SearchResultViewModel.swift

//  SearchResultViewModel.swift
//  RxExample
//
//  Created by Krunoslav Zaher on 4/3/15.
//  Modified by Chuck Krutsinger on 2/20/19.
//
//  Copyright © 2015 Krunoslav Zaher. All rights reserved.
//

import RxSwift
import RxCocoa

class SearchResultViewModel {

    var title: Driver<String>
    var imageURLs: Driver<[URL]>

    init(searchResult: WikipediaSearchResult) {
        let URLs = configureImageURLs(searchResult)

        self.imageURLs = URLs.asDriver(onErrorJustReturn: [])
        self.title = configureTitle(URLs, searchResult).asDriver(onErrorJustReturn: "Error during fetching")
    }
}

fileprivate func configureTitle(_ imageURLs: Observable<[URL]>,
                                _ searchResult: WikipediaSearchResult) -> Observable<String>
{
    let loadingValue: [URL]? = nil
    
    return imageURLs
        .map(Optional.init)
        .startWith(loadingValue)
        .map { URLs in
            if let URLs = URLs {
                return "\(searchResult.title) (\(URLs.count) pictures)"
            }
            else {
                return "\(searchResult.title) (loading…)"
            }
        }
        .retryOnBecomesReachable("⚠️ Service offline ⚠️", reachabilityService: Dependencies.sharedDependencies.reachabilityService)
}

fileprivate func configureImageURLs(_ searchResult: WikipediaSearchResult) -> Observable<[URL]>
{
    return DefaultWikipediaAPI.sharedAPI.articleContent(searchResult)
        .observeOn(Dependencies.sharedDependencies.backgroundWorkScheduler)
        .map { page in
            do {
                return try parseImageURLsfromHTMLSuitableForDisplay(page.text as NSString)
            } catch {
                return []
            }
        }
        .share(replay: 1)
}