499 lines
14 KiB
TypeScript
499 lines
14 KiB
TypeScript
/*
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* Source: https://github.com/mozilla/vtt.js/blob/master/dist/vtt.js
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*/
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import VTTCue from './vttcue';
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class StringDecoder {
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// eslint-disable-next-line @typescript-eslint/no-unused-vars
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decode(data: string | any, options?: Object): string | never {
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if (!data) {
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return '';
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}
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if (typeof data !== 'string') {
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throw new Error('Error - expected string data.');
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}
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return decodeURIComponent(encodeURIComponent(data));
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}
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}
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// Try to parse input as a time stamp.
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export function parseTimeStamp(input: string) {
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function computeSeconds(h, m, s, f) {
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return (h | 0) * 3600 + (m | 0) * 60 + (s | 0) + parseFloat(f || 0);
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}
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const m = input.match(/^(?:(\d+):)?(\d{2}):(\d{2})(\.\d+)?/);
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if (!m) {
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return null;
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}
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if (parseFloat(m[2]) > 59) {
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// Timestamp takes the form of [hours]:[minutes].[milliseconds]
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// First position is hours as it's over 59.
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return computeSeconds(m[2], m[3], 0, m[4]);
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}
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// Timestamp takes the form of [hours (optional)]:[minutes]:[seconds].[milliseconds]
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return computeSeconds(m[1], m[2], m[3], m[4]);
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}
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// A settings object holds key/value pairs and will ignore anything but the first
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// assignment to a specific key.
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class Settings {
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private readonly values: { [key: string]: any } = Object.create(null);
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// Only accept the first assignment to any key.
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set(k: string, v: any) {
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if (!this.get(k) && v !== '') {
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this.values[k] = v;
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}
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}
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// Return the value for a key, or a default value.
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// If 'defaultKey' is passed then 'dflt' is assumed to be an object with
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// a number of possible default values as properties where 'defaultKey' is
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// the key of the property that will be chosen; otherwise it's assumed to be
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// a single value.
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get(k: string, dflt?: any, defaultKey?: string): any {
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if (defaultKey) {
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return this.has(k) ? this.values[k] : dflt[defaultKey];
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}
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return this.has(k) ? this.values[k] : dflt;
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}
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// Check whether we have a value for a key.
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has(k: string): boolean {
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return k in this.values;
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}
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// Accept a setting if its one of the given alternatives.
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alt(k: string, v: any, a: any[]) {
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for (let n = 0; n < a.length; ++n) {
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if (v === a[n]) {
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this.set(k, v);
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break;
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}
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}
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}
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// Accept a setting if its a valid (signed) integer.
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integer(k: string, v: any) {
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if (/^-?\d+$/.test(v)) {
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// integer
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this.set(k, parseInt(v, 10));
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}
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}
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// Accept a setting if its a valid percentage.
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percent(k: string, v: any): boolean {
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if (/^([\d]{1,3})(\.[\d]*)?%$/.test(v)) {
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const percent = parseFloat(v);
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if (percent >= 0 && percent <= 100) {
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this.set(k, percent);
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return true;
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}
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}
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return false;
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}
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}
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// Helper function to parse input into groups separated by 'groupDelim', and
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// interpret each group as a key/value pair separated by 'keyValueDelim'.
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function parseOptions(
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input: string,
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callback: (k: string, v: any) => void,
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keyValueDelim: RegExp,
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groupDelim?: RegExp,
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) {
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const groups = groupDelim ? input.split(groupDelim) : [input];
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for (const i in groups) {
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if (typeof groups[i] !== 'string') {
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continue;
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}
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const kv = groups[i].split(keyValueDelim);
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if (kv.length !== 2) {
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continue;
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}
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const k = kv[0];
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const v = kv[1];
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callback(k, v);
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}
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}
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const defaults = new VTTCue(0, 0, '');
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// 'middle' was changed to 'center' in the spec: https://github.com/w3c/webvtt/pull/244
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// Safari doesn't yet support this change, but FF and Chrome do.
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const center = (defaults.align as string) === 'middle' ? 'middle' : 'center';
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function parseCue(input: string, cue: VTTCue, regionList: Region[]) {
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// Remember the original input if we need to throw an error.
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const oInput = input;
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// 4.1 WebVTT timestamp
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function consumeTimeStamp(): number | never {
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const ts = parseTimeStamp(input);
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if (ts === null) {
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throw new Error('Malformed timestamp: ' + oInput);
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}
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// Remove time stamp from input.
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input = input.replace(/^[^\sa-zA-Z-]+/, '');
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return ts;
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}
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// 4.4.2 WebVTT cue settings
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function consumeCueSettings(input: string, cue: VTTCue) {
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const settings = new Settings();
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parseOptions(
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input,
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function (k, v) {
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let vals;
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switch (k) {
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case 'region':
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// Find the last region we parsed with the same region id.
