Vending maching

// From Core Text Reference

//  ViewController.swift
//  VendingMachine
//
//  Created by Pasan Premaratne on 1/19/16.
//  Copyright © 2016 Treehouse. All rights reserved.
//

import UIKit

private let reuseIdentifier = "vendingItem"
private let screenWidth = UIScreen.mainScreen().bounds.width

class ViewController: UIViewController, UICollectionViewDataSource, UICollectionViewDelegate {

    @IBOutlet weak var collectionView: UICollectionView!
    @IBOutlet weak var totalLabel: UILabel!
    @IBOutlet weak var balanceLabel: UILabel!
    @IBOutlet weak var quantityLabel: UILabel!

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        setupCollectionViewCells()
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    // MARK: - UICollectionView

    func setupCollectionViewCells() {
        let layout: UICollectionViewFlowLayout = UICollectionViewFlowLayout()
// https://developer.apple.com/library/prerelease/ios/documentation/UIKit/Reference/UICollectionViewFlowLayout_class/
// it works with collection view objects to adjust layout information dynamically.
// you can see objects layout such as size, headers, and footers
// found in UIKit Framework Reference

        layout.sectionInset = UIEdgeInsets(top: 20, left: 0, bottom: 10, right: 0) // sets margins(paddings)
        let padding: CGFloat = 10  //specialized float holds 32 bit or 64 part of Core Graphics
//Core Graphics Framework Reference
//https://developer.apple.com/library/tvos/documentation/CoreGraphics/Reference/CoreGraphics_Framework/index.html

        layout.itemSize = CGSize(width: (screenWidth / 3) - padding, height: (screenWidth / 3) - padding)
//struct CGSize { var width: CGFloat var height: CGFloat init() init(width width: CGFloat, height height: CGFloat) }
// so as you can see it is a struct, and when the struct is called it is in form CGSize(param: value) like all structs that get called

        layout.minimumInteritemSpacing = 10 // minimum spacing between items in same row. var minimumInteritemSpacing: CG Float
        layout.minimumLineSpacing = 10 // minimum spacing between lines of items in grid. . var minimumLineSpacing: CG Float

        collectionView.collectionViewLayout = layout // var collectionView: UICollectionView? {get}, collection view object
//using this layout object, collection view object sets value of this property when new layout object is assigned to it.
// I don’t know collectionViewLayout
    }

    func collectionView(collectionView: UICollectionView, numberOfItemsInSection section: Int) -> Int {
        return 12  // UICollectionView takes ordered collection of data items and presents them using customizable layouts.
       // numberOfItemsInSection is all about State of Collection View, returns number of items in specific section
    // fund numberOfItemsInSection(_ section: Int) -> Int  // section|index of section you want to count items.
    }

    func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) ->
// locating items and views in collection view fund cellForItemAtIndexPath(_ indexPath: NSIndexPath) ->  UICollectionViewCell?
          // indexPath| The index path that specifies the section and item number of the cell


UICollectionViewCell {
        let cell = collectionView.dequeueReusableCellWithReuseIdentifier(reuseIdentifier, forIndexPath: indexPath) as! VendingItemCell
        // func dequeueReusableCellWithReuseIdentifier(_ identifier: String, forIndexPath indexPath: NSIndexPath) -> UICollectionViewCell

// identifier | reuse identifier for the specified cell. This parameter must not be nil.
// indexPath | index path specifying location of cell. data source receives this information when it is asked
// for the cell and should just pass it along. This method uses the index path to perform additional
// configuration view.
// return value is a UICollectionReusableView

        return cell
    }

    func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
        updateCellBackgroundColor(indexPath, selected: true)

// this is under Declaration, Parameters or Managing the Selected Cells.

// optional fund collectionView(_ collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath)

// collectionView | collection view object that is notifying you of the selection change.
// indexPath | The index path of the cell that was selected.

    }

    func collectionView(collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath) {

// didDeselectItemAtIndexPath,

//optional func collectionView(_collectionView: UICollectionView, didDeselectItemAtIndexPath indexPath: NSIndexPath)

// so the api is exactly the same as this example code.

        updateCellBackgroundColor(indexPath, selected: false)  // not sure where this fits in.
    }

    func collectionView(collectionView: UICollectionView, didHighlightItemAtIndexPath indexPath: NSIndexPath) {
        updateCellBackgroundColor(indexPath, selected: true)
// Under Managing Cell Highlighting

    }

    func collectionView(collectionView: UICollectionView, didUnhighlightItemAtIndexPath indexPath: NSIndexPath) {
        updateCellBackgroundColor(indexPath, selected: false)
    } // exactly same as API in UIKit Framework Reference except update..blah is plugged in. below is where it really shines.

    func updateCellBackgroundColor(indexPath: NSIndexPath, selected: Bool) {
        if let cell = collectionView.cellForItemAtIndexPath(indexPath) {

// Getting Views for Items, cellForItemAtIndexPath asks data source object for the
// cell that corresponds to the specified item in the collection view.
// not same as API below

// func collectionView(_ collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell

// notice above collection view is bound to a variable so becomes an attribute or
// stored property? so cellForItemAtIndexPath was a extension name to a parameter to
// collectionView func
// an then is stored to variable calls its own parameter.
// collectionView.cellForItemAtIndexPath(indexPath) so it must call NSIndexPath?
// so What is NSIndexPath, it was set to true at one point
// The NSIndexPath class represents the path to a specific node in a tree of nested array
// collections. This path is known as an index path. Nested arrays create paths to different arrays.

//Foundation framework reference to facilitate the identification of rows and sections in
// “UITableView” objects and the identification of items and sections in “UICollectionView” objects.

            cell.contentView.backgroundColor = selected ? UIColor(red: 41/255.0, green: 211/255.0, blue: 241/255.0, alpha: 1.0) : UIColor.clearColor()
        }
    }

    // MARK: - Helper Methods
}