import * as Token from 'token-types';
import { EndOfStreamError } from 'strtok3';
import initDebug from 'debug';

import * as common from '../common/Util.js';
import { AbstractID3Parser } from '../id3v2/AbstractID3Parser.js';
import { InfoTagHeaderTag, type IXingInfoTag, LameEncoderVersion, readXingHeader } from './XingTag.js';
import { makeUnexpectedFileContentError } from '../ParseError.js';

const debug = initDebug('music-metadata:parser:mpeg');

export class MpegContentError extends makeUnexpectedFileContentError('MPEG'){
}

/**
 * Cache buffer size used for searching synchronization preabmle
 */
const maxPeekLen = 1024;

type MPEG4Channel = 'front-center' | 'front-left' | 'front-right' | 'side-left' | 'side-right' | 'back-left' | 'back-right' | 'back-center' | 'LFE-channel';

type MPEG4ChannelConfiguration = MPEG4Channel[] | undefined;

/**
 * MPEG-4 Audio definitions
 * Ref:  https://wiki.multimedia.cx/index.php/MPEG-4_Audio
 */
const MPEG4 = {

  /**
   * Audio Object Types
   */
  AudioObjectTypes: [
    'AAC Main',
    'AAC LC', // Low Complexity
    'AAC SSR', // Scalable Sample Rate
    'AAC LTP' // Long Term Prediction
  ],

  /**
   * Sampling Frequencies
   * https://wiki.multimedia.cx/index.php/MPEG-4_Audio#Sampling_Frequencies
   */
  SamplingFrequencies: [
    96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350, null, null, -1]

  /**
   * Channel Configurations
   */
};

const MPEG4_ChannelConfigurations: MPEG4ChannelConfiguration[] = [
  undefined,
  ['front-center'],
  ['front-left', 'front-right'],
  ['front-center', 'front-left', 'front-right'],
  ['front-center', 'front-left', 'front-right', 'back-center'],
  ['front-center', 'front-left', 'front-right', 'back-left', 'back-right'],
  ['front-center', 'front-left', 'front-right', 'back-left', 'back-right', 'LFE-channel'],
  ['front-center', 'front-left', 'front-right', 'side-left', 'side-right', 'back-left', 'back-right', 'LFE-channel']
];

/**
 * MPEG Audio Layer I/II/III frame header
 * Ref: https://www.mp3-tech.org/programmer/frame_header.html
 * Bit layout: AAAAAAAA AAABBCCD EEEEFFGH IIJJKLMM
 * Ref: https://wiki.multimedia.cx/index.php/ADTS
 */
class MpegFrameHeader {

  public static SyncByte1 = 0xFF;
  public static SyncByte2 = 0xE0;

  public static VersionID = [2.5, null, 2, 1];
  public static LayerDescription = [0, 3, 2, 1];
  public static ChannelMode = ['stereo', 'joint_stereo', 'dual_channel', 'mono'];

  private static bitrate_index: { [bitrate_index: number]: { [codec_index: number]: number; }; } = {
    1: {11: 32, 12: 32, 13: 32, 21: 32, 22: 8, 23: 8},
    2: {11: 64, 12: 48, 13: 40, 21: 48, 22: 16, 23: 16},
    3: {11: 96, 12: 56, 13: 48, 21: 56, 22: 24, 23: 24},
    4: {11: 128, 12: 64, 13: 56, 21: 64, 22: 32, 23: 32},
    5: {11: 160, 12: 80, 13: 64, 21: 80, 22: 40, 23: 40},
    6: {11: 192, 12: 96, 13: 80, 21: 96, 22: 48, 23: 48},
    7: {11: 224, 12: 112, 13: 96, 21: 112, 22: 56, 23: 56},
    8: {11: 256, 12: 128, 13: 112, 21: 128, 22: 64, 23: 64},
    9: {11: 288, 12: 160, 13: 128, 21: 144, 22: 80, 23: 80},
    10: {11: 320, 12: 192, 13: 160, 21: 160, 22: 96, 23: 96},
    11: {11: 352, 12: 224, 13: 192, 21: 176, 22: 112, 23: 112},
    12: {11: 384, 12: 256, 13: 224, 21: 192, 22: 128, 23: 128},
    13: {11: 416, 12: 320, 13: 256, 21: 224, 22: 144, 23: 144},
    14: {11: 448, 12: 384, 13: 320, 21: 256, 22: 160, 23: 160}
  };

  private static sampling_rate_freq_index: { [sample_rate_index: number]: { [index: number]: number; }; } = {
    1: {0: 44100, 1: 48000, 2: 32000},
    2: {0: 22050, 1: 24000, 2: 16000},
    2.5: {0: 11025, 1: 12000, 2: 8000}
  };

  private static samplesInFrameTable = [
    /* Layer   I    II   III */
    [0, 384, 1152, 1152], // MPEG-1
    [0, 384, 1152, 576] // MPEG-2(.5
  ];

