Trio/Dependencies/LoopKit/LoopKitUI/Views/DismissibleKeyboardTextField.swift

//
//  DismissibleKeyboardTextField.swift
//  LoopKitUI
//
//  Created by Michael Pangburn on 7/22/20.
//  Copyright © 2020 LoopKit Authors. All rights reserved.
//

import SwiftUI


public struct DismissibleKeyboardTextField: UIViewRepresentable {
    @Binding var text: String
    var placeholder: String
    var font: UIFont
    var textColor: UIColor
    var textAlignment: NSTextAlignment
    var keyboardType: UIKeyboardType
    var autocapitalizationType: UITextAutocapitalizationType
    var autocorrectionType: UITextAutocorrectionType
    var shouldBecomeFirstResponder: Bool
    var maxLength: Int?

    public init(
        text: Binding<String>,
        placeholder: String,
        font: UIFont = .preferredFont(forTextStyle: .body),
        textColor: UIColor = .label,
        textAlignment: NSTextAlignment = .natural,
        keyboardType: UIKeyboardType = .default,
        autocapitalizationType: UITextAutocapitalizationType = .sentences,
        autocorrectionType: UITextAutocorrectionType = .default,
        shouldBecomeFirstResponder: Bool = false,
        maxLength: Int? = nil
    ) {
        self._text = text
        self.placeholder = placeholder
        self.font = font
        self.textColor = textColor
        self.textAlignment = textAlignment
        self.keyboardType = keyboardType
        self.autocapitalizationType = autocapitalizationType
        self.autocorrectionType = autocorrectionType
        self.shouldBecomeFirstResponder = shouldBecomeFirstResponder
        self.maxLength = maxLength
    }

    public func makeUIView(context: Context) -> UITextField {
        let textField = UITextField()
        textField.inputAccessoryView = makeDoneToolbar(for: textField)
        textField.addTarget(context.coordinator, action: #selector(Coordinator.textChanged), for: .editingChanged)
        textField.addTarget(context.coordinator, action: #selector(Coordinator.editingDidBegin), for: .editingDidBegin)
        textField.delegate = context.coordinator
        return textField
    }

    private func makeDoneToolbar(for textField: UITextField) -> UIToolbar {
        let toolbar = UIToolbar(frame: CGRect(x: 0, y: 0, width: UIScreen.main.bounds.width, height: 50))
        let flexibleSpace = UIBarButtonItem(barButtonSystemItem: .flexibleSpace, target: nil, action: nil)
        let doneButton = UIBarButtonItem(barButtonSystemItem: .done, target: textField, action: #selector(UITextField.resignFirstResponder))
        doneButton.tintColor = textColor
        toolbar.items = [flexibleSpace, doneButton]
        toolbar.sizeToFit()
        return toolbar
    }

    public func updateUIView(_ textField: UITextField, context: Context) {
        textField.text = text
        textField.placeholder = placeholder
        textField.font = font
        textField.textColor = textColor
        textField.textAlignment = textAlignment
        textField.keyboardType = keyboardType
        textField.autocapitalizationType = autocapitalizationType
        textField.autocorrectionType = autocorrectionType

        if shouldBecomeFirstResponder && !context.coordinator.didBecomeFirstResponder {
            // See https://developer.apple.com/documentation/uikit/uiresponder/1621113-becomefirstresponder for why
            // we check the window property here (otherwise it might crash)
            if textField.window != nil && textField.becomeFirstResponder() {
                context.coordinator.didBecomeFirstResponder = true
            }
        } else if !shouldBecomeFirstResponder && context.coordinator.didBecomeFirstResponder {
            context.coordinator.didBecomeFirstResponder = false
        }
    }

    public func makeCoordinator() -> Coordinator {
        Coordinator(self, maxLength: maxLength)
    }

    public final class Coordinator: NSObject {
        var parent: DismissibleKeyboardTextField
        let maxLength: Int?

        // Track in the coordinator to ensure the text field only becomes first responder once,
        // rather than on every state change.
        var didBecomeFirstResponder = false

        init(_ parent: DismissibleKeyboardTextField, maxLength: Int?) {
            self.parent = parent
            self.maxLength = maxLength
        }

        @objc fileprivate func textChanged(_ textField: UITextField) {
            parent.text = textField.text ?? ""
        }
        
        @objc fileprivate func editingDidBegin(_ textField: UITextField) {
            // Even though we are likely already on .main, we still need to queue this cursor (selection) change in
            // order for it to work
            DispatchQueue.main.async {
                textField.moveCursorToEnd()
            }
        }
    }
}

extension DismissibleKeyboardTextField.Coordinator: UITextFieldDelegate {
    public func textField(_ textField: UITextField, shouldChangeCharactersIn range: NSRange, replacementString string: String) -> Bool {
        guard let maxLength = maxLength else {
            return true
        }
        let currentString: NSString = (textField.text ?? "") as NSString
        let newString: NSString =
            currentString.replacingCharacters(in: range, with: string) as NSString
        return newString.length <= maxLength
    }
}