//
//  Carousel.swift
//  MVMCoreUI
//
//  Created by Scott Pfeil on 7/2/19.
//  Copyright © 2019 Verizon Wireless. All rights reserved.
//

import UIKit

open class Carousel: ViewConstrainingView {
    let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
    var currentIndex = 1
    var numberOfCards = 0
    var molecules: [[AnyHashable : Any]]?
    
    var collectionViewHeight: NSLayoutConstraint?

    open override func setupView() {
        super.setupView()
        guard collectionView.superview == nil else {
            return
        }
        collectionView.translatesAutoresizingMaskIntoConstraints = false
        collectionView.dataSource = self
        collectionView.delegate = self
        collectionView.showsHorizontalScrollIndicator = false
        collectionView.backgroundColor = .clear
        addSubview(collectionView)
        pinView(toSuperView: collectionView)
        
        collectionViewHeight = collectionView.heightAnchor.constraint(equalToConstant: 300)
        collectionViewHeight?.isActive = true
    }
    
    /// Registers the cells with the collection view
    func registerCells(with json: [AnyHashable : Any]?, delegateObject: MVMCoreUIDelegateObject?) {
        if let molecules = json?.optionalArrayForKey(KeyMolecules) as? [[AnyHashable: Any]] {
            for molecule in molecules {
                if let info = getMoleculeInfo(with: molecule, delegateObject: delegateObject) {
                    collectionView.register(info.class, forCellWithReuseIdentifier: info.identifier)
                }
            }
        }
    }
    
    /// Updates the layout being used
    func setupLayout(with json:[AnyHashable: Any]?, delegateObject: MVMCoreUIDelegateObject?) {
        let layout = UICollectionViewFlowLayout()
        layout.scrollDirection = .horizontal
        layout.minimumLineSpacing = json?["spacing"] as? CGFloat ?? 0
        layout.minimumInteritemSpacing = 0
        //layout.itemSize = CGSize(width: 300, height: 200)
        collectionView.collectionViewLayout = layout
    }
    
    func prepareMolecules(_ json: [AnyHashable : Any]?) {
        guard let newMolecules = json?.optionalArrayForKey(KeyMolecules) as? [[AnyHashable: Any]] else {
            numberOfCards = 0
            molecules = nil
            return
        }
        
        numberOfCards = newMolecules.count
        molecules = newMolecules
        if json?.boolForKey("loop") ?? false && newMolecules.count > 2 {
            // Sets up the row data with a buffer cell on each side (for illusion of endless scroll... also has one more buffer cell on right since we can peek that cell).
            molecules?.insert(newMolecules.last!, at: 0)
            molecules?.append(newMolecules.first!)
            molecules?.append(newMolecules[1])
        }
    }
    
    open override func setWithJSON(_ json: [AnyHashable : Any]?, delegateObject: MVMCoreUIDelegateObject?, additionalData: [AnyHashable : Any]?) {
        super.setWithJSON(json, delegateObject: delegateObject, additionalData: additionalData)
        
        collectionViewHeight?.constant = json?.optionalCGFloatForKey("height") ?? 300

        registerCells(with: json, delegateObject: delegateObject)
        setupLayout(with: json, delegateObject: delegateObject)
        prepareMolecules(json)
        collectionView.reloadData()
        
        // Go to starting cell. layoutIfNeeded is needed otherwise cellForItem returns nil for peaking logic.
        collectionView.scrollToItem(at: IndexPath(row: currentIndex, section: 0), at: .left, animated: false)
        collectionView.layoutIfNeeded()
    }
    
    open override func setAsMolecule() {
        super.setAsMolecule()
        updateViewHorizontalDefaults = false
    }

    // MARK: - Convenience
    /// Returns the (identifier, class) of the molecule for the given map.
    func getMoleculeInfo(with molecule: [AnyHashable: Any]?, delegateObject: MVMCoreUIDelegateObject?) -> (identifier: String, class: AnyClass, molecule: [AnyHashable: Any])? {
        guard let molecule = molecule,
            let moleculeClass = MVMCoreUIMoleculeMappingObject.shared()?.getMoleculeClass(withJSON: molecule),
            let moleculeName = moleculeClass.name?(forReuse: molecule, delegateObject: delegateObject) ?? molecule.optionalStringForKey(KeyMoleculeName) else {
                return nil
        }
        return (moleculeName, moleculeClass, molecule)
    }
}

extension Carousel: UICollectionViewDelegate {
    
}

extension Carousel: UICollectionViewDataSource {
    public func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return molecules?.count ?? 0
    }
    
    public func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
        guard let molecule = molecules?[indexPath.row],
            let moleculeInfo = getMoleculeInfo(with: molecule, delegateObject: nil) else {
                return UICollectionViewCell()
        }
        let cell = collectionView.dequeueReusableCell(withReuseIdentifier: moleculeInfo.identifier, for: indexPath)
        if let protocolCell = cell as? MVMCoreUIMoleculeViewProtocol {
            protocolCell.reset?()
            protocolCell.setWithJSON(moleculeInfo.molecule, delegateObject: nil, additionalData: nil)
            protocolCell.updateView(collectionView.bounds.width)
        }
        return cell
    }
}