package notification

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

// Handler handles notification requests routed via X-Resource header.
// Supports: send-email, send-gotify, list-messages, delete-message,
// delete-all-messages, list-applications, create-application, delete-application.
type Handler struct {
	smtpHost    string
	smtpPort    string
	smtpFrom    string
	smtpUser    string
	smtpPass    string
	gotify      *GotifyClient
}

// NewHandler creates a notification handler from environment variables.
func NewHandler() *Handler {
	var gotify *GotifyClient
	gotifyURL := os.Getenv("GOTIFY_URL")
	if gotifyURL != "" {
		gotify = NewGotifyClient(
			gotifyURL,
			os.Getenv("GOTIFY_APP_TOKEN"),
			os.Getenv("GOTIFY_CLIENT_TOKEN"),
		)
	}

	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"),
		gotify:   gotify,
	}
}

// ServeHTTP routes requests by X-Upstream-Path (set by dispatcher after resource matching).
func (h *Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	resource := r.Header.Get("X-Resource")

	switch resource {
	// --- Email ---
	case "send-email":
		h.handleSendEmail(w, r)

	// --- Gotify Messages ---
	case "send-message":
		h.handleSendGotify(w, r)
	case "list-messages":
		h.handleListMessages(w, r)
	case "delete-message":
		h.handleDeleteMessage(w, r)
	case "delete-all-messages":
		h.handleDeleteAllMessages(w, r)

	// --- Gotify Applications ---
	case "list-applications":
		h.handleListApplications(w, r)
	case "create-application":
		h.handleCreateApplication(w, r)
	case "delete-application":
		h.handleDeleteApplication(w, r)

	default:
		h.writeJSON(w, http.StatusNotFound, map[string]string{
			"error": fmt.Sprintf("unknown resource: %s", resource),
		})
	}
}

// --- Email ---

type SendEmailRequest struct {
	To      string `json:"to"`
	CC      string `json:"cc,omitempty"`
	Subject string `json:"subject"`
	Body    string `json:"body"`
}

func (h *Handler) handleSendEmail(w http.ResponseWriter, r *http.Request) {
	var req SendEmailRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request: " + err.Error()})
		return
	}

	if req.To == "" {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing 'to' field"})
		return
	}

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

	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, req.To, subject, req.Body,
	)

	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{req.To}, []byte(msg)); err != nil {
		log.Printf("error sending email to %s: %v", req.To, err)
		h.writeJSON(w, http.StatusInternalServerError, map[string]string{"error": "failed to send email: " + err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, map[string]string{
		"status":    "success",
		"messageId": fmt.Sprintf("email-%s", req.To),
	})
}

// --- Gotify Messages ---

func (h *Handler) handleSendGotify(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	var msg GotifyMessage
	if err := json.NewDecoder(r.Body).Decode(&msg); err != nil {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request: " + err.Error()})
		return
	}

	result, err := h.gotify.SendMessage(msg)
	if err != nil {
		log.Printf("error sending gotify message: %v", err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, result)
}

func (h *Handler) handleListMessages(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	limit := 50
	if l := r.URL.Query().Get("limit"); l != "" {
		if parsed, err := strconv.Atoi(l); err == nil && parsed > 0 {
			limit = parsed
		}
	}

	result, err := h.gotify.ListMessages(limit)
	if err != nil {
		log.Printf("error listing gotify messages: %v", err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, result)
}

func (h *Handler) handleDeleteMessage(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	var req struct {
		ID int `json:"id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request: " + err.Error()})
		return
	}

	if req.ID == 0 {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing 'id' field"})
		return
	}

	if err := h.gotify.DeleteMessage(req.ID); err != nil {
		log.Printf("error deleting gotify message %d: %v", req.ID, err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

func (h *Handler) handleDeleteAllMessages(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	if err := h.gotify.DeleteAllMessages(); err != nil {
		log.Printf("error deleting all gotify messages: %v", err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, map[string]string{"status": "all messages deleted"})
}

// --- Gotify Applications ---

func (h *Handler) handleListApplications(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	result, err := h.gotify.ListApplications()
	if err != nil {
		log.Printf("error listing gotify applications: %v", err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, result)
}

func (h *Handler) handleCreateApplication(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	var app GotifyApplication
	if err := json.NewDecoder(r.Body).Decode(&app); err != nil {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request: " + err.Error()})
		return
	}

	result, err := h.gotify.CreateApplication(app)
	if err != nil {
		log.Printf("error creating gotify application: %v", err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusCreated, result)
}

func (h *Handler) handleDeleteApplication(w http.ResponseWriter, r *http.Request) {
	if h.gotify == nil {
		h.writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": "Gotify not configured"})
		return
	}

	var req struct {
		ID int `json:"id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid request: " + err.Error()})
		return
	}

	if req.ID == 0 {
		h.writeJSON(w, http.StatusBadRequest, map[string]string{"error": "missing 'id' field"})
		return
	}

	if err := h.gotify.DeleteApplication(req.ID); err != nil {
		log.Printf("error deleting gotify application %d: %v", req.ID, err)
		h.writeJSON(w, http.StatusBadGateway, map[string]string{"error": err.Error()})
		return
	}

	h.writeJSON(w, http.StatusOK, map[string]string{"status": "deleted"})
}

// --- Helpers ---

func (h *Handler) writeJSON(w http.ResponseWriter, status int, data interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(data)
}