SweeterSwift/Source/UIView+Sweeter.swift

//
//  UIView+Sweeter.swift
//
//  Created by Yonat Sharon on 2019-02-08.
//

import UIKit

public extension UIView {
    /// Sweeter: Set constant attribute. Example: `constrain(.width, to: 17)`
    @discardableResult func constrain(
        _ at: NSLayoutConstraint.Attribute,
        to: CGFloat = 0,
        ratio: CGFloat = 1,
        relation: NSLayoutConstraint.Relation = .equal,
        priority: UILayoutPriority = .required,
        identifier: String? = nil
    ) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(
            item: self, attribute: at, relatedBy: relation,
            toItem: nil, attribute: .notAnAttribute, multiplier: ratio, constant: to
        )
        constraint.priority = priority
        constraint.identifier = identifier
        addConstraintWithoutConflict(constraint)
        return constraint
    }

    /// Sweeter: Pin subview at a specific place. Example: `constrain(label, at: .top)`
    @discardableResult func constrain(
        _ subview: UIView,
        at: NSLayoutConstraint.Attribute,
        diff: CGFloat = 0,
        ratio: CGFloat = 1,
        relation: NSLayoutConstraint.Relation = .equal,
        priority: UILayoutPriority = .required,
        identifier: String? = nil
    ) -> NSLayoutConstraint {
        let constraint = NSLayoutConstraint(
            item: subview, attribute: at, relatedBy: relation,
            toItem: self, attribute: at, multiplier: ratio, constant: diff
        )
        constraint.priority = priority
        constraint.identifier = identifier
        addConstraintWithoutConflict(constraint)
        return constraint
    }

    /// Sweeter: Pin two subviews to each other. Example:
    ///
    /// `constrain(label, at: .leading, to: textField)`
    ///
    /// `constrain(textField, at: .top, to: label, at: .bottom, diff: 8)`
    @discardableResult func constrain(
        _ subview: UIView,
        at: NSLayoutConstraint.Attribute,
        to subview2: UIView,
        at at2: NSLayoutConstraint.Attribute = .notAnAttribute,
        diff: CGFloat = 0,
        ratio: CGFloat = 1,
        relation: NSLayoutConstraint.Relation = .equal,
        priority: UILayoutPriority = .required,
        identifier: String? = nil
    ) -> NSLayoutConstraint {
        let at2real = at2 == .notAnAttribute ? at : at2
        let constraint = NSLayoutConstraint(
            item: subview, attribute: at, relatedBy: relation,
            toItem: subview2, attribute: at2real, multiplier: ratio, constant: diff
        )
        constraint.priority = priority
        constraint.identifier = identifier
        addConstraintWithoutConflict(constraint)
        return constraint
    }

    /// Sweeter: Add subview pinned to specific places. Example: `addConstrainedSubview(button, constrain: .centerX, .centerY)`
    @discardableResult func addConstrainedSubview(_ subview: UIView, constrain: NSLayoutConstraint.Attribute...) -> [NSLayoutConstraint] {
        return addConstrainedSubview(subview, constrainedAttributes: constrain)
    }

    @discardableResult internal func addConstrainedSubview(_ subview: UIView, constrainedAttributes: [NSLayoutConstraint.Attribute]) -> [NSLayoutConstraint] {
        subview.translatesAutoresizingMaskIntoConstraints = false
        addSubview(subview)
        return constrainedAttributes.map { self.constrain(subview, at: $0) }
    }

    internal func addConstraintWithoutConflict(_ constraint: NSLayoutConstraint) {
        removeConstraints(constraints.filter {
            constraint.firstItem === $0.firstItem
                && constraint.secondItem === $0.secondItem
                && constraint.firstAttribute == $0.firstAttribute
                && constraint.secondAttribute == $0.secondAttribute
        })
        addConstraint(constraint)
    }

    /// Sweeter: Search the view hierarchy recursively for a subview that conforms to `predicate`
    func viewInHierarchy(frontFirst: Bool = true, where predicate: (UIView) -> Bool) -> UIView? {
        if predicate(self) { return self }
        let views = frontFirst ? subviews.reversed() : subviews
        for subview in views {
            if let found = subview.viewInHierarchy(frontFirst: frontFirst, where: predicate) {
                return found
            }
        }
        return nil
    }

    /// Sweeter: Search the view hierarchy recursively for a subview with `aClass`
    func viewWithClass<T>(_ aClass: T.Type, frontFirst: Bool = true) -> T? {
        return viewInHierarchy(frontFirst: frontFirst, where: { $0 is T }) as? T
    }

    /// Sweeter: The color used to tint the view, as inherited from its superviews.
    var actualTintColor: UIColor {
        var tintedView: UIView? = self
        while let currentView = tintedView, nil == currentView.tintColor {
            tintedView = currentView.superview
        }
        return tintedView?.tintColor ?? UIColor(red: 0, green: 0.5, blue: 1, alpha: 1)
    }
}