  // B(20,19): MPEG Audio versionIndex ID
  public versionIndex: number;
  // C(18,17): Layer description
  public layer: number;
  // D(16): Protection bit
  public isProtectedByCRC: boolean;
  // E(15,12): Bitrate index
  public bitrateIndex: number | null = null;
  // F(11,10): Sampling rate frequency index
  public sampRateFreqIndex: number | null = null;
  // G(9): Padding bit
  public padding: boolean | null = null;
  // H(8): Private bit
  public privateBit: boolean | null = null;
  // I(7,6): Channel Mode
  public channelModeIndex?: number | null = null;
  // J(5,4): Mode extension (Only used in Joint stereo)
  public modeExtension: number | null = null;
  // K(3): Copyright
  public isCopyrighted?: boolean;
  // L(2): Original
  public isOriginalMedia: boolean | null = null;
  // M(3): The original bit indicates, if it is set, that the frame is located on its original media.
  public emphasis?: number;

  public version: number | null = null;
  public channelMode?: string;
  public bitrate: number | null = null;
  public samplingRate: number | null = null;

  public container?: string;
  public codec?: string;
  public codecProfile?: string;

  public frameLength = 0;

  public mp4ChannelConfig: MPEG4ChannelConfiguration;

  public constructor(buf: Uint8Array, off: number) {
    // B(20,19): MPEG Audio versionIndex ID
    this.versionIndex = common.getBitAllignedNumber(buf, off + 1, 3, 2);
    // C(18,17): Layer description
    this.layer = MpegFrameHeader.LayerDescription[common.getBitAllignedNumber(buf, off + 1, 5, 2)];

    if (this.versionIndex > 1 && this.layer === 0) {
      this.parseAdtsHeader(buf, off); // Audio Data Transport Stream (ADTS)
    } else {
      this.parseMpegHeader(buf, off); // Conventional MPEG header
    }

    // D(16): Protection bit (if true 16-bit CRC follows header)
    this.isProtectedByCRC = !common.isBitSet(buf, off + 1, 7);
  }

  public calcDuration(numFrames: number): number | null {
    return this.samplingRate == null ? null : (numFrames * this.calcSamplesPerFrame() / this.samplingRate);
  }

  public calcSamplesPerFrame(): number {
    return MpegFrameHeader.samplesInFrameTable[this.version === 1 ? 0 : 1][this.layer];
  }

  public calculateSideInfoLength(): number | null {
    if (this.layer !== 3) return 2;
    if (this.channelModeIndex === 3) {
      // mono
      if (this.version === 1) {
        return 17;
      }if (this.version === 2 || this.version === 2.5) {
        return 9;
      }
    } else {
      if (this.version === 1) {
        return 32;
      }if (this.version === 2 || this.version === 2.5) {
        return 17;
      }
    }
    return null;
  }

  public calcSlotSize(): number | null {
    return [null, 4, 1, 1][this.layer];
  }

  private parseMpegHeader(buf: Uint8Array, off: number): void {
    this.container = 'MPEG';
    // E(15,12): Bitrate index
    this.bitrateIndex = common.getBitAllignedNumber(buf, off + 2, 0, 4);
    // F(11,10): Sampling rate frequency index
    this.sampRateFreqIndex = common.getBitAllignedNumber(buf, off + 2, 4, 2);
    // G(9): Padding bit
    this.padding = common.isBitSet(buf, off + 2, 6);
    // H(8): Private bit
    this.privateBit = common.isBitSet(buf, off + 2, 7);
    // I(7,6): Channel Mode
    this.channelModeIndex = common.getBitAllignedNumber(buf, off + 3, 0, 2);
    // J(5,4): Mode extension (Only used in Joint stereo)
    this.modeExtension = common.getBitAllignedNumber(buf, off + 3, 2, 2);
    // K(3): Copyright
    this.isCopyrighted = common.isBitSet(buf, off + 3, 4);
    // L(2): Original
    this.isOriginalMedia = common.isBitSet(buf, off + 3, 5);
    // M(3): The original bit indicates, if it is set, that the frame is located on its original media.
    this.emphasis = common.getBitAllignedNumber(buf, off + 3, 7, 2);

