NetNewsWire/Account/Sources/Account/OPMLNormalizer.swift

//
//  OPMLNormalizer.swift
//  Account
//
//  Created by Maurice Parker on 3/31/20.
//  Copyright © 2020 Ranchero Software, LLC. All rights reserved.
//

import Foundation
import Parser

final class OPMLNormalizer {
	
	var normalizedOPMLItems = [RSOPMLItem]()
	
	static func normalize(_ items: [RSOPMLItem]) -> [RSOPMLItem] {
		let opmlNormalizer = OPMLNormalizer()
		opmlNormalizer.normalize(items)
		return opmlNormalizer.normalizedOPMLItems
	}
	
	private func normalize(_ items: [RSOPMLItem], parentFolder: RSOPMLItem? = nil) {
		var feedsToAdd = [RSOPMLItem]()

		for item in items {

			if let _ = item.feedSpecifier {
				if !feedsToAdd.contains(where: { $0.feedSpecifier?.feedURL == item.feedSpecifier?.feedURL }) {
					feedsToAdd.append(item)
				}
				continue
			}

			guard let _ = item.titleFromAttributes else {
				// Folder doesn’t have a name, so it won’t be created, and its items will go one level up.
				if let itemChildren = item.children {
					normalize(itemChildren, parentFolder: parentFolder)
				}
				continue
			}

			feedsToAdd.append(item)
			if let itemChildren = item.children {
				if let parentFolder = parentFolder {
					normalize(itemChildren, parentFolder: parentFolder)
				} else {
					normalize(itemChildren, parentFolder: item)
				}
			}
		}

		if let parentFolder = parentFolder {
			for feed in feedsToAdd {
				if !(parentFolder.children?.contains(where: { $0.feedSpecifier?.feedURL == feed.feedSpecifier?.feedURL}) ?? false) {
					parentFolder.addChild(feed)
				}
			}
		} else {
			for feed in feedsToAdd {
				normalizedOPMLItems.append(feed)
			}
		}
		
	}
	
}