package bkosmi

import (
	"context"
	"encoding/json"
	"fmt"
	"net/http"
	"sync"
	"time"

	"github.com/gorilla/websocket"
	"github.com/sirupsen/logrus"
)

// GraphQL WebSocket message types
const (
	typeConnectionInit      = "connection_init"
	typeConnectionAck       = "connection_ack"
	typeConnectionError     = "connection_error"
	typeConnectionKeepAlive = "ka"
	typeStart               = "start"
	typeData                = "data"
	typeError               = "error"
	typeComplete            = "complete"
	typeStop                = "stop"
	typeNext                = "next"
)

// GraphQLMessage represents a GraphQL WebSocket message
type GraphQLMessage struct {
	ID      string          `json:"id,omitempty"`
	Type    string          `json:"type"`
	Payload json.RawMessage `json:"payload,omitempty"`
}

// NewMessagePayload represents the payload structure for new messages
type NewMessagePayload struct {
	Data struct {
		NewMessage struct {
			Body string `json:"body"`
			Time int64  `json:"time"`
			User struct {
				DisplayName string `json:"displayName"`
				Username    string `json:"username"`
			} `json:"user"`
		} `json:"newMessage"`
	} `json:"data"`
}

// GraphQLClient manages the WebSocket connection to Kosmi's GraphQL API
type GraphQLClient struct {
	conn            *websocket.Conn
	url             string
	roomID          string
	log             *logrus.Entry
	subscriptionID  string
	mu              sync.RWMutex
	connected       bool
	reconnectDelay  time.Duration
	messageHandlers []func(*NewMessagePayload)
	ctx             context.Context
	cancel          context.CancelFunc
}

// NewGraphQLClient creates a new GraphQL WebSocket client
func NewGraphQLClient(url, roomID string, log *logrus.Entry) *GraphQLClient {
	ctx, cancel := context.WithCancel(context.Background())
	return &GraphQLClient{
		url:             url,
		roomID:          roomID,
		log:             log,
		reconnectDelay:  5 * time.Second,
		messageHandlers: []func(*NewMessagePayload){},
		ctx:             ctx,
		cancel:          cancel,
	}
}

// Connect establishes the WebSocket connection and performs the GraphQL handshake
func (c *GraphQLClient) Connect() error {
	c.log.Infof("Connecting to Kosmi GraphQL WebSocket: %s", c.url)

	// Set up WebSocket dialer with graphql-ws subprotocol
	dialer := websocket.Dialer{
		Subprotocols:    []string{"graphql-ws"},
		ReadBufferSize:  1024,
		WriteBufferSize: 1024,
	}

	// Connect to WebSocket
	conn, resp, err := dialer.Dial(c.url, http.Header{})
	if err != nil {
		if resp != nil {
			c.log.Errorf("WebSocket dial failed with status %d: %v", resp.StatusCode, err)
		}
		return fmt.Errorf("failed to connect to WebSocket: %w", err)
	}
	defer resp.Body.Close()

	c.mu.Lock()
	c.conn = conn
	c.mu.Unlock()

	c.log.Info("WebSocket connection established")

	// Send connection_init message
	initMsg := GraphQLMessage{
		Type:    typeConnectionInit,
		Payload: json.RawMessage(`{}`),
	}

	if err := c.writeMessage(initMsg); err != nil {
		return fmt.Errorf("failed to send connection_init: %w", err)
	}

	c.log.Debug("Sent connection_init message")

	// Wait for connection_ack
	if err := c.waitForConnectionAck(); err != nil {
		return fmt.Errorf("failed to receive connection_ack: %w", err)
	}

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

	c.log.Info("GraphQL WebSocket handshake completed")

	return nil
}

// waitForConnectionAck waits for the connection_ack message
func (c *GraphQLClient) waitForConnectionAck() error {
	c.mu.RLock()
	conn := c.conn
	c.mu.RUnlock()

	// Set a timeout for the ack
	conn.SetReadDeadline(time.Now().Add(10 * time.Second))
	defer conn.SetReadDeadline(time.Time{})

	for {
		var msg GraphQLMessage
		if err := conn.ReadJSON(&msg); err != nil {
			return fmt.Errorf("failed to read message: %w", err)
		}

		c.log.Debugf("Received message type: %s", msg.Type)

		switch msg.Type {
		case typeConnectionAck:
			c.log.Info("Received connection_ack")
			return nil
		case typeConnectionError:
			return fmt.Errorf("connection error: %s", string(msg.Payload))
		case typeConnectionKeepAlive:
			c.log.Debug("Received keep-alive")
			// Continue waiting for ack
		default:
			c.log.Warnf("Unexpected message type during handshake: %s", msg.Type)
		}
	}
}

// SubscribeToMessages subscribes to new messages in the room
func (c *GraphQLClient) SubscribeToMessages() error {
	c.mu.Lock()
	if !c.connected {
		c.mu.Unlock()
		return fmt.Errorf("not connected")
	}
	c.subscriptionID = "newMessage-1"
	c.mu.Unlock()

