TwitterPlugin.cs

using Microsoft.EntityFrameworkCore;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;
using System;
using System.ComponentModel.DataAnnotations.Schema;

namespace DNWS
{
    class Following
    {
        public int FollowingId { get; set; }
        public string Name { get; set; }
    }
    class User
    {
        public int UserId { get; set; }
        public string Name { get; set; }
        public string Password { get; set; }
        public List<Following> Following { get; set; } // Bug in SQLite implemention in EF7, no FK!
    }
    class Tweet
    {
        public int TweetId { get; set; }
        public string Message { get; set; }
        public string User { get; set; } // Bug in SQLite implemention in EF7, no FK!

        public DateTime DateCreated { get; set; }
    }
    // Ref: https://docs.microsoft.com/en-us/ef/core/get-started/netcore/new-db-sqlite
    class TweetContext : DbContext
    {
        public DbSet<Tweet> Tweets { get; set; }
        public DbSet<User> Users { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            optionsBuilder.UseSqlite("Data Source=tweet.db");
        }
    }

    class Twitter
    {
        User user;
        public Twitter(string name)
        {
            if (name == null || name == "")
            {
                throw new Exception("User name is required");
            }
            user = GetUser(name);
        }
        public string GetUsername()
        {
            return user.Name;
        }
        public static void RemoveUser(){
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            using(var newContext = new TweetContext){
                list<User> userlist = newContext.Users.Where(b => b.Name.Equals(user)).ToList();
                if(userlist.Count <= 0){
                    throw new Exception("User not found");
                }
                newContext.Users.Remove(userlist[0]);
                newContext.SaveChanges();
            }
        }
        public void RemoveFollowing(string followingName)
        {
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            if (followingName == null)
            {
                throw new Exception("Following not found");
            }
            using (var context = new TweetContext())
            {
                Following following = new Following();
                following.Name = followingName;
                user.Following.Remove(following);
                context.Users.Update(user);
                context.SaveChanges();
            }
        }
        public void AddFollowing(string followingName)
        {
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            if (followingName == null)
            {
                throw new Exception("Following not found");
            }
            using (var context = new TweetContext())
            {
                if (user.Following == null)
                {
                    user.Following = new List<Following>();
                }
                List<Following> followings = user.Following.Where(b => b.Name == followingName).ToList();
                if (followings.Count > 0) return;
                Following following = new Following();
                following.Name = followingName;
                user.Following.Add(following);
                context.Users.Update(user);
                context.SaveChanges();
            }
        }
        public List<Tweet> GetTimeline(User aUser)
        {
            if (aUser == null)
            {
                throw new Exception("User is not set");
            }
            List<Tweet> timeline;
            using (var context = new TweetContext())
            {
                timeline = context.Tweets.Where(b => b.User.Equals(aUser.Name)).OrderBy(b => b.DateCreated).ToList();
            }
            return timeline;
        }
        public List<Tweet> GetUserTimeline()
        {
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            return GetTimeline(user);
        }

        public List<Tweet> GetFollowingTimeline()
        {
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            List<Tweet> timeline = new List<Tweet>();
            using (var context = new TweetContext())
            {
                List<Following> followings = user.Following;
                if (followings == null || followings.Count == 0)
                {
                    return null;
                }
                foreach (Following following in followings)
                {
                    User followingUser = GetUser(following.Name);
                    timeline.AddRange(GetTimeline(followingUser));
                }
            }
            timeline = timeline.OrderBy(b => b.DateCreated).ToList();
            return timeline;
        }

        public List<Following> GetFollowing(){
            if(user == null){
                throw new Exception("User is not set");
            }
            using (var newContext = new TweetContext()){
                List<Following> following = user.Following;
                if( following == null || following.Count == 0){
                    return null;
                }
                return following;
            } 
        }//taught by 600611001

        public void PostTweet(string message)
        {
            if (user == null)
            {
                throw new Exception("User is not set");
            }
            Tweet tweet = new Tweet();
            tweet.User = user.Name;
            tweet.Message = message;
            tweet.DateCreated = DateTime.Now;
            using (var context = new TweetContext())
            {
                context.Tweets.Add(tweet);
                context.SaveChanges();
            }
        }
        public static void AddUser(string name, string password)
        {
            User user = new User();
            user.Name = name;
            user.Password = password;
            using (var context = new TweetContext())
            {
                List<User> userlist = context.Users.Where(b => b.Name.Equals(name)).ToList();
                if (userlist.Count > 0)
                {
                    throw new Exception("User already exists");
                }
                context.Users.Add(user);
                context.SaveChanges();
            }
        }

        public static bool IsValidUser(string name, string password)
        {
            using (var context = new TweetContext())
            {
                List<User> userlist = context.Users.Where(b => b.Name.Equals(name) && b.Password.Equals(password)).ToList();
                if (userlist.Count == 1)
                {
                    return true;
                }
            }
            return false;
        }

        private User GetUser(string name)
        {
            using (var context = new TweetContext())
            {
                try
                {
                    List<User> users = context.Users.Where(b => b.Name.Equals(name)).Include(b => b.Following).ToList();
                    return users[0];
                }
                catch (Exception)
                {
                    return null;
                }
            }
        }

