/// <summary>
/// Highlights chosen terms in a text, extracting the most relevant sections.
/// </summary>
/// <param name="input">Text to highlight terms in.</param>
/// <param name="fieldName">Name of the field to highlight.</param>
/// <param name="query">Search query.</param>
/// <param name="engine">Search engine. Use <c>null</c> to fallback to simple string highlighting method.</param>
/// <param name="preMatch">Pre matching HTML.</param>
/// <param name="postMatch">Post matching HTML.</param>
/// <returns>Highlighted text fragments.</returns>
public string Highlight(
string input,
string fieldName,
ISearchQuery query,
ISearchEngine engine = null,
string preMatch = "<strong>",
string postMatch = "</strong>")
{
Guard.NotEmpty(fieldName, nameof(fieldName));
if (query?.Term == null || input.IsEmpty())
{
return(input);
}
string hilite = null;
if (engine != null)
{
try
{
hilite = engine.Highlight(input, fieldName, preMatch, postMatch);
}
catch { }
}
if (hilite.HasValue())
{
return(hilite);
}
return(input.HighlightKeywords(query.Term, preMatch, postMatch));
}