// server.js
const http = require('http');
const path = require('path');
const fs = require('fs');
http.createServer((request, response) => {
  // 請(qǐng)求體
  console.log(new Date(), ':', JSON.stringify(request));
  // 需要加載的html文件
  const file = path.resolve(__dirname, './demo2.html');
  // 判斷文件是否存在
  fs.exists(file, exists => {
    if(!exists) console.log ('文件不存在，沙雕！');
    else {
      response.writeHeader(200, { "Content-Type" : "text/html" });
      response.end(fs.readFileSync(file, 'utf-8'));
    }
  });
}).listen(8090); // 監(jiān)聽(tīng)8090端口
/*
 * demo2.html
 * 獲取麥克風(fēng)并錄制聲音
 */
let audioCtx = null; // 音頻上下文
let source = null; // 音頻源
let audioStream = null; // 錄音產(chǎn)生的音頻流
let analyserNode = null; // 用于分析音頻實(shí)時(shí)數(shù)據(jù)的節(jié)點(diǎn)
let animationFrame = null; // 定時(shí)器
function recordSound () {
  navigator.mediaDevices
    .getUserMedia({ 'audio': true })
    .then(initAudioData)
    .catch(e => {
      console.log('出問(wèn)題了，沙雕:', e);
    });
}
// 停止錄制
function stopRecord () {
  // 關(guān)閉麥克風(fēng)
  const tracks = audioStream.getAudioTracks();
  for (let i = 0, len = tracks.length; i < len; i++) {
    tracks[i].stop();
  }
  // 斷開(kāi)音頻節(jié)點(diǎn)
  analyserNode.disconnect();
  source.disconnect();
  analyserNode = null;
  source = null;
  // 清除定時(shí)器
  clearInterval(animationFrame);
}
// 事件綁定
document.querySelector('#record').onclick = recordSound;
document.querySelector('#stop').onclick = stopRecord;

// 音頻數(shù)據(jù)處理
function initAudioData (stream) {
  audioStream = stream;
  // 創(chuàng)建音頻上下文
  audioCtx = new (window.AudioContext || window.webkitAudioContext)();
  // 創(chuàng)建音頻源
  source = audioCtx.createMediaStreamSource(audioStream);
  // 創(chuàng)建音頻分析節(jié)點(diǎn)
  analyserNode = audioCtx.createAnalyser();
  // fftSize決定了能夠獲取到的音頻數(shù)據(jù)的數(shù)量
  analyserNode.fftSize = 4096;      
  // 音頻源連接至analyserNode
  source.connect(analyserNode);
  // analyserNode再連接至揚(yáng)聲器播放
  analyserNode.connect(audioCtx.destination);
  // 簡(jiǎn)單用定時(shí)器來(lái)繪制波形圖，當(dāng)然也可以用requestAnimationFrame來(lái)以屏幕刷新的評(píng)率來(lái)反復(fù)執(zhí)行繪制函數(shù)
  animateFrame = setInterval(drawWaver, 60);
}

// 繪制圖形
function drawWaver () {
  const originData = new Float32Array(analyserNode.fftSize);
  const positives = [];
  const negatives = [];
  // 獲取當(dāng)前的實(shí)時(shí)音頻數(shù)據(jù)
  analyserNode.getFloatTimeDomainData(originData);
  // 每12位數(shù)據(jù)取一個(gè)最大值一個(gè)最小值 4096 / 12 = 341.3333
  for (let i = 0; i < 341; i++) {
    let temp = originData.slice(i * 12, (i + 1) * 12);
    positives.push(Math.max.apply(null, temp));
    negatives.push(Math.min.apply(null, temp));
  }
  // 創(chuàng)建canvas上下文
  let canvas = document.querySelector('#canvas');
  if (canvas.getContext) {
    let ctx = canvas.getContext('2d');
    canvas.width = positives.length * 4;
    let x = 0;
    let y = 100;
    ctx.fillStyle = '#fa541c';
    // canvas高度200，橫坐標(biāo)在canvas中點(diǎn)100px的位置，橫坐標(biāo)上方繪制正數(shù)據(jù)，下方繪制負(fù)數(shù)據(jù)
    for (let k = 0; k < positives.length; k++) {
      // 每個(gè)矩形寬3px，間隔1px，圖形總長(zhǎng)度即為 length * 4
      ctx.fillRect(x + 4 * k, y - (100 * positives[k]), 3, 100 * positives[k]);
      ctx.fillRect(x + 4 * k, 100, 3, 100 * Math.abs(negatives[k]));
    }
  }
}