package xai

import (
	"encoding/base64"
	"encoding/binary"
	"encoding/json"
	"fmt"
	"log"
	"sync"

	"github.com/gorilla/websocket"
)

const (
	// WebSocket endpoint for xAI realtime API
	RealtimeURL = "wss://api.x.ai/v1/realtime"
)

// AudioHandler is called when audio is received from xAI
type AudioHandler func(pcm []int16)

// TranscriptHandler is called when transcript text is received
type TranscriptHandler func(text string)

// SpeechHandler is called when speech is detected (for interruptions)
type SpeechHandler func()

// Client manages a WebSocket connection to xAI Voice Agent API
type Client struct {
	apiKey string
	conn   *websocket.Conn
	mu     sync.Mutex

	// Callbacks
	onAudio         AudioHandler
	onTranscript    TranscriptHandler
	onSpeechStarted SpeechHandler

	// State
	connected bool
	done      chan struct{}
}

// New creates a new xAI client
func New(apiKey string) *Client {
	return &Client{
		apiKey: apiKey,
		done:   make(chan struct{}),
	}
}

// OnAudio sets the callback for received audio
func (c *Client) OnAudio(handler AudioHandler) {
	c.onAudio = handler
}

// OnTranscript sets the callback for received transcripts
func (c *Client) OnTranscript(handler TranscriptHandler) {
	c.onTranscript = handler
}

// OnSpeechStarted sets the callback for when user starts speaking (for interruptions)
func (c *Client) OnSpeechStarted(handler SpeechHandler) {
	c.onSpeechStarted = handler
}

// Connect establishes WebSocket connection to xAI
func (c *Client) Connect() error {
	header := make(map[string][]string)
	header["Authorization"] = []string{"Bearer " + c.apiKey}

	dialer := websocket.Dialer{}
	conn, _, err := dialer.Dial(RealtimeURL, header)
	if err != nil {
		return fmt.Errorf("failed to connect to xAI: %w", err)
	}

	c.conn = conn
	c.connected = true

	// Start message receiver
	go c.receiveLoop()

	log.Println("[xAI] Connected to Voice Agent API")
	return nil
}

// ConfigureSession sets up the voice session
func (c *Client) ConfigureSession(voice, instructions string) error {
	msg := SessionUpdate{
		Type: "session.update",
		Session: Session{
			Voice:        voice,
			Instructions: instructions,
			TurnDetection: &TurnDetection{
				Type: "server_vad",
			},
			Audio: &AudioConfig{
				Input: &AudioFormatConfig{
					Format: AudioFormat{Type: "audio/pcm", Rate: 48000},
				},
				Output: &AudioFormatConfig{
					Format: AudioFormat{Type: "audio/pcm", Rate: 48000},
				},
			},
		},
	}

	return c.sendJSON(msg)
}

// SendAudio sends PCM audio data to xAI
// pcm should be int16 samples at 48kHz mono
func (c *Client) SendAudio(pcm []int16) error {
	// Convert int16 slice to bytes (little endian)
	buf := make([]byte, len(pcm)*2)
	for i, sample := range pcm {
		binary.LittleEndian.PutUint16(buf[i*2:], uint16(sample))
	}

	// Encode to base64
	encoded := base64.StdEncoding.EncodeToString(buf)

	msg := InputAudioBufferAppend{
		Type:  "input_audio_buffer.append",
		Audio: encoded,
	}

	return c.sendJSON(msg)
}

// Close closes the WebSocket connection
func (c *Client) Close() {
	c.mu.Lock()
	defer c.mu.Unlock()

	if c.conn != nil {
		close(c.done)
		c.conn.Close()
		c.connected = false
		log.Println("[xAI] Connection closed")
	}
}

// IsConnected returns connection status
func (c *Client) IsConnected() bool {
	return c.connected
}

// sendJSON sends a JSON message over WebSocket
func (c *Client) sendJSON(v any) error {
	c.mu.Lock()
	defer c.mu.Unlock()

	if c.conn == nil {
		return fmt.Errorf("not connected")
	}

	data, err := json.Marshal(v)
	if err != nil {
		return err
	}

	return c.conn.WriteMessage(websocket.TextMessage, data)
}

// receiveLoop handles incoming messages from xAI
func (c *Client) receiveLoop() {
	defer func() {
		c.connected = false
	}()

	for {
		select {
		case <-c.done:
			return
		default:
		}

		_, message, err := c.conn.ReadMessage()
		if err != nil {
			if websocket.IsCloseError(err, websocket.CloseNormalClosure) {
				log.Println("[xAI] Connection closed normally")
			} else {
				log.Printf("[xAI] Read error: %v", err)
			}
			return
		}

		c.handleMessage(message)
	}
}

// handleMessage processes an incoming WebSocket message
func (c *Client) handleMessage(data []byte) {
	// Parse base message to get type
	var base ServerMessage
	if err := json.Unmarshal(data, &base); err != nil {
		log.Printf("[xAI] Failed to parse message: %v", err)
		return
	}

	switch base.Type {
	case "session.updated":
		log.Println("[xAI] Session configured successfully")

	case "session.created":
		log.Println("[xAI] Session created")

	case "conversation.created":
		log.Println("[xAI] Conversation created")

	case "response.output_audio.delta":
		var msg ResponseOutputAudioDelta
		if err := json.Unmarshal(data, &msg); err != nil {
			log.Printf("[xAI] Failed to parse audio delta: %v", err)
			return
		}
		c.handleAudioDelta(msg.Delta)

	case "response.output_audio.done":
		// Audio stream complete for this response
		log.Println("[xAI] Audio response complete")

	case "response.output_audio_transcript.delta":
		// Could extract transcript text here
		var raw map[string]any
		json.Unmarshal(data, &raw)
		if delta, ok := raw["delta"].(string); ok && c.onTranscript != nil {
			c.onTranscript(delta)
		}

	case "response.done":
		log.Println("[xAI] Response complete")

	case "input_audio_buffer.speech_started":
		log.Println("[xAI] Speech started (VAD)")
		if c.onSpeechStarted != nil {
			c.onSpeechStarted()
		}

	case "input_audio_buffer.speech_stopped":
		log.Println("[xAI] Speech stopped (VAD)")

	case "error":
		var msg ErrorMessage
		if err := json.Unmarshal(data, &msg); err == nil {
			log.Printf("[xAI] Error: %s - %s", msg.Error.Code, msg.Error.Message)
		}

	default:
		// Log unhandled message types for debugging
		log.Printf("[xAI] Received: %s", base.Type)
	}
}

// handleAudioDelta processes received audio data
func (c *Client) handleAudioDelta(base64Audio string) {
	if c.onAudio == nil {
		return
	}

	// Decode base64
	audioBytes, err := base64.StdEncoding.DecodeString(base64Audio)
	if err != nil {
		log.Printf("[xAI] Failed to decode audio: %v", err)
		return
	}

	// Convert bytes to int16 (little endian)
	pcm := make([]int16, len(audioBytes)/2)
	for i := 0; i < len(pcm); i++ {
		pcm[i] = int16(binary.LittleEndian.Uint16(audioBytes[i*2:]))
	}

	c.onAudio(pcm)
}