//
//  Stack.swift
//  MVMCoreUI
//
//  Created by Scott Pfeil on 1/16/20.
//  Copyright © 2020 Verizon Wireless. All rights reserved.
//

import Foundation

open class Stack<T>: Container where T: StackModelProtocol {
    var contentView: UIView = MVMCoreUICommonViewsUtility.commonView()
    var stackModel: T? {
        get { return model as? T }
    }
    var stackItems: [UIView] = []
    
    // MARK: - Helpers
    public func pinView(_ view: UIView, toView: UIView, attribute: NSLayoutConstraint.Attribute, relation: NSLayoutConstraint.Relation, priority: UILayoutPriority, constant: CGFloat) {
        let constraint = NSLayoutConstraint(item: view, attribute: attribute, relatedBy: relation, toItem: toView, attribute: attribute, multiplier: 1.0, constant: constant)
        constraint.priority = priority
        constraint.isActive = true
    }
    
    /// Restacks the existing items.
    func restack() {
        removeAllItemViews()
        guard let stackModel = stackModel else { return }
        let stackItems = self.stackItems
        self.stackItems = []
        let lastItemIndex = stackModel.molecules.lastIndex(where: { (item) -> Bool in
            return !item.gone
        })
        
        // Adds the views
        let totalSpace = getTotalSpace()
        for (index, view) in stackItems.enumerated() {
            addView(view, stackModel.molecules[index], totalSpacing: totalSpace, lastItem: lastItemIndex == index)
        }
    }
    
    /// Removes all stack items views from the view.
    func removeAllItemViews() {
        for item in stackItems {
            item.removeFromSuperview()
        }
    }

    // MARK: - Inits
    public override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    public init(withJSON json: [AnyHashable: Any]?, delegateObject: MVMCoreUIDelegateObject?, additionalData: [AnyHashable : Any]?) {
        super.init(frame: CGRect.zero)
        setWithJSON(json, delegateObject: delegateObject, additionalData: additionalData)
    }
    
    public required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    // MARK: - MFViewProtocol
    public override func setupView() {
        super.setupView()
        guard contentView.superview == nil else {
            return
        }
        MVMCoreUIUtility.setMarginsFor(contentView, leading: 0, top: 0, trailing: 0, bottom: 0)
        translatesAutoresizingMaskIntoConstraints = false
        backgroundColor = .clear
        addSubview(contentView)
        containerHelper.constrainView(contentView)
        contentView.setContentHuggingPriority(.defaultHigh, for: .vertical)
        contentView.setContentHuggingPriority(.defaultHigh, for: .horizontal)
    }
    
    public override func updateView(_ size: CGFloat) {
        super.updateView(size)
        for item in stackItems {
            (item as? MVMCoreViewProtocol)?.updateView(size)
        }
    }
    
    // MARK: - MVMCoreUIMoleculeViewProtocol
    public override func reset() {
        super.reset()
        backgroundColor = .clear
        for item in stackItems {
            (item as? MoleculeViewProtocol)?.reset?()
        }
    }
    
    public override func setWithModel(_ model: MoleculeModelProtocol?, _ delegateObject: MVMCoreUIDelegateObject?, _ additionalData: [AnyHashable : Any]?) {
        let previousModel = self.model
        super.setWithModel(model, delegateObject, additionalData)
        removeAllItemViews()
        
        // If the items in the stack are different, clear them, create new ones.
        if (previousModel == nil) || Self.nameForReuse(previousModel, delegateObject) != Self.nameForReuse(model, delegateObject) {
            stackItems = []
            createStackItemsFromModel(model, delegateObject, additionalData)
        } else {
            setStackItemsFromModel(model, delegateObject, additionalData)
        }
        
        restack()
    }
    
    public override class func nameForReuse(_ model: MoleculeModelProtocol?, _ delegateObject: MVMCoreUIDelegateObject?) -> String? {
        // This will aggregate names of molecules to make an id.
        guard let model = model as? T else {
            return "stack<>"
        }
        var name = "stack<"
        for case let item in model.molecules {
            if let moleculeName = item.moleculeName {
                if let moleculeClass = MVMCoreUIMoleculeMappingObject.shared()?.moleculeMapping[moleculeName] as? ModelMoleculeViewProtocol.Type,
                    let nameForReuse = moleculeClass.nameForReuse(item, delegateObject) {
                    name.append(nameForReuse + ",")
                } else {
                    name.append(moleculeName + ",")
                }
            }
        }
        name.append(">")
        return name
    }
    
    // Need to update to take into account first spacing flag
    public override class func estimatedHeight(forRow molecule: MoleculeModelProtocol?, delegateObject: MVMCoreUIDelegateObject?) -> CGFloat? {
        guard let model = molecule as? T else { return 0 }
        let horizontal = model.axis == .horizontal
        var estimatedHeight: CGFloat = 0
        for case let item in model.molecules {
            if item.gone { continue }
            let height = (MVMCoreUIMoleculeMappingObject.shared()?.getMoleculeClass(item) as? ModelMoleculeViewProtocol.Type)?.estimatedHeight(forRow: item, delegateObject: delegateObject) ?? 0
            if !horizontal {
                // Vertical stack aggregates the items
                let spacing = item.spacing ?? model.spacing
                estimatedHeight += (height + spacing)
            } else {
                // Horizontal stack takes the tallest item.
                estimatedHeight = max(estimatedHeight, height)
            }
        }
        return estimatedHeight
    }
    
    public override class func requiredModules(_ molecule: MoleculeModelProtocol?, delegateObject: MVMCoreUIDelegateObject?, error: AutoreleasingUnsafeMutablePointer<MVMCoreErrorObject?>?) -> [String]? {
        guard let model = molecule as? T else { return nil }
        var modules: [String] = []
        for case let item in model.molecules {
            if let modulesForMolecule = (MVMCoreUIMoleculeMappingObject.shared()?.getMoleculeClass(item) as? ModelMoleculeViewProtocol.Type)?.requiredModules(item, delegateObject: delegateObject, error: error) {
                modules += modulesForMolecule
            }
        }
        return modules.count > 0 ? modules : nil
    }
    
