/*
TShock, a server mod for Terraria
Copyright (C) 2011-2015 Nyx Studios (fka. The TShock Team)

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.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

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.Linq;
using System.Net;
using HttpServer;
using TShockAPI;
using TShockAPI.DB;

namespace Rests
{
	public class SecureRest : Rest
	{
		public struct TokenData
		{
			public static readonly TokenData None = default(TokenData);

			public string Username { get; set; }
			public string UserGroupName { get; set; }
		}

		public Dictionary<string, TokenData> Tokens { get; protected set; }
		public Dictionary<string, TokenData> AppTokens { get; protected set; }

		public SecureRest(IPAddress ip, int port)
			: base(ip, port)
		{
			Tokens = new Dictionary<string, TokenData>();
			AppTokens = new Dictionary<string, TokenData>();
			
			Register(new RestCommand("/v2/token/create", NewTokenV2) { DoLog = false });
			Register(new SecureRestCommand("/token/destroy/{token}", DestroyToken));
			Register(new SecureRestCommand("/v3/token/destroy/all", DestroyAllTokens, RestPermissions.restmanage));

			foreach (KeyValuePair<string, TokenData> t in TShockAPI.TShock.RESTStartupTokens)
			{
				AppTokens.Add(t.Key, t.Value);
			}

			foreach (KeyValuePair<string, TokenData> t in TShock.Config.ApplicationRestTokens)
			{
				AppTokens.Add(t.Key, t.Value);
			}

			// TODO: Get rid of this when the old REST permission model is removed.
			if (TShock.Config.RestApiEnabled && !TShock.Config.RestUseNewPermissionModel)
			{
				string warningMessage = string.Concat(
					"You're using the old REST permission model which is highly vulnerable in matter of security. ",
					"The old model will be removed with the next maintenance release of TShock. In order to switch to the new model, ",
					"change the config setting \"RestUseNewPermissionModel\" to true."
				);
				TShock.Log.Warn(warningMessage);
				Console.ForegroundColor = ConsoleColor.Red;
				Console.WriteLine(warningMessage);
				Console.ForegroundColor = ConsoleColor.Gray;
			}
			else if (TShock.Config.RestApiEnabled)
			{
				string warningMessage = string.Concat(
					"You're using the new more secure REST permission model which can lead to compatibility problems ",
					"with existing REST services. If compatibility problems occur, you can switch back to the unsecure permission ",
					"model by changing the config setting \"RestUseNewPermissionModel\" to false, which is not recommended."
				);
				TShock.Log.ConsoleInfo(warningMessage);
			}
		}

		private void AddTokenToBucket(string ip)
		{
			if (tokenBucket.ContainsKey(ip))
			{
				tokenBucket[ip] += 1;
			}
			else
			{
				tokenBucket.Add(ip, 1);
			}
		}

		private object DestroyToken(RestRequestArgs args)
		{
			var token = args.Verbs["token"];
			try
			{
				Tokens.Remove(token);
			}
			catch (Exception)
			{
				return new RestObject("400")
				{ Error = "The specified token queued for destruction failed to be deleted." };
			}
			return new RestObject()
			{ Response = "Requested token was successfully destroyed." };
		}

		private object DestroyAllTokens(RestRequestArgs args)
		{
			Tokens.Clear();

			return new RestObject()
			{ Response = "All tokens were successfully destroyed." };
		}

		private object NewTokenV2(RestRequestArgs args)
		{
			var user = args.Parameters["username"];
			var pass = args.Parameters["password"];
			var context = args.Context;

