id3.js

var AV = require('av');

const ENCODINGS = ['latin1', 'utf16-bom', 'utf16-be', 'utf8'];

var ID3Stream = AV.Base.extend({
    constructor: function(header, stream) {
        this.header = header;
        this.stream = stream;
        this.offset = 0;
    },
    
    read: function() {
        if (!this.data) {
            this.data = {};
            
            // read all frames
            var frame;
            while (frame = this.readFrame()) {
                // if we already have an instance of this key, add it to an array
                if (frame.key in this.data) {
                    if (!Array.isArray(this.data[frame.key]))
                        this.data[frame.key] = [this.data[frame.key]];
                        
                    this.data[frame.key].push(frame.value);
                } else {
                    this.data[frame.key] = frame.value;
                }
            }
        }

        return this.data;
    },
    
    readFrame: function() {
        if (this.offset >= this.header.length)
            return null;
        
        // get the header    
        var header = this.readHeader();
        var decoder = header.identifier;
        
        if (header.identifier.charCodeAt(0) === 0) {
            this.offset += this.header.length + 1;
            return null;
        }
        
        // map common frame names to a single type
        if (!this.frameTypes[decoder]) {
            for (var key in this.map) {
                if (this.map[key].indexOf(decoder) !== -1) {
                    decoder = key;
                    break;
                }
            }
        }

        if (this.frameTypes[decoder]) {
            // decode the frame
            var frame = this.decodeFrame(header, this.frameTypes[decoder]),
                keys = Object.keys(frame);
            
            // if it only returned one key, use that as the value    
            if (keys.length === 1)
                frame = frame[keys[0]];
            
            var result = {
                value: frame
            };
            
        } else {
            // No frame type found, treat it as binary
            var result = {
                value: this.stream.readBuffer(Math.min(header.length, this.header.length - this.offset))
            };
        }

        result.key = this.names[header.identifier] ? this.names[header.identifier] : header.identifier;
        
        // special sauce for cover art, which should just be a buffer
        if (result.key === 'coverArt')
            result.value = result.value.data;

        this.offset += 10 + header.length;
        return result;
    },

    decodeFrame: function(header, fields) {
        var stream = this.stream,
            start = stream.offset;
            
        var encoding = 0, ret = {};
        var len = Object.keys(fields).length, i = 0;
        
        for (var key in fields) {
            var type = fields[key];
            var rest = header.length - (stream.offset - start);
            i++;
            
            // check for special field names
            switch (key) {
                case 'encoding':
                    encoding = stream.readUInt8();
                    continue;
                
                case 'language':
                    ret.language = stream.readString(3);
                    continue;
            }
            
            // check types
            switch (type) {                    
                case 'latin1':
                    ret[key] = stream.readString(i === len ? rest : null, 'latin1');
                    break;
                    
                case 'string':
                    ret[key] = stream.readString(i === len ? rest : null, ENCODINGS[encoding]);
                    break;
                    
                case 'binary':
                    ret[key] = stream.readBuffer(rest)
                    break;
                    
                case 'int16':
                    ret[key] = stream.readInt16();
                    break;
                    
                case 'int8':
                    ret[key] = stream.readInt8();
                    break;
                    
                case 'int24':
                    ret[key] = stream.readInt24();
                    break;
                    
                case 'int32':
                    ret[key] = stream.readInt32();
                    break;
                    
                case 'int32+':
                    ret[key] = stream.readInt32();
                    if (rest > 4)
                        throw new Error('Seriously dude? Stop playing this song and get a life!');
                        
                    break;
                    
                case 'date':
                    var val = stream.readString(8);
                    ret[key] = new Date(val.slice(0, 4), val.slice(4, 6) - 1, val.slice(6, 8));
                    break;
                    
                case 'frame_id':
                    ret[key] = stream.readString(4);
                    break;
                    
                default:
                    throw new Error('Unknown key type ' + type);
            }
        }
        
        // Just in case something went wrong...
        var rest = header.length - (stream.offset - start);
        if (rest > 0)
            stream.advance(rest);
        
        return ret;
    }
});

// ID3 v2.3 and v2.4 support
exports.ID3v23Stream = ID3Stream.extend({
    readHeader: function() {
        var identifier = this.stream.readString(4);        
        var length = 0;
        
        if (this.header.major === 4) {
            for (var i = 0; i < 4; i++)
                length = (length << 7) + (this.stream.readUInt8() & 0x7f);
        } else {
            length = this.stream.readUInt32();
        }
        
        return {
            identifier: identifier,
            length: length,
            flags: this.stream.readUInt16()
        };
    },
    
    map: {
        text: [
            // Identification Frames
            'TIT1', 'TIT2', 'TIT3', 'TALB', 'TOAL', 'TRCK', 'TPOS', 'TSST', 'TSRC',

