class BookingController: UIViewController, UITableViewDelegate, UITableViewDataSource {

	// NEVER do something like this!!!
	//	create a UITableViewCell subclass
	//let calendarCell = UITableViewCell()
	
	override func viewDidLoad() {
		super.viewDidLoad()
		view.backgroundColor = .gray // Manager.Colors.dark
		
		if let img = UIImage(named: "Background Image") {
			addBackgroundImage(image: img)
		}
		setupTableContent()
	}
	
	private func addBackgroundImage(image: UIImage) {
		let backgroundImage = UIImageView(image: image)
		backgroundImage.frame = view.bounds
		backgroundImage.alpha = 0.5
		view.addSubview(backgroundImage)
	}
	
	override var preferredStatusBarStyle: UIStatusBarStyle { .lightContent }
	
	private func setupTableContent() {
		let tableView = UITableView()
		tableView.backgroundColor = .clear
		tableView.delegate = self
		tableView.dataSource = self
		tableView.translatesAutoresizingMaskIntoConstraints =  false
		tableView.estimatedRowHeight = 80
		tableView.rowHeight = UITableView.automaticDimension
		view.addSubview(tableView)
		
		// register CalendarCell class
		tableView.register(CalendarCell.self, forCellReuseIdentifier: "calendarCell")
		
		[tableView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor),
		 tableView.leadingAnchor.constraint(equalTo: view.leadingAnchor),
		 tableView.trailingAnchor.constraint(equalTo: view.trailingAnchor),
		 tableView.bottomAnchor.constraint(equalTo: view.bottomAnchor)].forEach({$0.isActive = true})
	}
	
	func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int { 1 }
	
	func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
		// dequeue a CalendarCell and set its Data
		let cell = tableView.dequeueReusableCell(withIdentifier: "calendarCell", for: indexPath) as! CalendarCell
		cell.initData()
		return cell
	}
	
	func tableView(_ tableView: UITableView, viewForFooterInSection section: Int) -> UIView? { UIView() }
}

// custom table view cell
class CalendarCell: UITableViewCell {

	let calendarView = CalendarView()

	// we will set the .constant on this constraint to set the height of the
	//	calendarView (and thus the height of the collection view)
	var calendarViewHeightConstraint: NSLayoutConstraint!
	
	override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
		super.init(style: style, reuseIdentifier: reuseIdentifier)
		commonInit()
	}
	required init?(coder: NSCoder) {
		super.init(coder: coder)
		commonInit()
	}
	func commonInit() -> Void {
		
		calendarView.translatesAutoresizingMaskIntoConstraints = false
		contentView.addSubview(calendarView)
		
		calendarView.topAnchor.constraint(equalTo: contentView.topAnchor).isActive = true
		calendarView.leadingAnchor.constraint(equalTo: contentView.leadingAnchor).isActive = true
		calendarView.trailingAnchor.constraint(equalTo: contentView.trailingAnchor).isActive = true
		
		// bottom anchor needs to have Priority less than required to avoid auto-layout complaints
		let c = calendarView.bottomAnchor.constraint(equalTo: contentView.bottomAnchor)
		c.priority = .defaultHigh
		c.isActive = true

		// initial height constant doesn't matter... it will be changed when we set the data
		calendarViewHeightConstraint = calendarView.heightAnchor.constraint(equalToConstant: 10.0)
		calendarViewHeightConstraint.isActive = true
		
	}

	var m: Int = 0 // tiene traccia del mese
	var y: Int = 0 // tiene traccia dell'anno
	var totalCellsNeeded: Int = 0 // number of cell

	func initData() {
		let calendar = Calendar.current
		
		m = Calendar.current.component(.month, from: Date())
		y = Calendar.current.component(.year, from: Date())
		
		let dateComponents = DateComponents(year: y, month: m)
		
		guard let startDate = calendar.date(from: dateComponents) else { fatalError("Something is wrong with the date!") }
		guard let range = calendar.range(of: .day, in: .month, for: startDate) else { fatalError("Something is wrong with the date!") }
		
		let numberOfDaysInMonth = range.count
		let startDayOfWeek = Calendar.current.component(.weekday, from: startDate)
		
		totalCellsNeeded = numberOfDaysInMonth + (startDayOfWeek - 1)
		
		let numRows = Int(ceil(Double(totalCellsNeeded) / Double(7)))
		
		// we now know the Height needed for the collection view
		//  you said your calendar cell height is 75, so...
		//  cvHeight = numRows * 75

		calendarViewHeightConstraint.constant = CGFloat(numRows * 75)

		// give these values to the calendarView to be used
		//	for the collection view data
		calendarView.startDayOfWeek = startDayOfWeek
		calendarView.totalCellsNeeded = totalCellsNeeded
		

	}

}

// CALENDAR VIEW

class CalendarView: UIView, UICollectionViewDelegate, UICollectionViewDataSource, UICollectionViewDelegateFlowLayout {
	
	// these are set by the cell class
	var startDayOfWeek: Int = 0
	var totalCellsNeeded: Int = 0 // number of cell
	
	override init(frame: CGRect) {
		super.init(frame: frame)
		backgroundColor = .red
		
		let collectionView = UICollectionView(frame: .zero, collectionViewLayout: UICollectionViewFlowLayout())
		collectionView.delegate = self
		collectionView.dataSource = self
		collectionView.translatesAutoresizingMaskIntoConstraints = false
		collectionView.backgroundColor = .clear
		addSubview(collectionView)
		
		collectionView.register(DaysCell.self, forCellWithReuseIdentifier: "cellDay")
		
		collectionView.topAnchor.constraint(equalTo: topAnchor).isActive = true
		collectionView.leadingAnchor.constraint(equalTo: leadingAnchor).isActive = true
		collectionView.trailingAnchor.constraint(equalTo: trailingAnchor).isActive = true
		collectionView.bottomAnchor.constraint(equalTo: bottomAnchor).isActive = true
		
		// no height anchor
		//collectionView.heightAnchor.constraint(equalToConstant: 200).isActive = true
		
	}
	
	required init?(coder: NSCoder) { fatalError("init(coder:) has not been implemented") }
	
	func collectionView(_ collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
		totalCellsNeeded
	}
	
	func collectionView(_ collectionView: UICollectionView, cellForItemAt indexPath: IndexPath) -> UICollectionViewCell {
		let cell = collectionView.dequeueReusableCell(withReuseIdentifier: "cellDay", for: indexPath) as! DaysCell

		// startDayOfWeek is 1-based
		cell.populateCell(indexPath.item - (startDayOfWeek - 1))

		return cell
	}
	
	func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> CGSize {
		.init(width: collectionView.frame.width / 7, height: 75)
	}
	
	func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat { 0 }
	
	func collectionView(_ collectionView: UICollectionView, layout collectionViewLayout: UICollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat { 0 }
}

// Day CELL

class DaysCell: UICollectionViewCell {
	private let dayLbl = UILabel()
	
	override init(frame: CGRect) {
		super.init(frame: frame)
		
		dayLbl.translatesAutoresizingMaskIntoConstraints = false
		addSubview(dayLbl)
		
		dayLbl.centerYAnchor.constraint(equalTo: centerYAnchor).isActive = true
		dayLbl.centerXAnchor.constraint(equalTo: centerXAnchor).isActive = true
	}
	
	required init?(coder: NSCoder) {
		fatalError("init(coder:) has not been implemented")
	}
	
	func populateCell(_ i: Int) -> Void {
		if i >= 0 {
			dayLbl.text = "\(i + 1)"
		}
	}
}