//
//  FileProviderEnumeratorFile.swift
//  PickerFileProvider
//
//  Created by Marino Faggiana on 30/04/18.
//  Copyright © 2018 TWS. All rights reserved.
//
//  Author Marino Faggiana <m.faggiana@twsweb.it>
//
//  This program is free software: you can redistribute it and/or modify
//  it under the terms of the GNU General Public License as published by
//  the Free Software Foundation, either version 3 of the License, or
//  (at your option) any later version.
//
//  This program is distributed in the hope that it will be useful,
//  but WITHOUT ANY WARRANTY; without even the implied warranty of
//  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//  GNU General Public License for more details.
//
//  You should have received a copy of the GNU General Public License
//  along with this program.  If not, see <http://www.gnu.org/licenses/>.
//


import FileProvider

class FileProviderEnumeratorFile: NSObject, NSFileProviderEnumerator {
    
    var enumeratedItemIdentifier: NSFileProviderItemIdentifier
    
    init(enumeratedItemIdentifier: NSFileProviderItemIdentifier) {
        
        self.enumeratedItemIdentifier = enumeratedItemIdentifier
        
        super.init()
    }
    
    func invalidate() {
        // TODO: perform invalidation of server connection if necessary
    }
    
    func enumerateItems(for observer: NSFileProviderEnumerationObserver, startingAt page: NSFileProviderPage) {
        
        var items: [NSFileProviderItemProtocol] = []

         guard let metadata = NCManageDatabase.sharedInstance.getMetadata(predicate: NSPredicate(format: "account = %@ AND fileID = %@", account, enumeratedItemIdentifier.rawValue)) else {
            observer.finishEnumerating(upTo: nil)
            return
        }
        
        guard let serverUrl = NCManageDatabase.sharedInstance.getServerUrl(metadata.directoryID) else {
            observer.finishEnumerating(upTo: nil)
            return
        }
        
        let item = FileProviderItem(metadata: metadata, serverUrl: serverUrl)
        items.append(item)
        
        observer.didEnumerate(items)
        observer.finishEnumerating(upTo: nil)
    

        /* TODO:
         - inspect the page to determine whether this is an initial or a follow-up request
         
         If this is an enumerator for a directory, the root container or all directories:
         - perform a server request to fetch directory contents
         If this is an enumerator for the active set:
         - perform a server request to update your local database
         - fetch the active set from your local database
         
         - inform the observer about the items returned by the server (possibly multiple times)
         - inform the observer that you are finished with this page
         */
    }
    
    func enumerateChanges(for observer: NSFileProviderChangeObserver, from anchor: NSFileProviderSyncAnchor) {
        /* TODO:
         - query the server for updates since the passed-in sync anchor
         
         If this is an enumerator for the active set:
         - note the changes in your local database
         
         - inform the observer about item deletions and updates (modifications + insertions)
         - inform the observer when you have finished enumerating up to a subsequent sync anchor
         */
    }
}