            // Involved Persons Frames
            'TPE1', 'TPE2', 'TPE3', 'TPE4', 'TOPE', 'TEXT', 'TOLY', 'TCOM', 'TMCL', 'TIPL', 'TENC',

            // Derived and Subjective Properties Frames
            'TBPM', 'TLEN', 'TKEY', 'TLAN', 'TCON', 'TFLT', 'TMED', 'TMOO',

            // Rights and Licence Frames
            'TCOP', 'TPRO', 'TPUB', 'TOWN', 'TRSN', 'TRSO',

            // Other Text Frames
            'TOFN', 'TDLY', 'TDEN', 'TDOR', 'TDRC', 'TDRL', 'TDTG', 'TSSE', 'TSOA', 'TSOP', 'TSOT',
            
            // Deprecated Text Frames
            'TDAT', 'TIME', 'TORY', 'TRDA', 'TSIZ', 'TYER',
            
            // Non-standard iTunes Frames
            'TCMP', 'TSO2', 'TSOC'
        ],
        
        url: [
            'WCOM', 'WCOP', 'WOAF', 'WOAR', 'WOAS', 'WORS', 'WPAY', 'WPUB'
        ]
    },
    
    frameTypes: {        
        text: {
            encoding: 1,
            value: 'string'
        },
        
        url: {
            value: 'latin1'
        },
        
        TXXX: {
            encoding: 1,
            description: 'string',
            value: 'string'
        },
        
        WXXX: {
            encoding: 1,
            description: 'string',
            value: 'latin1',
        },
        
        USLT: {
            encoding: 1,
            language: 1,
            description: 'string',
            value: 'string'
        },
        
        COMM: {
            encoding: 1,
            language: 1,
            description: 'string',
            value: 'string'
        },
        
        APIC: {
            encoding: 1,
            mime: 'latin1',
            type: 'int8',
            description: 'string',
            data: 'binary'
        },
        
        UFID: {
            owner: 'latin1',
            identifier: 'binary'
        },

        MCDI: {
            value: 'binary'
        },
        
        PRIV: {
            owner: 'latin1',
            value: 'binary'
        },
        
        GEOB: {
            encoding: 1,
            mime: 'latin1',
            filename: 'string',
            description: 'string',
            data: 'binary'
        },
        
        PCNT: {
            value: 'int32+'
        },
        
        POPM: {
            email: 'latin1',
            rating: 'int8',
            counter: 'int32+'
        },
        
        AENC: {
            owner: 'latin1',
            previewStart: 'int16',
            previewLength: 'int16',
            encryptionInfo: 'binary'
        },
        
        ETCO: {
            format: 'int8',
            data: 'binary'  // TODO
        },
        
        MLLT: {
            framesBetweenReference: 'int16',
            bytesBetweenReference: 'int24',
            millisecondsBetweenReference: 'int24',
            bitsForBytesDeviation: 'int8',
            bitsForMillisecondsDev: 'int8',
            data: 'binary' // TODO
        },
        
        SYTC: {
            format: 'int8',
            tempoData: 'binary' // TODO
        },
        
        SYLT: {
            encoding: 1,
            language: 1,
            format: 'int8',
            contentType: 'int8',
            description: 'string',
            data: 'binary' // TODO
        },
        
        RVA2: {
            identification: 'latin1',
            data: 'binary' // TODO
        },
        
        EQU2: {
            interpolationMethod: 'int8',
            identification: 'latin1',
            data: 'binary' // TODO
        },
        
        RVRB: {
            left: 'int16',
            right: 'int16',
            bouncesLeft: 'int8',
            bouncesRight: 'int8',
            feedbackLL: 'int8',
            feedbackLR: 'int8',
            feedbackRR: 'int8',
            feedbackRL: 'int8',
            premixLR: 'int8',
            premixRL: 'int8'
        },
        
        RBUF: {
            size: 'int24',
            flag: 'int8',
            offset: 'int32'
        },
        
        LINK: {
            identifier: 'frame_id',
            url: 'latin1',
            data: 'binary' // TODO stringlist?
        },
        
        POSS: {
            format: 'int8',
            position: 'binary' // TODO
        },
        