    this.version = MpegFrameHeader.VersionID[this.versionIndex];
    this.channelMode = MpegFrameHeader.ChannelMode[this.channelModeIndex];

    this.codec = `MPEG ${this.version} Layer ${this.layer}`;

    // Calculate bitrate
    const bitrateInKbps = this.calcBitrate();
    if (!bitrateInKbps) {
      throw new MpegContentError('Cannot determine bit-rate');
    }
    this.bitrate = bitrateInKbps * 1000;

    // Calculate sampling rate
    this.samplingRate = this.calcSamplingRate();
    if (this.samplingRate == null) {
      throw new MpegContentError('Cannot determine sampling-rate');
    }
  }

  private parseAdtsHeader(buf: Uint8Array, off: number): void {
    debug("layer=0 => ADTS");
    this.version = this.versionIndex === 2 ? 4 : 2;
    this.container = `ADTS/MPEG-${this.version}`;
    const profileIndex = common.getBitAllignedNumber(buf, off + 2, 0, 2);
    this.codec = 'AAC';
    this.codecProfile = MPEG4.AudioObjectTypes[profileIndex];

    debug(`MPEG-4 audio-codec=${this.codec}`);

    const samplingFrequencyIndex = common.getBitAllignedNumber(buf, off + 2, 2, 4);
    this.samplingRate = MPEG4.SamplingFrequencies[samplingFrequencyIndex];
    debug(`sampling-rate=${this.samplingRate}`);

    const channelIndex = common.getBitAllignedNumber(buf, off + 2, 7, 3);
    this.mp4ChannelConfig = MPEG4_ChannelConfigurations[channelIndex];
    debug(`channel-config=${this.mp4ChannelConfig ? this.mp4ChannelConfig.join('+') : '?'}`);

    this.frameLength = common.getBitAllignedNumber(buf, off + 3, 6, 2) << 11;
  }

  private calcBitrate(): number | null {
    if (this.bitrateIndex === 0x00 || // free
      this.bitrateIndex === 0x0F) { // reserved
      return null;
    }
    if (this.version && this.bitrateIndex) {
      const codecIndex = 10 * Math.floor(this.version) + this.layer;
      return MpegFrameHeader.bitrate_index[this.bitrateIndex][codecIndex];
    }
    return null;
  }

  private calcSamplingRate(): number | null {
    if (this.sampRateFreqIndex === 0x03 || this.version === null || this.sampRateFreqIndex == null) return null; // 'reserved'
    return MpegFrameHeader.sampling_rate_freq_index[this.version][this.sampRateFreqIndex];
  }
}

/**
 * MPEG Audio Layer I/II/III
 */
const FrameHeader = {
  len: 4,

  get: (buf: Uint8Array, off: number): MpegFrameHeader => {
    return new MpegFrameHeader(buf, off);
  }
};

function getVbrCodecProfile(vbrScale: number): string {
  return `V${Math.floor((100 - vbrScale) / 10)}`;
}

export class MpegParser extends AbstractID3Parser {

  private frameCount = 0;
  private syncFrameCount = -1;
  private countSkipFrameData = 0;
  private totalDataLength = 0;

  private audioFrameHeader? : MpegFrameHeader;
  private bitrates: number[] = [];
  private offset = 0;
  private frame_size = 0;
  private crc: number | null = null;

  private calculateEofDuration = false;
  private samplesPerFrame: number | null = null;

  private buf_frame_header = new Uint8Array(4);

  /**
   * Number of bytes already parsed since beginning of stream / file
   */
  private mpegOffset: number | null = null;

  private syncPeek = {
    buf: new Uint8Array(maxPeekLen),
    len: 0
  };

