using SharpChat.SockChat.S2CPackets;
using System.Globalization;
using System.Text;

namespace SharpChat.ClientCommands;

public class NickClientCommand : ClientCommand {
    private const int MAX_GRAPHEMES = 16;
    private const int MAX_BYTES = MAX_GRAPHEMES * 10;

    public bool IsMatch(ClientCommandContext ctx) {
        return ctx.NameEquals("nick");
    }

    public async Task Dispatch(ClientCommandContext ctx) {
        long msgId = ctx.Chat.RandomSnowflake.Next();
        bool setOthersNick = ctx.User.Can(UserPermissions.SetOthersNickname);

        if(!setOthersNick && !ctx.User.Can(UserPermissions.SetOwnNickname)) {
            await ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.COMMAND_NOT_ALLOWED, true, $"/{ctx.Name}"));
            return;
        }

        User? targetUser = null;
        int offset = 0;

        if(setOthersNick && long.TryParse(ctx.Args.FirstOrDefault(), out long targetUserId) && targetUserId > 0) {
            targetUser = ctx.Chat.Users.FirstOrDefault(u => u.UserId == targetUserId.ToString());
            ++offset;
        }

        targetUser ??= ctx.User;

        if(ctx.Args.Length < offset) {
            await ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.COMMAND_FORMAT_ERROR));
            return;
        }

        string nickStr = string.Join('_', ctx.Args.Skip(offset))
            .Replace("\n", string.Empty).Replace("\r", string.Empty)
            .Replace("\f", string.Empty).Replace("\t", string.Empty)
            .Replace(' ', '_').Trim();

        if(nickStr == targetUser.UserName)
            nickStr = string.Empty;
        else if(string.IsNullOrEmpty(nickStr))
            nickStr = string.Empty;
        else {
            StringInfo nsi = new(nickStr);
            if(Encoding.UTF8.GetByteCount(nickStr) > MAX_BYTES
                || nsi.LengthInTextElements > MAX_GRAPHEMES)
                nickStr = nsi.SubstringByTextElements(0, Math.Min(nsi.LengthInTextElements, MAX_GRAPHEMES)).Trim();
        }

        if(!string.IsNullOrWhiteSpace(nickStr) && ctx.Chat.Users.Any(u => u.NameEquals(nickStr))) {
            await ctx.Chat.SendTo(ctx.User, new CommandResponseS2CPacket(msgId, LCR.NAME_IN_USE, true, nickStr));
            return;
        }

        string? previousName = targetUser.UserId == ctx.User.UserId ? (targetUser.NickName ?? targetUser.UserName) : null;
        await ctx.Chat.UpdateUser(targetUser, nickName: nickStr, silent: previousName == null);
    }
}