    // MARK: - Subclassables

    /// Can be subclassed to create views when we get stack item models and have no views yet
    func createStackItemsFromModel(_ model: MoleculeModelProtocol?, _ delegateObject: MVMCoreUIDelegateObject?, _ additionalData: [AnyHashable : Any]?) {
    }
    
    /// Can be subclassed to set stack items with model when we already have views
    func setStackItemsFromModel(_ model: MoleculeModelProtocol?, _ delegateObject: MVMCoreUIDelegateObject?, _ additionalData: [AnyHashable : Any]?) {
        guard let models = stackModel?.molecules else { return }
        for (index, element) in models.enumerated() {
            (stackItems[index] as? ModelMoleculeViewProtocol)?.setWithModel(element, delegateObject, additionalData)
        }
    }
    
    // MARK: - Adding to stack
    /// Gets the percent modifier. This value is used to help properly calculate percent for stack items when spacing is involved.
    private func getTotalSpace() -> CGFloat {
        guard let stackModel = stackModel else { return 0.0 }
        var totalSpace: CGFloat = 0.0
        var firstMoleculeFound = false
        for stackItemModel in stackModel.molecules {
            guard !stackItemModel.gone else { continue }
            let spacing = stackItemModel.spacing ?? stackModel.spacing
            if firstMoleculeFound {
                totalSpace += spacing
            } else {
                firstMoleculeFound = true
                totalSpace += (stackModel.useStackSpacingBeforeFirstItem ? spacing : stackItemModel.spacing ?? 0)
            }
        }
        return totalSpace
    }
    
    /// Adds the stack item view
    private func addView(_ view: UIView,_ model: StackItemModelProtocol, totalSpacing: CGFloat, lastItem: Bool) {
        guard let stackModel = self.stackModel else { return }
        guard !model.gone else {
            // Gone views do not show
            stackItems.append(view)
            return
        }
        contentView.addSubview(view)
        view.translatesAutoresizingMaskIntoConstraints = false
                
        let spacing = model.spacing ?? stackModel.spacing
        if let container = view as? ContainerProtocol {
            let verticalAlignment = (model as? ContainerModelProtocol)?.verticalAlignment ?? (container.view as? MVMCoreUIViewConstrainingProtocol)?.verticalAlignment?() ?? (model.percent == nil && stackModel.axis == .vertical ? .fill : (stackModel.axis == .vertical ? .leading : .center))
            let horizontalAlignment = (model as? ContainerModelProtocol)?.horizontalAlignment ?? (container.view as? MVMCoreUIViewConstrainingProtocol)?.horizontalAlignment?() ?? (stackModel.axis == .vertical || model.percent == nil ? .fill : .leading)
                container.alignHorizontal(horizontalAlignment)
                container.alignVertical(verticalAlignment)
        }
           
        let first = contentView.subviews.count == 1
        if stackModel.axis == .vertical {
            if first {
                pinView(view, toView: contentView, attribute: .top, relation: .equal, priority: .required, constant: stackModel.useStackSpacingBeforeFirstItem ? spacing : model.spacing ?? 0)
            } else if let previousView = stackItems.last(where: { item in
                return !model.gone
            }) {
                view.topAnchor.constraint(equalTo: previousView.bottomAnchor, constant: spacing).isActive = true
            }
            pinView(view, toView: contentView, attribute: .leading, relation: .equal, priority: .required, constant: 0)
            pinView(contentView, toView: view, attribute: .trailing, relation: .equal, priority: .required, constant: 0)
            if let percent = model.percent {
                let multiplier = CGFloat(percent)/100.0
                let constant = multiplier * totalSpacing
                view.heightAnchor.constraint(equalTo: contentView.heightAnchor, multiplier: multiplier, constant: -constant).isActive = true
            }
            if lastItem {
                pinView(contentView, toView: view, attribute: .bottom, relation: .equal, priority: .required, constant: 0)
            }
        } else {
            if first {
                // First horizontal item has no spacing by default unless told otherwise.
                pinView(view, toView: contentView, attribute: .leading, relation: .equal, priority: .required, constant: stackModel.useStackSpacingBeforeFirstItem ? spacing : model.spacing ?? 0)
            } else if let previousView = stackItems.last(where: { item in
                return !model.gone
            }) {
                view.leftAnchor.constraint(equalTo: previousView.rightAnchor, constant: spacing).isActive = true
            }
            pinView(view, toView: contentView, attribute: .top, relation: .equal, priority: .required, constant: 0)
            pinView(contentView, toView: view, attribute: .bottom, relation: .equal, priority: .required, constant: 0)
            if let percent = model.percent {
                let multiplier = CGFloat(percent)/100.0
                let constant = multiplier * totalSpacing
                view.widthAnchor.constraint(equalTo: contentView.widthAnchor, multiplier: multiplier, constant: -constant).isActive = true
            }
            if lastItem {
                pinView(contentView, toView: view, attribute: .right, relation: .equal, priority: .required, constant: 0)
            }
        }
        stackItems.append(view)
    }
}