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for (let i = regionList.length - 1; i >= 0; i--) {
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if (regionList[i].id === v) {
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settings.set(k, regionList[i].region);
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break;
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}
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}
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break;
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case 'vertical':
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settings.alt(k, v, ['rl', 'lr']);
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break;
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case 'line':
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vals = v.split(',');
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settings.integer(k, vals[0]);
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if (settings.percent(k, vals[0])) {
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settings.set('snapToLines', false);
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}
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settings.alt(k, vals[0], ['auto']);
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if (vals.length === 2) {
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settings.alt('lineAlign', vals[1], ['start', center, 'end']);
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}
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break;
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case 'position':
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vals = v.split(',');
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settings.percent(k, vals[0]);
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if (vals.length === 2) {
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settings.alt('positionAlign', vals[1], [
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'start',
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center,
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'end',
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'line-left',
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'line-right',
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'auto',
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]);
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}
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break;
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case 'size':
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settings.percent(k, v);
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break;
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case 'align':
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settings.alt(k, v, ['start', center, 'end', 'left', 'right']);
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break;
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}
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},
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/:/,
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/\s/,
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);
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// Apply default values for any missing fields.
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cue.region = settings.get('region', null);
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cue.vertical = settings.get('vertical', '');
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let line = settings.get('line', 'auto');
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if (line === 'auto' && defaults.line === -1) {
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// set numeric line number for Safari
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line = -1;
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}
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cue.line = line;
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cue.lineAlign = settings.get('lineAlign', 'start');
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cue.snapToLines = settings.get('snapToLines', true);
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cue.size = settings.get('size', 100);
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cue.align = settings.get('align', center);
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let position = settings.get('position', 'auto');
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if (position === 'auto' && defaults.position === 50) {
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// set numeric position for Safari
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position =
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cue.align === 'start' || cue.align === 'left'
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? 0
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: cue.align === 'end' || cue.align === 'right'
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? 100
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: 50;
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}
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cue.position = position;
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}
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function skipWhitespace() {
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input = input.replace(/^\s+/, '');
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}
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// 4.1 WebVTT cue timings.
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skipWhitespace();
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cue.startTime = consumeTimeStamp(); // (1) collect cue start time
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skipWhitespace();
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if (input.slice(0, 3) !== '-->') {
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// (3) next characters must match '-->'
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throw new Error(
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"Malformed time stamp (time stamps must be separated by '-->'): " +
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oInput,
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);
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}
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input = input.slice(3);
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skipWhitespace();
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cue.endTime = consumeTimeStamp(); // (5) collect cue end time
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// 4.1 WebVTT cue settings list.
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skipWhitespace();
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consumeCueSettings(input, cue);
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}
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export function fixLineBreaks(input: string): string {
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return input.replace(/<br(?: \/)?>/gi, '\n');
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}
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type Region = {
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id: string;
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region: any;
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};
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export class VTTParser {
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private state:
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| 'INITIAL'
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| 'HEADER'
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| 'ID'
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| 'CUE'
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| 'CUETEXT'
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| 'NOTE'
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| 'BADWEBVTT'
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| 'BADCUE' = 'INITIAL';
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private buffer: string = '';
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private decoder: StringDecoder = new StringDecoder();
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private regionList: Region[] = [];
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private cue: VTTCue | null = null;
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public oncue?: (cue: VTTCue) => void;
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public onparsingerror?: (error: Error) => void;
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public onflush?: () => void;
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parse(data?: string): VTTParser {
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const _this = this;
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// If there is no data then we won't decode it, but will just try to parse
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// whatever is in buffer already. This may occur in circumstances, for
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// example when flush() is called.
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if (data) {
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// Try to decode the data that we received.
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_this.buffer += _this.decoder.decode(data, { stream: true });
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}
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function collectNextLine(): string {
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let buffer: string = _this.buffer;
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let pos = 0;
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buffer = fixLineBreaks(buffer);
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while (
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pos < buffer.length &&
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buffer[pos] !== '\r' &&
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buffer[pos] !== '\n'
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) {
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++pos;
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}
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const line: string = buffer.slice(0, pos);
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// Advance the buffer early in case we fail below.
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if (buffer[pos] === '\r') {
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++pos;
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}
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if (buffer[pos] === '\n') {
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++pos;
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}
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_this.buffer = buffer.slice(pos);
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return line;
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}
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// 3.2 WebVTT metadata header syntax
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function parseHeader(input) {
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parseOptions(
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input,
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function (k, v) {
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// switch (k) {
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// case 'region':
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// 3.3 WebVTT region metadata header syntax
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// console.log('parse region', v);
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// parseRegion(v);
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// break;
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// }
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},
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/:/,
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);
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}
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// 5.1 WebVTT file parsing.
