/// <summary>
/// Returns the left part from the first ocurrence of the given substring (without the substring).
/// </summary>
/// <remarks>
/// Features driven by this set of rules:
/// <list type="bullet">
/// <item><description>null.LeftFromFirst(*) --> null</description></item>
/// <item><description>null and string.Empty are always substrings of a not null string</description></item>
/// /// <item><description>string.Empty only contains itself and null</description></item>
/// <item><description>*.LeftFromFirst(notFound) --> null</description></item>
/// </list>
/// </remarks>
public static string LeftFromFirst(this SubstrExtensionPoint sp, string substring, StringComparison comparison = StringComparison.Ordinal)
{
string e = sp.ExtendedValue;
return(e.Safe(s =>
{
substring = substring.EmptyIfNull();
int indexOfSubstringStart = s.IndexOf(substring, comparison) >= 0 ?
s.IndexOf(substring, comparison) : -1;
return indexOfSubstringStart < 0 ? null : sp.Left(indexOfSubstringStart);
}));
}
/// <summary>
/// Returns the left part from the last ocurrence of the given substring (without the substring).
/// </summary>
/// <remarks>
/// Features driven by this set of rules:
/// <list type="bullet">
/// <item><description>null.LeftFromLast(*) --> null</description></item>
/// <item><description>null and string.Empty are always substrings of a not null string</description></item>
/// /// <item><description>string.Empty only contains itself and null</description></item>
/// <item><description>*.LeftFromLast(notFound) --> null</description></item>
/// </list>
/// </remarks>
public static string LeftFromLast(this SubstrExtensionPoint sp, string substring, StringComparison comparison = StringComparison.Ordinal)
{
string e = sp.ExtendedValue;
return(e.Safe(s =>
{
substring = substring.EmptyIfNull();
int indexOfSubstringStart = -1;
if (substring.IsEmpty())
{
indexOfSubstringStart = 0;
}
else if (s.LastIndexOf(substring, comparison) >= 0)
{
indexOfSubstringStart = s.LastIndexOf(substring, comparison);
}
return indexOfSubstringStart < 0 ? null : sp.Left(indexOfSubstringStart);
}));
}
