using System;

namespace MathInterpreter.Core;

/// <summary>
///     Provides utility methods for scanning character streams for certain parts of a maths expression
/// </summary>
public static class ExpressionScanner
{
    /// <summary>
    ///     Scans the given expression for an operator (+, -, *, /)
    /// </summary>
    /// <param name="expression">Expression to process</param>
    /// <returns>A scan result containing the operator found and the remaining part of the expression</returns>
    /// <exception cref="OperatorException">Thrown if none or an unknown operator is found</exception>
    public static ScanResult<Operator> ScanOperator(ReadOnlySpan<char> expression)
    {
        // TODO
        throw new NotImplementedException();
    }

    /// <summary>
    ///     Scans the given expression for an operand which is a number which have to have an integral
    ///     part and may have a fractional part. It may also have a sign (+, -) in front of it.
    /// </summary>
    /// <param name="expression">Expression to process</param>
    /// <returns>A scan result containing the parsed number and the remaining part expression</returns>
    /// <exception cref="ExpressionFormatException">Thrown if a problem with the format of the number is found</exception>
    public static ScanResult<double> ScanOperand(ReadOnlySpan<char> expression)
    {
        // TODO
        throw new NotImplementedException();
    }

    /// <summary>
    ///     Scans the given expression for a whole number which may have a sign (+, -) in front of it
    /// </summary>
    /// <param name="expression">Expression to process</param>
    /// <param name="allowSign">Flag indicating if a pre-fix sign (+, -) is allowed or not</param>
    /// <returns>A scan result containing the parsed number and the remaining part expression</returns>
    /// <exception cref="NumberFormatException">Thrown if no or an invalid number is found</exception>
    public static ScanResult<int> ScanNumber(ReadOnlySpan<char> expression, bool allowSign)
    {
        // TODO
        throw new NotImplementedException();
    }
}