//
//  FileProviderEnumerator.swift
//  Files
//
//  Created by Marino Faggiana on 26/03/18.
//  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 FileProviderEnumerator: NSObject, NSFileProviderEnumerator {
    
    var enumeratedItemIdentifier: NSFileProviderItemIdentifier
    var serverUrl: String?
    var providerData: FileProviderData
    
    init(enumeratedItemIdentifier: NSFileProviderItemIdentifier, providerData: FileProviderData) {
        
        self.enumeratedItemIdentifier = enumeratedItemIdentifier
        self.providerData = providerData
        
        // Select ServerUrl
        if #available(iOSApplicationExtension 11.0, *) {

            if (enumeratedItemIdentifier == .rootContainer) {
                serverUrl = providerData.homeServerUrl
            } else {
                
                let metadata = providerData.getTableMetadataFromItemIdentifier(enumeratedItemIdentifier)
                if metadata != nil  {
                    if let directorySource = NCManageDatabase.sharedInstance.getTableDirectory(predicate: NSPredicate(format: "directoryID == %@", metadata!.directoryID))  {
                        serverUrl = directorySource.serverUrl + "/" + metadata!.fileName
                    }
                }
            }
        }
        
        super.init()
    }

    func invalidate() {
        // Update the WorkingSet -> Favorite
        providerData.updateFavoriteForWorkingSet()
    }

    func enumerateItems(for observer: NSFileProviderEnumerationObserver, startingAt page: NSFileProviderPage) {
        
        var items: [NSFileProviderItemProtocol] = []
        var metadatasFromDB: [tableMetadata]?

        /* ONLY iOS 11*/
        guard #available(iOS 11, *) else {
            observer.finishEnumerating(upTo: nil)
            return
        }
        
        /*** WorkingSet ***/
        if enumeratedItemIdentifier == .workingSet {
            
            var itemIdentifierMetadata = [NSFileProviderItemIdentifier:tableMetadata]()
            
            // ***** Tags *****
            let tags = NCManageDatabase.sharedInstance.getTags(predicate: NSPredicate(format: "account == %@", providerData.account))
            for tag in tags {
                
                guard let metadata = NCManageDatabase.sharedInstance.getMetadata(predicate: NSPredicate(format: "fileID == %@", tag.fileID))  else {
                    continue
                }
                
                providerData.createFileIdentifierOnFileSystem(metadata: metadata)
                    
                itemIdentifierMetadata[providerData.getItemIdentifier(metadata: metadata)] = metadata
            }
            
            // ***** Favorite *****
            providerData.listFavoriteIdentifierRank = NCManageDatabase.sharedInstance.getTableMetadatasDirectoryFavoriteIdentifierRank()
            for (identifier, _) in providerData.listFavoriteIdentifierRank {
             
                guard let metadata = NCManageDatabase.sharedInstance.getMetadata(predicate: NSPredicate(format: "fileID == %@", identifier)) else {
                    continue
                }
               
                itemIdentifierMetadata[ providerData.getItemIdentifier(metadata: metadata)] = metadata
            }
            
            // create items
            for (_, metadata) in itemIdentifierMetadata {
                let parentItemIdentifier = providerData.getParentItemIdentifier(metadata: metadata)
                if parentItemIdentifier != nil {
                    let item = FileProviderItem(metadata: metadata, parentItemIdentifier: parentItemIdentifier!, providerData: providerData)
                    items.append(item)
                }
            }
            
            observer.didEnumerate(items)
            observer.finishEnumerating(upTo: nil)
            
        } else {
        
        /*** ServerUrl ***/
            
            guard let serverUrl = serverUrl else {
                observer.finishEnumerating(upTo: nil)
                return
            }
            
            // Select items from database
            if let directory = NCManageDatabase.sharedInstance.getTableDirectory(predicate: NSPredicate(format: "account == %@ AND serverUrl == %@", providerData.account, serverUrl))  {
                metadatasFromDB = NCManageDatabase.sharedInstance.getMetadatas(predicate: NSPredicate(format: "directoryID == %@", directory.directoryID), sorted: "fileName", ascending: true)
            }
            
            // Calculate current page
            if (page != NSFileProviderPage.initialPageSortedByDate as NSFileProviderPage && page != NSFileProviderPage.initialPageSortedByName as NSFileProviderPage) {
                
                var numPage = Int(String(data: page.rawValue, encoding: .utf8)!)!
                
