ViewController.swift

//
//  ViewController.swift
//  ExpandableTextViewDemo
//
//  Created by Abhishek Thapliyal on 20/07/20.
//  Copyright © 2020 Abhishek Thapliyal. All rights reserved.
//

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var placeHolderLabel: UILabel!
    @IBOutlet weak var commentTextView: UITextView!
    @IBOutlet weak var bottomConstraint: NSLayoutConstraint!
    @IBOutlet weak var commentConstraint: NSLayoutConstraint!
    
    private let maxHeight: CGFloat = 100
    private let minHeight: CGFloat = 50
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.setupInitials()
    }
    
    private func setupInitials() {
        self.setupKeyboardNotifications()
        self.setupGesture()
        self.setupTextView()
    }
    
    @IBAction func sendCommentAction(_ sender: Any) {
        self.handleSubmitComment()
    }
    
    private func handleSubmitComment() {
        guard let text = self.commentTextView.text else { return }
        let comment = text.trimmingCharacters(in: .whitespacesAndNewlines)
        if comment.isEmpty { return }
        self.commentConstraint.constant = self.minHeight
        UIView.animate(withDuration: 0.1, animations: {
            self.view.layoutIfNeeded()
        }) { _ in
            self.commentTextView.text = nil
            self.commentTextView.resignFirstResponder()
        }
    }
    
}

extension ViewController {
    
    private func setupKeyboardNotifications() {
        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillShow(_:)),
                                               name: UIResponder.keyboardWillShowNotification,
                                               object: nil)

        NotificationCenter.default.addObserver(self,
                                               selector: #selector(keyboardWillHide(_:)),
                                               name: UIResponder.keyboardWillHideNotification,
                                               object: nil)
    }
    
    @objc
    private func keyboardWillShow(_ sender: Notification) {
        guard let info = sender.userInfo,
            let frame = (info[UIResponder.keyboardFrameEndUserInfoKey] as? NSValue)?.cgRectValue else {
                return
        }
                
        self.bottomConstraint.constant = frame.size.height
        UIView.animate(withDuration: 0.3) {
            self.view.layoutIfNeeded()
        }
    }
    
    @objc
    private func keyboardWillHide(_ sender: Notification) {
        self.bottomConstraint.constant = 0
        self.view.layoutIfNeeded()
    }
    
}

extension ViewController {
    
    private func setupGesture() {
        let gesture = UITapGestureRecognizer(target: self,
                                             action: #selector(handleGesture(_:)))
        self.view.addGestureRecognizer(gesture)
    }
    
    @objc
    func handleGesture(_ sender: UITapGestureRecognizer) {
        self.view.endEditing(true)
    }
    
}

extension ViewController: UITextViewDelegate {
    
    private func setupTextView() {
        self.commentTextView.delegate = self
    }
    
    func textViewDidEndEditing(_ textView: UITextView) {
        self.placeHolderLabel.isHidden = !textView.text.isEmpty
    }
    
    func textViewDidChange(_ textView: UITextView) {
        
        var height = self.minHeight
        
        if textView.contentSize.height <= self.minHeight {
            height = self.minHeight
        } else if textView.contentSize.height >= self.maxHeight {
            height = self.maxHeight
        } else {
            height = textView.contentSize.height
        }
        
        self.placeHolderLabel.isHidden = !textView.text.isEmpty
        
        self.commentConstraint.constant = height
        UIView.animate(withDuration: 0.1) {
            self.view.layoutIfNeeded()
        }
    }
    
}