using System;
using System.IO;
using Newtonsoft.Json;
using Newtonsoft.Json.Linq;

namespace Penumbra.GameData.Util
{
    public readonly struct GamePath : IComparable
    {
        public const int MaxGamePathLength = 256;

        private readonly string _path;

        private GamePath( string path, bool _ )
            => _path = path;

        public GamePath( string? path )
        {
            if( path != null && path.Length < MaxGamePathLength )
            {
                _path = Lower( Trim( ReplaceSlash( path ) ) );
            }
            else
            {
                _path = "";
            }
        }

        public GamePath( FileInfo file, DirectoryInfo baseDir )
            => _path = CheckPre( file, baseDir ) ? Lower( Trim( ReplaceSlash( Substring( file, baseDir ) ) ) ) : "";

        private static bool CheckPre( FileInfo file, DirectoryInfo baseDir )
            => file.FullName.StartsWith( baseDir.FullName ) && file.FullName.Length < MaxGamePathLength;

        private static string Substring( FileInfo file, DirectoryInfo baseDir )
            => file.FullName.Substring( baseDir.FullName.Length );

        private static string ReplaceSlash( string path )
            => path.Replace( '\\', '/' );

        private static string Trim( string path )
            => path.TrimStart( '/' );

        private static string Lower( string path )
            => path.ToLowerInvariant();

        public static GamePath GenerateUnchecked( string path )
            => new( path, true );

        public static GamePath GenerateUncheckedLower( string path )
            => new( Lower( path ), true );

        public static implicit operator string( GamePath gamePath )
            => gamePath._path;

        public static explicit operator GamePath( string gamePath )
            => new( gamePath );

        public bool Empty
            => _path.Length == 0;

        public string Filename()
        {
            var idx = _path.LastIndexOf( "/", StringComparison.Ordinal );
            return idx == -1 ? _path : idx == _path.Length - 1 ? "" : _path.Substring( idx + 1 );
        }

        public int CompareTo( object? rhs )
        {
            return rhs switch
            {
                string path   => string.Compare( _path, path, StringComparison.InvariantCulture ),
                GamePath path => string.Compare( _path, path._path, StringComparison.InvariantCulture ),
                _             => -1,
            };
        }

        public override string ToString()
            => _path;
    }

    public class GamePathConverter : JsonConverter
    {
        public override bool CanConvert( Type objectType )
            => objectType == typeof( GamePath );

        public override object ReadJson( JsonReader reader, Type objectType, object? existingValue, JsonSerializer serializer )
        {
            var token = JToken.Load( reader );
            return token.ToObject< GamePath >();
        }

        public override bool CanWrite
            => true;

        public override void WriteJson( JsonWriter writer, object? value, JsonSerializer serializer )
        {
            if( value != null )
            {
                var v = ( GamePath )value;
                serializer.Serialize( writer, v.ToString() );
            }
        }
    }
}