                if (metadatasFromDB != nil) {
                    items = self.selectItems(numPage: numPage, account: providerData.account, metadatas: metadatasFromDB!)
                    observer.didEnumerate(items)
                }
                if (items.count == providerData.itemForPage) {
                    numPage += 1
                    let providerPage = NSFileProviderPage("\(numPage)".data(using: .utf8)!)
                    observer.finishEnumerating(upTo: providerPage)
                } else {
                    observer.finishEnumerating(upTo: nil)
                }
                return
            }
            
            // Read 
            var fileName: String?
            var serverUrlForFileName = self.providerData.homeServerUrl
            
            if serverUrl != self.providerData.homeServerUrl {
                fileName = (serverUrl as NSString).lastPathComponent
                serverUrlForFileName = (serverUrl as NSString).deletingLastPathComponent
            }
            
            let ocNetworking = OCnetworking.init(delegate: nil, metadataNet: nil, withUser: providerData.accountUser, withUserID: providerData.accountUserID, withPassword: providerData.accountPassword, withUrl: providerData.accountUrl)
            ocNetworking?.readFile(fileName, serverUrl: serverUrlForFileName, account: providerData.account, success: { (metadata) in
                
                if self.providerData.listServerUrlEtag[serverUrl] == nil || self.providerData.listServerUrlEtag[serverUrl] != metadata!.etag || metadatasFromDB == nil {
                    
                    ocNetworking?.readFolder(serverUrl, depth: "1", account: self.providerData.account, success: { (metadatas, metadataFolder, directoryID) in
                        
                        if metadataFolder != nil {
                            // Update directory etag
                            NCManageDatabase.sharedInstance.setDirectory(serverUrl: serverUrl, serverUrlTo: nil, etag: metadataFolder!.etag, fileID: metadataFolder!.fileID, encrypted: metadataFolder!.e2eEncrypted)
                            // Save etag for this serverUrl
                            self.providerData.listServerUrlEtag[serverUrl] = metadataFolder!.etag
                        }
                        
                        if metadatas != nil {
                            
                            NCManageDatabase.sharedInstance.deleteMetadata(predicate: NSPredicate(format: "directoryID == %@ AND (status == %d OR status == %d)", directoryID!, k_metadataStatusNormal, k_metadataStatusHide), clearDateReadDirectoryID: directoryID!)
                            
                            NCManageDatabase.sharedInstance.setDateReadDirectory(directoryID: directoryID!)

                            let metadatasInDownload = NCManageDatabase.sharedInstance.getMetadatas(predicate: NSPredicate(format: "directoryID == %@ AND (status == %d OR status == %d OR status == %d OR status == %d)", directoryID!, k_metadataStatusWaitDownload, k_metadataStatusInDownload, k_metadataStatusDownloading, k_metadataStatusDownloadError), sorted: nil, ascending: false)
                            
                            _ = NCManageDatabase.sharedInstance.addMetadatas(metadatas as! [tableMetadata], serverUrl: serverUrl)
                            if metadatasInDownload != nil {
                                _ = NCManageDatabase.sharedInstance.addMetadatas(metadatasInDownload!, serverUrl: serverUrl)
                            }
                        }
                        
                        metadatasFromDB = NCManageDatabase.sharedInstance.getMetadatas(predicate: NSPredicate(format: "directoryID == %@", directoryID!), sorted: "fileName", ascending: true)
                        
                        self.selectFirstPageItems(metadatasFromDB, observer: observer)
                        
                    }, failure: { (errorMessage, errorCode) in
                        
                        self.selectFirstPageItems(metadatasFromDB, observer: observer)
                    })
                    
                } else {
                    
                    self.selectFirstPageItems(metadatasFromDB, observer: observer)
                }
                
            }, failure: { (message, errorCode) in
                
                 self.selectFirstPageItems(metadatasFromDB, observer: observer)
            })
        }
    }
    
    func enumerateChanges(for observer: NSFileProviderChangeObserver, from anchor: NSFileProviderSyncAnchor) {
        
        guard #available(iOS 11, *) else { return }
    
        var itemsDelete = [NSFileProviderItemIdentifier]()
        var itemsUpdate = [FileProviderItem]()
        
