/// <summary>
/// Get the number of elements in a nested <see cref="SequenceResult{T1, T2}"/>,
/// constructed and matched via Parser Combinators.
/// </summary>
/// <typeparam name="T1">Type of the first element in the <see cref="SequenceResult{T1, T2}"/>.</typeparam>
/// <typeparam name="T2">Type of the second element in the <see cref="SequenceResult{T1, T2}"/>.</typeparam>
/// <param name="result">The <see cref="SequenceResult{T1, T2}"/> to count the number of elements in.</param>
/// <returns>The number of elements in a left-leaning nested <see cref="SequenceResult{T1, T2}"/>.</returns>
public static int Count <T1, T2>(this SequenceResult <T1, T2> result)
{
var depth = 0;
var type = result.GetType();
while (type.IsGenericType &&
type.GetGenericTypeDefinition() == typeof(SequenceResult <,>))
{
depth++;
type = type.GetGenericArguments()[0];
}
return(depth + 1);
}
/// <summary>
/// Get the item at the nth index in the given nested <see cref="SequenceResult{T1, T2}"/>,
/// constructed and matched via Parser Combinators. Uses reflection to access elements dynamically,
/// allowing the user to get to elements of very long sequences.
/// </summary>
/// <typeparam name="T1">Type of the first element in the <see cref="SequenceResult{T1, T2}"/>.</typeparam>
/// <typeparam name="T2">Type of the second element in the <see cref="SequenceResult{T1, T2}"/>.</typeparam>
/// <param name="result">The element at the nth index of this nested <see cref="SequenceResult{T1, T2}"/>, as an object.</param>
/// <param name="index">Index to get the element of.</param>
/// <exception cref="ArgumentOutOfRangeException">Thrown if the index is less than 0 or greater than the number of elements in the sequence.</exception>
/// <returns>The element matched in the given sequence at the given index.</returns>
public static object ItemN <T1, T2>(this SequenceResult <T1, T2> result, int index)
{
var count = Count(result);
if (index < 0 || index >= count)
{
throw new ArgumentOutOfRangeException("index", "Index must be a positive number less than the number of nested elements");
}
object current = result;
for (int i = 0; i < count - index - 1; i++)
{
current = current.GetType().GetProperty("First").GetValue(current);
}
return((index == 0)
? current
: current.GetType().GetProperty("Next").GetValue(current));
}
/// <summary>
/// Attempts to match an input string starting at the given index.
/// </summary>
/// <param name="input">String to match.</param>
/// <param name="index">Index to begin matching at.</param>
/// <returns>An <see cref="IParseResult{T}"/> containing the parsed value.</returns>
public override IParseResult <SequenceResult <T1, T2> > Parse(string input, int index)
{
var i = index;
var result1 = Parser1.Parse(input, i);
if (!result1.Success)
{
var failure = (ParseFail <T1>)result1;
return(new ParseFail <SequenceResult <T1, T2> >(failure.FailureType, failure.Index, failure.Message));
}
i += result1.Length;
var result2 = Parser2.Parse(input, i);
if (!result2.Success)
{
var failure = (ParseFail <T2>)result2;
return(new ParseFail <SequenceResult <T1, T2> >(failure.FailureType, failure.Index, failure.Message));
}
var value = new SequenceResult <T1, T2>(result1.Value, result2.Value);
return(new ParseSuccess <SequenceResult <T1, T2> >(string.Concat(result1.Text, result2.Text), value, index));
}
