/// <summary>
/// Reads WebVTT media captions from a given <see cref="TextReader"/>.
/// </summary>
/// <param name="reader">Text reader to read the captions.</param>
/// <returns>A task that represents the asynchronous read operation.</returns>
public static async Task <MediaCaptions> ReadMediaCaptionsAsync(
TextReader reader)
{
if (reader == null)
{
throw new ArgumentNullException("reader");
}
// Process stream header line
var line = await reader.ReadLineAsync()
.ConfigureAwait(false);
if (string.IsNullOrWhiteSpace(line) ||
line.Length < 6 ||
false == line.StartsWith(Constants.WebVttHeaderToken) ||
line.Length >= 7 && line[6] != '\t' && line[6] != ' ')
{
throw new InvalidDataException("The stream does not start with the correct WebVTT file signature.");
}
var result = new MediaCaptions();
// Process (skip over) optional headers from the stream
while (false == string.IsNullOrEmpty(line))
{
line = await reader.ReadLineAsync()
.ConfigureAwait(false);
}
// Process media caption blocks.
List <RegionDefinition> regions = new List <RegionDefinition>();
List <Style> styles = new List <Style>();
List <Cue> cues = new List <Cue>();
BaseBlock block;
do
{
block = await WebVttParser.ReadBlockAsync(reader)
.ConfigureAwait(false);
RegionDefinition region = block as RegionDefinition;
Style style = block as Style;
Cue cue = block as Cue;
if (cues.Count == 0)
{
if (region != null)
{
regions.Add(region);
}
else if (style != null)
{
styles.Add(style);
}
}
else if (region != null || style != null)
{
throw new InvalidDataException("Region or style blocks cannot be mixed with cue blocks.");
}
if (cue != null)
{
cues.Add(cue);
}
}while (block != null);
if (regions.Count > 0)
{
result.Regions = regions.ToArray();
}
if (styles.Count > 0)
{
result.Styles = styles.ToArray();
}
if (cues.Count > 0)
{
result.Cues = cues.ToArray();
}
return(result);
}
/// <summary>
/// Reads WebVTT Region definition block from the stream.
/// </summary>
/// <param name="firstLine">First line of the block read from the reader.</param>
/// <param name="reader">Text reader to read the region block.</param>
/// <returns>A task that represents the asynchronous read operation.</returns>
private static async Task <RegionDefinition> ReadRegionAsync(
string firstLine,
TextReader reader)
{
string line = firstLine;
if (line.Length > Constants.RegionToken.Length &&
false == string.IsNullOrWhiteSpace(line.Substring(Constants.RegionToken.Length)))
{
throw new InvalidDataException(string.Format("Invalid characters found after region definition header: {0}", line));
}
var content = new StringBuilder(100);
while (false == string.IsNullOrEmpty(line))
{
line = await reader.ReadLineAsync()
.ConfigureAwait(false);
if (false == string.IsNullOrEmpty(line))
{
if (line.Contains(Constants.ArrowToken))
{
throw new InvalidDataException(string.Format("Region definition must not contain '{0}'.", Constants.ArrowToken));
}
content.SafeAppendLine(line);
}
}
var result = new RegionDefinition()
{
RawContent = content.Length > 0 ? content.ToString() : null
};
if (result.RawContent != null)
{
var settings = WebVttParser.ParseSettings(result.RawContent);
if (settings != null)
{
string value;
if (WebVttParser.TryGetStringSetting(Constants.RegionIdName, settings, out value))
{
result.Id = value;
}
double percent;
if (WebVttParser.TryGetPercentSetting(Constants.WidthName, settings, out percent))
{
result.WidthPercent = percent;
}
Anchor anchor;
if (WebVttParser.TryGetAnchorSetting(Constants.RegionAnchorName, settings, out anchor))
{
result.RegionAnchor = anchor;
}
if (WebVttParser.TryGetAnchorSetting(Constants.ViewPortAnchorName, settings, out anchor))
{
result.ViewPortAnchor = anchor;
}
if (WebVttParser.TryGetStringSetting(Constants.ScrollName, settings, out value))
{
result.Scroll = string.Equals(value, Constants.ScrollUpValue, StringComparison.OrdinalIgnoreCase);
}
int lines;
if (WebVttParser.TryGetIntSetting(Constants.LinesName, settings, out lines))
{
result.Lines = lines;
}
}
}
return(result);
}