task 1 completed

Author: rofr

Twitter.Core/Class1.cs

@@ -0,0 +1,20 @@
+using System;
+
+namespace Twitter.Core
+{
+    public class Tweet
+    {
+        public readonly int Id;
+        public readonly string UserName;
+        public readonly string Message;
+        public readonly DateTime PostedAt;
+
+        public Tweet(int id, string userName, string message, DateTime postedAt)
+        {
+            Id = id;
+            UserName = userName;
+            Message = message;
+            PostedAt = postedAt;
+        }
+    }
+}

Twitter.Core/Tweet.cs

@@ -0,0 +1,77 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Twitter.Core
+{
+    public class Twitter
+    {
+        private int nextTweetId = 1;
+
+        /// <summary>
+        /// Users indexed by user name
+        /// </summary>
+        public IDictionary<string, User> UsersByName { get; private set; }
+
+        /// <summary>
+        /// Tweets ordered id.
+        /// </summary>
+        public IDictionary<int, Tweet> AllTweets { get; private set; }
+
+        public Twitter()
+        {
+            AllTweets = new SortedDictionary<int, Tweet>();
+            UsersByName = new SortedDictionary<string, User>();
+        }
+
+        public int PostTweet(string userName, string message, DateTime when)
+        {
+            EnsureUserExists(userName);
+            var tweet = new Tweet(nextTweetId++, userName, message, when);
+            AllTweets.Add(tweet.Id, tweet);
+            return tweet.Id;
+        }
+
+        public void Follow(string followerName, string followeeName)
+        {
+            if (UsersByName.TryGetValue(followerName, out var follower))
+            {
+                if (UsersByName.TryGetValue(followeeName, out var followee))
+                {
+                    follower.Followees.Add(followee);
+                    followee.Followers.Add(follower);
+                    return;
+                }
+                throw new ArgumentException("No such user: " + followeeName);
+            }
+            throw new ArgumentException("No such user: " + followerName);
+        }
+
+        public Tweet[] GetAllTweets(int skip = 0, int take = 20)
+        {
+            return AllTweets
+                .Values
+                .Skip(skip)
+                .Take(take)
+                .ToArray();
+        }
+
+        public Tweet[] GetUserTweets(string userName, int skip = 0, int take = 20)
+        {
+            if (UsersByName.TryGetValue(userName, out var user))
+            {
+                return user.Tweets.Skip(skip).Take(take).ToArray();
+            }
+            throw new ArgumentException("No such user: " + userName);
+        }
+
+        private void EnsureUserExists(string userName)
+        {
+            if (!UsersByName.ContainsKey(userName))
+            {
+                var user = new User(userName);
+                UsersByName.Add(userName, user);
+            }
+        }
+    }
+}

Twitter.Core/Twitter.cs

@@ -0,0 +1,34 @@
+using System.Collections.Generic;
+
+namespace Twitter.Core
+{
+    public class User
+    {
+        public readonly string Name;
+
+        /// <summary>
+        /// This users tweets
+        /// </summary>
+        public List<Tweet> Tweets { get; private set; }
+
+        /// <summary>
+        /// Users that follow this user
+        /// </summary>
+        /// <value>The followers.</value>
+        public List<User> Followers { get; private set; }
+
+        /// <summary>
+        /// Users this user follows
+        /// </summary>
+        public List<User> Followees { get; private set; }
+
+        public User(string name)
+        {
+            Name = name;
+            Tweets = new List<Tweet>();
+            Followees = new List<User>();
+            Followers = new List<User>();
+        }
+
+    }
+}