using System;

namespace MathInterpreter.Core;

/// <summary>
///     Result object of scan operations
/// </summary>
/// <typeparam name="T">Type of the parsed value</typeparam>
public readonly ref struct ScanResult<T> where T : struct
{
    /// <summary>
    ///     Creates a new scan result based on a successfully parsed value - if parsing failed an Exception
    ///     would have been thrown and this constructor would not be called
    /// </summary>
    /// <param name="value">Parsed value</param>
    /// <param name="length">Number of characters (digits) of the parsed value</param>
    /// <param name="remainingExpression">Remaining part of the expression after extracting and parsing the value</param>
    /// <exception cref="ArgumentOutOfRangeException">Thrown if an invalid argument is provided</exception>
    public ScanResult(T value, int length, ReadOnlySpan<char> remainingExpression)
    {
        if (length < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(length), "Length must be non-negative");
        }
    
        Value = value;
        Length = length;
        RemainingExpression = remainingExpression;
    }

    /// <summary>
    ///     Gets the parsed value
    /// </summary>
    public T Value { get; }

    /// <summary>
    ///     Gets the number of characters (digits) of the parsed value
    /// </summary>
    public int Length { get; }

    /// <summary>
    ///     Gets the remaining part of the expression after extracting and parsing the value
    /// </summary>
    public ReadOnlySpan<char> RemainingExpression { get; }
}