export default class Recorder {
    constructor(stream, config) {
        //兼容
        window.URL = window.URL || window.webkitURL;
        navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;

        config = config || {};
        config.sampleBits = config.sampleBits || 16;   //采样数位 8, 16
        config.sampleRate = config.sampleRate || 16000; //采样率(1/6 44100)

        this.context = new (window.webkitAudioContext || window.AudioContext)();
        this.audioInput = this.context.createMediaStreamSource(stream);
        this.createScript = this.context.createScriptProcessor || this.context.createJavaScriptNode;
        this.recorder = this.createScript.apply(this.context, [4096, 1, 1]);

        this.audioData = {
            size: 0,          //录音文件长度
            buffer: [],    //录音缓存
            inputSampleRate: this.context.sampleRate,   //输入采样率
            inputSampleBits: 16,     //输入采样数位 8, 16
            outputSampleRate: config.sampleRate,   //输出采样率
            oututSampleBits: config.sampleBits,       //输出采样数位 8, 16
            input: function (data) {
                this.buffer.push(new Float32Array(data));
                this.size += data.length;
            },
            compress: function () { //合并压缩
                //合并
                let data = new Float32Array(this.size);
                let offset = 0;
                for (let i = 0; i < this.buffer.length; i++) {
                    data.set(this.buffer[i], offset);
                    offset += this.buffer[i].length;
                }
                //压缩
                let compression = parseInt(this.inputSampleRate / this.outputSampleRate);
                let length = data.length / compression;
                let result = new Float32Array(length);
                let index = 0, j = 0;
                while (index < length) {
                    result[index] = data[j];
                    j += compression;
                    index++;
                }
                return result;
            },
            encodeWAV: function () {
                let sampleRate = Math.min(this.inputSampleRate, this.outputSampleRate);
                let sampleBits = Math.min(this.inputSampleBits, this.oututSampleBits);
                let bytes = this.compress();
                let dataLength = bytes.length * (sampleBits / 8);
                let buffer = new ArrayBuffer(44 + dataLength);
                let data = new DataView(buffer);

                let channelCount = 1;//单声道
                let offset = 0;

                let writeString = function (str) {
                    for (let i = 0; i < str.length; i++) {
                        data.setUint8(offset + i, str.charCodeAt(i));
                    }
                };

                // 资源交换文件标识符
                writeString('RIFF');
                offset += 4;
                // 下个地址开始到文件尾总字节数,即文件大小-8
                data.setUint32(offset, 36 + dataLength, true);
                offset += 4;
                // WAV文件标志
                writeString('WAVE');
                offset += 4;
                // 波形格式标志
                writeString('fmt ');
                offset += 4;
                // 过滤字节,一般为 0x10 = 16
                data.setUint32(offset, 16, true);
                offset += 4;
                // 格式类别 (PCM形式采样数据)
                data.setUint16(offset, 1, true);
                offset += 2;
                // 通道数
                data.setUint16(offset, channelCount, true);
                offset += 2;
                // 采样率,每秒样本数,表示每个通道的播放速度
                data.setUint32(offset, sampleRate, true);
                offset += 4;
                // 波形数据传输率 (每秒平均字节数) 单声道×每秒数据位数×每样本数据位/8
                data.setUint32(offset, channelCount * sampleRate * (sampleBits / 8), true);
                offset += 4;
                // 快数据调整数 采样一次占用字节数 单声道×每样本的数据位数/8
                data.setUint16(offset, channelCount * (sampleBits / 8), true);
                offset += 2;
                // 每样本数据位数
                data.setUint16(offset, sampleBits, true);
                offset += 2;
                // 数据标识符
                writeString('data');
                offset += 4;
                // 采样数据总数,即数据总大小-44
                data.setUint32(offset, dataLength, true);
                offset += 4;
                // 写入采样数据
                if (sampleBits === 8) {
                    for (let i = 0; i < bytes.length; i++, offset++) {
                        let s = Math.max(-1, Math.min(1, bytes[i]));
                        let val = s < 0 ? s * 0x8000 : s * 0x7FFF;
                        val = parseInt(255 / (65535 / (val + 32768)));
                        data.setInt8(offset, val, true);
                    }
                } else {
                    for (let i = 0; i < bytes.length; i++, offset += 2) {
                        let s = Math.max(-1, Math.min(1, bytes[i]));
                        data.setInt16(offset, s < 0 ? s * 0x8000 : s * 0x7FFF, true);
                    }
                }
                return new Blob([data], {type: 'audio/wav'});
            }
        };
    }

    //开始录音
    start() {
        this.audioInput.connect(this.recorder);
        this.recorder.connect(this.context.destination);

        //音频采集
        let self = this;
        this.recorder.onaudioprocess = function (e) {
            self.audioData.input(e.inputBuffer.getChannelData(0));
        };
    };

    //停止
    stop() {
        this.recorder.disconnect();
    };

    //获取音频文件
    getBlob() {
        this.stop();
        return this.audioData.encodeWAV();
    };

    //回放
    play(audio) {
        audio.src = window.URL.createObjectURL(this.getBlob());
    };

    //清理缓存的录音数据
    clear() {
        this.audioData.buffer = [];
        this.audioData.size = 0;
    };

    static throwError(message) {
        console.log("Error:" + message);
        throw new function () {
            this.toString = function () {
                return message;
            }
        };
    };

    static canRecording() {
        return (navigator.getUserMedia != null);
    }

    static get(callback, config) {
        if (callback) {
            if (Recorder.canRecording()) {
                navigator.getUserMedia(
                    {audio: true}, //只启用音频
                    function (stream) {
                        let rec = new Recorder(stream, config);
                        callback(rec);
                    },
                    function (error) {
                        switch (error.code || error.name) {
                            case 'PERMISSION_DENIED':
                            case 'PermissionDeniedError':
                                Recorder.throwError('用户拒绝提供信息。');
                                break;
                            case 'NOT_SUPPORTED_ERROR':
                            case 'NotSupportedError':
                                Recorder.throwError('浏览器不支持硬件设备。');
                                break;
                            case 'MANDATORY_UNSATISFIED_ERROR':
                            case 'MandatoryUnsatisfiedError':
                                Recorder.throwError('无法发现指定的硬件设备。');
                                break;
                            default:
                                Recorder.throwError('无法打开麦克风。异常信息:' + (error.code || error.name));
                                break;
                        }
                    });
            } else {
                Recorder.throwError('当前浏览器不支持录音功能。');
                return;
            }
        }
    };
}