namespace Compiler;

public sealed class Diagnostic(DiagnosticSeverity severity, string message, string? help, FileInfo? file)
{
    public static DiagnosticBuilder Info(string message) => new DiagnosticBuilder(DiagnosticSeverity.Info, message);
    public static DiagnosticBuilder Warning(string message) => new DiagnosticBuilder(DiagnosticSeverity.Warning, message);
    public static DiagnosticBuilder Error(string message) => new DiagnosticBuilder(DiagnosticSeverity.Error, message);

    public readonly DiagnosticSeverity Severity = severity;
    public readonly string Message = message;
    public readonly string? Help = help;
    public readonly FileInfo? File = file;
}

public sealed class DiagnosticBuilder(DiagnosticSeverity severity, string message)
{
    private FileInfo? file;
    private string? help;

    public DiagnosticBuilder At(string fileName, int line, int column, int length)
    {
        file = new FileInfo(fileName, line, column, length);
        return this;
    }

    public DiagnosticBuilder At(string fileName, Token? token)
    {
        if (token != null)
        {
            At(fileName, token.Line, token.Column, token.Length);
        }

        return this;
    }

    public DiagnosticBuilder At(string fileName, Node? node)
    {
        if (node != null && node.Tokens.Count != 0)
        {
            // todo(nub31): Calculate length based on last token
            At(fileName, node.Tokens[0]);
        }

        return this;
    }

    public DiagnosticBuilder WithHelp(string helpMessage)
    {
        help = helpMessage;
        return this;
    }

    public Diagnostic Build()
    {
        return new Diagnostic(severity, message, help, file);
    }
}

public sealed class FileInfo(string file, int line, int column, int length)
{
    public readonly string File = file;
    public readonly int Line = line;
    public readonly int Column = column;
    public readonly int Length = length;
}

public enum DiagnosticSeverity
{
    Info,
    Warning,
    Error,
}

public sealed class CompileException(Diagnostic diagnostic) : Exception
{
    public readonly Diagnostic Diagnostic = diagnostic;
}

public static class DiagnosticFormatter
{
    public static void Print(Diagnostic diagnostic, TextWriter writer)
    {
        var (label, color) = diagnostic.Severity switch
        {
            DiagnosticSeverity.Info => ("info", Ansi.Cyan),
            DiagnosticSeverity.Warning => ("warning", Ansi.Yellow),
            DiagnosticSeverity.Error => ("error", Ansi.Red),
            _ => ("unknown", Ansi.Reset),
        };

        writer.Write(color);
        writer.Write(label);
        writer.Write(Ansi.Reset);
        writer.Write(": ");
        writer.WriteLine(diagnostic.Message);

        if (diagnostic.File is null)
            return;

        var file = diagnostic.File;
        var lineNumberWidth = diagnostic.File.Line.ToString().Length;

        writer.WriteLine($" {new string(' ', lineNumberWidth)}{file.File}:{file.Line}:{file.Column}");
        writer.WriteLine($"{new string(' ', lineNumberWidth)} | ");

        var sourceLine = TryReadLine(file.File, file.Line);
        if (sourceLine != null)
        {
            writer.Write($"{file.Line.ToString().PadLeft(lineNumberWidth)} | ");
            writer.WriteLine(sourceLine);

            writer.Write(new string(' ', lineNumberWidth));
            writer.Write(" | ");
            writer.Write(new string(' ', file.Column - 1));
            writer.Write(color);
            writer.Write(new string('^', Math.Max(1, file.Length)));
            writer.WriteLine(Ansi.Reset);
        }

        writer.WriteLine($"{new string(' ', lineNumberWidth)} |");

        if (!string.IsNullOrWhiteSpace(diagnostic.Help))
        {
            writer.WriteLine($"   = help: {diagnostic.Help}");
        }
    }

    private static string? TryReadLine(string file, int line)
    {
        try
        {
            using var reader = new StreamReader(file);
            for (var i = 1; i < line; i++)
            {
                if (reader.ReadLine() == null)
                    return null;
            }

            return reader.ReadLine();
        }
        catch
        {
            return null;
        }
    }

    private static class Ansi
    {
        public const string Reset = "\e[0m";
        public const string Red = "\e[31m";
        public const string Yellow = "\e[33m";
        public const string Cyan = "\e[36m";
    }
}