// app/build.gradle
plugins {
  id 'com.android.application'
  id 'kotlin-android'
}
 
android {
  compileSdkVersion 34
  defaultConfig {
    applicationId "com.example.videocall"
    minSdkVersion 21
    targetSdkVersion 34
    // 需啟用對攝像頭、麥克風權(quán)限
  }
  buildFeatures { viewBinding true }
  kotlinOptions { jvmTarget = "1.8" }
}
 
dependencies {
  implementation 'org.webrtc:google-webrtc:1.0.32006' // 官方 AAR
  implementation 'org.jetbrains.kotlinx:kotlinx-coroutines-android:1.6.4'
  implementation 'com.squareup.okhttp3:okhttp:4.10.0'    // WebSocket
}

// =======================================================
// 文件: AndroidManifest.xml
// 描述: 攝像頭與麥克風權(quán)限
// =======================================================
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.videocall">
  <uses-permission android:name="android.permission.CAMERA"/>
  <uses-permission android:name="android.permission.RECORD_AUDIO"/>
  <uses-permission android:name="android.permission.INTERNET"/>
  <application>
    <activity android:name=".MainActivity"
        android:theme="@style/Theme.AppCompat.NoActionBar"
        android:exported="true">
      <intent-filter>
        <action android:name="android.intent.action.MAIN"/>
        <category android:name="android.intent.category.LAUNCHER"/>
      </intent-filter>
    </activity>
  </application>
</manifest>
 
// =======================================================
// 文件: res/layout/activity_main.xml
// 描述: 本地與遠端畫面 + 控制按鈕
// =======================================================
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent" android:layout_height="match_parent">
 
  <!-- 遠端畫面 -->
  <org.webrtc.SurfaceViewRenderer
      android:id="@+id/remoteView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"/>
 
  <!-- 本地預(yù)覽（右上角小窗口） -->
  <org.webrtc.SurfaceViewRenderer
      android:id="@+id/localView"
      android:layout_width="120dp"
      android:layout_height="160dp"
      android:layout_margin="16dp"
      android:layout_gravity="top|end"/>
 
  <!-- 按鈕欄 -->
  <LinearLayout
      android:orientation="horizontal"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_gravity="bottom|center"
      android:gravity="center"
      android:padding="16dp">
 
    <Button android:id="@+id/btnCall"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="呼叫"/>
    <Button android:id="@+id/btnHangup"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="掛斷" android:layout_marginStart="16dp"/>
    <Button android:id="@+id/btnSwitch"
        android:layout_width="wrap_content" android:layout_height="wrap_content"
        android:text="切換攝像頭" android:layout_marginStart="16dp"/>
  </LinearLayout>
</FrameLayout>
 
// =======================================================
// 文件: SignalingClient.kt
// 描述: WebSocket 信令客戶端
// =======================================================
package com.example.videocall
 
import kotlinx.coroutines.*
import okhttp3.*
import org.json.JSONObject
import java.util.concurrent.TimeUnit
 
class SignalingClient(
  private val serverUrl: String,
  private val listener: Listener
) : WebSocketListener() {
 
  interface Listener {
    fun onOffer(sdp: String)
    fun onAnswer(sdp: String)
    fun onCandidate(sdpMid: String, sdpMLineIndex: Int, candidate: String)
  }
 
  private val client = OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS)
    .build()
  private var ws: WebSocket? = null
 
  fun connect() {
    val req = Request.Builder().url(serverUrl).build()
    ws = client.newWebSocket(req, this)
  }
  fun close() { ws?.close(1000, "bye") }
 
  fun sendOffer(sdp: String) {
    val obj = JSONObject().apply {
      put("type", "offer"); put("sdp", sdp)
    }
    ws?.send(obj.toString())
  }
  fun sendAnswer(sdp: String) {
    val obj = JSONObject().apply {
      put("type", "answer"); put("sdp", sdp)
    }
    ws?.send(obj.toString())
  }
  fun sendCandidate(c: PeerConnection.IceCandidate) {
    val obj = JSONObject().apply {
      put("type", "candidate")
      put("sdpMid", c.sdpMid); put("sdpMLineIndex", c.sdpMLineIndex)
      put("candidate", c.sdp)
    }
    ws?.send(obj.toString())
  }
 
  override fun onMessage(webSocket: WebSocket, text: String) {
    val obj = JSONObject(text)
    when (obj.getString("type")) {
      "offer" -> listener.onOffer(obj.getString("sdp"))
      "answer"-> listener.onAnswer(obj.getString("sdp"))
      "candidate"-> listener.onCandidate(
        obj.getString("sdpMid"), obj.getInt("sdpMLineIndex"),
        obj.getString("candidate")
      )
    }
  }
}
 