  /**
   * Called after ID3 headers have been parsed
   */
  public async postId3v2Parse(): Promise<void> {

    this.metadata.setFormat('lossless', false);

    try {
      let quit = false;
      while (!quit) {
        await this.sync();
        quit = await this.parseCommonMpegHeader();
      }
    } catch (err) {
      if (err instanceof EndOfStreamError) {
        debug("End-of-stream");
        if (this.calculateEofDuration) {
          if (this.samplesPerFrame !== null) {
            const numberOfSamples = this.frameCount * this.samplesPerFrame;
            this.metadata.setFormat('numberOfSamples', numberOfSamples);
            if (this.metadata.format.sampleRate) {
              const duration = numberOfSamples / this.metadata.format.sampleRate;
              debug(`Calculate duration at EOF: ${duration} sec.`, duration);
              this.metadata.setFormat('duration', duration);
            }
          }
        }
      } else {
        throw err;
      }
    }
  }

  /**
   * Called after file has been fully parsed, this allows, if present, to exclude the ID3v1.1 header length
   */
  protected finalize() {

    const format = this.metadata.format;
    const hasID3v1 = !!this.metadata.native.ID3v1;
    if (this.mpegOffset !== null) {
      if (format.duration && this.tokenizer.fileInfo.size) {
        const mpegSize = this.tokenizer.fileInfo.size - this.mpegOffset - (hasID3v1 ? 128 : 0);
        if (format.codecProfile && format.codecProfile[0] === 'V') {
          this.metadata.setFormat('bitrate', mpegSize * 8 / format.duration);
        }
      }
      if (this.tokenizer.fileInfo.size && format.codecProfile === 'CBR') {
        const mpegSize = this.tokenizer.fileInfo.size - this.mpegOffset - (hasID3v1 ? 128 : 0);
        if (this.frame_size !== null && this.samplesPerFrame !== null) {
          const numberOfSamples = Math.round(mpegSize / this.frame_size) * this.samplesPerFrame;
          this.metadata.setFormat('numberOfSamples', numberOfSamples);
          if (format.sampleRate && !format.duration) {
            const duration = numberOfSamples / format.sampleRate;
            debug("Calculate CBR duration based on file size: %s", duration);
            this.metadata.setFormat('duration', duration);
          }
        }
      }
    }
  }

  private async sync(): Promise<void> {

    let gotFirstSync = false;

    while (true) {
      let bo = 0;
      this.syncPeek.len = await this.tokenizer.peekBuffer(this.syncPeek.buf, {length: maxPeekLen, mayBeLess: true});
      if (this.syncPeek.len <= 163) {
        throw new EndOfStreamError();
      }
      while (true) {
        if (gotFirstSync && (this.syncPeek.buf[bo] & 0xE0) === 0xE0) {
          this.buf_frame_header[0] = MpegFrameHeader.SyncByte1;
          this.buf_frame_header[1] = this.syncPeek.buf[bo];
          await this.tokenizer.ignore(bo);
          debug(`Sync at offset=${this.tokenizer.position - 1}, frameCount=${this.frameCount}`);
          if (this.syncFrameCount === this.frameCount) {
            debug(`Re-synced MPEG stream, frameCount=${this.frameCount}`);
            this.frameCount = 0;
            this.frame_size = 0;
          }
          this.syncFrameCount = this.frameCount;
          return; // sync
        }
          gotFirstSync = false;
          bo = this.syncPeek.buf.indexOf(MpegFrameHeader.SyncByte1, bo);
          if (bo === -1) {
            if (this.syncPeek.len < this.syncPeek.buf.length) {
              throw new EndOfStreamError();
            }
            await this.tokenizer.ignore(this.syncPeek.len);
            break; // continue with next buffer
          }
            ++bo;
            gotFirstSync = true;
      }
    }
  }

  /**
   * Combined ADTS & MPEG (MP2 & MP3) header handling
   * @return {Promise<boolean>} true if parser should quit
   */
  private async parseCommonMpegHeader(): Promise<boolean> {

    if (this.frameCount === 0) {
      this.mpegOffset = this.tokenizer.position - 1;
    }

    await this.tokenizer.peekBuffer(this.buf_frame_header.subarray(1), {length: 3});

    let header: MpegFrameHeader;
    try {
      header = FrameHeader.get(this.buf_frame_header, 0);
    } catch (err) {
      await this.tokenizer.ignore(1);
      if (err instanceof Error) {
        this.metadata.addWarning(`Parse error: ${err.message}`);
        return false; // sync
      }throw err;
    }
    await this.tokenizer.ignore(3);

    this.metadata.setFormat('container', header.container);
    this.metadata.setFormat('codec', header.codec);
    this.metadata.setFormat('lossless', false);
    this.metadata.setFormat('sampleRate', header.samplingRate);

    this.frameCount++;
    return header.version !== null && header.version >= 2 && header.layer === 0 ? this.parseAdts(header) : this.parseAudioFrameHeader(header);
  }

