ViewController.swift

//
//  ViewController.swift
//  ShoppingList
//
//  Created by Julian Moorhouse on 03/08/2019.
//  Copyright © 2019 Mindwarp Consultancy Ltd. All rights reserved.
//

import UIKit

class ViewController: UITableViewController {
    var shoppingList = [String]()
    
    override func viewDidLoad() {
        super.viewDidLoad()

        title = "Shopping List"
        
        navigationItem.rightBarButtonItem = UIBarButtonItem(barButtonSystemItem: .add, target: self, action: #selector(promptForItem))
        
        let reset = UIBarButtonItem(barButtonSystemItem: .trash, target: self, action: #selector(resetList))
        
        let share = UIBarButtonItem(barButtonSystemItem: .action, target: self, action: #selector(shareTapped))
        
        navigationItem.leftBarButtonItems = [reset, share]
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return shoppingList.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Product", for: indexPath)
        cell.textLabel?.text = shoppingList[indexPath.row]
        return cell
    }

    @objc func resetList() {
        shoppingList.removeAll(keepingCapacity: true)
        tableView.reloadData()
    }
    
    @objc func promptForItem() {
        let ac = UIAlertController(title: "Enter item", message: nil, preferredStyle: .alert)
        ac.addTextField()
        
        let submitAction = UIAlertAction(title: "Submit", style: .default) {
            [weak self, weak ac] action in // specifies input into closure, ac is a weak reference
            // using ac? as its a weak reference
            guard let answer = ac?.textFields?[0].text?.lowercased() else { return }

            self?.shoppingList.insert(answer, at: 0)
            
            let indexPath = IndexPath(row: 0, section: 0)
            self?.tableView.insertRows(at: [indexPath], with:  .automatic)
        }
        
        ac.addAction(submitAction)
        present(ac, animated: true)
    }
    
    @objc func shareTapped() {
        
        let list = shoppingList.joined(separator: "\n")

        let vc = UIActivityViewController(activityItems: [list], applicationActivities: [])
        vc.popoverPresentationController?.barButtonItem = navigationItem.rightBarButtonItem
        present(vc, animated: true)
    }
}