// =======================================================
// 文件: MainActivity.kt
// 描述: 核心視頻通話邏輯
// =======================================================
package com.example.videocall
 
import android.Manifest
import android.os.Bundle
import android.util.Log
import androidx.appcompat.app.AppCompatActivity
import androidx.core.app.ActivityCompat
import com.example.videocall.databinding.ActivityMainBinding
import kotlinx.coroutines.*
import org.webrtc.*
 
class MainActivity : AppCompatActivity(), SignalingClient.Listener {
 
  private lateinit var binding: ActivityMainBinding
 
  // WebRTC
  private lateinit var peerFactory: PeerConnectionFactory
  private var peerConnection: PeerConnection? = null
  private lateinit var localVideoSource: VideoSource
  private lateinit var localAudioSource: AudioSource
  private lateinit var localVideoTrack: VideoTrack
  private lateinit var localAudioTrack: AudioTrack
  private lateinit var videoCapturer: VideoCapturer
 
  private lateinit var signalingClient: SignalingClient
  private val coroutineScope = CoroutineScope(Dispatchers.Main)
 
  override fun onCreate(s: Bundle?) {
    super.onCreate(s)
    binding = ActivityMainBinding.inflate(layoutInflater)
    setContentView(binding.root)
 
    // 1. 權(quán)限申請
    ActivityCompat.requestPermissions(this,
      arrayOf(Manifest.permission.CAMERA, Manifest.permission.RECORD_AUDIO), 1)
 
    // 2. 初始化 PeerConnectionFactory
    PeerConnectionFactory.initialize(
      PeerConnectionFactory.InitializationOptions.builder(this)
        .createInitializationOptions()
    )
    peerFactory = PeerConnectionFactory.builder().createPeerConnectionFactory()
 
    // 3. 初始化本地采集與渲染
    initLocalMedia()
 
    // 4. 初始化信令
    signalingClient = SignalingClient("wss://your.signaling.server", this)
    signalingClient.connect()
 
    // 5. 按鈕事件
    binding.btnCall.setOnClickListener { startCall() }
    binding.btnHangup.setOnClickListener { hangUp() }
    binding.btnSwitch.setOnClickListener { switchCamera() }
  }
 
  private fun initLocalMedia() {
    // SurfaceViewRenderer 初始化
    binding.localView.init(EglBase.create().eglBaseContext, null)
    binding.remoteView.init(EglBase.create().eglBaseContext, null)
 
    // 攝像頭捕獲
    val enumerator = Camera2Enumerator(this)
    val camName = enumerator.deviceNames[0]
    videoCapturer = enumerator.createCapturer(camName, null)
    val surfaceTextureHelper = SurfaceTextureHelper.create("CaptureThread",
      EglBase.create().eglBaseContext)
    localVideoSource = peerFactory.createVideoSource(videoCapturer.isScreencast)
    videoCapturer.initialize(surfaceTextureHelper, this, localVideoSource.capturerObserver)
    videoCapturer.startCapture(1280, 720, 30)
 
    localVideoTrack = peerFactory.createVideoTrack("ARDAMSv0", localVideoSource)
    localVideoTrack.addSink(binding.localView)
 
    localAudioSource = peerFactory.createAudioSource(MediaConstraints())
    localAudioTrack = peerFactory.createAudioTrack("ARDAMSa0", localAudioSource)
  }
 