  /**
   * @return {Promise<boolean>} true if parser should quit
   */
  private async parseAudioFrameHeader(header: MpegFrameHeader): Promise<boolean> {

    this.metadata.setFormat('numberOfChannels', header.channelMode === 'mono' ? 1 : 2);
    this.metadata.setFormat('bitrate', header.bitrate);

    if (this.frameCount < 20 * 10000) {
      debug('offset=%s MP%s bitrate=%s sample-rate=%s', this.tokenizer.position - 4, header.layer, header.bitrate, header.samplingRate);
    }
    const slot_size = header.calcSlotSize();
    if (slot_size === null) {
      throw new MpegContentError('invalid slot_size');
    }

    const samples_per_frame = header.calcSamplesPerFrame();
    debug(`samples_per_frame=${samples_per_frame}`);
    const bps = samples_per_frame / 8.0;
    if (header.bitrate !== null && header.samplingRate != null) {
      const fsize = (bps * header.bitrate / header.samplingRate) + ((header.padding) ? slot_size : 0);
      this.frame_size = Math.floor(fsize);
    }

    this.audioFrameHeader = header;
    if (header.bitrate !== null) {
      this.bitrates.push(header.bitrate);
    }

    // xtra header only exists in first frame
    if (this.frameCount === 1) {
      this.offset = FrameHeader.len;
      await this.skipSideInformation();
      return false;
    }

    if (this.frameCount === 3) {
      // the stream is CBR if the first 3 frame bitrates are the same
      if (this.areAllSame(this.bitrates)) {
        // Actual calculation will be done in finalize
        this.samplesPerFrame = samples_per_frame;
        this.metadata.setFormat('codecProfile', 'CBR');
        if (this.tokenizer.fileInfo.size)
          return true; // Will calculate duration based on the file size
      } else if (this.metadata.format.duration) {
        return true; // We already got the duration, stop processing MPEG stream any further
      }
      if (!this.options.duration) {
        return true; // Enforce duration not enabled, stop processing entire stream
      }
    }

    // once we know the file is VBR attach listener to end of
    // stream so we can do the duration calculation when we
    // have counted all the frames
    if (this.options.duration && this.frameCount === 4) {
      this.samplesPerFrame = samples_per_frame;
      this.calculateEofDuration = true;
    }

    this.offset = 4;
    if (header.isProtectedByCRC) {
      await this.parseCrc();
      return false;
    }
      await this.skipSideInformation();
      return false;
  }

  private async parseAdts(header: MpegFrameHeader): Promise<boolean> {
    const buf = new Uint8Array(3);
    await this.tokenizer.readBuffer(buf);
    header.frameLength += common.getBitAllignedNumber(buf, 0, 0, 11);
    this.totalDataLength += header.frameLength;
    this.samplesPerFrame = 1024;

    if (header.samplingRate !== null) {
      const framesPerSec = header.samplingRate / this.samplesPerFrame;
      const bytesPerFrame = this.frameCount === 0 ? 0 : this.totalDataLength / this.frameCount;
      const bitrate = 8 * bytesPerFrame * framesPerSec + 0.5;
      this.metadata.setFormat('bitrate', bitrate);
      debug(`frame-count=${this.frameCount}, size=${header.frameLength} bytes, bit-rate=${bitrate}`);
    }

    await this.tokenizer.ignore(header.frameLength > 7 ? header.frameLength - 7 : 1);

