//
//  PlaceholderTextView.swift
//  Tusker
//
//  Created by Shadowfacts on 8/29/18.
//  Copyright © 2018 Shadowfacts. All rights reserved.
//

import UIKit

// Source: https://finnwea.com/blog/adding-placeholders-to-uitextviews-in-swift/
extension UITextView: UITextViewDelegate {
    
    override open var bounds: CGRect {
        didSet {
            resizePlaceholder()
        }
    }
    
    var placeholder: String? {
        get {
            return (viewWithTag(100) as? UILabel)?.text
        }
        set {
            if let placeholderLabel = viewWithTag(100) as? UILabel {
                placeholderLabel.text = newValue
                placeholderLabel.sizeToFit()
            } else {
                guard let newValue = newValue else { return }
                addPlaceholder(newValue)
            }
        }
    }
    
    public func textViewDidChange(_ textView: UITextView) {
        if let placeholderLabel = viewWithTag(100) as? UILabel {
            placeholderLabel.isHidden = !text.isEmpty
        }
    }
    
    private func resizePlaceholder() {
        guard let placeholderLabel = viewWithTag(100) as? UILabel else { fatalError() }
        let labelX = textContainer.lineFragmentPadding
        let labelY = textContainerInset.top
        let labelWidth = frame.width - (labelX * 2)
        let labelHeight = placeholderLabel.frame.height
        placeholderLabel.frame = CGRect(x: labelX, y: labelY, width: labelWidth, height: labelHeight)
    }
    
    private func addPlaceholder(_ placeholderText: String) {
        let placeholderLabel = UILabel()
        
        placeholderLabel.text = placeholderText
        placeholderLabel.sizeToFit()
        placeholderLabel.font = font
        placeholderLabel.textColor = .lightGray
        placeholderLabel.tag = 100
        
        placeholderLabel.isHighlighted = !text.isEmpty
        
        addSubview(placeholderLabel)
        resizePlaceholder()
        delegate = self
        
    }
}