using System;
using System.Xml;
using System.Xml.Linq;
using CommandLine;
using Sprache;
using XNeedle.Parser;
using XNeedle.Parser.Elements;
using XNeedle.Transformation;
using XNeedle.Formats;

namespace XNeedle
{
    class Program
    {
        public class Options
        {
            [Value(0, MetaName = "xn", Required = true, HelpText = "XN transformation definition")]
            public required string XnDefinition { get; set; }

            [Option('i', "input", HelpText = "Input XML file", Required = true)]
            public required string Input { get; set; }

            [Option('o', "output", HelpText = "Output XML file", Required = true)]
            public required string Output { get; set; }

            [Option('v', "verbose", Required = false, HelpText = "Set output to verbose messages.")]
            public bool Verbose { get; set; }
        }
        static void Main(string[] args)
        {
              CommandLine.Parser.Default.ParseArguments<Options>(args)
                .WithParsed(RunOptions)
                .WithNotParsed(HandleParseError);
        }

        static void RunOptions(Options opts)
        {
            // Auto-discover operations via reflection
            BangOperation.RegisterAll();

            var rawSource = File.ReadAllText(opts.XnDefinition);
            var xnSource = XnParser.StripComments(rawSource);
            IEnumerable<Part> rules;
            try
            {
                rules = XnParser.Rules.Parse(xnSource);
            }
            catch (ParseException ex)
            {
                var lines = rawSource.Split('\n');
                int line = ex.Position?.Line ?? -1;
                int col = ex.Position?.Column ?? -1;
                bool showPosition = (line != -1) && (col != -1);

                if (showPosition)
                {
                    var msg = ex.Message;
                    var hint = (msg.Contains("expected }") && !msg.Contains("expected ';'"))
                        ? "Hint: a missing ';' terminator may be located just after this position"
                        : "";
                    Console.Error.WriteLine($"{opts.XnDefinition}({line},{col}): parse error: {msg}");
                    var srcLine = line <= lines.Length ? lines[line - 1].TrimEnd() : "";
                    var pointer = new string(' ', Math.Max(0, col - 1)) + "^";
                    Console.Error.WriteLine($"  {srcLine}");
                    Console.Error.WriteLine($"  {pointer}");
                    if (!string.IsNullOrEmpty(hint))
                    {
                        Console.Error.WriteLine($"\n{hint}");
                    }
                }
                else
                {
                    Console.Error.WriteLine($"{opts.XnDefinition}: parse error: {ex.Message}");
                }
                return;
            }
            var doc = XDocument.Load(opts.Input, LoadOptions.PreserveWhitespace);
            var encoding = XmlRoundtripWriter.DetectEncoding(File.ReadAllBytes(opts.Input));
            var sloc = new SourceLocation(opts.Input, encoding);
            try
            {
                foreach (var rule in rules.OfType<Rule>())
                    rule.Transform(doc, sloc);
            }
            catch (RequireException ex)
            {
                Console.Error.WriteLine($"{ex.SLoc.FilePath}({ex.SLoc.LineNumber}): require error: {ex.UserMessage}");
                return;
            }
            using var writer = XmlRoundtripWriter.Create(opts.Input, opts.Output);
            doc.WriteTo(writer);
            Console.WriteLine($"Applied \"{opts.XnDefinition}\" to \"{opts.Input}\" and saved result to \"{opts.Output}\"");
        }

        static void HandleParseError(IEnumerable<Error> errs) {}
    }
}