n.mu.Lock()
	if time.Since(n.last) < 500*time.Millisecond {
		n.mu.Unlock()
		time.Sleep(500 * time.Millisecond)
		n.mu.Lock()
	}
	n.last = time.Now()
	n.mu.Unlock()

	url := fmt.Sprintf("https://api.telegram.org/bot%s/sendMessage", n.cfg.BotToken)
	body, _ := json.Marshal(map[string]string{
		"chat_id":    n.cfg.ChatID,
		"text":       text,
		"parse_mode": "Markdown",
	})

	req, err := http.NewRequest(http.MethodPost, url, bytes.NewReader(body))
	if err != nil {
		return err
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := n.client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode >= 300 {
		return fmt.Errorf("telegram API status %d", resp.StatusCode)
	}
	return nil
}

// FleetEvent formats a fleet alert message.
func FleetEvent(action, hostID, detail string) string {
	return fmt.Sprintf("🔧 *forge-mesh* · `%s`\nhost: `%s`\n%s", action, hostID, detail)
}

// CrucibleEvent formats a batch terminal alert.
func CrucibleEvent(jobID string, hostCount int, cmd string) string {
	return fmt.Sprintf("⚗️ *crucible batch* · `%s`\nhosts: %d\ncmd: `%s`", jobID, hostCount, cmd)
}