ViewController.swift

//
//  ViewController.swift
//  Project9-Challenge3
//

import UIKit

class ViewController: UITableViewController {

    var petitions = [Petition]()
    var filteredPetitions = [Petition]()
    
    // use empty string for no filter
    var filterKeyword: String = ""
    
    override func viewDidLoad() {
        super.viewDidLoad()

        let urlString: String
            
        if navigationController?.tabBarItem.tag == 0 {
            urlString = "https://api.whitehouse.gov/v1/petitions.json?limit=100"
        }
        else {
            urlString = "https://api.whitehouse.gov/v1/petitions.json?signatureCountFloor=10000&limit=100"
        }
        
        title = "White House petitions"

        navigationItem.rightBarButtonItem = UIBarButtonItem(title: "Credits", style: .plain, target: self, action: #selector(showCredits))

        navigationItem.leftBarButtonItem = UIBarButtonItem(title: "Filter", style: .plain, target: self, action: #selector(askFilter))

        if let url = URL(string: urlString) {
            if let data = try? Data(contentsOf: url) {
                parse(json: data)
                return
            }
        }
        
        showError()
    }
    
    @objc func showCredits() {
        let ac = UIAlertController(title: "Credits", message: "Petitions from WE the PEOPLE at petitions.whitehouse.gov", preferredStyle: .alert)
        ac.addAction(UIAlertAction(title: "OK", style: .default))
        present(ac, animated: true)
    }
    
    @objc func askFilter() {
        let ac = UIAlertController(title: "Filter", message: "Filter the petitions on the following keyword (leave empty to reset filtering)", preferredStyle: .alert)
        ac.addTextField()

        ac.addAction(UIAlertAction(title: "Cancel", style: .cancel))
        ac.addAction(UIAlertAction(title: "OK", style: .default) {
            [weak self, weak ac] _ in
            self?.filterKeyword = ac?.textFields?[0].text ?? ""
            
            // project 9 challenge 3
            // no need for weak self (already weak as per above)
            DispatchQueue.global().async {
                self?.filterData()

                DispatchQueue.main.async {
                    self?.tableView.reloadData()
                }
            }
        })
        
        present(ac, animated: true)

    }
    
    @objc func filterData() {
        if filterKeyword.isEmpty {
            filteredPetitions = petitions
            navigationItem.leftBarButtonItem?.title = "Filter"
            return
        }

        navigationItem.leftBarButtonItem?.title = "Filter (current: \(filterKeyword))"

        // keep only petition whose title or body contains keyword
        filteredPetitions = petitions.filter() { petition in
            // use range instead of contains to filter in case insentive manner
            // (see https://www.hackingwithswift.com/example-code/strings/how-to-run-a-case-insensitive-search-for-one-string-inside-another)
            if let _ = petition.title.range(of: filterKeyword, options: .caseInsensitive) {
                return true
            }
            if let _ =  petition.body.range(of: filterKeyword, options: .caseInsensitive) {
                return true
            }
            return false
        }
    }
    
    func showError() {
        let ac = UIAlertController(title: "Loading error", message: "There was a problem loading the feed; please check your connection and try again", preferredStyle: .alert)
        ac.addAction(UIAlertAction(title: "OK", style: .default))
        present(ac, animated: true)
    }
    
    func parse(json: Data) {
        let decoder = JSONDecoder()
        
        if let jsonPetitions = try? decoder.decode(Petitions.self, from: json) {
            petitions = jsonPetitions.results
            filterData()
            tableView.reloadData()
        }
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return filteredPetitions.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "Cell", for: indexPath)
        let petition = filteredPetitions[indexPath.row]
        cell.textLabel?.text = petition.title
        cell.detailTextLabel?.text = petition.body
        return cell
    }
    
    override func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let vc = DetailViewController()
        vc.detailItem = filteredPetitions[indexPath.row]
        navigationController?.pushViewController(vc, animated: true)
    }
}