NetNewsWire/Frameworks/Account/AccountTests/Feedly/TestGetPagedStreamContentsService.swift

//
//  TestGetPagedStreamContentsService.swift
//  AccountTests
//
//  Created by Kiel Gillard on 28/10/19.
//  Copyright © 2019 Ranchero Software, LLC. All rights reserved.
//

import XCTest
@testable import Account

final class TestGetPagedStreamContentsService: FeedlyGetStreamContentsService {
	
	var parameterTester: ((FeedlyResourceId, String?, Date?, Bool?) -> ())?
	var getStreamContentsExpectation: XCTestExpectation?
	var pages = [String: FeedlyStream]()
	
	func addAtLeastOnePage(for resource: FeedlyResourceId, continuations: [String], numberOfEntriesPerPage count: Int)  {
		pages = [String: FeedlyStream](minimumCapacity: continuations.count + 1)
		
		// A continuation is an identifier for the next page.
		// The first page has a nil identifier.
		// The last page has no next page, so the next continuation value for that page is nil.
		// Therefore, each page needs to know the identifier of the next page.
		for index in -1..<continuations.count {
			let nextIndex = index + 1
			let continuation: String? = nextIndex < continuations.count ? continuations[nextIndex] : nil
			let page = makeStreamContents(for: resource, continuation: continuation, between: 0..<count)
			let key = TestGetPagedStreamContentsService.getPagingKey(for: resource, continuation: index < 0 ? nil : continuations[index])
			pages[key] = page
		}
	}
	
	private func makeStreamContents(for resource: FeedlyResourceId, continuation: String?, between range: Range<Int>) -> FeedlyStream {
		let entries = range.map { index -> FeedlyEntry in
			let content = FeedlyEntry.Content(content: "Content \(index)",
				direction: .leftToRight)
			
			let origin = FeedlyOrigin(title: "Origin \(index)",
				streamId: resource.id,
				htmlUrl: "http://localhost/feedly/origin/\(index)")
			
			return FeedlyEntry(id: "/articles/\(index)",
				title: "Article \(index)",
				content: content,
				summary: content,
				author: nil,
				crawled: Date(),
				recrawled: nil,
				origin: origin,
				canonical: nil,
				alternate: nil,
				unread: true,
				tags: nil,
				categories: nil,
				enclosure: nil)
		}
		
		let stream = FeedlyStream(id: resource.id, updated: nil, continuation: continuation, items: entries)
		
		return stream
	}
	
	static func getPagingKey(for stream: FeedlyResourceId, continuation: String?) -> String {
		return "\(stream.id)@\(continuation ?? "")"
	}
	
	func getStreamContents(for resource: FeedlyResourceId, continuation: String?, newerThan: Date?, unreadOnly: Bool?, completion: @escaping (Result<FeedlyStream, Error>) -> ()) {
		let key = TestGetPagedStreamContentsService.getPagingKey(for: resource, continuation: continuation)
		guard let page = pages[key] else {
			XCTFail("Missing page for \(resource.id) and continuation \(String(describing: continuation)). Test may time out because the completion will not be called.")
			return
		}
		parameterTester?(resource, continuation, newerThan, unreadOnly)
		DispatchQueue.main.async {
			completion(.success(page))
			self.getStreamContentsExpectation?.fulfill()
		}
	}
}