BadSourcePosition.cs

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using BadScript2.IO;
 
namespace BadScript2.Common;
 
public class BadSourcePosition
{
    private string? m_PositionInfo;
 
    private string? m_Text;
 
    public BadSourcePosition(string? fileName, string source, int index, int length)
    {
        FileName = fileName?.Replace('\\', '/');
        Source = source;
        Index = index;
        Length = length;
    }
 
 
    private BadSourcePosition(string fileName, int index, int length) : this(
        fileName,
        BadFileSystem.ReadAllText(fileName),
        index,
        length
    ) { }
 
    public string? FileName { get; }
 
    public string Source { get; }
 
    public int Index { get; }
 
    public int Length { get; }
 
    public string Text => m_Text ??= GetExcerpt(0);
 
    public static BadSourcePosition Create(string fileName, string source, int index, int length)
    {
        return new BadSourcePosition(fileName, source, index, length);
    }
 
    public static BadSourcePosition FromFile(string fileName, int index, int length)
    {
        return new BadSourcePosition(fileName, index, length);
    }
 
    public static BadSourcePosition FromSource(string source, int index, int length)
    {
        return new BadSourcePosition("<nofile>", source, index, length);
    }
 
 
    public string GetExcerpt(int len = 10)
    {
        return GetExcerpt(len, len);
    }
 
 
    public string GetExcerpt(int left, int right)
    {
        int start = Math.Max(0, Index - left);
        int end = Math.Min(Source.Length, Index + Length + right);
 
        return Source.Substring(start, end - start);
    }
 
    public string GetPositionInfo()
    {
        if (m_PositionInfo != null)
        {
            return m_PositionInfo;
        }
 
        int line = 1;
 
        for (int i = 0; i < Index; i++)
        {
            if (Source[i] == '\n')
            {
                line++;
            }
        }
 
        m_PositionInfo = $"file://{FileName} : Line {line}";
 
        return m_PositionInfo;
    }
 
    public BadSourcePosition Combine(BadSourcePosition other)
    {
        if (FileName != other.FileName && Source != other.Source)
        {
            throw new InvalidOperationException("Cannot combine positions from different sources");
        }
 
        return Index < other.Index
            ? new BadSourcePosition(FileName, Source, Index, other.Index + other.Length - Index)
            : new BadSourcePosition(FileName, Source, other.Index, Index + Length - other.Index);
    }
}