Textfield Formatter

//
//  BottomSheet.swift
//  Squirrel-SwiftUI
//
//  Created by Amritpal Singh on 24/05/20.
//  Copyright © 2020 sidhu.com. All rights reserved.
//

import SwiftUI

class TextFieldFormatter: ObservableObject {
    
    enum Formatter {
        case expiry
        case cardNumber
        case non // No formatter is required
    }
    
    @Published var text = "" {
        didSet {
            if oldValue != text {
                if text.count > characterLimit && oldValue.count <= characterLimit {
                    text = oldValue
                } else {
                    text = formattedText()
                }
            }
        }
    }
    let characterLimit: Int
    let formaterType: Formatter
    init(limit: Int = 5, type: Formatter = .non){
        characterLimit = limit
        formaterType = type
    }
    
    func formattedText() -> String {
        switch formaterType {
        case .expiry:
            return formattedExpiry()
        case .cardNumber:
            return formattedCardNumber()
        case .non:
            return text
        }
    }
    
    func formattedExpiry() -> String {
        let allDigits = self.text.digits
        
        var formattedText = ""
        if allDigits.count == 1 {
            formattedText = "\(allDigits[0])"
        } else if allDigits.count == 2 {
            if let number = Int("\(allDigits[0])\(allDigits[1])"),
                number <= 12 {
                formattedText = "\(allDigits[0])\(allDigits[1])"
            } else {
                formattedText = "\(allDigits[0])"
            }
        } else if allDigits.count == 3 {
            formattedText = "\(allDigits[0])\(allDigits[1])/\(allDigits[2])"
        } else if allDigits.count >= 4 {
            formattedText = "\(allDigits[0])\(allDigits[1])/\(allDigits[2])\((allDigits[3]))"
        }
        return formattedText
    }
    
    func formattedCardNumber() -> String {
        let trimmedString = text.components(separatedBy: .whitespaces).joined()

        let arrOfCharacters = Array(trimmedString)
        var modifiedCreditCardString = ""

        if(arrOfCharacters.count > 0) {
            for i in 0...arrOfCharacters.count-1 {
                modifiedCreditCardString.append(arrOfCharacters[i])
                if((i+1) % 4 == 0 && i+1 != arrOfCharacters.count) {
                    modifiedCreditCardString.append(" ")
                }
            }
        }
        return modifiedCreditCardString
    }
}

extension String {
    var digits: [Int] {
        var result = [Int]()
        
        for char in self {
            if let number = Int(String(char)) {
                result.append(number)
            }
        }
        
        return result
    }
    
    func widthWithConstrainedHeight(height: CGFloat, font: UIFont = UIFont(name: "Avenir-normal", size: 14) ?? .systemFont(ofSize: 14)) -> CGFloat {
        let constraintRect = CGSize(width: CGFloat.greatestFiniteMagnitude, height: height)
        let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin,
                                            attributes: [NSAttributedString.Key.font: font], context: nil)
        return boundingBox.width
    }
}

struct CustomTextField: UIViewRepresentable {
    
    class Coordinator: NSObject, UITextFieldDelegate {
        
        @Binding var text: String
        var didBecomeFirstResponder = false
        var textChanged: ((_ text: String?) -> Void)?
        var textColor: UIColor = UIColor.black
        var didTapReturnButton: (() -> Void)? = nil
        
        init(text: Binding<String>,
             textColor: UIColor?,
             didChangeText: ((_ text: String?) -> Void)?,
             didTapReturnButton: (() -> Void)?) {
            _text = text
            self.textColor = textColor ?? .black
            textChanged = didChangeText
            self.didTapReturnButton = didTapReturnButton
        }
        
        @objc func didChangeText(_ textField: UITextField) {
            DispatchQueue.main.async {
                self.text = textField.text ?? ""
            }
            
            print("Text changed")
            textChanged?(text)
        }
        
        func textFieldShouldReturn(_ textField: UITextField) -> Bool {
            didTapReturnButton?()
            return true
        }
        
    }
    
    @Binding var text: String
    @Binding var isFirstResponder: Bool
    var placeholder: String = "Search"
    var font: UIFont? = UIFont(name: "Avenir-normal", size: 17)
    var placeholderFont: UIFont? = nil
    var textColor: UIColor = UIColor.black
    var keyboardType: UIKeyboardType = .numberPad
    var returnType: UIReturnKeyType = .default
    var textChanged: ((_ text: String?) -> Void)? = nil
    var didTapReturnButton: (() -> Void)? = nil

    func makeUIView(context: UIViewRepresentableContext<CustomTextField>) -> UITextField {
        let textField = UITextField(frame: .zero)
        textField.addTarget(context.coordinator, action: #selector(context.coordinator.didChangeText(_:)), for: .editingChanged)
        textField.tintColor = textColor
        textField.textColor = textColor
        textField.keyboardType = keyboardType
        textField.returnKeyType = returnType
        textField.delegate = context.coordinator
        textField.placeholder = placeholder
        textField.clearButtonMode = .whileEditing
        textField.font = font
        
        if let font = placeholderFont {
            let attributes = [
                NSAttributedString.Key.font : font
            ]
            textField.attributedPlaceholder = NSAttributedString(string: placeholder, attributes:attributes)
        }
        return textField
    }
    
    func makeCoordinator() -> CustomTextField.Coordinator {
        return Coordinator(text: $text,
                           textColor: textColor,
                           didChangeText: textChanged,
                           didTapReturnButton: didTapReturnButton)
    }
    
    func updateUIView(_ uiView: UITextField, context: UIViewRepresentableContext<CustomTextField>) {
        uiView.text = text
        if isFirstResponder && !context.coordinator.didBecomeFirstResponder  {
            uiView.becomeFirstResponder()
            context.coordinator.didBecomeFirstResponder = true
        }
    }
}