    }
    public class TwitterPlugin : IPlugin
    {
        public HTTPResponse PostProcessing(HTTPResponse response)
        {
            throw new NotImplementedException();
        }

        public void PreProcessing(HTTPRequest request)
        {
            throw new NotImplementedException();
        }

        private StringBuilder GenTimeline(Twitter twitter, StringBuilder sb)
        {
            sb.Append("Say something<br />");
            sb.Append("<form method=\"post\">");
            sb.Append("<input type=\"text\" name=\"message\"></input>");
            sb.Append("<input type=\"submit\" name=\"action\" value=\"tweet\" /> <br />");
            sb.Append("</form>");
            sb.Append("Follow someone<br />");
            sb.Append("<form method=\"post\">");
            sb.Append("<input type=\"text\" name=\"following\"></input>");
            sb.Append("<input type=\"submit\" name=\"action\" value=\"following\" /> <br />");
            sb.Append("</form>");
            sb.Append(String.Format("<h3><b>{0}</b>'s timeline</h3><br />", twitter.GetUsername()));
            List<Tweet> tweets = twitter.GetUserTimeline();
            foreach (Tweet tweet in tweets)
            {
                sb.Append("[" + tweet.DateCreated + "]" + tweet.User + ":" + tweet.Message + "<br />");
            }
            sb.Append("<br /><br />");
            sb.Append("<h3>Following timeline</h3><br />");
            tweets = twitter.GetFollowingTimeline();
            if (tweets == null)
            {
                sb.Append("Your following list is empty, follow someone!");
            }
            else
            {
                foreach (Tweet tweet in tweets)
                {
                    sb.Append("[" + tweet.DateCreated + "] " + tweet.User + ":" + tweet.Message + "<br />");
                }
            }
            return sb;
        }

        protected StringBuilder GenLoginPage(StringBuilder sb)
        {
            sb.Append("<h2>Login</h2>");
            sb.Append("<form method=\"get\">");
            sb.Append("Username: <input type=\"text\" name=\"user\" value=\"\" /> <br />");
            sb.Append("Password: <input type=\"password\" name=\"password\" value=\"\" /> <br />");
            sb.Append("<input type=\"submit\" name=\"action\" value=\"login\" /> <br />");
            sb.Append("</form>");
            sb.Append("<br /><br /><br />");
            sb.Append("<h2>New user</h2>");
            sb.Append("<form method=\"get\">");
            sb.Append("Username: <input type=\"text\" name=\"user\" value=\"\" /> <br />");
            sb.Append("Password: <input type=\"password\" name=\"password\" value=\"\" /> <br />");
            sb.Append("<input type=\"submit\" name=\"action\" value=\"newuser\" /> <br />");
            sb.Append("</form>");
            return sb;
        }
        public virtual HTTPResponse GetResponse(HTTPRequest request)//taught by 600611001
        {
            HTTPResponse response = new HTTPResponse(200);
            StringBuilder sb = new StringBuilder();
            string user = request.getRequestByKey("user");
            string password = request.getRequestByKey("password");
            string action = request.getRequestByKey("action");
            string following = request.getRequestByKey("following");
            string message = request.getRequestByKey("message");
            if (user == null) // no user? show login screen
            {
                sb.Append("<h1>Twitter</h1>");
                sb = GenLoginPage(sb);
            }
            else
            {
                if (action == null) // No action? go to homepage
                {
                    try
                    {
                        Twitter twitter = new Twitter(user);
                        sb.Append(String.Format("<h1>{0}'s Twitter</h1>", user));
                        sb = GenTimeline(twitter, sb);
                    }
                    catch (Exception ex)
                    {
                        sb.Append(String.Format("Error [{0}], please go back to <a href=\"/twitter\">login page</a> to try again", ex.Message));
                    }
                }
                else
                {
                    if (action.Equals("newuser"))
                    {
                        if (user != null && password != null && user != "" && password != "")
                        {
                            try
                            {
                                Twitter.AddUser(user, password);
                                sb.Append("User added successfully, please go back to <a href=\"/twitter\">login page</a> to login");
                            }
                            catch (Exception ex)
                            {
                                sb.Append(String.Format("Error adding user with error [{0}], please go back to <a href=\"/twitter\">login page</a> to try again", ex.Message));
                            }
                        }
                    }
                    else if (action.Equals("login"))
                    {
                        if (user != null && password != null && user != "" && password != "")
                        {
                            if (Twitter.IsValidUser(user, password))
                            {
                                sb.Append(String.Format("Welcome {0}, please go back to <a href=\"/twitter?user={0}\">tweet page</a> to begin", user));
                            }
                            else
                            {
                                sb.Append("Error login, please go back to <a href=\"/twitter\">login page</a> to try again");
                            }
                        }
                    }
                    else
                    {
                        Twitter twitter = new Twitter(user);
                        sb.Append(String.Format("<h1>{0}'s Twitter</h1>", user));
                        if (action.Equals("following"))
                        {
                            try
                            {
                                twitter.AddFollowing(following);
                                sb = GenTimeline(twitter, sb);
                            }
                            catch (Exception ex)
                            {
                                sb.Append(String.Format("Error [{0}], please go back to <a href=\"/twitter\">login page</a> to try again", ex.Message));
                            }
                        }
                        else if (action.Equals("tweet"))
                        {
                            try
                            {
                                twitter.PostTweet(message);
                                sb = GenTimeline(twitter, sb);
                            }
                            catch (Exception ex)
                            {
                                Console.WriteLine(ex.ToString());
                                sb.Append(String.Format("Error [{0}], please go back to <a href=\"/twitter\">login page</a> to try again", ex.Message));
                            }
                        }
                    }
                }
            }
            response.body = Encoding.UTF8.GetBytes(sb.ToString());
            return response;
        }
    }
}