package ironnotify

import (
	"context"
	"errors"
	"fmt"
	"sync"
)

// Errors
var (
	ErrNotInitialized = errors.New("ironnotify: client not initialized")
	ErrTitleRequired  = errors.New("ironnotify: notification title is required")
	ErrAPIKeyRequired = errors.New("ironnotify: API key is required")
)

// Client is the IronNotify client.
type Client struct {
	options   Options
	transport *Transport
	queue     *OfflineQueue
	isOnline  bool

	connectionState    ConnectionState
	onNotification     NotificationHandler
	onUnreadCount      UnreadCountHandler
	onConnectionChange ConnectionStateHandler

	mu sync.RWMutex
}

// Global client instance
var globalClient *Client
var globalMu sync.RWMutex

// NewClient creates a new IronNotify client.
func NewClient(options Options) (*Client, error) {
	if options.APIKey == "" {
		return nil, ErrAPIKeyRequired
	}

	opts := options.WithDefaults()

	client := &Client{
		options:         opts,
		transport:       NewTransport(opts.APIBaseURL, opts.APIKey, opts.HTTPTimeout, opts.Debug),
		isOnline:        true,
		connectionState: StateDisconnected,
	}

	if opts.EnableOfflineQueue {
		client.queue = NewOfflineQueue(opts.MaxOfflineQueueSize, opts.Debug)
	}

	if opts.Debug {
		fmt.Println("[IronNotify] Client initialized")
	}

	return client, nil
}

// Init initializes the global client.
func Init(apiKey string, opts ...func(*Options)) error {
	options := DefaultOptions()
	options.APIKey = apiKey

	for _, opt := range opts {
		opt(&options)
	}

	client, err := NewClient(options)
	if err != nil {
		return err
	}

	globalMu.Lock()
	globalClient = client
	globalMu.Unlock()

	return nil
}

// WithDebug enables debug mode.
func WithDebug(debug bool) func(*Options) {
	return func(o *Options) {
		o.Debug = debug
	}
}

// WithAPIBaseURL sets the API base URL.
func WithAPIBaseURL(url string) func(*Options) {
	return func(o *Options) {
		o.APIBaseURL = url
	}
}

// WithOfflineQueue enables or disables the offline queue.
func WithOfflineQueue(enabled bool) func(*Options) {
	return func(o *Options) {
		o.EnableOfflineQueue = enabled
	}
}

// getGlobalClient returns the global client.
func getGlobalClient() (*Client, error) {
	globalMu.RLock()
	defer globalMu.RUnlock()

	if globalClient == nil {
		return nil, ErrNotInitialized
	}
	return globalClient, nil
}

// Notify sends a notification using the global client.
func Notify(eventType, title string, opts ...NotifyOption) SendResult {
	client, err := getGlobalClient()
	if err != nil {
		return SendResult{Success: false, Error: err.Error()}
	}
	return client.Notify(eventType, title, opts...)
}

// NotifyOption is a function that modifies a NotificationPayload.
type NotifyOption func(*NotificationPayload)

// WithMessage sets the message.
func WithMessage(message string) NotifyOption {
	return func(p *NotificationPayload) {
		p.Message = message
	}
}

// WithSeverity sets the severity.
func WithSeverity(severity SeverityLevel) NotifyOption {
	return func(p *NotificationPayload) {
		p.Severity = severity
	}
}

// WithUserID sets the user ID.
func WithUserID(userID string) NotifyOption {
	return func(p *NotificationPayload) {
		p.UserID = userID
	}
}

// WithMetadataOpt sets metadata.
func WithMetadataOpt(metadata map[string]any) NotifyOption {
	return func(p *NotificationPayload) {
		p.Metadata = metadata
	}
}

// Notify sends a notification.
func (c *Client) Notify(eventType, title string, opts ...NotifyOption) SendResult {
	payload := &NotificationPayload{
		EventType: eventType,
		Title:     title,
		Severity:  SeverityInfo,
	}

	for _, opt := range opts {
		opt(payload)
	}

	return c.SendPayload(payload)
}

// Event creates an event builder using the global client.
func Event(eventType string) *EventBuilder {
	client, err := getGlobalClient()
	if err != nil {
		// Return a builder that will fail on send
		return &EventBuilder{eventType: eventType}
	}
	return client.Event(eventType)
}

// Event creates an event builder.
func (c *Client) Event(eventType string) *EventBuilder {
	return newEventBuilder(c, eventType)
}