        USER: {
            encoding: 1,
            language: 1,
            value: 'string'
        },
        
        OWNE: {
            encoding: 1,
            price: 'latin1',
            purchaseDate: 'date',
            seller: 'string'
        },
        
        COMR: {
            encoding: 1,
            price: 'latin1',
            validUntil: 'date',
            contactURL: 'latin1',
            receivedAs: 'int8',
            seller: 'string',
            description: 'string',
            logoMime: 'latin1',
            logo: 'binary'
        },
        
        ENCR: {
            owner: 'latin1',
            methodSymbol: 'int8',
            data: 'binary'
        },
        
        GRID: {
            owner: 'latin1',
            groupSymbol: 'int8',
            data: 'binary'
        },
        
        SIGN: {
            groupSymbol: 'int8',
            signature: 'binary'
        },
        
        SEEK: {
            value: 'int32'
        },
        
        ASPI: {
            dataStart: 'int32',
            dataLength: 'int32',
            numPoints: 'int16',
            bitsPerPoint: 'int8',
            data: 'binary' // TODO
        },
        
        // Deprecated ID3 v2.3 frames
        IPLS: {
            encoding: 1,
            value: 'string' // list?
        },
        
        RVAD: {
            adjustment: 'int8',
            bits: 'int8',
            data: 'binary' // TODO
        },
        
        EQUA: {
            adjustmentBits: 'int8',
            data: 'binary' // TODO
        }
    },
    
    names: {
        // Identification Frames
        'TIT1': 'grouping',
        'TIT2': 'title',
        'TIT3': 'subtitle',
        'TALB': 'album',
        'TOAL': 'originalAlbumTitle',
        'TRCK': 'trackNumber',
        'TPOS': 'diskNumber',
        'TSST': 'setSubtitle',
        'TSRC': 'ISRC',

        // Involved Persons Frames
        'TPE1': 'artist',
        'TPE2': 'albumArtist',
        'TPE3': 'conductor',
        'TPE4': 'modifiedBy',
        'TOPE': 'originalArtist',
        'TEXT': 'lyricist',
        'TOLY': 'originalLyricist',
        'TCOM': 'composer',
        'TMCL': 'musicianCreditsList',
        'TIPL': 'involvedPeopleList',
        'TENC': 'encodedBy',

        // Derived and Subjective Properties Frames
        'TBPM': 'tempo',
        'TLEN': 'length',
        'TKEY': 'initialKey',
        'TLAN': 'language',
        'TCON': 'genre',
        'TFLT': 'fileType',
        'TMED': 'mediaType',
        'TMOO': 'mood',

        // Rights and Licence Frames
        'TCOP': 'copyright',
        'TPRO': 'producedNotice',
        'TPUB': 'publisher',
        'TOWN': 'fileOwner',
        'TRSN': 'internetRadioStationName',
        'TRSO': 'internetRadioStationOwner',

        // Other Text Frames
        'TOFN': 'originalFilename',
        'TDLY': 'playlistDelay',
        'TDEN': 'encodingTime',
        'TDOR': 'originalReleaseTime',
        'TDRC': 'recordingTime',
        'TDRL': 'releaseTime',
        'TDTG': 'taggingTime',
        'TSSE': 'encodedWith',
        'TSOA': 'albumSortOrder',
        'TSOP': 'performerSortOrder',
        'TSOT': 'titleSortOrder',
        
        // User defined text information
        'TXXX': 'userText',
        
        // Unsynchronised lyrics/text transcription
        'USLT': 'lyrics',

        // Attached Picture Frame
        'APIC': 'coverArt',

        // Unique Identifier Frame
        'UFID': 'uniqueIdentifier',

        // Music CD Identifier Frame
        'MCDI': 'CDIdentifier',

        // Comment Frame
        'COMM': 'comments',
        
        // URL link frames
        'WCOM': 'commercialInformation',
        'WCOP': 'copyrightInformation',
        'WOAF': 'officialAudioFileWebpage',
        'WOAR': 'officialArtistWebpage',
        'WOAS': 'officialAudioSourceWebpage',
        'WORS': 'officialInternetRadioStationHomepage',
        'WPAY': 'payment',
        'WPUB': 'officialPublisherWebpage',

