/**
 * package mediaserver
 *
 * WebSocket to RTMP 代理服务
 * 接收 Web端 通过 WebSocket 发送的 WebM 数据，转换为 FLV 并推送到 RTMP
 *
 * 技术栈：
 * - WebSocket: gorilla/websocket
 * - WebM 解析: github.com/at-wat/ebml-go
 * - FLV 封装: github.com/yutopp/go-flv
 * - RTMP 推送: 通过内部流管道
 */
package mediaserver

import (
	"bytes"
	"encoding/binary"
	"fmt"
	"io"
	"log"
	"net/http"
	"sync"
	"time"

	"github.com/at-wat/ebml-go"
	"github.com/gorilla/websocket"
)

// WebMToRTMPProxy WebSocket to RTMP 代理
type WebMToRTMPProxy struct {
	rtmpServer *RTMPServer
	upgrader   websocket.Upgrader
	sessions   map[string]*ProxySession
	sessionsMu sync.RWMutex
}

// ProxySession 代理会话
type ProxySession struct {
	ID        string
	StreamID  string
	UserID    string
	RoomID    string
	Conn      *websocket.Conn
	Stream    *RTMPStream
	StopChan  chan struct{}
	StartTime time.Time

	// WebM 解析状态
	webmBuffer    *bytes.Buffer
	headerParsed  bool
	videoTrackNum uint64
	audioTrackNum uint64

	// 时间戳
	baseTimestamp uint32
	lastTimestamp uint32
}

// WebMHeader WebM 文件头信息
type WebMHeader struct {
	EBMLVersion        uint64 `ebml:"EBMLVersion"`
	EBMLReadVersion    uint64 `ebml:"EBMLReadVersion"`
	EBMLMaxIDLength    uint64 `ebml:"EBMLMaxIDLength"`
	EBMLMaxSizeLength  uint64 `ebml:"EBMLMaxSizeLength"`
	DocType            string `ebml:"DocType"`
	DocTypeVersion     uint64 `ebml:"DocTypeVersion"`
	DocTypeReadVersion uint64 `ebml:"DocTypeReadVersion"`
}

// WebMSegment WebM Segment
type WebMSegment struct {
	Info   WebMSegmentInfo   `ebml:"Info"`
	Tracks WebMTracks        `ebml:"Tracks"`
	Cluster []WebMCluster    `ebml:"Cluster"`
}

// WebMSegmentInfo Segment 信息
type WebMSegmentInfo struct {
	TimecodeScale uint64 `ebml:"TimecodeScale"`
	Duration      float64 `ebml:"Duration,omitempty"`
	MuxingApp     string `ebml:"MuxingApp,omitempty"`
	WritingApp    string `ebml:"WritingApp,omitempty"`
}

// WebMTracks 轨道信息
type WebMTracks struct {
	TrackEntry []WebMTrackEntry `ebml:"TrackEntry"`
}

// WebMTrackEntry 轨道条目
type WebMTrackEntry struct {
	TrackNumber uint64 `ebml:"TrackNumber"`
	TrackType   uint64 `ebml:"TrackType"` // 1=video, 2=audio
	CodecID     string `ebml:"CodecID"`
	Video       *WebMVideoTrack `ebml:"Video,omitempty"`
	Audio       *WebMAudioTrack `ebml:"Audio,omitempty"`
}

// WebMVideoTrack 视频轨道
type WebMVideoTrack struct {
	PixelWidth  uint64 `ebml:"PixelWidth"`
	PixelHeight uint64 `ebml:"PixelHeight"`
}

// WebMAudioTrack 音频轨道
type WebMAudioTrack struct {
	SamplingFrequency float64 `ebml:"SamplingFrequency"`
	Channels          uint64  `ebml:"Channels"`
	BitDepth          uint64  `ebml:"BitDepth,omitempty"`
}

// WebMCluster WebM Cluster
type WebMCluster struct {
	Timecode    uint64           `ebml:"Timecode"`
	SimpleBlock []ebml.Block     `ebml:"SimpleBlock,omitempty"`
}

