RefreshControl1.swift

//
//  RefreshControl.swift
//
//  Created by mukesh awal on 1/22/20.
//  Copyright © 2020. All rights reserved.
//
/******************************************************************
 -uses RxSwift and RxCocoa
 -add instance of this class to background of your scroll view
 ******************************    points  ***********************************
                
        left top *                                      * right top
                 |                                      |
                 |                                      |
                 |                                      |
                 |                                      |
     left bottom *                                      * right bottom
                 ------------------ * -------------------
                                middle bottom
 ******************************************************************/

import UIKit
import RxCocoa
import RxSwift


/// add instance of this class to background of your scroll view. 
///you can set size of refresh circle using "setRefreshCircleSize". 
///you can set fillColor of refresh control using "setFillColor" , 
///set Max Height Of Refresh Control using "setMaxHeightOfRefreshControl", 
///set color of refresh circle using "setRefreshCircleColor",
class RefreshControl: UIView {
    
    //MARK: - properties
    
    //enum for observers
    enum Observer{
        case contentOffset
        case panGesture
    }
    
    //enum for radius of refresh circle
    enum RefreshCircleSize : CGFloat{
        case small = 12.0
        case medium = 17.0
        case large = 22.0
    }
    
    /// indicates refreshing status
    private var refreshingStatus = false
    
    let bag = DisposeBag()
    
    //MARK: - layers
    private let shapeLayer = CAShapeLayer()
    private let circleLayer = CAShapeLayer()
    
    //MARK: - points on path of border
    var leftTop = CGPoint()
    var rightTop = CGPoint()
    var leftBottom = CGPoint()
    var rightBottom = CGPoint()
    var midBottom = CGPoint()
    
    ///content offset of scroll view that  keeps updated according to scroll detected
    private var scrollViewContentYOffset: CGFloat = 0
    
    ///dynamic xposition of panGesture over scroll view
    private var xPositionOfPan : CGFloat = 0
    
    /// y offset for middle bottom point
    private var middleBottomPointYOffset : CGFloat = 0
    
    ///y offset for bottom edge points
    private var edgeBottomPointYOffset : CGFloat = 0
    
    /// center point for circle
    private var centerForCircle : CGPoint = CGPoint(x: 0, y: 0)
    
    ///threshold drag value
    private var thresholdDrag : CGFloat = 130
    
    ///maximum height of refresh control
    private var maxHeightOfRefreshControl: CGFloat = 170
    
    ///size of refresh circle
    private var refreshCircleSize : RefreshCircleSize = .medium
    
    ///called when user refresh is triggered
    private var onRefreshing : () -> Void = {
        debugPrint("refresh triggerd. Implement setOnRefreshing of RefreshControl to call your own function.")
    }
    
    ///fill color of refresh control
    var setFillColor : UIColor = UIColor.appYellow {
        didSet{
            shapeLayer.fillColor = setFillColor.cgColor
        }
    }
    
    ///color of refresh circle
    var setRefreshCircleColor : UIColor = UIColor.white {
        didSet{
            circleLayer.strokeColor = setRefreshCircleColor.cgColor
        }
    }
    
    //MARK: - set
    ///set maxHeight of refreshControl. minimum is 130
    var setMaxHeightOfRefreshControl : CGFloat = 0 {
        didSet{
            maxHeightOfRefreshControl = max(setMaxHeightOfRefreshControl, 170)
        }
    }
    
    //set size of refresh circle
    var setRefreshCircleSize : RefreshCircleSize = RefreshCircleSize.medium {
        didSet{
            refreshCircleSize = setRefreshCircleSize
        }
    }
    
    //set function to be called after refresh is triggerd
    var setOnRefreshing : () -> Void = {} {
        didSet{
            onRefreshing = setOnRefreshing
        }
    }
    
    ///return super view as scroll view. may be table view or collection view too. if superView doesnot exist then return nil
    var containerScrollView : UIScrollView? {
        return superview as? UIScrollView
    }
    
    //MARK: - initializer
    override init(frame : CGRect) {
        super.init(frame: frame)
        
    }
    
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    
}