/*************************************************************************
 * ModernUO                                                              *
 * Copyright 2019-2024 - ModernUO Development Team                       *
 * Email: hi@modernuo.com                                                *
 * File: Commands.cs                                                     *
 *                                                                       *
 * This program is free software: you can redistribute it and/or modify  *
 * it under the terms of the GNU General Public License as published by  *
 * the Free Software Foundation, either version 3 of the License, or     *
 * (at your option) any later version.                                   *
 *                                                                       *
 * You should have received a copy of the GNU General Public License     *
 * along with this program.  If not, see <http://www.gnu.org/licenses/>. *
 *************************************************************************/

using System;
using System.Collections.Generic;
using System.Reflection;
using System.Runtime.InteropServices;
using Server.Logging;

namespace Server;

public delegate void CommandEventHandler(CommandEventArgs e);

public class CommandEventArgs
{
    public CommandEventArgs(Mobile mobile, string command, string argString, string[] arguments)
    {
        Mobile = mobile;
        Command = command;
        ArgString = argString;
        Arguments = arguments;
    }

    public Mobile Mobile { get; }

    public string Command { get; }

    public string ArgString { get; }

    public string[] Arguments { get; }

    public int Length => Arguments.Length;

    public string GetString(int index) => index < 0 || index >= Arguments.Length ? "" : Arguments[index];

    public int GetInt32(int index) => index < 0 || index >= Arguments.Length ? 0 : Utility.ToInt32(Arguments[index]);

    public uint GetUInt32(int index) =>
        index < 0 || index >= Arguments.Length ? 0 : Utility.ToUInt32(Arguments[index]);

    public bool GetBoolean(int index) => index >= 0 && index < Arguments.Length && Utility.ToBoolean(Arguments[index]);

    public double GetDouble(int index) =>
        index < 0 || index >= Arguments.Length ? 0.0 : Utility.ToDouble(Arguments[index]);

    public TimeSpan GetTimeSpan(int index) =>
        index < 0 || index >= Arguments.Length ? TimeSpan.Zero : Utility.ToTimeSpan(Arguments[index]);
}

public static partial class EventSink
{
    public static event Action<CommandEventArgs> Command;
    public static void InvokeCommand(CommandEventArgs e) => Command?.Invoke(e);
}

public class CommandEntry : IComparable<CommandEntry>
{
    public CommandEntry(string command, CommandEventHandler handler, AccessLevel accessLevel)
    {
        Command = command;
        Handler = handler;
        AccessLevel = accessLevel;
    }

    public string Command { get; }

    public CommandEventHandler Handler { get; }

    public AccessLevel AccessLevel { get; }

    public int CompareTo(CommandEntry e) => string.CompareOrdinal(Command, e?.Command);

    public static List<CommandEntry> GetList()
    {
        var commands = new List<CommandEntry>(CommandSystem.Entries.Values);

        commands.Sort();
        commands.Reverse();

        for (var i = 0; i < commands.Count; ++i)
        {
            var e = commands[i];

            for (var j = i + 1; j < commands.Count; ++j)
            {
                var c = commands[j];

                if (e.Handler.Method == c.Handler.Method)
                {
                    commands.RemoveAt(j);
                    --j;
                }
            }
        }

        return commands;
    }
}

public record CommandInfo(AccessLevel AccessLevel, string Name, string[] Aliases, string Usage, string[] Modifiers, string Description);

public class CommandInfoSorter : IComparer<CommandInfo>
{
    public int Compare(CommandInfo a, CommandInfo b)
    {
        if (a == null && b == null)
        {
            return 0;
        }

        var v = b?.AccessLevel.CompareTo(a?.AccessLevel) ?? 1;

        return v != 0 ? v : string.CompareOrdinal(a?.Name, b?.Name);
    }
}

public static class CommandSystem
{
    private static readonly ILogger logger = LogFactory.GetLogger(typeof(CommandSystem));

    public static string Prefix { get; set; } = "[";

    public static Dictionary<string, CommandEntry> Entries { get; } = new(StringComparer.OrdinalIgnoreCase);

    public static AccessLevel BadCommandIgnoreLevel { get; set; } = AccessLevel.Player;

    public static string[] Split(string value)
    {
        var array = value.ToCharArray();
        var list = new List<string>();

        var start = 0;

        while (start < array.Length)
        {
            var c = array[start];

            if (c == '"')
            {
                ++start;
                var end = start;

                while (end < array.Length)
                {
                    if (array[end] != '"' || array[end - 1] == '\\')
                    {
                        ++end;
                    }
                    else
                    {
                        break;
                    }
                }

                list.Add(value.Substring(start, end - start));

                start = end + 2;
            }
            else if (c != ' ')
            {
                var end = start;

                while (end < array.Length)
                {
                    if (array[end] != ' ')
                    {
                        ++end;
                    }
                    else
                    {
                        break;
                    }
                }

                list.Add(value.Substring(start, end - start));

                start = end + 1;
            }
            else
            {
                ++start;
            }
        }

        return list.ToArray();
    }

    public static void Register(string command, AccessLevel access, CommandEventHandler handler)
    {
        DoRegister(command, access, handler);

        var mi = handler.Method;
        var aliasesAttr = mi.GetCustomAttribute(typeof(AliasesAttribute), false) as AliasesAttribute;
        var aliases = aliasesAttr?.Aliases;

        if (aliases == null)
        {
            return;
        }

        foreach (var alias in aliases)
        {
            DoRegister(alias, access, handler);
        }
    }

    private static void DoRegister(string command, AccessLevel accessLevel, CommandEventHandler handler)
    {
        ref var commandEntry = ref CollectionsMarshal.GetValueRefOrAddDefault(Entries, command, out var exists);
        if (exists)
        {
            if (commandEntry.AccessLevel == accessLevel && commandEntry.Handler == handler)
            {
                return;
            }

            logger.Warning("Command {Command} already registered to {Handler}.", command, commandEntry.Handler.Method.Name);
            return;
        }

        commandEntry = new CommandEntry(command, handler, accessLevel);
    }

    public static bool Handle(Mobile from, string text, MessageType type = MessageType.Regular)
    {
        if (!text.StartsWithOrdinal(Prefix) && type != MessageType.Command)
        {
            return false;
        }

        if (type != MessageType.Command)
        {
            text = text[Prefix.Length..];
        }

        var indexOf = text.IndexOfOrdinal(' ');

        string command;
        string[] args;
        string argString;

        if (indexOf >= 0)
        {
            argString = text[(indexOf + 1)..];

            command = text[..indexOf];
            args = Split(argString);
        }
        else
        {
            argString = "";
            command = text.ToLower();
            args = Array.Empty<string>();
        }

        Entries.TryGetValue(command, out var entry);

        if (entry != null)
        {
            if (from.AccessLevel >= entry.AccessLevel)
            {
                if (entry.Handler != null)
                {
                    var e = new CommandEventArgs(from, command, argString, args);
                    entry.Handler(e);
                    EventSink.InvokeCommand(e);
                }
            }
            else
            {
                if (from.AccessLevel <= BadCommandIgnoreLevel)
                {
                    return false;
                }

                from.SendMessage("You do not have access to that command.");
            }
        }
        else
        {
            if (from.AccessLevel <= BadCommandIgnoreLevel)
            {
                return false;
            }

            from.SendMessage("That is not a valid command.");
        }

        return true;
    }
}