// NewWebMToRTMPProxy 创建代理服务
func NewWebMToRTMPProxy(rtmpServer *RTMPServer) *WebMToRTMPProxy {
	return &WebMToRTMPProxy{
		rtmpServer: rtmpServer,
		upgrader: websocket.Upgrader{
			CheckOrigin: func(r *http.Request) bool {
				return true // 允许跨域
			},
			ReadBufferSize:  1024 * 1024,
			WriteBufferSize: 1024 * 1024,
		},
		sessions: make(map[string]*ProxySession),
	}
}

// HandleWebSocket 处理 WebSocket 连接
func (p *WebMToRTMPProxy) HandleWebSocket(w http.ResponseWriter, r *http.Request) {
	log.Printf("🔌 [WSProxy] 收到 WebSocket 连接请求: %s from %s", r.URL.String(), r.RemoteAddr)

	// 检查 WebSocket 升级头
	if r.Header.Get("Upgrade") != "websocket" {
		log.Printf("❌ [WSProxy] 不是 WebSocket 请求: Upgrade=%s", r.Header.Get("Upgrade"))
		http.Error(w, "Not a WebSocket request", http.StatusBadRequest)
		return
	}

	// 获取参数
	streamID := r.URL.Query().Get("stream_id")
	userID := r.URL.Query().Get("user_id")
	roomID := r.URL.Query().Get("room_id")
	token := r.URL.Query().Get("token")

	log.Printf("📋 [WSProxy] 参数: stream_id=%s user_id=%s room_id=%s token=%v",
		streamID, userID, roomID, token != "")

	if streamID == "" || userID == "" {
		log.Printf("❌ [WSProxy] 缺少必要参数")
		http.Error(w, "Missing stream_id or user_id", http.StatusBadRequest)
		return
	}

	// 验证 token（简化版，生产环境需要更严格的验证）
	if token == "" {
		log.Printf("⚠️ [WSProxy] 缺少 token: stream=%s", streamID)
	}

	// 升级到 WebSocket
	log.Printf("🔄 [WSProxy] 尝试 WebSocket 升级...")
	conn, err := p.upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Printf("❌ [WSProxy] WebSocket 升级失败: %v (可能原因: 中间件干扰、响应已写入)", err)
		return
	}

	log.Printf("✅ [WSProxy] WebSocket 升级成功 | Stream:%s User:%s Room:%s", streamID, userID, roomID)

	// 获取或创建 RTMP 流
	stream := p.rtmpServer.GetStream(streamID)
	if stream == nil {
		// 自动创建流
		var err error
		stream, err = p.rtmpServer.GenerateStreamURLs(roomID, userID)
		if err != nil {
			log.Printf("❌ [WSProxy] 创建流失败: %v", err)
			conn.Close()
			return
		}
		// 更新 streamID 为实际生成的
		streamID = stream.ID
	}

	// 创建会话
	session := &ProxySession{
		ID:            fmt.Sprintf("%s_%d", userID, time.Now().UnixNano()),
		StreamID:      streamID,
		UserID:        userID,
		RoomID:        roomID,
		Conn:          conn,
		Stream:        stream,
		StopChan:      make(chan struct{}),
		StartTime:     time.Now(),
		webmBuffer:    bytes.NewBuffer(nil),
		headerParsed:  false,
	}

	// 注册会话
	p.sessionsMu.Lock()
	p.sessions[session.ID] = session
	p.sessionsMu.Unlock()

	// 激活流
	stream.mu.Lock()
	stream.IsActive = true
	stream.mu.Unlock()

	// 处理连接
	go p.handleSession(session)
}

// handleSession 处理会话
func (p *WebMToRTMPProxy) handleSession(session *ProxySession) {
	log.Printf("▶️ [WSProxy] 开始处理会话 | Stream:%s User:%s", session.StreamID, session.UserID)

	messageCount := 0
	totalBytes := int64(0)

	defer func() {
		// 清理
		p.sessionsMu.Lock()
		delete(p.sessions, session.ID)
		p.sessionsMu.Unlock()

		session.Conn.Close()
		close(session.StopChan)

