Coding sample #2 for DALI Lab application

ChatViewController.swift

//
//  ChatViewController.swift
//  Flash Chat
//
//  Created by Shreyas Agnihotri on 1/10/19.
//  Copyright (c) 2019 Shreyas Agnihotri. All rights reserved.
//

import UIKit
import Firebase
import ChameleonFramework

class ChatViewController: UIViewController, UITableViewDelegate, UITableViewDataSource, UITextFieldDelegate {
    
    // Global variables
    @IBOutlet var heightConstraint: NSLayoutConstraint!
    @IBOutlet var sendButton: UIButton!
    @IBOutlet var messageTextfield: UITextField!
    @IBOutlet var messageTableView: UITableView!
    
    var messageArray: [Message] = [Message]()   // List of all messages in chat
    var topButton = UIButton()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // Sets up delegates to fetch and send data
        messageTableView.delegate = self
        messageTableView.dataSource = self
        messageTextfield.delegate = self

        // Sets up table view cell design
        messageTableView.register(UINib(nibName: "MessageCell", bundle: nil) , forCellReuseIdentifier: "customMessageCell")
        
        let tapGesture = UITapGestureRecognizer(target: self, action: #selector (tableViewTapped))
        messageTableView.addGestureRecognizer(tapGesture)
        
        configureTableView()    // Sets table's display properties
        retrieveMessages()      // Fetches messages from Firebase
        
        messageTableView.separatorStyle = .none     // Removes lines between rows
    }
    
    
    // MARK: TableView Delegate Methods
    
    // Sets image, message text, and sender for a given message in the table
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        
        let cell = tableView.dequeueReusableCell(withIdentifier: "customMessageCell", for: indexPath) as! CustomMessageCell
        
        cell.messageBody.text = messageArray[indexPath.row].messageBody
        cell.senderUsername.text = messageArray[indexPath.row].sender
        cell.avatarImageView.image = UIImage(named: "egg")
        
        // Sets background to blue if message is from logged in user.
        if cell.senderUsername.text == Auth.auth().currentUser?.email! {
            cell.avatarImageView.backgroundColor = UIColor.flatMint()
            cell.messageBackground.backgroundColor = UIColor.flatSkyBlue()
        }
        
        // Sets background to grey if message is from another user.
        else {
            cell.avatarImageView.backgroundColor = UIColor.flatWatermelon()
            cell.messageBackground.backgroundColor = UIColor.flatGray()
        }
        
        return cell
    }
    
    // Sets number of rows in table to number of messages
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return messageArray.count
    }
    
    // Stops accepting message input when user clicks off of keyboard and textbox
    @objc func tableViewTapped() {
        messageTextfield.endEditing(true)
    }
    
    // Sets display properties of table
    func configureTableView() {
        messageTableView.rowHeight = UITableView.automaticDimension
        messageTableView.estimatedRowHeight = 120.0
    }
    
    
    // MARK: TextField Delegate Methods
    
    // Moves message content upwards to accomodate keyboard when user begins typing (animated)
    func textFieldDidBeginEditing(_ textField: UITextField) {
        
        UIView.animate(withDuration: 0.5) {
            self.heightConstraint.constant = 308    // Necessary height to fit keyboard & textbox
            self.view.layoutIfNeeded()
        }
    }
    
    // Moves message content downward once keyboard is dismissed (animated)
    func textFieldDidEndEditing(_ textField: UITextField) {
        
        UIView.animate(withDuration: 0.5) {
            self.heightConstraint.constant = 50     // Necessary height to fit textbox
            self.view.layoutIfNeeded()
        }
    }
    
    
    //MARK: Send & Recieve Messages from Firebase
    
    @IBAction func sendPressed(_ sender: AnyObject) {
        
        // Disables user's ability to compose and send messages until message is sent to Firebase
        messageTextfield.endEditing(true)
        messageTextfield.isEnabled = false
        sendButton.isEnabled = false
        
        // Fetches database of messages and creates dictionary representing message with [user, message]
        let messagesDB = Database.database().reference().child("Messages")
        let messageDictionary = ["Sender": Auth.auth().currentUser?.email,
                                 "MessageBody": messageTextfield.text!]
        
        // Adds sent message to database
        messagesDB.childByAutoId().setValue(messageDictionary) { (error, reference) in
            
            // Print statements for error debugging
            if error != nil {
                print(error!)
            }
            else {
                print("Message saved successfully!")
            }
            
            // Re-establishes user's ability to compose and send messages
            self.messageTextfield.isEnabled = true
            self.sendButton.isEnabled = true
            self.messageTextfield.text = ""
        }
    }
    
    // Fetches messages from Firebase and adds them to list of messages in chat
    func retrieveMessages() {
        
        let messageDB = Database.database().reference().child("Messages")       // Fetches database
        
        // Loops through children of database (dictionaries of messages)
        messageDB.observe(.childAdded) { (snapshot) in
            
            let snapshotValue = snapshot.value as! Dictionary<String, String>   // Unwraps snapshot as [user, message]
            let text = snapshotValue["MessageBody"]!
            let sender = snapshotValue["Sender"]!
            
            // Creates new message with data from current message dictionary
            let message = Message()
            message.messageBody = text
            message.sender = sender
            
            self.messageArray.append(message)
            
            // Updates table with new message
            self.configureTableView()
            self.messageTableView.reloadData()
            
            // Scrolls table to bottom-most message
            let iPath = NSIndexPath(row: self.messageTableView.numberOfRows(inSection: 0)-1,
                                    section: self.messageTableView.numberOfSections-1)
            self.messageTableView.scrollToRow(at: iPath as IndexPath,
                                              at: UITableView.ScrollPosition.bottom,
                                              animated: true)
        }
    }
    
    
    // MARK: Logout Method
    
    // Signs user out of Firebase and returns to sign-in screen
    @IBAction func logOutPressed(_ sender: AnyObject) {
        
        do {
            try Auth.auth().signOut()
            navigationController?.popToRootViewController(animated: true)
        }
        catch {
            print("error: there was a problem logging out")
        }
    }
}