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try {
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let line: string = '';
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if (_this.state === 'INITIAL') {
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// We can't start parsing until we have the first line.
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if (!/\r\n|\n/.test(_this.buffer)) {
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return this;
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}
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line = collectNextLine();
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// strip of UTF-8 BOM if any
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// https://en.wikipedia.org/wiki/Byte_order_mark#UTF-8
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const m = line.match(/^()?WEBVTT([ \t].*)?$/);
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if (!m?.[0]) {
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throw new Error('Malformed WebVTT signature.');
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}
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_this.state = 'HEADER';
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}
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let alreadyCollectedLine = false;
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while (_this.buffer) {
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// We can't parse a line until we have the full line.
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if (!/\r\n|\n/.test(_this.buffer)) {
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return this;
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}
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if (!alreadyCollectedLine) {
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line = collectNextLine();
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} else {
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alreadyCollectedLine = false;
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}
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switch (_this.state) {
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case 'HEADER':
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// 13-18 - Allow a header (metadata) under the WEBVTT line.
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if (/:/.test(line)) {
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parseHeader(line);
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} else if (!line) {
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// An empty line terminates the header and starts the body (cues).
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_this.state = 'ID';
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}
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continue;
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case 'NOTE':
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// Ignore NOTE blocks.
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if (!line) {
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_this.state = 'ID';
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}
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continue;
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case 'ID':
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// Check for the start of NOTE blocks.
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if (/^NOTE($|[ \t])/.test(line)) {
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_this.state = 'NOTE';
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break;
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}
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// 19-29 - Allow any number of line terminators, then initialize new cue values.
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if (!line) {
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continue;
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}
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_this.cue = new VTTCue(0, 0, '');
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_this.state = 'CUE';
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// 30-39 - Check if self line contains an optional identifier or timing data.
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if (line.indexOf('-->') === -1) {
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_this.cue.id = line;
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continue;
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}
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// Process line as start of a cue.
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/* falls through */
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case 'CUE':
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// 40 - Collect cue timings and settings.
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if (!_this.cue) {
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_this.state = 'BADCUE';
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continue;
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}
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try {
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parseCue(line, _this.cue, _this.regionList);
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} catch (e) {
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// In case of an error ignore rest of the cue.
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_this.cue = null;
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_this.state = 'BADCUE';
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continue;
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}
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_this.state = 'CUETEXT';
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continue;
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case 'CUETEXT':
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{
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const hasSubstring = line.indexOf('-->') !== -1;
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// 34 - If we have an empty line then report the cue.
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// 35 - If we have the special substring '-->' then report the cue,
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// but do not collect the line as we need to process the current
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// one as a new cue.
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if (!line || (hasSubstring && (alreadyCollectedLine = true))) {
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// We are done parsing self cue.
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if (_this.oncue && _this.cue) {
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_this.oncue(_this.cue);
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}
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_this.cue = null;
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_this.state = 'ID';
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continue;
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}
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if (_this.cue === null) {
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continue;
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}
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if (_this.cue.text) {
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_this.cue.text += '\n';
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}
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_this.cue.text += line;
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}
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continue;
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case 'BADCUE':
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// 54-62 - Collect and discard the remaining cue.
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if (!line) {
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_this.state = 'ID';
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}
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}
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}
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} catch (e) {
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// If we are currently parsing a cue, report what we have.
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if (_this.state === 'CUETEXT' && _this.cue && _this.oncue) {
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_this.oncue(_this.cue);
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}
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_this.cue = null;
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// Enter BADWEBVTT state if header was not parsed correctly otherwise
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// another exception occurred so enter BADCUE state.
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_this.state = _this.state === 'INITIAL' ? 'BADWEBVTT' : 'BADCUE';
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}
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return this;
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}
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flush(): VTTParser {
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const _this = this;
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try {
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// Finish decoding the stream.
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// _this.buffer += _this.decoder.decode();
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// Synthesize the end of the current cue or region.
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if (_this.cue || _this.state === 'HEADER') {
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_this.buffer += '\n\n';
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_this.parse();
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}
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// If we've flushed, parsed, and we're still on the INITIAL state then
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// that means we don't have enough of the stream to parse the first
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// line.
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if (_this.state === 'INITIAL' || _this.state === 'BADWEBVTT') {
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throw new Error('Malformed WebVTT signature.');
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}
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} catch (e) {
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if (_this.onparsingerror) {
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_this.onparsingerror(e);
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}
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}
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if (_this.onflush) {
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_this.onflush();
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}
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return this;
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}
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}
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