package notification

import (
	"encoding/json"
	"fmt"
	"log"
	"net/http"
	"net/smtp"
	"os"
)

// SendMsgRequest represents a sendMsg API request.
type SendMsgRequest struct {
	Format  string            `json:"format"`  // "smtp" or "sms"
	Title   string            `json:"title"`
	Message string            `json:"message"`
	Priority int             `json:"priority,omitempty"`
	Extras  map[string]string `json:"extras,omitempty"` // e.g., {"to_email": "user@example.com", "phone": "+1234567890"}
}

// SendMsgResponse represents a sendMsg API response.
type SendMsgResponse struct {
	Status  string `json:"status"`
	MessageID string `json:"messageId,omitempty"`
	Error  string `json:"error,omitempty"`
}

// Handler handles sendMsg requests and forwards to appropriate channel (email, SMS, or Gotify push).
type Handler struct {
	smtpHost     string
	smtpPort     string
	smtpFrom     string
	smtpUser     string
	smtpPass     string
	smsAPIURL    string
	smsAPIKey    string
	gotifyURL    string
	gotifyToken  string
}

// NewHandler creates a new notification handler from environment variables.
func NewHandler() *Handler {
	return &Handler{
		smtpHost:    os.Getenv("SMTP_HOST"),
		smtpPort:    os.Getenv("SMTP_PORT"),
		smtpFrom:    os.Getenv("SMTP_FROM"),
		smtpUser:    os.Getenv("SMTP_USER"),
		smtpPass:    os.Getenv("SMTP_PASS"),
		smsAPIURL:   os.Getenv("SMS_API_URL"),
		smsAPIKey:   os.Getenv("SMS_API_KEY"),
		gotifyURL:   os.Getenv("GOTIFY_URL"),
		gotifyToken: os.Getenv("GOTIFY_TOKEN"),
	}
}

// ServeHTTP handles sendMsg requests.
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodPost {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	var req SendMsgRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		w.Header().Set("Content-Type", "application/json")
		w.WriteHeader(http.StatusBadRequest)
		json.NewEncoder(w).Encode(SendMsgResponse{
			Status: "error",
			Error:  "invalid request: " + err.Error(),
		})
		return
	}

	// Route based on format
	var resp SendMsgResponse
	switch req.Format {
	case "smtp":
		resp = h.sendEmail(req)
	case "sms":
		resp = h.sendSMS(req)
	default:
		resp = SendMsgResponse{
			Status: "error",
			Error:  "unsupported format: " + req.Format,
		}
	}

	w.Header().Set("Content-Type", "application/json")
	if resp.Error != "" {
		w.WriteHeader(http.StatusInternalServerError)
	} else {
		w.WriteHeader(http.StatusOK)
	}
	json.NewEncoder(w).Encode(resp)
}

// sendEmail sends an email via SMTP.
func (h *Handler) sendEmail(req SendMsgRequest) SendMsgResponse {
	toEmail := req.Extras["to_email"]
	if toEmail == "" {
		return SendMsgResponse{
			Status: "error",
			Error:  "missing to_email in extras",
		}
	}

	subject := req.Title
	if subject == "" {
		subject = "Notification"
	}

	// Construct email body
	body := req.Message
	if req.Extras != nil {
		if cc := req.Extras["cc"]; cc != "" {
			body = fmt.Sprintf("CC: %s\n\n%s", cc, body)
		}
	}

	msg := fmt.Sprintf(
		"From: %s\r\nTo: %s\r\nSubject: %s\r\nContent-Type: text/plain; charset=UTF-8\r\n\r\n%s",
		h.smtpFrom, toEmail, subject, body,
	)

	// Send via SMTP
	smtpAddr := fmt.Sprintf("%s:%s", h.smtpHost, h.smtpPort)
	auth := smtp.PlainAuth("", h.smtpUser, h.smtpPass, h.smtpHost)

	if err := smtp.SendMail(smtpAddr, auth, h.smtpFrom, []string{toEmail}, []byte(msg)); err != nil {
		log.Printf("error sending email to %s: %v", toEmail, err)
		return SendMsgResponse{
			Status: "error",
			Error:  "failed to send email: " + err.Error(),
		}
	}

	return SendMsgResponse{
		Status:    "success",
		MessageID: fmt.Sprintf("email-%s", toEmail),
	}
}

// sendSMS sends an SMS via configured provider.
// Placeholder: integrate with Twilio, AWS SNS, or similar.
func (h *Handler) sendSMS(req SendMsgRequest) SendMsgResponse {
	phone := req.Extras["phone"]
	if phone == "" {
		return SendMsgResponse{
			Status: "error",
			Error:  "missing phone in extras",
		}
	}

	// TODO: Implement SMS provider integration (Twilio, AWS SNS, etc.)
	// For now, return error
	return SendMsgResponse{
		Status: "error",
		Error:  "SMS not implemented yet",
	}
}