  private fun createPeerConnection() {
    val iceServers = listOf(
      PeerConnection.IceServer.builder("stun:stun.l.google.com:19302").createIceServer()
    )
    val rtcConfig = PeerConnection.RTCConfiguration(iceServers).apply {
      continualGatheringPolicy = PeerConnection.ContinualGatheringPolicy.GATHER_CONTINUALLY
    }
    peerConnection = peerFactory.createPeerConnection(rtcConfig, object : PeerConnection.Observer {
      override fun onIceCandidate(c: IceCandidate) {
        signalingClient.sendCandidate(c)
      }
      override fun onAddStream(stream: MediaStream) {
        runOnUiThread {
          stream.videoTracks[0].addSink(binding.remoteView)
        }
      }
      override fun onConnectionChange(newState: PeerConnection.PeerConnectionState) {
        Log.d("PC", "State = $newState")
      }
      // 省略其他回調(diào)
      override fun onIceConnectionChange(state: PeerConnection.IceConnectionState) {}
      override fun onIceGatheringChange(state: PeerConnection.IceGatheringState) {}
      override fun onSignalingChange(state: PeerConnection.SignalingState) {}
      override fun onIceCandidatesRemoved(candidates: Array<out IceCandidate>?) {}
      override fun onRemoveStream(stream: MediaStream?) {}
      override fun onDataChannel(dc: DataChannel?) {}
      override fun onRenegotiationNeeded() {}
      override fun onTrack(transceiver: RtpTransceiver?) {}
    })
    // 添加音視頻軌道
    peerConnection?.addTrack(localVideoTrack)
    peerConnection?.addTrack(localAudioTrack)
  }
 
  private fun startCall() {
    createPeerConnection()
    peerConnection?.createOffer(object : SdpObserver {
      override fun onCreateSuccess(desc: SessionDescription) {
        peerConnection?.setLocalDescription(this, desc)
        signalingClient.sendOffer(desc.description)
      }
      override fun onSetSuccess() {}
      override fun onCreateFailure(e: String) { }
      override fun onSetFailure(e: String) { }
    }, MediaConstraints())
  }
 
  private fun hangUp() {
    peerConnection?.close(); peerConnection = null
    signalingClient.close()
  }
 
  private fun switchCamera() {
    (videoCapturer as CameraVideoCapturer).switchCamera(null)
  }
 
  // ===== SignalingClient.Listener 回調(diào) =====
  override fun onOffer(sdp: String) {
    if (peerConnection == null) createPeerConnection()
    val offer = SessionDescription(SessionDescription.Type.OFFER, sdp)
    peerConnection?.setRemoteDescription(object: SdpObserver {
      override fun onSetSuccess() {
        peerConnection?.createAnswer(object : SdpObserver {
          override fun onCreateSuccess(desc: SessionDescription) {
            peerConnection?.setLocalDescription(this, desc)
            signalingClient.sendAnswer(desc.description)
          }
          override fun onSetSuccess() {}
          override fun onCreateFailure(e: String) {}
          override fun onSetFailure(e: String) {}
        }, MediaConstraints())
      }
      override fun onCreateSuccess(p0: SessionDescription?) {}
      override fun onCreateFailure(p0: String?) {}
      override fun onSetFailure(p0: String?) {}
    }, offer)
  }
 
  override fun onAnswer(sdp: String) {
    val answer = SessionDescription(SessionDescription.Type.ANSWER, sdp)
    peerConnection?.setRemoteDescription(object: SdpObserver {
      override fun onSetSuccess() {}
      override fun onCreateSuccess(p0: SessionDescription?) {}
      override fun onCreateFailure(p0: String?) {}
      override fun onSetFailure(p0: String?) {}
    }, answer)
  }
 
  override fun onCandidate(sdpMid: String, sdpMLineIndex: Int, cand: String) {
    val candidate = IceCandidate(sdpMid, sdpMLineIndex, cand)
    peerConnection?.addIceCandidate(candidate)
  }
}
 
// =======================================================
// 文件: SdpObserver.kt
// 描述: 簡化版 SdpObserver
// =======================================================
package com.example.videocall
 
import org.webrtc.SdpObserver
import org.webrtc.SessionDescription
 
abstract class SimpleSdpObserver : SdpObserver {
  override fun onCreateSuccess(desc: SessionDescription?) {}
  override fun onSetSuccess() {}
  override fun onCreateFailure(error: String?) {}
  override fun onSetFailure(error: String?) {}
}

val parameters = sender.parameters
parameters.encodings[0].maxBitrateBps = newRate
sender.parameters = parameters