Attractor/App/Backend/History/BrowserHistory.swift

//
//  BrowserHistory.swift
//  App
//
//  Created by James Magahern on 8/14/20.
//

import Foundation
import CoreData

class BrowserHistory
{
    static public let shared = BrowserHistory()
    
    lazy fileprivate var persistentContainer: NSPersistentContainer = {
        let container = NSPersistentContainer(name: "History")
        container.loadPersistentStores { description, error in
            assert(error == nil)
        }
        
        return container
    }()
    
    public func didNavigate(toURL url: URL, title: String) {
        let dataContext = persistentContainer.viewContext
        
        let entity = HistoryItemEntity(context: dataContext)
        entity.url = url
        entity.lastVisited = Date()
        entity.title = title
        entity.host = url.host
        
        do { try dataContext.save() }
        catch {
            let nserror = error as NSError
            fatalError("Failed saving persistent entity to store: \(nserror), \(nserror.userInfo)")
        }
    }
    
    public func allHistory() -> [HistoryItem] {
        let dataContext = persistentContainer.viewContext
        
        let fetchRequest: NSFetchRequest<HistoryItemEntity> = HistoryItemEntity.fetchRequest()
        let entities: [HistoryItemEntity] = (try? dataContext.fetch(fetchRequest)) ?? []
        
        return entities.map { (entity) -> HistoryItem in
            HistoryItem(entity: entity)
        }
    }
    
    public func visitedToplevelHistoryItems(matching: String) -> [HistoryItem] {
        let dataContext = persistentContainer.viewContext
        
        let fetchRequest: NSFetchRequest<HistoryItemEntity> = HistoryItemEntity.fetchRequest()
        fetchRequest.predicate = NSPredicate(format: """
                                             host CONTAINS[cd] %@
                                             OR title CONTAINS[cd] %@
                                             OR url ENDSWITH[cd] %@
                                             """, matching, matching, matching)
        fetchRequest.fetchLimit = 200
        fetchRequest.sortDescriptors = [ NSSortDescriptor(key: "visitCount", ascending: false) ]
        
        let entities: [HistoryItemEntity] = (try? dataContext.fetch(fetchRequest)) ?? []
        let allItems: [HistoryItem] = entities.map { HistoryItem(entity: $0) }
        
        var topLevelItems: [URL: (HistoryItem, Int)] = [:]
        for item in allItems {
            if item.url.pathComponents.count <= 2 {
                var score = 1
                let topLevelURL = item.url.topLevelURL()
                var topLevelItem = topLevelItems[topLevelURL] ?? (item, 0)
                topLevelItem.0.url = topLevelURL
                if item.url.path == "/" || item.url.path == "" {
                    score += 10
                    topLevelItem.0.title = item.title
                }
                topLevelItem.1 += score
                topLevelItems[topLevelURL] = topLevelItem
                
                if topLevelItems.count == 20 {
                    break
                }
            }
        }
        
        return topLevelItems.values.map { return $0.0 }.sorted { (item1, item2) -> Bool in
            return topLevelItems[item1.url]!.1 > topLevelItems[item2.url]!.1
        }
    }
}

extension URL
{
    public func topLevelURL() -> URL {
        if var components = URLComponents(url: self, resolvingAgainstBaseURL: false) {
            components.query = nil
            components.queryItems = nil
            components.fragment = nil
            if let url = components.url {
                return url
            }
        }
        
        return self
    }
}