        // Report the deleted items
        //
        if enumeratedItemIdentifier == .workingSet {
            providerData.queueTradeSafe.sync() {
                for (itemIdentifier, _) in providerData.fileProviderSignalDeleteWorkingSetItemIdentifier {
                    itemsDelete.append(itemIdentifier)
                }
            }
            providerData.queueTradeSafe.sync(flags: .barrier) {
                providerData.fileProviderSignalDeleteWorkingSetItemIdentifier.removeAll()
            }
        } else {
            providerData.queueTradeSafe.sync() {
                for (itemIdentifier, _) in providerData.fileProviderSignalDeleteContainerItemIdentifier {
                    itemsDelete.append(itemIdentifier)
                }
            }
            providerData.queueTradeSafe.sync(flags: .barrier) {
                providerData.fileProviderSignalDeleteContainerItemIdentifier.removeAll()
            }
        }
            
        // Report the updated items
        //
        if enumeratedItemIdentifier == .workingSet {
            providerData.queueTradeSafe.sync() {
                for (itemIdentifier, item) in providerData.fileProviderSignalUpdateWorkingSetItem {
                    let account = providerData.getAccountFromItemIdentifier(itemIdentifier)
                    if account != nil && account == providerData.account {
                        itemsUpdate.append(item)
                    } else {
                        itemsDelete.append(itemIdentifier)
                    }
                }
            }
            providerData.queueTradeSafe.sync(flags: .barrier) {
                providerData.fileProviderSignalUpdateWorkingSetItem.removeAll()
            }
        } else {
            providerData.queueTradeSafe.sync(flags: .barrier) {
                for (itemIdentifier, item) in providerData.fileProviderSignalUpdateContainerItem {
                    let account = providerData.getAccountFromItemIdentifier(itemIdentifier)
                    if account != nil && account == providerData.account {
                        itemsUpdate.append(item)
                    } else {
                        itemsDelete.append(itemIdentifier)
                    }
                }
            }
            providerData.queueTradeSafe.sync(flags: .barrier) {
                providerData.fileProviderSignalUpdateContainerItem.removeAll()
            }
        }
            
        observer.didDeleteItems(withIdentifiers: itemsDelete)
        observer.didUpdate(itemsUpdate)
            
        let data = "\(providerData.currentAnchor)".data(using: .utf8)
        observer.finishEnumeratingChanges(upTo: NSFileProviderSyncAnchor(data!), moreComing: false)
    }
    
    func currentSyncAnchor(completionHandler: @escaping (NSFileProviderSyncAnchor?) -> Void) {
        let data = "\(providerData.currentAnchor)".data(using: .utf8)
        completionHandler(NSFileProviderSyncAnchor(data!))
    }
    
    // --------------------------------------------------------------------------------------------
    //  MARK: - User Function
    // --------------------------------------------------------------------------------------------

    func selectFirstPageItems(_ metadatas: [tableMetadata]?, observer: NSFileProviderEnumerationObserver) {
        
        var items: [NSFileProviderItemProtocol] = []
        
        if (metadatas != nil) {
            items = self.selectItems(numPage: 0, account: self.providerData.account, metadatas: metadatas!)
            observer.didEnumerate(items)
        }
        if (items.count == self.providerData.itemForPage) {
            let providerPage = NSFileProviderPage("1".data(using: .utf8)!)
            observer.finishEnumerating(upTo: providerPage)
        } else {
            observer.finishEnumerating(upTo: nil)
        }
    }
    
    func selectItems(numPage: Int, account: String, metadatas: [tableMetadata]) -> [NSFileProviderItemProtocol] {
        
        var items: [NSFileProviderItemProtocol] = []
        let start = numPage * providerData.itemForPage + 1
        let stop = start + (providerData.itemForPage - 1)
        var counter = 0
        
        autoreleasepool {
            
            for metadata in metadatas {
                
                // E2EE Remove
                if metadata.e2eEncrypted || metadata.status == Int(k_metadataStatusHide) || (metadata.session != "" && metadata.session != k_download_session_extension && metadata.session != k_upload_session_extension) {
                    continue
                }
                
                counter += 1
                if (counter >= start && counter <= stop) {
                    
                    providerData.createFileIdentifierOnFileSystem(metadata: metadata)
                    
                    let parentItemIdentifier = providerData.getParentItemIdentifier(metadata: metadata)
                    if parentItemIdentifier != nil {
                        let item = FileProviderItem(metadata: metadata, parentItemIdentifier: parentItemIdentifier!, providerData: providerData)
                        items.append(item)
                    }
                }
            }
        }
        return items
    }

}