private static IEnumerable <Caption> SearchTrackForPhrases(CaptionTrack track, string[] phrases)
{
const string fullTextSeperator = " ";
var startByCaption = new Dictionary <Caption, int>();
//aggregate captions into fullText to enable matching phrases across caption boundaries
var fullText = track.Captions.OrderBy(c => c.At).Aggregate(string.Empty, (fullText, caption) =>
{
//remember at what index in the fullText the caption starts
startByCaption.Add(caption, fullText.Length == 0 ? 0 : fullText.Length + fullTextSeperator.Length);
return(fullText.Length == 0 ? caption.Text : fullText + fullTextSeperator + caption.Text);
});
return(fullText.GetMatches(phrases).Select(match =>
{
//find first and last captions containing parts of the phrase
var first = startByCaption.Last(x => x.Value <= match.Index);
var last = startByCaption.Last(x => first.Value <= x.Value && x.Value < match.Index + match.Length);
//return a single caption for all captions containing the phrase
return new Caption
{
At = first.Key.At,
Text = startByCaption
.Where(x => first.Value <= x.Value && x.Value <= last.Value)
.Select(x => x.Key.Text)
.Join(fullTextSeperator)
};
}));
}
} //required by serializer
/// <summary>Use this to clone a Captiontrack to include in a VideoSerachResult.
/// Captions will be set to matchingCaptions instead of cloning track.Captions.</summary>
/// <param name="track">The track to clone.</param>
/// <param name="matchingCaptions">The matching captions.</param>
internal CaptionTrack(CaptionTrack track, Caption[] matchingCaptions)
{
this.LanguageName = track.LanguageName;
this.Captions = matchingCaptions;
}