		// 标记流为非活动
		if session.Stream != nil {
			session.Stream.mu.Lock()
			session.Stream.IsActive = false
			session.Stream.mu.Unlock()
		}

		log.Printf("🔌 [WSProxy] 连接关闭 | Stream:%s User:%s | 收到消息:%d 总字节:%d",
			session.StreamID, session.UserID, messageCount, totalBytes)
	}()

	for {
		select {
		case <-session.StopChan:
			log.Printf("⏹️ [WSProxy] 收到停止信号 | Stream:%s", session.StreamID)
			return
		default:
		}

		// 读取 WebSocket 消息
		messageType, data, err := session.Conn.ReadMessage()
		if err != nil {
			if websocket.IsUnexpectedCloseError(err, websocket.CloseGoingAway, websocket.CloseAbnormalClosure) {
				log.Printf("⚠️ [WSProxy] 读取错误: %v | Stream:%s", err, session.StreamID)
			} else {
				log.Printf("ℹ️ [WSProxy] 连接关闭: %v | Stream:%s", err, session.StreamID)
			}
			return
		}

		messageCount++
		totalBytes += int64(len(data))

		// 记录首次收到消息
		if messageCount == 1 {
			log.Printf("📥 [WSProxy] 首次收到消息 | Stream:%s Type:%d Size:%d", session.StreamID, messageType, len(data))
		}

		// 每 100 条消息记录一次统计
		if messageCount%100 == 0 {
			log.Printf("📊 [WSProxy] 消息统计 | Stream:%s Count:%d TotalBytes:%d", session.StreamID, messageCount, totalBytes)
		}

		if messageType != websocket.BinaryMessage {
			log.Printf("⚠️ [WSProxy] 忽略非二进制消息 | Type:%d", messageType)
			continue
		}

		// 处理 WebM 数据
		if err := p.processWebMData(session, data); err != nil {
			log.Printf("⚠️ [WSProxy] 处理 WebM 数据失败: %v", err)
		}
	}
}

// processWebMData 处理 WebM 数据
func (p *WebMToRTMPProxy) processWebMData(session *ProxySession, data []byte) error {
	// 将数据追加到缓冲区
	session.webmBuffer.Write(data)

	// 尝试解析 WebM 数据
	return p.parseAndConvert(session)
}

// parseAndConvert 解析 WebM 并转换为 FLV
func (p *WebMToRTMPProxy) parseAndConvert(session *ProxySession) error {
	bufData := session.webmBuffer.Bytes()
	if len(bufData) < 4 {
		return nil // 数据不足
	}

	// 检查 EBML 头部
	if !session.headerParsed {
		// 尝试解析头部
		if err := p.parseWebMHeader(session, bufData); err != nil {
			// 头部不完整，等待更多数据
			return nil
		}
		session.headerParsed = true
		log.Printf("📦 [WSProxy] WebM 头部解析完成 | Stream:%s", session.StreamID)
	}

	// 解析 Cluster 并转换
	return p.parseWebMClusters(session)
}

// parseWebMHeader 解析 WebM 头部
func (p *WebMToRTMPProxy) parseWebMHeader(session *ProxySession, data []byte) error {
	reader := bytes.NewReader(data)
	
	// 解析 EBML 头
	var header struct {
		EBML struct {
			EBMLVersion uint64 `ebml:"EBMLVersion"`
			DocType     string `ebml:"DocType"`
		} `ebml:"EBML"`
	}
	
	if err := ebml.Unmarshal(reader, &header); err != nil {
		return err
	}

	log.Printf("📦 [WSProxy] WebM DocType: %s", header.EBML.DocType)
	return nil
}

// parseWebMClusters 解析 WebM Clusters
func (p *WebMToRTMPProxy) parseWebMClusters(session *ProxySession) error {
	// 简化处理：直接将 WebM 数据转换为 FLV
	// 实际实现需要完整解析 WebM 的 Cluster/SimpleBlock
	
	bufData := session.webmBuffer.Bytes()
	if len(bufData) < 100 {
		return nil
	}

	// 寻找 Cluster 标记 (0x1F43B675)
	clusterMarker := []byte{0x1F, 0x43, 0xB6, 0x75}
	
	for {
		idx := bytes.Index(bufData, clusterMarker)
		if idx == -1 || idx+12 > len(bufData) {
			break
		}