    // Consume remaining header and frame data
    if (this.frameCount === 3) {
      this.metadata.setFormat('codecProfile', header.codecProfile);
      if (header.mp4ChannelConfig) {
        this.metadata.setFormat('numberOfChannels', header.mp4ChannelConfig.length);
      }
      if (this.options.duration) {
        this.calculateEofDuration = true;
      } else {
        return true; // Stop parsing after the third frame
      }
    }
    return false;
  }

  private async parseCrc(): Promise<void> {
    this.crc = await this.tokenizer.readNumber(Token.INT16_BE);
    this.offset += 2;
    return this.skipSideInformation();
  }

  private async skipSideInformation(): Promise<void> {
    if (this.audioFrameHeader) {
      const sideinfo_length = this.audioFrameHeader.calculateSideInfoLength();
      if (sideinfo_length !== null) {
        await this.tokenizer.readToken(new Token.Uint8ArrayType(sideinfo_length));
        // side information
        this.offset += sideinfo_length;
        await this.readXtraInfoHeader();
        return;
      }
    }
  }

  private async readXtraInfoHeader(): Promise<IXingInfoTag | null> {

    const headerTag = await this.tokenizer.readToken(InfoTagHeaderTag);
    this.offset += InfoTagHeaderTag.len;  // 12

    switch (headerTag) {

      case 'Info':
        this.metadata.setFormat('codecProfile', 'CBR');
        return this.readXingInfoHeader();

      case 'Xing': {
        const infoTag = await this.readXingInfoHeader();
        if (infoTag.vbrScale !== null) {
          const codecProfile = getVbrCodecProfile(infoTag.vbrScale);
          this.metadata.setFormat('codecProfile', codecProfile);
        }
        return null;
      }

      case 'Xtra':
        // ToDo: ???
        break;

      case 'LAME': {
        const version = await this.tokenizer.readToken(LameEncoderVersion);
        if (this.frame_size !== null && this.frame_size >= this.offset + LameEncoderVersion.len) {
          this.offset += LameEncoderVersion.len;
          this.metadata.setFormat('tool', `LAME ${version}`);
          await this.skipFrameData(this.frame_size - this.offset);
          return null;
        }
          this.metadata.addWarning('Corrupt LAME header');
          break;
      }
      // ToDo: ???
    }

    // ToDo: promise duration???
    const frameDataLeft = this.frame_size - this.offset;
    if (frameDataLeft < 0) {
      this.metadata.addWarning(`Frame ${this.frameCount}corrupt: negative frameDataLeft`);
    } else {
      await this.skipFrameData(frameDataLeft);
    }
    return null;

  }

  /**
   * Ref: http://gabriel.mp3-tech.org/mp3infotag.html
   * @returns {Promise<string>}
   */
  private async readXingInfoHeader(): Promise<IXingInfoTag> {

    const offset = this.tokenizer.position;
    const infoTag = await readXingHeader(this.tokenizer);
    this.offset += this.tokenizer.position - offset;

    if (infoTag.lame) {
      this.metadata.setFormat('tool', `LAME ${common.stripNulls(infoTag.lame.version)}`);
      if (infoTag.lame.extended) {
        // this.metadata.setFormat('trackGain', infoTag.lame.extended.track_gain);
        this.metadata.setFormat('trackPeakLevel', infoTag.lame.extended.track_peak);
        if (infoTag.lame.extended.track_gain) {
          this.metadata.setFormat('trackGain', infoTag.lame.extended.track_gain.adjustment);
        }
        if (infoTag.lame.extended.album_gain) {
          this.metadata.setFormat('albumGain', infoTag.lame.extended.album_gain.adjustment);
        }
        this.metadata.setFormat('duration', infoTag.lame.extended.music_length / 1000);
      }
    }

    if (infoTag.streamSize && this.audioFrameHeader && infoTag.numFrames !== null) {
      const duration = this.audioFrameHeader.calcDuration(infoTag.numFrames);
      this.metadata.setFormat('duration', duration);
      debug('Get duration from Xing header: %s', this.metadata.format.duration);
      return infoTag;
    }

    // frames field is not present
    const frameDataLeft = this.frame_size - this.offset;

    await this.skipFrameData(frameDataLeft);
    return infoTag;
  }

  private async skipFrameData(frameDataLeft: number): Promise<void> {
    if (frameDataLeft < 0) throw new MpegContentError('frame-data-left cannot be negative');
    await this.tokenizer.ignore(frameDataLeft);
    this.countSkipFrameData += frameDataLeft;
  }

  private areAllSame(array: unknown[]) {
    const first = array[0];
    return array.every(element => {
      return element === first;
    });
  }
}