// SendPayload sends a notification payload.
func (c *Client) SendPayload(payload *NotificationPayload) SendResult {
	result := c.transport.Send(context.Background(), payload)

	if !result.Success && c.options.EnableOfflineQueue && c.queue != nil {
		c.queue.Add(*payload)
		c.mu.Lock()
		c.isOnline = false
		c.mu.Unlock()
		return SendResult{
			Success:        result.Success,
			NotificationID: result.NotificationID,
			Error:          result.Error,
			Queued:         true,
		}
	}

	return result
}

// GetNotifications retrieves notifications.
func (c *Client) GetNotifications(limit, offset int, unreadOnly bool) ([]Notification, error) {
	return c.transport.GetNotifications(context.Background(), limit, offset, unreadOnly)
}

// GetNotificationsContext retrieves notifications with context.
func (c *Client) GetNotificationsContext(ctx context.Context, limit, offset int, unreadOnly bool) ([]Notification, error) {
	return c.transport.GetNotifications(ctx, limit, offset, unreadOnly)
}

// GetUnreadCount returns the unread notification count.
func (c *Client) GetUnreadCount() (int, error) {
	return c.transport.GetUnreadCount(context.Background())
}

// MarkAsRead marks a notification as read.
func (c *Client) MarkAsRead(notificationID string) error {
	return c.transport.MarkAsRead(context.Background(), notificationID)
}

// MarkAllAsRead marks all notifications as read.
func (c *Client) MarkAllAsRead() error {
	return c.transport.MarkAllAsRead(context.Background())
}

// OnNotification sets the notification handler.
func (c *Client) OnNotification(handler NotificationHandler) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.onNotification = handler
}

// OnUnreadCountChange sets the unread count change handler.
func (c *Client) OnUnreadCountChange(handler UnreadCountHandler) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.onUnreadCount = handler
}

// OnConnectionStateChange sets the connection state change handler.
func (c *Client) OnConnectionStateChange(handler ConnectionStateHandler) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.onConnectionChange = handler
}

// ConnectionState returns the current connection state.
func (c *Client) ConnectionState() ConnectionState {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.connectionState
}

// Connect connects to real-time notifications.
func (c *Client) Connect() {
	c.setConnectionState(StateConnected)
	if c.options.Debug {
		fmt.Println("[IronNotify] Connected (WebSocket not implemented)")
	}
}

// Disconnect disconnects from real-time notifications.
func (c *Client) Disconnect() {
	c.setConnectionState(StateDisconnected)
}

// SubscribeToUser subscribes to a user's notifications.
func (c *Client) SubscribeToUser(userID string) {
	if c.options.Debug {
		fmt.Printf("[IronNotify] Subscribed to user: %s\n", userID)
	}
}

// SubscribeToApp subscribes to app-wide notifications.
func (c *Client) SubscribeToApp() {
	if c.options.Debug {
		fmt.Println("[IronNotify] Subscribed to app notifications")
	}
}

// Flush flushes the offline queue.
func (c *Client) Flush() {
	if c.queue == nil || c.queue.IsEmpty() {
		return
	}

	if !c.transport.IsOnline(context.Background()) {
		return
	}

	c.mu.Lock()
	c.isOnline = true
	c.mu.Unlock()

	notifications := c.queue.GetAll()
	for i := len(notifications) - 1; i >= 0; i-- {
		result := c.transport.Send(context.Background(), &notifications[i])
		if result.Success {
			c.queue.Remove(i)
		} else {
			break
		}
	}
}

// FlushContext flushes the offline queue with context.
func (c *Client) FlushContext(ctx context.Context) {
	if c.queue == nil || c.queue.IsEmpty() {
		return
	}

	if !c.transport.IsOnline(ctx) {
		return
	}

	c.mu.Lock()
	c.isOnline = true
	c.mu.Unlock()

	notifications := c.queue.GetAll()
	for i := len(notifications) - 1; i >= 0; i-- {
		result := c.transport.Send(ctx, &notifications[i])
		if result.Success {
			c.queue.Remove(i)
		} else {
			break
		}
	}
}

// Close closes the client.
func (c *Client) Close() {
	c.Disconnect()
	c.transport.Close()
}

// setConnectionState sets the connection state and calls the handler.
func (c *Client) setConnectionState(state ConnectionState) {
	c.mu.Lock()
	c.connectionState = state
	handler := c.onConnectionChange
	c.mu.Unlock()

	if handler != nil {
		handler(state)
	}
}

// Flush flushes the global client's offline queue.
func Flush() {
	client, err := getGlobalClient()
	if err != nil {
		return
	}
	client.Flush()
}

// Close closes the global client.
func Close() {
	globalMu.Lock()
	defer globalMu.Unlock()

	if globalClient != nil {
		globalClient.Close()
		globalClient = nil
	}
}