ArticleViewModel.swift

//
//  NewsFeedViewModel.swift
//  NYTimes
//
//  Created by Waseem Akram on 29/07/20.
//  Copyright © 2020 Waseem Akram. All rights reserved.
//

import Foundation
import Combine

class ArticleViewModel: ObservableObject {
    
    var htmlScrapUtlity = HTMLScraperUtility()
    
    @Published var articles = [Article]()
    @Published var isArticlesLoading = false
    @Published var searchText = ""
    
    var cancellableTask: AnyCancellable? = nil
    var searchResults : [Article] {
        if searchText.isEmpty {
            return articles
        } else {
            return articles.filter { $0.title.lowercased().contains(searchText.lowercased()) || $0.subtitle.lowercased().contains(searchText.lowercased()) || $0.author.lowercased().contains(searchText.lowercased()) }
        }
    }
    
    func loadArticles(for category: Category) {
        guard let url = URL(string: category.url) else { return }
        self.isArticlesLoading = true
        self.cancellableTask?.cancel() //cancel last subscription to prevent race condition
        self.cancellableTask = URLSession.shared.dataTaskPublisher(for: url)
            .map(\.data) //extract Data() from tuple
            .flatMap(htmlScrapUtlity.scrapArticle(from:)) //send data to scrap function that will return article objects (array)
            .sink { (completion) in
                self.isArticlesLoading = false //once we got articles, close the loader
            } receiveValue: { [unowned self] (articles) in
                self.articles = articles
            }
    }
    
    deinit {
        cancellableTask = nil
    }
}