		// 解析 Cluster 大小
		sizeStart := idx + 4
		clusterSize, bytesRead := readVarInt(bufData[sizeStart:])
		if bytesRead == 0 {
			break
		}

		totalSize := idx + 4 + bytesRead + int(clusterSize)
		if totalSize > len(bufData) {
			// Cluster 不完整
			break
		}

		// 提取 Cluster 数据
		clusterData := bufData[idx:totalSize]
		
		// 转换为 FLV 并广播
		if err := p.convertClusterToFLV(session, clusterData); err != nil {
			log.Printf("⚠️ [WSProxy] 转换 Cluster 失败: %v", err)
		}

		// 从缓冲区移除已处理的数据
		bufData = bufData[totalSize:]
	}

	// 更新缓冲区
	session.webmBuffer.Reset()
	session.webmBuffer.Write(bufData)

	return nil
}

// readVarInt 读取 EBML 变长整数
func readVarInt(data []byte) (uint64, int) {
	if len(data) == 0 {
		return 0, 0
	}

	first := data[0]
	var length int
	var mask byte

	switch {
	case first&0x80 != 0:
		length = 1
		mask = 0x7F
	case first&0x40 != 0:
		length = 2
		mask = 0x3F
	case first&0x20 != 0:
		length = 3
		mask = 0x1F
	case first&0x10 != 0:
		length = 4
		mask = 0x0F
	case first&0x08 != 0:
		length = 5
		mask = 0x07
	case first&0x04 != 0:
		length = 6
		mask = 0x03
	case first&0x02 != 0:
		length = 7
		mask = 0x01
	case first&0x01 != 0:
		length = 8
		mask = 0x00
	default:
		return 0, 0
	}

	if len(data) < length {
		return 0, 0
	}

	value := uint64(data[0] & mask)
	for i := 1; i < length; i++ {
		value = (value << 8) | uint64(data[i])
	}

	return value, length
}

// convertClusterToFLV 将 WebM Cluster 转换为 FLV 并广播
func (p *WebMToRTMPProxy) convertClusterToFLV(session *ProxySession, clusterData []byte) error {
	// 解析 Cluster 时间戳
	timecodeMarker := []byte{0xE7} // Timecode element ID
	timecodeIdx := bytes.Index(clusterData, timecodeMarker)
	
	var timestamp uint32 = session.lastTimestamp
	if timecodeIdx != -1 && timecodeIdx+1 < len(clusterData) {
		tcSize, bytesRead := readVarInt(clusterData[timecodeIdx+1:])
		if bytesRead > 0 && timecodeIdx+1+bytesRead+int(tcSize) <= len(clusterData) {
			tcData := clusterData[timecodeIdx+1+bytesRead : timecodeIdx+1+bytesRead+int(tcSize)]
			for _, b := range tcData {
				timestamp = (timestamp << 8) | uint32(b)
			}
		}
	}

	// 解析 SimpleBlock
	simpleBlockMarker := []byte{0xA3} // SimpleBlock element ID
	blockData := clusterData
	
	for {
		blockIdx := bytes.Index(blockData, simpleBlockMarker)
		if blockIdx == -1 || blockIdx+1 >= len(blockData) {
			break
		}

		// 解析 block 大小
		sizeStart := blockIdx + 1
		blockSize, bytesRead := readVarInt(blockData[sizeStart:])
		if bytesRead == 0 {
			break
		}

		dataStart := sizeStart + bytesRead
		dataEnd := dataStart + int(blockSize)
		if dataEnd > len(blockData) {
			break
		}

		// 提取 block 内容
		block := blockData[dataStart:dataEnd]
		if len(block) < 4 {
			blockData = blockData[dataEnd:]
			continue
		}

		// 解析 track number（变长）
		trackNum, trackBytes := readVarInt(block)
		if trackBytes == 0 {
			blockData = blockData[dataEnd:]
			continue
		}

