using SharpChat.Auth;
using SharpChat.Bans;
using SharpChat.Configuration;
using SharpChat.SockChat.S2CPackets;

namespace SharpChat.C2SPacketHandlers {
    public class AuthC2SPacketHandler(
        AuthClient authClient,
        BansClient bansClient,
        Channel defaultChannel,
        CachedValue<int> maxMsgLength,
        CachedValue<int> maxConns
    ) : C2SPacketHandler {
        private readonly Channel DefaultChannel = defaultChannel ?? throw new ArgumentNullException(nameof(defaultChannel));
        private readonly CachedValue<int> MaxMessageLength = maxMsgLength ?? throw new ArgumentNullException(nameof(maxMsgLength));
        private readonly CachedValue<int> MaxConnections = maxConns ?? throw new ArgumentNullException(nameof(maxConns));

        public bool IsMatch(C2SPacketHandlerContext ctx) {
            return ctx.CheckPacketId("1");
        }

        public async Task Handle(C2SPacketHandlerContext ctx) {
            string[] args = ctx.SplitText(3);

            string? authMethod = args.ElementAtOrDefault(1);
            string? authToken = args.ElementAtOrDefault(2);

            if(string.IsNullOrWhiteSpace(authMethod) || string.IsNullOrWhiteSpace(authToken)) {
                await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.AuthInvalid));
                ctx.Connection.Dispose();
                return;
            }

            if(authMethod.All(c => c is >= '0' and <= '9') && authToken.Contains(':')) {
                string[] tokenParts = authToken.Split(':', 2);
                authMethod = tokenParts[0];
                authToken = tokenParts[1];
            }

            try {
                AuthResult authResult = await authClient.AuthVerifyAsync(
                    ctx.Connection.RemoteAddress,
                    authMethod,
                    authToken
                );

                BanInfo? banInfo = await bansClient.BanGetAsync(authResult.UserId, ctx.Connection.RemoteAddress);
                if(banInfo is not null) {
                    Logger.Write($"<{ctx.Connection.Id}> User is banned.");
                    await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.Banned, banInfo.IsPermanent ? DateTimeOffset.MaxValue : banInfo.ExpiresAt));
                    ctx.Connection.Dispose();
                    return;
                }

                await ctx.Chat.ContextAccess.WaitAsync();
                try {
                    User? user = ctx.Chat.Users.FirstOrDefault(u => u.UserId == authResult.UserId);

                    if(user == null)
                        user = new User(
                            authResult.UserId,
                            authResult.UserName ?? $"({authResult.UserId})",
                            authResult.UserColour,
                            authResult.UserRank,
                            authResult.UserPermissions
                        );
                    else
                        await ctx.Chat.UpdateUser(
                            user,
                            userName: authResult.UserName ?? $"({authResult.UserId})",
                            colour: authResult.UserColour,
                            rank: authResult.UserRank,
                            perms: authResult.UserPermissions
                        );

                    // Enforce a maximum amount of connections per user
                    if(ctx.Chat.Connections.Count(conn => conn.User == user) >= MaxConnections) {
                        await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.MaxSessions));
                        ctx.Connection.Dispose();
                        return;
                    }

                    ctx.Connection.BumpPing();
                    ctx.Connection.User = user;
                    await ctx.Connection.Send(new CommandResponseS2CPacket(0, LCR.WELCOME, false, $"Welcome to Flashii Chat, {user.UserName}!"));

                    if(File.Exists("welcome.txt")) {
                        IEnumerable<string> lines = File.ReadAllLines("welcome.txt").Where(x => !string.IsNullOrWhiteSpace(x));
                        string? line = lines.ElementAtOrDefault(RNG.Next(lines.Count()));

                        if(!string.IsNullOrWhiteSpace(line))
                            await ctx.Connection.Send(new CommandResponseS2CPacket(0, LCR.WELCOME, false, line));
                    }

                    await ctx.Chat.HandleJoin(user, DefaultChannel, ctx.Connection, MaxMessageLength);
                } finally {
                    ctx.Chat.ContextAccess.Release();
                }
            } catch(AuthFailedException ex) {
                Logger.Write($"<{ctx.Connection.Id}> Failed to authenticate: {ex}");
                await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.AuthInvalid));
                ctx.Connection.Dispose();
                throw;
            } catch(Exception ex) {
                Logger.Write($"<{ctx.Connection.Id}> Failed to authenticate: {ex}");
                await ctx.Connection.Send(new AuthFailS2CPacket(AuthFailS2CPacket.Reason.Exception));
                ctx.Connection.Dispose();
                throw;
            }
        }
    }
}