LeadKit/TIUIElements/Sources/Views/StatefulButton/StatefulButton.swift

//
//  Copyright (c) 2020 Touch Instinct
//
//  Permission is hereby granted, free of charge, to any person obtaining a copy
//  of this software and associated documentation files (the Software), to deal
//  in the Software without restriction, including without limitation the rights
//  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
//  copies of the Software, and to permit persons to whom the Software is
//  furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
//  THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
//  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
//  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
//  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
//  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
//  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
//  THE SOFTWARE.
//

import TISwiftUtils
import TIUIKitCore
import UIKit

public extension UIControl.State {
    // All the bits from 17 - 24 (from 1 << 16 until 1 << 23) are there for your application to use
    // while 25 - 32 (from 1 << 24 until 1 << 31) are there for internal frameworks to use.
    // https://developer.apple.com/documentation/uikit/uicontrolstate/uicontrolstateapplication?language=objc
    // https://developer.apple.com/documentation/uikit/uicontrolstate/uicontrolstatereserved?language=objc
    // https://stackoverflow.com/a/43760213
    static var loading = Self(rawValue: 1 << 16 | Self.disabled.rawValue) // includes disabled state
}

open class StatefulButton: BaseInitializableButton {

    public enum ActivityIndicatorPosition {
        case beforeTitle(padding: CGFloat)
        case center
    }

    @available(iOS 15.0, *)
    public enum ActivityIndicatorPlacement {
        case placement(NSDirectionalRectEdge, padding: CGFloat)
        case center
    }

    public typealias StateEventPropagations = [State: Bool]

    public var isLoading = false {
        didSet {
            if isLoading {
                if activityIndicator == nil {
                    configureDefaultActivityIndicator()
                }

                updateAppearance(to: .loading)

                activityIndicator?.startAnimating()
            } else {
                activityIndicator?.stopAnimating()
            }
        }
    }

    public var additionalHitTestMargins: UIEdgeInsets = .zero

    public var onDisabledStateTapHandler: VoidClosure?

    // MARK: - Internal properties

    var activityIndicator: ActivityIndicator? {
        willSet {
            activityIndicator?.removeFromSuperview()
        }
        didSet {
            if let activityIndicator = activityIndicator {
                addSubview(activityIndicator)
            }
        }
    }

    var activityIndicatorShouldCenterInView = false

    var onStateChanged: ParameterClosure<State>?

    // MARK: - Private properties

    private var eventPropagations: StateEventPropagations = [:]

    public func setEventPropagation(_ eventPropagation: Bool, for state: State) {
        eventPropagations[state] = eventPropagation
    }

    // MARK: - UIButton override

    open override func setImage(_ image: UIImage?, for state: UIControl.State) {
        guard state != .loading else {
            return
        }

        super.setImage(image, for: state)
    }

    // MARK: - UIControl override

    open override var state: UIControl.State {
        if isLoading {
            return super.state.union(.loading)
        } else {
            return super.state
        }
    }

    override open var isEnabled: Bool {
        didSet {
            updateAppearance()
        }
    }

    override open var isHighlighted: Bool {
        didSet {
            updateAppearance()
        }
    }

    open override var isSelected: Bool {
        didSet {
            updateAppearance()
        }
    }

    // MARK: - UIView override

    open override func layoutSubviews() {
        super.layoutSubviews()

        guard let activityIndicator, isLoading else {
            return
        }

        if activityIndicatorShouldCenterInView {
            let indicatorSize = activityIndicatorSize

            activityIndicator.frame = CGRect(origin: CGPoint(x: bounds.midX - indicatorSize.width / 2,
                                                             y: bounds.midY - indicatorSize.height / 2),
                                             size: indicatorSize)
        } else {
            activityIndicator.frame = imageView?.frame ?? .zero
        }
    }

    open override func point(inside point: CGPoint, with event: UIEvent?) -> Bool {
        let insetBounds = CGRect(x: bounds.minX - additionalHitTestMargins.left,
                                 y: bounds.minY - additionalHitTestMargins.top,
                                 width: bounds.width + additionalHitTestMargins.right,
                                 height: bounds.height + additionalHitTestMargins.bottom)

        return super.point(inside: point, with: event)
        || insetBounds.contains(point)
    }

    open override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        let pointInsideView = self.point(inside: point, with: event)

        if !isEnabled && pointInsideView, event?.allTouches?.isEmpty == false {
            onDisabledStateTapHandler?()
        }

        let touchEventReceiver = super.hitTest(point, with: event)

        let shouldPropagateEvent = (eventPropagations[state] ?? true) || isHidden

        if pointInsideView && touchEventReceiver == nil && !shouldPropagateEvent {
            return self // disable propagation
        }

        return touchEventReceiver
    }

    // MARK: - Public

    open func configure(activityIndicator: ActivityIndicator) {
        self.activityIndicator = activityIndicator
        activityIndicator.translatesAutoresizingMaskIntoConstraints = false

        setNeedsLayout()
    }

    open func configureDefaultActivityIndicator() {
        let systemIndicator: UIActivityIndicatorView

        if #available(iOS 13.0, *) {
            systemIndicator = UIActivityIndicatorView(style: .medium)
        } else {
            systemIndicator = UIActivityIndicatorView(style: .gray)
        }

        configure(activityIndicator: systemIndicator)
    }

    open func apply(state: State) {
        isSelected = state.isSelected
        isEnabled = !state.isDisabled
        isHighlighted = state.isHightlightted
        isLoading = state.isLoading
    }

    // MARK: - Internal

    var activityIndicatorSize: CGSize {
        activityIndicator?.intrinsicContentSize ?? .zero
    }

    // MARK: - Private

    private func updateAppearance() {
        if isLoading {
            updateAppearance(to: .loading)
        } else if isEnabled {
            if isHighlighted {
                updateAppearance(to: .highlighted)
            } else {
                updateAppearance(to: .normal)
            }
        } else {
            updateAppearance(to: .disabled)
        }
    }

    private func updateAppearance(to state: State) {
        onStateChanged?(state)
    }
}

private extension UIControl.State {
    var isHightlightted: Bool {
        contains([.highlighted])
    }

    var isSelected: Bool {
        contains([.selected])
    }

    var isDisabled: Bool {
        contains([.disabled])
    }

    var isLoading: Bool {
        contains([.loading])
    }
}