			return this.NewTokenInternal(user, pass, context);
		}

		private RestObject NewTokenInternal(string username, string password, IHttpContext context)
		{
			int tokens = 0;
			if (tokenBucket.TryGetValue(context.RemoteEndPoint.Address.ToString(), out tokens))
			{
				if (tokens >= Math.Max(TShock.Config.RESTMaximumRequestsPerInterval, 5))
				{
					TShock.Log.ConsoleError("A REST login from {0} was blocked as it currently has {1} tokens", context.RemoteEndPoint.Address.ToString(), tokens);
					tokenBucket[context.RemoteEndPoint.Address.ToString()] += 1; // Tokens over limit, increment by one and reject request
					return new RestObject("403")
					{
						Error = "Username or password may be incorrect or this account may not have sufficient privileges."
					};
				}
				if (!TShock.Config.RESTLimitOnlyFailedLoginRequests)
					tokenBucket[context.RemoteEndPoint.Address.ToString()] += 1; // Tokens under limit, increment by one and process request
			}
			else
			{
				if (!TShock.Config.RESTLimitOnlyFailedLoginRequests)
					tokenBucket.Add(context.RemoteEndPoint.Address.ToString(), 1); // First time request, set to one and process request
			}

			User userAccount = TShock.Users.GetUserByName(username);
			if (userAccount == null)
			{
				AddTokenToBucket(context.RemoteEndPoint.Address.ToString());
				return new RestObject("403") { Error = "Username or password may be incorrect or this account may not have sufficient privileges." };
			}

			if (!userAccount.VerifyPassword(password))
			{
				AddTokenToBucket(context.RemoteEndPoint.Address.ToString());
				return new RestObject("403") { Error = "Username or password may be incorrect or this account may not have sufficient privileges." };
			}

			Group userGroup = TShock.Utils.GetGroup(userAccount.Group);
			if (!userGroup.HasPermission(RestPermissions.restapi) && userAccount.Group != "superadmin")
			{
				AddTokenToBucket(context.RemoteEndPoint.Address.ToString());
				return new RestObject("403")
				{ Error = "Username or password may be incorrect or this account may not have sufficient privileges." };
			}

			string tokenHash;
			var rand = new Random();
			var randbytes = new byte[32];
			do
			{
				rand.NextBytes(randbytes);
				tokenHash = randbytes.Aggregate("", (s, b) => s + b.ToString("X2"));
			} while (Tokens.ContainsKey(tokenHash));

			Tokens.Add(tokenHash, new TokenData { Username = userAccount.Name, UserGroupName = userGroup.Name });

			AddTokenToBucket(context.RemoteEndPoint.Address.ToString());

			RestObject response = new RestObject() { Response = "Successful login" };
			response["token"] = tokenHash;
			return response;
		}

		protected override object ExecuteCommand(RestCommand cmd, RestVerbs verbs, IParameterCollection parms, IRequest request, IHttpContext context)
		{
			if (!cmd.RequiresToken)
				return base.ExecuteCommand(cmd, verbs, parms, request, context);

			var token = parms["token"];
			if (token == null)
				return new RestObject("401")
				{ Error = "Not authorized. The specified API endpoint requires a token." };

			SecureRestCommand secureCmd = (SecureRestCommand)cmd;
			TokenData tokenData;
			if (!Tokens.TryGetValue(token, out tokenData) && !AppTokens.TryGetValue(token, out tokenData))
				return new RestObject("403")
				{ Error = "Not authorized. The specified API endpoint requires a token, but the provided token was not valid." };

			// TODO: Get rid of this when the old REST permission model is removed.
			if (TShock.Config.RestUseNewPermissionModel)
			{
				Group userGroup = TShock.Groups.GetGroupByName(tokenData.UserGroupName);
				if (userGroup == null)
				{
					Tokens.Remove(token);

					return new RestObject("403")
					{ Error = "Not authorized. The provided token became invalid due to group changes, please create a new token." };
				}

				if (secureCmd.Permissions.Length > 0 && secureCmd.Permissions.All(perm => !userGroup.HasPermission(perm)))
				{
					return new RestObject("403")
					{ Error = string.Format("Not authorized. User \"{0}\" has no access to use the specified API endpoint.", tokenData.Username) };
				}
			}

			object result = secureCmd.Execute(verbs, parms, tokenData, request, context);
			if (cmd.DoLog && TShock.Config.LogRest)
				TShock.Utils.SendLogs(string.Format(
					"\"{0}\" requested REST endpoint: {1}", tokenData.Username, this.BuildRequestUri(cmd, verbs, parms, false)),
					Color.PaleVioletRed);

			return result;
		}
	}
}