	// GraphQL subscription query for new messages
	query := fmt.Sprintf(`
		subscription {
			newMessage(roomId: "%s") {
				body
				time
				user {
					displayName
					username
				}
			}
		}
	`, c.roomID)

	payload := map[string]interface{}{
		"query":     query,
		"variables": map[string]interface{}{},
	}

	payloadJSON, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal subscription payload: %w", err)
	}

	msg := GraphQLMessage{
		ID:      c.subscriptionID,
		Type:    typeStart,
		Payload: payloadJSON,
	}

	if err := c.writeMessage(msg); err != nil {
		return fmt.Errorf("failed to send subscription: %w", err)
	}

	c.log.Infof("Subscribed to messages in room: %s", c.roomID)

	return nil
}

// OnMessage registers a handler for incoming messages
func (c *GraphQLClient) OnMessage(handler func(*NewMessagePayload)) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.messageHandlers = append(c.messageHandlers, handler)
}

// Listen starts listening for messages from the WebSocket
func (c *GraphQLClient) Listen() {
	c.log.Info("Starting message listener")

	for {
		select {
		case <-c.ctx.Done():
			c.log.Info("Message listener stopped")
			return
		default:
			c.mu.RLock()
			conn := c.conn
			c.mu.RUnlock()

			if conn == nil {
				c.log.Warn("Connection is nil, stopping listener")
				return
			}

			var msg GraphQLMessage
			if err := conn.ReadJSON(&msg); err != nil {
				if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
					c.log.Errorf("WebSocket error: %v", err)
				}
				c.log.Warn("Connection closed, stopping listener")
				c.mu.Lock()
				c.connected = false
				c.mu.Unlock()
				return
			}

			c.handleMessage(&msg)
		}
	}
}

// handleMessage processes incoming GraphQL messages
func (c *GraphQLClient) handleMessage(msg *GraphQLMessage) {
	c.log.Debugf("Received GraphQL message type: %s", msg.Type)

	switch msg.Type {
	case typeNext, typeData:
		// Parse the message payload
		var payload NewMessagePayload
		if err := json.Unmarshal(msg.Payload, &payload); err != nil {
			c.log.Errorf("Failed to parse message payload: %v", err)
			return
		}

		// Call all registered handlers
		c.mu.RLock()
		handlers := c.messageHandlers
		c.mu.RUnlock()

		for _, handler := range handlers {
			handler(&payload)
		}

	case typeConnectionKeepAlive:
		c.log.Debug("Received keep-alive")

	case typeError:
		c.log.Errorf("GraphQL error: %s", string(msg.Payload))

	case typeComplete:
		c.log.Infof("Subscription %s completed", msg.ID)

	default:
		c.log.Debugf("Unhandled message type: %s", msg.Type)
	}
}

// SendMessage sends a message to the Kosmi room
func (c *GraphQLClient) SendMessage(text string) error {
	c.mu.RLock()
	if !c.connected {
		c.mu.RUnlock()
		return fmt.Errorf("not connected")
	}
	c.mu.RUnlock()

	// GraphQL mutation to send a message
	mutation := fmt.Sprintf(`
		mutation {
			sendMessage(roomId: "%s", body: "%s") {
				id
			}
		}
	`, c.roomID, escapeGraphQLString(text))

	payload := map[string]interface{}{
		"query":     mutation,
		"variables": map[string]interface{}{},
	}

	payloadJSON, err := json.Marshal(payload)
	if err != nil {
		return fmt.Errorf("failed to marshal mutation payload: %w", err)
	}

	msg := GraphQLMessage{
		ID:      fmt.Sprintf("sendMessage-%d", time.Now().UnixNano()),
		Type:    typeStart,
		Payload: payloadJSON,
	}

	if err := c.writeMessage(msg); err != nil {
		return fmt.Errorf("failed to send message: %w", err)
	}

	c.log.Debugf("Sent message: %s", text)

	return nil
}

// writeMessage writes a GraphQL message to the WebSocket
func (c *GraphQLClient) writeMessage(msg GraphQLMessage) error {
	c.mu.RLock()
	conn := c.conn
	c.mu.RUnlock()

	if conn == nil {
		return fmt.Errorf("connection is nil")
	}

	return conn.WriteJSON(msg)
}

// Close closes the WebSocket connection
func (c *GraphQLClient) Close() error {
	c.log.Info("Closing GraphQL client")

	c.cancel()

	c.mu.Lock()
	defer c.mu.Unlock()

	if c.conn != nil {
		// Send close message
		closeMsg := websocket.FormatCloseMessage(websocket.CloseNormalClosure, "")
		c.conn.WriteMessage(websocket.CloseMessage, closeMsg)
		c.conn.Close()
		c.conn = nil
	}

	c.connected = false

	return nil
}

// IsConnected returns whether the client is connected
func (c *GraphQLClient) IsConnected() bool {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.connected
}

// escapeGraphQLString escapes special characters in GraphQL strings
func escapeGraphQLString(s string) string {
	// Replace special characters that need escaping in GraphQL
	jsonBytes, err := json.Marshal(s)
	if err != nil {
		return s
	}
	// Remove surrounding quotes from JSON string
	if len(jsonBytes) >= 2 {
		return string(jsonBytes[1 : len(jsonBytes)-1])
	}
	return string(jsonBytes)
}