/// <summary>
/// To
/// </summary>
/// <param name="text"></param>
/// <param name="formatProvider"></param>
/// <param name="defaultVal"></param>
/// <returns></returns>
public static DateTimeSpan To(
string text,
IFormatProvider formatProvider = null,
DateTimeSpan defaultVal = default)
{
if (formatProvider is null)
{
formatProvider = DateTimeFormatInfo.CurrentInfo;
}
return(DateTimeSpan.TryParse(text, formatProvider, out var dateTimeSpan)
? dateTimeSpan
: defaultVal);
}
/// <summary>
/// Computes a natural language date/time addition or subtraction expression such as Jan 1, 2000 + 5 days, returns the result of this expression. Returns null if input is not valid.
/// </summary>
/// <param name="expression">A natural language date/time addition or subtraction expression. Example: "Jan 1, 2000 + 5 days"</param>
/// <returns></returns>
public static string Calculate(string expression)
{
string result = null;
const char Plus = '+';
const char Minus = '-';
string[] parts = expression.Split(new char[] { Plus, Minus });
if (parts.Length != 2)
{
return(null);
}
char[] operandInput = expression.Replace(parts[0], string.Empty).Replace(parts[1], string.Empty).Trim().ToCharArray();
if (operandInput.Length != 1)
{
return(null);
}
char operand = operandInput[0];
if (operand != Plus && operand != Minus)
{
return(null);
}
if (!TryParseBetter(parts[0], out DateTime dateTime1))
{
return(null);
}
if (TryParseBetter(parts[1], out DateTime dateTime2))
{
switch (operand)
{
case Plus: result = PrettifyDateTime(Calculator.Add(dateTime1, dateTime2)); break;
case Minus: result = Calculator.Subtract(dateTime1, dateTime2).ToString(); break;
}
}
else if (DateTimeSpan.TryParse(parts[1], out DateTimeSpan dateTimeSpan))
{
switch (operand)
{
case Plus: result = PrettifyDateTime(Calculator.Add(dateTime1, dateTimeSpan)); break;
case Minus: result = PrettifyDateTime(Calculator.Subtract(dateTime1, dateTimeSpan)); break;
}
}
return(result);
}
/// <summary>
/// Is
/// </summary>
/// <param name="text"></param>
/// <param name="formatProvider"></param>
/// <param name="matchedCallback"></param>
/// <returns></returns>
public static bool Is(
string text,
IFormatProvider formatProvider = null,
Action <DateTimeSpan> matchedCallback = null)
{
if (string.IsNullOrWhiteSpace(text))
{
return(false);
}
if (formatProvider is null)
{
formatProvider = DateTimeFormatInfo.CurrentInfo;
}
return(DateTimeSpan.TryParse(text, formatProvider, out var dateTimeSpan)
.IfTrueThenInvoke(matchedCallback, dateTimeSpan));
}
public static string ExplainSyntaxError(string expression)
{
string[] parts = expression.Split(new char[] { '+', '-' });
if (parts.Length < 2)
{
return(Properties.Resources.SyntaxErrorNoOperand);
}
if (parts.Length > 2)
{
return(Properties.Resources.SyntaxErrorTooManyOperands);
}
if (!DateTime.TryParse(parts[0], out _))
{
return(string.Format(Properties.Resources.SyntaxErrorPart1NotValid, parts[0]));
}
if (!DateTime.TryParse(parts[1], out _) && !DateTimeSpan.TryParse(parts[1], out _))
{
return(string.Format(Properties.Resources.SyntaxErrorPart2NotValid, parts[1]));
}
return(Properties.Resources.Usage);
}