		// 解析相对时间戳（2 bytes, big-endian）
		if trackBytes+2 > len(block) {
			blockData = blockData[dataEnd:]
			continue
		}
		relativeTimestamp := binary.BigEndian.Uint16(block[trackBytes : trackBytes+2])
		
		// 解析 flags (1 byte)
		flagsIdx := trackBytes + 2
		if flagsIdx >= len(block) {
			blockData = blockData[dataEnd:]
			continue
		}
		flags := block[flagsIdx]
		
		// 帧数据
		frameData := block[flagsIdx+1:]
		if len(frameData) == 0 {
			blockData = blockData[dataEnd:]
			continue
		}

		// 计算绝对时间戳
		absoluteTimestamp := timestamp + uint32(relativeTimestamp)
		session.lastTimestamp = absoluteTimestamp

		// 判断是视频还是音频（简化：假设 track 1 是视频，track 2 是音频）
		isVideo := trackNum == 1
		isKeyframe := (flags & 0x80) != 0

		// 创建 FLV tag 并广播
		var flvTag []byte
		if isVideo {
			flvTag = p.createFLVVideoTag(absoluteTimestamp, frameData, isKeyframe)
		} else {
			flvTag = p.createFLVAudioTag(absoluteTimestamp, frameData)
		}

		if flvTag != nil {
			p.broadcastFLVTag(session, flvTag)
		}

		blockData = blockData[dataEnd:]
	}

	return nil
}

// createFLVVideoTag 创建 FLV 视频 tag
// VP8 -> FLV (需要转换为 H.264，这里简化处理)
func (p *WebMToRTMPProxy) createFLVVideoTag(timestamp uint32, data []byte, isKeyframe bool) []byte {
	// 注意：VP8 不能直接封装到 FLV，需要转码为 H.264
	// 这里使用一个简化的方案：将 VP8 数据作为自定义格式封装
	// 实际生产环境需要使用 FFmpeg 或硬件编码器进行转码

	// FLV Video Tag Header:
	// FrameType (4 bits): 1=keyframe, 2=inter frame
	// CodecID (4 bits): 7=AVC (H.264)
	
	// 由于 VP8 无法直接放入 FLV，这里使用一个变通方案
	// 将 VP8 数据标记为私有编码格式
	
	frameType := byte(2) // inter frame
	if isKeyframe {
		frameType = 1 // keyframe
	}
	
	// 使用 CodecID=12 (VP8 - 非标准，仅用于内部传输)
	// 或者可以考虑在服务端进行实时转码
	codecID := byte(12) // 自定义：VP8
	
	header := (frameType << 4) | codecID
	
	// 构建完整数据
	videoData := make([]byte, 1+len(data))
	videoData[0] = header
	copy(videoData[1:], data)
	
	return p.createFLVTag(9, timestamp, videoData) // 9 = video
}

// createFLVAudioTag 创建 FLV 音频 tag
// Opus -> FLV (需要转换为 AAC，这里简化处理)
func (p *WebMToRTMPProxy) createFLVAudioTag(timestamp uint32, data []byte) []byte {
	// 注意：Opus 不能直接封装到 FLV，需要转码为 AAC
	// 这里使用简化方案
	
	// FLV Audio Tag Header:
	// SoundFormat (4 bits): 10=AAC, 13=Opus (非标准)
	// SoundRate (2 bits): 3=44kHz
	// SoundSize (1 bit): 1=16-bit
	// SoundType (1 bit): 1=stereo
	
	// 使用自定义格式标记 Opus
	soundFormat := byte(13) // 自定义：Opus
	soundRate := byte(3)    // 44kHz
	soundSize := byte(1)    // 16-bit
	soundType := byte(1)    // stereo
	
	header := (soundFormat << 4) | (soundRate << 2) | (soundSize << 1) | soundType
	
	// 构建完整数据
	audioData := make([]byte, 1+len(data))
	audioData[0] = header
	copy(audioData[1:], data)
	
	return p.createFLVTag(8, timestamp, audioData) // 8 = audio
}

// createFLVTag 创建 FLV tag
func (p *WebMToRTMPProxy) createFLVTag(tagType byte, timestamp uint32, data []byte) []byte {
	dataSize := len(data)
	tagSize := 11 + dataSize + 4

	tag := make([]byte, tagSize)

