import * as net from "net";

export interface IImapServerMessage {
  id: string;
  subject: string;
  sender: string;
  recipient: string;
  date: Date;
  body: string;
}

export interface IImapServerInbox {
  name: string;
  messages: IImapServerMessage[];
}

export interface IImapServerUser {
  username: string;
  password: string;
  inboxes: Map<string, IImapServerInbox>;
}

export class ImapServer {
  public users: Map<string, IImapServerUser>;
  private server: net.Server;

  constructor() {
    this.users = new Map();
    this.server = net.createServer(this.handleConnection.bind(this));
  }

  // Add a user for authentication
  public addUser(username: string, password: string): void {
    if (this.users.has(username)) {
      throw new Error(`User "${username}" already exists.`);
    }
    this.users.set(username, { username, password, inboxes: new Map() });
  }

  // Add an inbox for a user
  public createInbox(username: string, inboxName: string): void {
    const user = this.users.get(username);
    if (!user) {
      throw new Error(`User "${username}" does not exist.`);
    }
    if (user.inboxes.has(inboxName)) {
      throw new Error(`Inbox "${inboxName}" already exists for user "${username}".`);
    }
    user.inboxes.set(inboxName, { name: inboxName, messages: [] });
  }

  // Start the server
  public start(port: number): void {
    this.server.listen(port, () => {
      console.log(`IMAP Server started on port ${port}`);
    });
  }

  // Stop the server
  public stop(): void {
    this.server.close(() => {
      console.log("IMAP Server stopped.");
    });
  }

  // Handle a new client connection
  private handleConnection(socket: net.Socket): void {
    let currentUser: IImapServerUser | null = null;
    let selectedInbox: IImapServerInbox | null = null;

    socket.write("* OK IMAP4rev1 Service Ready\r\n");

    socket.on("data", (data) => {
      const command = data.toString().trim();
      console.log(`Received command: ${command}`);

      const [tag, keyword, ...args] = command.split(" ");
      let response = "";

      try {
        switch (keyword.toUpperCase()) {
          case "LOGIN": {
            const [username, password] = args;
            const user = this.users.get(username);
            if (user && user.password === password) {
              currentUser = user;
              response = `${tag} OK LOGIN completed`;
            } else {
              response = `${tag} NO LOGIN failed`;
            }
            break;
          }

          case "LIST": {
            if (!currentUser) {
              response = `${tag} NO Not authenticated`;
              break;
            }
            const inboxNames = Array.from(currentUser.inboxes.keys()).map((inbox) => `* LIST () "/" ${inbox}`);
            response = `${inboxNames.join("\r\n")}\r\n${tag} OK LIST completed`;
            break;
          }

          case "SELECT": {
            if (!currentUser) {
              response = `${tag} NO Not authenticated`;
              break;
            }
            const inboxName = args[0];
            const inbox = currentUser.inboxes.get(inboxName);
            if (inbox) {
              selectedInbox = inbox;
              response = `* FLAGS (\\Answered \\Flagged \\Deleted \\Seen \\Draft)\r\n* EXISTS ${inbox.messages.length}\r\n${tag} OK [READ-WRITE] SELECT completed`;
            } else {
              response = `${tag} NO SELECT failed: No such mailbox`;
            }
            break;
          }

          case "FETCH": {
            if (!selectedInbox) {
              response = `${tag} NO No mailbox selected`;
              break;
            }
            const [id] = args;
            const message = selectedInbox.messages.find((msg) => msg.id === id);
            if (message) {
              response = `* ${id} FETCH (BODY[TEXT] {${message.body.length}}\r\n${message.body}\r\n)\r\n${tag} OK FETCH completed`;
            } else {
              response = `${tag} NO FETCH failed: No such message`;
            }
            break;
          }

          case "LOGOUT": {
            response = `* BYE IMAP4rev1 Server logging out\r\n${tag} OK LOGOUT completed`;
            socket.write(response + "\r\n");
            socket.end();
            return;
          }

          default: {
            response = `${tag} BAD Unknown command`;
            break;
          }
        }
      } catch (error) {
        response = `${tag} BAD Error: ${error.message}`;
      }

      socket.write(response + "\r\n");
    });

    socket.on("close", () => {
      console.log("Client disconnected.");
    });

    socket.on("error", (err) => {
      console.error("Socket error:", err);
    });
  }
}