        // User Defined URL Link Frame
        'WXXX': 'url',

        'PRIV': 'private',
        'GEOB': 'generalEncapsulatedObject',
        'PCNT': 'playCount',
        'POPM': 'rating',
        'AENC': 'audioEncryption',
        'ETCO': 'eventTimingCodes',
        'MLLT': 'MPEGLocationLookupTable',
        'SYTC': 'synchronisedTempoCodes',
        'SYLT': 'synchronisedLyrics',
        'RVA2': 'volumeAdjustment',
        'EQU2': 'equalization',
        'RVRB': 'reverb',
        'RBUF': 'recommendedBufferSize',
        'LINK': 'link',
        'POSS': 'positionSynchronisation',
        'USER': 'termsOfUse',
        'OWNE': 'ownership',
        'COMR': 'commercial',
        'ENCR': 'encryption',
        'GRID': 'groupIdentifier',
        'SIGN': 'signature',
        'SEEK': 'seek',
        'ASPI': 'audioSeekPointIndex',

        // Deprecated ID3 v2.3 frames
        'TDAT': 'date',
        'TIME': 'time',
        'TORY': 'originalReleaseYear',
        'TRDA': 'recordingDates',
        'TSIZ': 'size',
        'TYER': 'year',
        'IPLS': 'involvedPeopleList',
        'RVAD': 'volumeAdjustment',
        'EQUA': 'equalization',
        
        // Non-standard iTunes frames
        'TCMP': 'compilation',
        'TSO2': 'albumArtistSortOrder',
        'TSOC': 'composerSortOrder'
    }
});

// ID3 v2.2 support
exports.ID3v22Stream = exports.ID3v23Stream.extend({    
    readHeader: function() {
        var id = this.stream.readString(3);
        
        if (this.frameReplacements[id] && !this.frameTypes[id])
            this.frameTypes[id] = this.frameReplacements[id];
        
        return {
            identifier: this.replacements[id] || id,
            length: this.stream.readUInt24()
        };
    },
    
    // map 3 char ID3 v2.2 names to 4 char ID3 v2.3/4 names
    replacements: {
        'UFI': 'UFID',
        'TT1': 'TIT1',
        'TT2': 'TIT2',
        'TT3': 'TIT3',
        'TP1': 'TPE1',
        'TP2': 'TPE2',
        'TP3': 'TPE3',
        'TP4': 'TPE4',
        'TCM': 'TCOM',
        'TXT': 'TEXT',
        'TLA': 'TLAN',
        'TCO': 'TCON',
        'TAL': 'TALB',
        'TPA': 'TPOS',
        'TRK': 'TRCK',
        'TRC': 'TSRC',
        'TYE': 'TYER',
        'TDA': 'TDAT',
        'TIM': 'TIME',
        'TRD': 'TRDA',
        'TMT': 'TMED',
        'TFT': 'TFLT',
        'TBP': 'TBPM',
        'TCR': 'TCOP',
        'TPB': 'TPUB',
        'TEN': 'TENC',
        'TSS': 'TSSE',
        'TOF': 'TOFN',
        'TLE': 'TLEN',
        'TSI': 'TSIZ',
        'TDY': 'TDLY',
        'TKE': 'TKEY',
        'TOT': 'TOAL',
        'TOA': 'TOPE',
        'TOL': 'TOLY',
        'TOR': 'TORY',
        'TXX': 'TXXX',
        
        'WAF': 'WOAF',
        'WAR': 'WOAR',
        'WAS': 'WOAS',
        'WCM': 'WCOM',
        'WCP': 'WCOP',
        'WPB': 'WPUB',
        'WXX': 'WXXX',
        
        'IPL': 'IPLS',
        'MCI': 'MCDI',
        'ETC': 'ETCO',
        'MLL': 'MLLT',
        'STC': 'SYTC',
        'ULT': 'USLT',
        'SLT': 'SYLT',
        'COM': 'COMM',
        'RVA': 'RVAD',
        'EQU': 'EQUA',
        'REV': 'RVRB',
        
        'GEO': 'GEOB',
        'CNT': 'PCNT',
        'POP': 'POPM',
        'BUF': 'RBUF',
        'CRA': 'AENC',
        'LNK': 'LINK',
        
        // iTunes stuff
        'TST': 'TSOT',
        'TSP': 'TSOP',
        'TSA': 'TSOA',
        'TCP': 'TCMP',
        'TS2': 'TSO2',
        'TSC': 'TSOC'
    },
    
    // replacements for ID3 v2.3/4 frames
    frameReplacements: {
        PIC: {
            encoding: 1,
            format: 'int24',
            type: 'int8',
            description: 'string',
            data: 'binary'
        },
        
        CRM: {
            owner: 'latin1',
            description: 'latin1',
            data: 'binary'
        }
    }
});