We want you to implement a simple text based chat based on Netty’s framework latest version. Chat is a channel based communication tool, so our fancy chat implementation should support multiple channels for users communications. There is one restriction though: a user can only join one channel at a time, when they join another they leave their current channel. Moreover, the same user can auth twice from different devices, and on both them they should be able to receive messages. ChatServer should handle the following commands:
● /login If the user doesn’t exists, create profile else login, after login join to last connected channel (use join logic, if client’s limit exceeded, keep connected, but without active channel).
● /join Try to join a channel (max 10 active clients per channel is needed). If client's limit exceeded - send error, otherwise join channel and send last N messages of activity.
● /leave Leave current channel.
● /disconnect Close connection to server.
● /list Send list of channels.
● /users Send list of unique users in current channel.
● Sends message to current channel Server must send a new message to all connected to this channel.
Requirements to the implementation:
● ChatHandler - main logic handler for chat/channel communications.
● InMemory storage with no persistence implemented, but extendable to it (interface + class implementation).
● Please pay extra attention to concurrency and thread safety.
● README.md with usage examples / commands description (can be a copy of this task assignment).
● Use Java/Kotlin for this test assessment.
● We should be able to check this server via a simple text based telnet command.
● MVP / Proof of Concept.
● We expect you to write an explanatory letter about your solution: common thoughts, used patterns, points of improvements or any other info you want to add to your solution but you have to cut out from implementation due to MVP/PoC restrictions.
./gradlew runApp architecture is quite extensible - to add new commands you need to add new classes and add them into the main service.
Same for external ports - specific repository implementation is easy to add.
I decided to store user and channel information in the channel attributes in this test, but overall for big chats such information
is stored on the server side.