	// Tag type
	tag[0] = tagType

	// Data size (24-bit big-endian)
	tag[1] = byte((dataSize >> 16) & 0xff)
	tag[2] = byte((dataSize >> 8) & 0xff)
	tag[3] = byte(dataSize & 0xff)

	// Timestamp (24-bit big-endian)
	tag[4] = byte((timestamp >> 16) & 0xff)
	tag[5] = byte((timestamp >> 8) & 0xff)
	tag[6] = byte(timestamp & 0xff)

	// Timestamp extended
	tag[7] = byte((timestamp >> 24) & 0xff)

	// Stream ID (always 0)
	tag[8] = 0
	tag[9] = 0
	tag[10] = 0

	// Data
	copy(tag[11:], data)

	// Previous tag size
	prevTagSize := 11 + dataSize
	tag[11+dataSize] = byte((prevTagSize >> 24) & 0xff)
	tag[11+dataSize+1] = byte((prevTagSize >> 16) & 0xff)
	tag[11+dataSize+2] = byte((prevTagSize >> 8) & 0xff)
	tag[11+dataSize+3] = byte(prevTagSize & 0xff)

	return tag
}

// broadcastFLVTag 广播 FLV tag 到订阅者
func (p *WebMToRTMPProxy) broadcastFLVTag(session *ProxySession, tag []byte) {
	if session.Stream == nil {
		return
	}

	// 缓存到 GOP
	session.Stream.mu.Lock()
	session.Stream.gopCache = append(session.Stream.gopCache, tag)
	if len(session.Stream.gopCache) > 300 {
		session.Stream.gopCache = session.Stream.gopCache[len(session.Stream.gopCache)-300:]
	}
	session.Stream.mu.Unlock()

	// 广播到 HTTP-FLV 订阅者
	p.rtmpServer.subMu.RLock()
	subs, exists := p.rtmpServer.subscribers[session.StreamID]
	if exists {
		for _, sub := range subs {
			select {
			case sub.DataChan <- tag:
			default:
				// 缓冲区满，跳过
			}
		}
	}
	p.rtmpServer.subMu.RUnlock()
}

// GetSession 获取会话
func (p *WebMToRTMPProxy) GetSession(sessionID string) *ProxySession {
	p.sessionsMu.RLock()
	defer p.sessionsMu.RUnlock()
	return p.sessions[sessionID]
}

// GetSessionsByStream 获取流的所有会话
func (p *WebMToRTMPProxy) GetSessionsByStream(streamID string) []*ProxySession {
	p.sessionsMu.RLock()
	defer p.sessionsMu.RUnlock()

	sessions := make([]*ProxySession, 0)
	for _, s := range p.sessions {
		if s.StreamID == streamID {
			sessions = append(sessions, s)
		}
	}
	return sessions
}

// CloseSession 关闭会话
func (p *WebMToRTMPProxy) CloseSession(sessionID string) {
	p.sessionsMu.Lock()
	session, exists := p.sessions[sessionID]
	if exists {
		delete(p.sessions, sessionID)
	}
	p.sessionsMu.Unlock()

	if session != nil {
		select {
		case <-session.StopChan:
		default:
			close(session.StopChan)
		}
		session.Conn.Close()
	}
}

// CloseAllSessions 关闭所有会话
func (p *WebMToRTMPProxy) CloseAllSessions() {
	p.sessionsMu.Lock()
	sessions := make([]*ProxySession, 0, len(p.sessions))
	for _, s := range p.sessions {
		sessions = append(sessions, s)
	}
	p.sessions = make(map[string]*ProxySession)
	p.sessionsMu.Unlock()

	for _, s := range sessions {
		select {
		case <-s.StopChan:
		default:
			close(s.StopChan)
		}
		s.Conn.Close()
	}
}

// 确保导入被使用
var _ io.Reader = (*bytes.Reader)(nil)